Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
- Crop Residues INTRODUCTION the potential for animal production through feeding crop residues is im- pressive. The United States produces annually about 44 million tons of wheat, 45 million tons of soybeans, and another 186 million tons of coarse feed grains, dry basis (U.S. Department of Agriculture, 19791. The feed grains consist primarily of corn, with lesser amounts of mile, barley, and oats. Grain-producing plants normally produce an equal or greater weight as vegetative material than as grain (Vetter and Boehlje, 19781. Therefore, a total of at least 300 million tons of straws, stalks, and stubbles are available in the United States each year (see Table 48) and another 40 million in Canada. Worldwide, over 1.5 billion tons of crop residues are produced each year (for definitions of residues and other terms see the glossary on p. 2101. The 300 million tons of residues have sufficient energy to meet the entire needs of the present beef cattle industry in the United States. How- ever, the concentration of digestible energy is sufficiently low to prevent the practical use of much of the residue without further treatment or processing. QUANTITY Corn is the most widely produced grain crop in the United States. Nor- mally, an amount of residue greater than the quantity of grain is produced 178
Crop Residues 179 above ground. Therefore, the production of 153 million tons of corn per year yields at least 153 million tons of corn residue, which is over one- half the total available residue supply (see Table 484. Wheat residue constitutes 15 percent of the total crop residue because grain production per land area is generally lower for wheat. Over 44 million tons of wheat straw are produced per year. Soybean residue accounts for another 15 percent of the crop residue (45 million metric tons) and grain sorghum 5 percent (16 million metric tons). Other small grains and crops account for the remaining residues (see Table 484. Crop residues are widely distributed. Corn residue is distributed throughout the Corn Belt. Illinois, Iowa, Indiana, Kansas, Minnesota, and Nebraska produce about 50 percent of the total crop residue supply. Wheat straw is more widely distributed over the United States, but tends to be con- centrated in the Great Plains States and the Northwest. Soybean production has been centered in the Corn Belt, but is expanding in the Southeast. Grain sorghum is produced primarily in the Great Plains States, with 77 percent produced in Texas, Kansas, and Nebraska. Peanuts, cotton, and rice are grown in the southern United States and California, and sugarcane is produced in Louisiana, Florida, Hawaii, and Texas. PHYSICAL CHARACTERISTICS Crop residues can be collected from the field, but because of their bulky characteristics and low market value per unit weight, transportation is generally uneconomical. Because of differences in plant structure, grain harvesting methods, and moisture content, residues vary concerning ease of harvest. Straws from small grains are easily collected dry behind the combine. Corn and especially grain sorghum residues often do not dry to the extent needed for dry storage, but they can be stored as silage. Soybean residue is difficult to harvest if allowed to drop on the ground behind the combine. Soil contamination during harvest can be a problem with all residues. Feeding of residues to livestock on the farm can be readily accomplished. Most of the residues are produced in the summer and fall; storage for extended periods may not be economical, but the greatest use for livestock feed generally occurs in the winter. Removal of crop residues from the soil may reduce soil filth (organic matter) and increase the risk of wind and water erosion. Depending upon soil type and topography, an average of one-half the total residue can be removed (Larson et al., 19781. If the residue is used on the farm and the resulting manure returned to the soil or if animals consume the residues by grazing, there should be little detrimental effect on soil from crop residue feeding.
180 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS TABLE 48 Estimated Supply of Crop Residues Dry Grain (Product) Crop Production ResidueDry Residue Percent of Source (tons x 1 06)a Coefficients(tons x 1 o6) Total Corn 153.0 1153.0 51.0 Soybean 45.2 145.2 15 .0 Wheat 44.2 144.2 14.7 Grain Sorghum 16.2 116.2 5.4 Barley 8.8 217.6 5.9 Oats 7.9 17.9 2.6 Cotton 2. 1 36.3 2. 1 Rice 5.6 15.6 1.9 Peanuts 1.6 1.52.4 0.8 Flax 0.3 30 9 0 3 Rye 0.6 10.6 0.2 Sugar Beets 4.3 0.140.6 0.2 Total 300.5 aFrom 1978 USDA Agricultural Statistics (1979). From Vetter and Boehlje (1978); cotton, peanuts, sugar beets, and flax from Corkern et al. (1979). Some of the residues, such as cotton by-products, rice milling by- products, and bagasse, that are produced at central locations have the advantage of being collected and available for processing or treatment. In fact, they may initially have a negative value because they present a disposal problem. NUTRITIVE VALUE Without treatment, crop residues are low in nutritional value. Because grain is harvested after the plant reaches physiological maturity, the veg- etative portion is high in cell walls and lignin and low in protein and digestible dry matter. It has been clearly shown that lignin inhibits diges- tion of cellulose and hemicellulose, making about 1.4 times the weight of the lignin in the matter indigestible (Van Soest, 19811. There is con- siderable variation in digestibility both among and within residues. Con- trolling and properly accounting for this variation may be the most important key to efficient use of crop residues. Corn Corn residue consists of 54 percent stalks, 12 percent leaves, 21 percent cobs, and 13 percent husks (Vetter, 19734. Husks and cobs are discharged
Crop Residues 181 from the rear of the combine and the mixture is referred to as husklage. The husk is the most digestible part of the corn plant, with the digestibility of the other parts being lower and more variable. Dry-matter digestibility of the various parts of the corn plant ranges from 40 to 70 percent and protein content from 2 to 7.5 percent (see Appendix Table 14. The corn residues contain 70 to 80 percent cell walls, with nearly equal quantities of cellulose and hemicellulose. Corn residue tends to be one of the richest sources of hemicellulose found in nature. The cornstalk decreases in digestibility and cell-soluble content with time after physiological maturity of the corn plant (Berger et al., 1979; McDonnell and Klopfenstein, 1980) (see Figure 11). Digestibility of cornstalks is affected by moisture, variety, and tem- perature, as well as by maturity (McDonnell and Klopfenstein, 19801. Stalks left in the field for grazing also decrease in nutritional value with time (Lamm and Ward, 19771. There is the possibility that the corn plant might be changed genetically to improve stalk digestibility. The brown midrib mutant is an example of such potential, but grain yields have been lower than for normal corn (Colenbrander et al., 1973; Kahn and Hendrix, 19771. . 70 65 60 > 50 ~5 TO O_ Y= -.193X + 63.22 R=.92 SE Y.X= 1.54 45 40 30 i 1 2 - - - 8 - - 1 1 1 3 4 5 6 7 WEEKLY CORN STALKLAGE SAMPLI NG, 1976 9 10 (Weeks) FIGURE 11 In vitro dry-matter disappearance (IVDMD) of cornstalks harvested over time. SOURCE: Berger et al. ( 1979).
1 82 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Different harvesting systems produce corncobs, husklage, and corn- stalks and stalklage; and stalk fields are available for grazing. Gestating beef cows are able to more than maintain weight on these residues (see Table 491. Growing calves gained weight (0.3 kg/day) on supplemented corncobs (Koers et al., 19701. Berger et al. (1979) obtained gains of 0.65 kg/day with growing calves fed supplemented stalklage harvested the same day as high-moisture (26 percent) grain. However, digestibilities as low as 36.9 percent have been reported (Paterson et al., 1979J, which would not support maintenance in calves. Wheat and Other Small Grain and Grass Straws Small grain straws are quite low in nutritional value; in addition to being high in lignin content and, therefore, low in digestibility, they are also very bulky. This tends to limit intake and adds to mechanical handling problems. Wheat straw is probably the poorest quality straw, and barley is only slightly better (see Table 494. Oat straw appears to have the highest nutritional value (Anderson, 19781. Acock (1978) has shown considerable variation in nutritional value of wheat straw (protein and digestibility). Location of production, variety, and time of straw harvest relative to grain harvest were all factors affecting value. Jackson (1978) also reported these variations, as well as that due to cultural practice. Wheat straw with only a protein-vitamin-mineral supplement will not maintain weight of gestating beef cows or calves. Acock et al. (1979) and Dinusson (1969) have shown that feeding one-third alfalfa hay with wheat straw can meet the protein needs of the gestating beef cow and give some weight gain (0.2 kg/day). Coombe et al . ~ 1979a) and Lesoing et al . ~ 1980a) have clearly demonstrated that chopped untreated wheat straw has little value for growing calves. Similar conclusions can be drawn for barley straw. Oat straw can probably meet the energy needs of the gestating beef TABLE 49 Dry Cow Daily Weight Gain (kg) on Various Corn Residue Systems (number of trials in parentheses) Stacked Source Grazing Stalks Stalklage Shucklage Iowa 0.03 (5) 0.40 (4) 0.08 (1) 0.20 (3) Nebraska 0.25 (6) 0.26 (2) 0.31 (1) SOURCE: Ward (1978).
Crop Residues 183 cow but has little value for growing animals (Saxena et al., 1971) unless treated to improve its nutritional value. Rice straw is somewhat unique in that lignin and high silicon content tend to limit digestibility. However, its feeding value would be similar to wheat straw (Garrett et al., 19791. Grass straws available after grass seed harvest have variable nutritive values. The variation is due to species (Guggolz et al., 1971), variety (Early and Anderson, 1978), and time of harvest (Durham and Hinman, 19791. Bluegrass straw supported small weight gains and normal production in gestating beef cows (Early and Anderson, 1978), but considerable amounts of supplemented grain were needed to produce 0.5 kg/day gain in calves (Durham and Hinman, 1979~. Rice and grass seed straws must often be removed from the field for agronomic reasons. Therefore, these straws present disposal problems for producers. Soybean Soybean residue is 30 to 35 percent pods and the remainder stalks (Vetter, 19731. Essentially no leaves are collectable. The pods are lower in cell walls and lignin content than stalks and higher in protein and dry-matter digestibility. Soybean stalks are very high in lignin content (20 to 23 percent) and therefore very low in digestibility. The pods may have some use in beef cow maintenance diets, but probably have little value for growing or lactating ruminants (Gupta et al., 19784. Grain Sorghum The grain sorghum plant is unique in that it does not die at physiological until a killing frost (Smith, 19771. The residue following grain harvest is green and moist (60 to 70 percent H2O), and quality changes little with time (see Appendix Table 11. The moist residue harvested and stored as silage is a good beef cow feed (McKee et al., 1977) and has potential in a diet for growing calves. Both protein content and dry-matter digestibility may be higher than for any residue except early harvested cornstalks or cornhusks. Bolsen et al. (1977) obtained over 0.5 kg/day gain with growing calves fed milo stover silage with protein supplement. They found an interesting and consistent positive associative effect of feeding this residue with forage sorghum silage (Bolsen et al., 19764. Ward et al. (1979) found that beef cows could be maintained during gestation on milo stubble fields. The cows gained about 0.3 kg/day, which is similar to the gain obtained with corn stalk grazing. maturity but continues to photosynthesize until a killing
184 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Other Residues In the ginning of cotton, 50 to 75 percent of the harvested material is residue, consisting of boll residues, leaves, stems, lint, and a small quan- tity of cottonseeds. The residue has a low nutritional value, characterized by its high lignin (14 percent) and low protein (5.6 percent) content. Use of gin trash with supplemental cottonseed meal for growing steers produced gains of 0.1 kg/day compared with 0.5 kg/day for steers fed sorghum silage (Holloway et al., 19741. Finishing steers gained more rapidly when the roughage portion of the diet consisted of 50 percent cottonseed hulls than when it contained 50 percent cotton gin trash (Jones et al., 19571. The estimated value of gin trash was 90 percent that of cottonseed hulls. In another study, gin trash was substituted for 10, 30, and 50 percent of alfalfa hay cubes in a diet consisting of 50 percent alfalfa and 50 percent concentrate (Brown et al., 19791. Milk production of dairy cattle was depressed slightly at the two higher levels. Efficiency of converting feed energy to milk energy was decreased with increasing levels of gin trash. Cottonseed hulls are a high-fiber, low-protein by-product of the cotton industry. They have been used as a roughage source for beef and dairy cattle. Cottonseed hulls substituted for alfalfa hay cubes at 10, 30, or 50 percent of the alfalfa resulted in no difference in milk production of dairy cattle (Brown et al., 19771. However, as the percentage of cottonseed hulls in the diet increased, the digestibilities of protein, energy, and fiber decreased. Hunt et al. (1971) also observed no differences in milk pro- duction when cottonseed hulls were included at 25, 35, and 45 percent of the diet. A comparison of bluegrass straw, wheat screenings, and pelleted and nonpelleted cottonseed hulls as roughage sources for yearling steers showed cottonseed hulls to be inferior to the other roughage sources (Heinemann, 19761. When each of the four sources constituted 13 percent of the diet, average daily gains were 1.4, 1.4, 1.3 and 1.2 kg/day, re- spectively. Feed conversion was least efficient for animals fed the cot- tonseed hull diets. Although high in fiber and lignin content, peanut hulls have a consid- erable amount of protein (8 percent). This protein value may vary with the quantity of peanut kernels that remain with the hulls during processing. Utley and McCormick ( 1972) examined the use of peanut hulls in a feedlot study with Hereford steers. The hulls were combined with concentrate at 0, 10, 20, and 30 percent of the diet and fed ad libitum for 84 days. The highest average daily gains, when adjusted for body fill, were on diets with 10 or 20 percent hulls, and the most efficient feed conversion was with the 10 percent hull diet. A second feedlot study showed no significant differences among diets. Dry-matter digestibility decreased with the ad
Crop Residues 185 dition of peanut hulls. Calhoun and Shelton (1973) also found that 10 percent peanut hulls was optimum for high-concentrate lamb diets. The use of 30 percent peanut hulls for growing steers was found equivalent to 30 percent cottonseed hulls (Burdick et al., 1975), and growth of wintering calves was satisfactory with a 60 percent peanut hull diet. Rice hulls are low in protein, high in fiber, and contain unusually large amounts of lignin (1 1-17 percent) and silica (22 percent). At 40 percent of the diet, scouring, with mucous and blood in the feces, has been observed with cattle (White, 19664. At 20 percent of the diet these symp- toms were not seen. McManus and Choung (1976) reported that raw rice hulls were rejected by sheep. Wintering steers accepted rice hulls at 25 percent of the diet, the remainder being prairie hay (Noland and Ford, 19541. Daily feed intake was restricted to 5.4 kg, and average daily gain was 0.8 kg, compared with 0.86 for an all prairie hay diet. Sugarcane bagasse is the residue of the crushing and milling of sugar- cane. It is very low in protein (~2 percent) and high in fiber. Randel (1970a) was unable to show any differences in performance of male calves initially weighing 114 to 454 kg fed a 20 or 30 percent bagasse diet at either 12.5 or 16 percent crude protein. Milk production of dairy cattle was not altered when a diet consisting of 22.5 percent bagasse, 20 percent molasses, and 57.5 percent concentrate was substituted for a conventional concentrate-sorghum silage diet (Randel, 1970b). Replacement of cotton- seed hulls with bagasse in a 25 percent roughage diet for lactating dairy cattle had no detrimental effect on milk production (Marshall and Van Horn, 19751. Clanton and Harris ( 1966) found that calves fed ensiled sugar beet tops that had been field-wilted achieved higher daily gains than calves fed unwilled ensiled beet tops or calves that were pastured on beet tops (0.61, 0.49, and 0.54 kg/day, respectively). In another study (Rush, 1977), average daily gain decreased linearly as beet tops were substituted for corn silage in a growing calf ration. Calves went from an average gain of 0.88 kg/day with no beet tops to 0.59 kg/day when beet tops were substituted for 60 percent of the corn silage. Levels of beet tops above 30 percent of the diet produced scouring. When pasturing cattle on beet tops, one hectare can carry one animal unit for 36 days with animal gain approximately 0.5 kg/day (Leonard et al., 19731. Sugar beet tops are best utilized when combined with another residue (such as cornstalks) or forage. Sugarcane tops are a fibrous feed that is normally discarded in the field during the harvesting of sugarcane. Growing cattle fed fresh tops for 1 12 days maintained their weight, while those fed ensiled tops lost 0.27 kg/ day (Estima et al., 19671. The addition of molasses or cassava roots had little effect on gain or feed consumption, but supplementing 1.5 kg/day
186 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS of cottonseed meal stimulated both intake and daily gain. In another study (Pate et al., 1971 J. growing steers full-fed on tops were unable to maintain their weight, losing 0.1 kg/day. Subsequent supplementation with 0.9 kg/ day of cottonseed meal increased gains to 1.1 kg/day and increased dry- matter intakes of cane top from 5.9 to 7.4 kg/day. Finishing cattle were fed cane tops at 0, 17, 34, and 51 percent of the diet (Pate and Coleman, 19751. Steers fed the 17 percent level gained as well as those receiving the control diet (0.9 kg/day), and feed efficiency was similar. Residues from sunflower seeds and faba bean production appeared to be quite high in digestibility (70.5 and 61.4 percent, respectively). Their feeding value would be expected to be quite high on the basis of these laboratory digestibilities, but animal growth data are unavailable (Kernan et al., 19801. Vegetable and fruit field residues consist of leaves, vines, culls? and unharvested crops. Thus, unlike other crop residues, which are almost universally low-quality roughages, these residues vary widely in their nutritional value and in their availability. The University of California summarized its previously unpublished research in the area of unusual feedstuffs for livestock (Leonard et al., 1973), from which much of the following information was taken. Lettuce contains approximately 93 percent moisture. On a dry basis it is comparable to some cereal grains, with a TDN of 70 percent and 7 percent digestible protein. Cattle prefer to consume the heads rather than the leaves. Cattle consumed up to 16 kg carrots/day in addition to sup- plement and gained about 0.1 kg/day. Fresh peaches can be fed at a rate of 9-14 kg/day, with no evidence of scouring. When 2.7 kg dried peaches were fed, scouring ensued, and shortly thereafter the animals refused the fruit. One-half this level was consumed for 10 days with no ill effects. Pears were consumed at a lower rate, and spoiled pears were more readily refused than spoiled peaches. Scouring also occurred with fresh prunes at levels over 6.8 kg/day. Dried prunes were fed at the level of 2.7 kg/day with no detrimental effects. Grapes have been fed to cattle at levels up to 16 kg/day and raisins at 2.7 kg/day with no ill effect. Consumption of peaches created a slight off flavor in milk. By-products from sweet corn production are available and of quite high value. The dry-matter digestibility of the stalks remaining after harvest of the ears is over 65 percent. Up to 20 percent of the ears are not harvested because of weather and other factors. The whole-plant material is over 66 percent digestible. Cannery residue is over 70 percent digestible. All of the products are high in moisture but also high in nutritive value, nearly equal to field corn silage. Pea vines are also high in nutritional value (63.4 percent TDN). They are collected at central locations and present a disposal problem.
Crop Residues 187 Leaf waste from cauliflower, a product of the packing shed, was sep- arated to provide a poultry meal fraction containing 375 to 620 mg/kg xanthophyll and 26 to 31 percent protein, and a cattle meal fraction that contained 17 to 21 percent protein (Livingston et al., 19721. The xantho- phylls were equivalent to dehydrated alfalfa meal as a pigmenting agent for broiler skin. Sweet potato vine meal has also been shown to be effective as a pigmenting agent (Garlich et al., 19741. Haines et al. (1959) fed celery tops to Hereford steers at 0, 10, 20, and 30 percent of a diet containing sorghum, soybean meal, citrus pulp, and citrus molasses for 112 days. Diets were isonitrogenous, and dehydrated Bermudagrass was fed ad libitum. Average daily gains were 1.01, 1.03, 0. 85, and 1 . 12 kg/day, respectively. Steers receiving the 20 percent celery top ration were the least efficient converters of concentrate and roughage. A digestion trial with four steers yielded a TDN of 79.5 percent. Crude protein was 25.0 percent on a dry-matter basis. Cassava, although not grown widely in the United States, is a major food crop in many areas of the tropics and could assume importance as both a human and animal food, since its yield of energy per unit land can be quite high. Because of the presence of a toxic glucoside, cassava leaves must be dried or boiled prior to feeding to reduce toxin levels. Cassava leaves have a high protein content (25 percent), although they may be deficient in methionine and tryptophan (Rogers and Milner, 19631. Use of cassava leaves in poultry diets results in poor growth unless supple- mented with methionine (Ross and Enriquez, 19691. PROCESSING METHODS If crop residues are to be used to meet the energy requirements of growing and lactating ruminants, their feeding value must be increased. There seem to be two possibilities for this at the present time. One is manipulation of harvest time or genetics to obtain higher-quality residues, and the other is to treat residues physically or chemically to increase digestibility and/ or intake. Corn Many chemicals have been screened in laboratory experiments for their potential to enhance digestibility. However, only four are being routinely used in experimentation with animals: sodium hydroxide, ammonia, cal- cium hydroxide, and potassium hydroxide. Chemical treatment breaks the ether linkages between lignin and cel- lulose or hemicellulose. The saponified lignin is not soluble in acid and
188 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS therefore may be measured by most methods (Lau and Van Soest, 1981~. However, the resultant increase in digestibility is still obtained. Modes of action for chemical treatment of crop residues have been described by Wailer (19761. Chemical treatment solubilized some of the hemicellulose while not changing the cellulose content. Extent of bacterial digestion in vitro was increased for both cellulose and hemicellulose. Chemical treatment, especially with sodium hydroxide, increased the rate of digestion for both cellulose and hemicellulose. Therefore, one could conclude that the modes of action of chemical treatment, especially treat- ment with sodium hydroxide, include ( 1 ) solubilization of hemicellulose, (2) increasing the extent of cellulose and hemicellulose digestion, and (3) increasing the rate of cellulose and hemicellulose digestion, possibly by swelling. During the past several years two systems for application of chemical treatments primarily with sodium hydroxide, have evolved (Jackson, 19771. One system, described by Rexen and Thomsen (1976), involves appli- cation of a concentrated sodium hydroxide solution prior to pelleting. Heat produced in pelleting causes the chemical reaction to go rapidly to com- pletion. The process involves collection and transportation of residue to a central processing plant, followed by chopping or grinding and mixing concentrated sodium hydroxide solution with the residue. Sodium hy- droxide serves as a pellet binder in addition to its effect on nutrient digestibility. A dense, hard pellet is then produced; excess moisture is removed in the cooling process. Response to pelleting of cornstalks is shown in Table 50. As indicated by the in vitro digestibility values, the stalks were of very low value. Both NaOH treatment and pelleting increased rate and efficiency of gains. The combination of pelleting and NaOH treatment was slightly more than additive. The diets contained one-half relatively low-quality alfalfa as well. While animal performance was not especially good, feeding the treated TABLE 50 Pelleted and Sodium Hydroxide-Treated Cornstalksa Chopped Pelleted Chopped Pelleted Performance Control Control NaOH Treated NaOH Treated Daily gain (kg) 0.16 0.28 0.24 0.31 Daily feed (kg) 6.3 6.5 6.6 5.4 Feed/gain ratio 0.026 0.043 0.036 0.057 IVDMDb 37.0 38.0 59.0 61 .0 aTwenty-two calves/treatment, 205 kg initial weight, 91-day trial. Diets were 50 percent alfalfa (50 percent IVDMD). bin vitro dry-matter disappearance. SOURCE: Klopfenstein, unpublished data.
Crop Residues 189 pellet diet approached economic feasibility. Pelleting (with sodium hy- droxide) better-quality stalks and feeding with higher-quality alfalfa may increase the economic feasibility. The primary advantage of pelleting is that the product can be stored and transported easily and will be consumed in large quantities by livestock because of its high bulk density. The major disadvantage is the cost of collection and transportation of bulky residues prior to treatment and pelleting. The second process is an on-the-farm method that involves collecting residues in the field behind the combine with a bunch wagon or with a stack wagon or baler. Following grinding or harvesting with a forage harvester, the residue is transported to the treatment area, mixed in a mixer wagon with the chemical, and sufficient water added to raise the moisture to 15 to 65 percent. Small-scale, one-step machines that handle small, square straw bales are marketed in Europe for this purpose. The material is then ensiled or fed after 24 to 48 hours of reaction. Results of studies with this type of treatment are encouraging. Steers gained over twice as rapidly and required approximately half as much feed per unit of gain with 4 g/100 g dry-matter sodium hydroxide treatment of corncobs (see Table 511. Table 52 summarizes three trials comparing performance of calves fed corn silage and chemically treated husklage. The husklage was treated with 3 g sodium hydroxide and 1 g calcium hydroxide/100 g dry matter and was fed as 80 percent of the diet with 20 percent supplement. Corn silage was fed as 90 percent of the diet with 10 percent supplement. The calves fed both corn silage and treated husklage gained 0.75 kg/day. Daily feed varied only slightly; therefore, feed/unit of gain was similar. Cornstalks were harvested with a forage harvester equipped with a stalker head at two stages of maturity (Berger et al., 19791. At each stage of harvest one-half of the stalks were chemically treated. The average response to chemical treatment was less than 10 percent improved feed efficiency. Unknown factors may be influencing the ability to accomplish large-scale treatment. Several researchers have shown that animal response to sodium hy- droxide treatment (digestibility or efficiency of gains) is less than labo- ratory predictions (Klopfenstein et al., 1972; Ololade et al., 1970; Rexen and Thomsen, 1976; Singh and Jackson, 19711. Ruminally fistulated lambs were used to measure the effect of increasing levels of sodium hydroxide treatment on rate of fiber passage and rate of ruminal fiber digestion (Berger et al., 19804. In vitro dry-matter diges- tibility increased from 45.1 percent for the control to 83.1 percent for the 8.0 g/100 g dry-matter sodium hydroxide diet. As the level of sodium hydroxide treatment increased, the in vivo rate of passage increased lin
1 90 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS TABLE 51 Performance of Steers Fed Sodium Hydroxide-Treated Corncobs 4 Percent Sodium Performance Control Hydroxidea Number of steers 5 15 Initial weight (kg) 205.0 203.0 Daily gain (kg) 0.30 0.73 Daily feed (kg)b 4. 1 5.4 Feed/gain ratio 14.3 7.5 aCorncobs constituted 80 percent of the diet. bDry basis. SOURCE: Koers et al. (1970). early. Rate of ruminal fiber digestion was measured using nylon bags containing 0.15 g cotton fiber. As level of sodium hydroxide in the diet increased, the rate of ruminal cotton digestion decreased linearly (r2 = .931. These data suggest that sodium intake, the effect of sodium hydroxide on plant-fiber digestion, and possibly a chloride anion deficiency affect rate of fiber passage and digestibility. Another possible effect of high sodium intakes in ruminants is on min- eral metabolism. If sodium load causes a mineral imbalance, then sup- plementation of other minerals may be necessary. Lambs were fed ad libitum either untreated corncobs, 4 g/ l DO g dry-matter sodium hydroxide- treated corncobs, 4 g/ lOO g dry-matter sodium hydroxide-treated corncobs TABLE 52 Silagea Treated Husklage Versus Corn Performance Treated Corn Silage Husklageh Daily gain (kg) 0.75 0.75 Daily feed (kg)t 7.26 7. 17 Feed/gain ratio 9.62 9.60 Feed cost (¢/kg) 9.35 7.7 Cost of gain (¢/kg) 90.0 74.0 aSummary of 3 trials, 96 calves/treatment. Treated with 3 g sodium hydroxide and 1 g calcium hy- droxide/100 g dry matter. 'Dry-matter basis. SOURCE: Klopfenstein (1978).
Crop Residues 191 plus supplemental minerals, or 3 g/100 g dry-matter sodium hydroxide: 1 g/100 g dry-matter potassium hydroxide-treated corncobs plus supple- mental minerals (Paterson et al., 1978b). Supplemental minerals were supplied in the diet by weight to provide ratios of 1 Na: 1 K, 2 Na: 1 Ca, 2 Na: 1 C1, and 6 Na: 1 Mg. No difference in sodium balance was apparent among treatments at the end of 21 days, but all animals fed the sodium hydroxide-treated cobs were in a negative sodium balance the first 14 days before returning to a positive balance after 21 days. Calcium, magnesium and phosphorus balance were not adversely affected either by sodium load or by supplementation with excess minerals. However, it did appear' that supplemental potassium and chloride may be necessary to prevent negative balances. Information on the application of ammonia (either as anhydrous gas or aqueous liquid) to crop residues indicates that it may also improve residue feeding quality. Ammonia appears to react in a manner similar to sodium hydroxide. However, the 'reaction time is much longer (up to 20 days) (Weiss et al., 1972) than with sodium hydroxide treatment (24 hours), and the residue must be stored in an airtight structure so there will be no loss of ammonia. The two major advantages of using ammonia are (1) the use of the residual nitrogen as a nonprotein nitrogen source in the diet and (2) no mineral residue remaining that might be detrimental to the animal or to the soil to which the manure is added. Research has shown that animals will not eat ammonia-treated residues unless the residues are aerated or mixed with a fermented feed so that the organic acids neutralize the ammonia (Waller, 19761. At ad libitum intakes the dry-matter digestibility of cornstalks was increased from 36.8 percent for sheep fed untreated stalks to 47.0 percent for sheep fed stalks with 2 g ammonia/100 g dry matter. The addition of 3 or 4 g ammonia/100 g dry matter did not further improve digestibility. The intake of the aerated stalks increased from 398 g to 997 g/day for lambs fed untreated stalks and 4 g ammonia/100 g dry-matter stalks, respectively (Paterson, 19791. Cattle performance on ammonium-treated cobs by the on-the-farm method is shown in Table 53. In this case am- monium hydroxide-treated cobs were fed in combination with calcium hydroxide-treated cobs. Ammonium treatment appeared to produce in- creased performance over calcium hydroxide treatment alone. Efficiency of gains produced by the mixture was superior to that of the 4 g sodium hydroxide-treated cobs. This would indicate that the ammonium hydrox- ide-treated cobs were quite'eft'iciently utilized. Intake was somewhat lower with ammonium hydroxide-treated cobs, probably because of free am- monia that still remained in the cobs at feeding time. While ammonia treatment requires a closed system, there are distinct advantages to its use.
192 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS TABLE 53 Performance of Growing Calves Fed Different Chemically Treated Cobs Average Daily Average Daily Feed/Gain NaOH:CaOHa Gain (kg) Feed (kg)b Ratio 4:0 1.17' 10.10 8.6 3:1 1.344 10.32 7.7 2:2 1.14' 9.87 8.7 1:3 1.274 9.97 7.8 0:4 0.97e 9.04 9.4 1/4 NH4f 1.16d 8.82 7.6 aSodium hydroxide:calcium hydroxide = 1 g each/100 g cob dry matter. bDry matter. Means in the same column with different superscripts differ significantly (P < .05). f4 g ammonium hydroxide and 4 g calcium hydroxide-treated cobs mixed 1:1 at feeding time. SOURCE: Waller and Klopfenstein (1975). Calcium hydroxide is less caustic than sodium hydroxide, and greater amounts may be necessary to obtain performance equal to sodium hy- droxide treatment alone. Since calcium is not metabolized in the same manner as sodium, the increased levels may not be as detrimental as a high sodium load. Digestion studies with corncobs, cornstalks, and wheat straw indicated that moisture level affected response to calcium hydroxide treatment (Pa- terson et al., 19801. Forty percent moisture was better than 20 or 60 percent moisture. Sixty percent residues fermented, while treated residues with 20 percent moisture appeared to have much of the calcium hydroxide unreacted. Even though a 40 percent moisture level increased digestibilities and intake, the treated residues showed signs of mold growth after 7 days. In an in vitro study, cobs treated with 5 g calcium hydroxide/100 g dry matter did not reach maximum digestibility for 10 days but cobs treated with 1 or 2 g sodium hydroxide replacing calcium hydroxide reached maximum digestibility by days 2 and 4, respectively (see Figure 121. It appears that in a practical system the combination of 1 g sodium hydroxide and 3 or 4 g calcium hydroxide/100 g dry matter could be used at 60 percent moisture, and the chemical dilignification reaction would proceed before the bases were neutralized through microbial fermentation. A cattle growth trial using corncobs demonstrates this by showing much greater response to cobs treated with 1 g sodium hydroxide plus 3 g calcium hydroxide than to cobs treated with calcium hydroxide alone (Table 53~.
80 70 60 > ~ 50 40 Crop Residues 193 2 NaOH:3 CaOH - 1 NaOH :4 CaOH 0 NaOH:5 CaOH Control 1 0 2 4 6 8 10 12 14 16 18 20 22 DAYS REACTION TIME FIGURE 12 In vitro dry-matter-disappearance (IVD~) for cobs with different combi- nations of sodium hydroxide (NaOH) and calcium hydroxide (CaOH). SOURCE: Paterson etal.(l980). Another system for increasing digestibility of crop residues is the use of high pressure steam with or without added chemicals (Bender et al., 1970; Guggolz et al., 1971; Klopfenstein et al., 1974; Klopfenstein and Bolsen, 1971; Umunna et al., 19721. In this system the fibrous material is moistened and placed in a pressure vessel; steam pressures of 14 to 28 kg/cm2 are applied for a few seconds and then the pressure is released. The reaction is a mild acid hydrolysis because some organic acids are produced in the reaction. Hemicellulose is solubilized, and probably the
194 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS digestibility of the cellulose is also increased. This process has been developed commercially using a continuous-flow digester (Bender et al., 19704. Digestibility of corncobs was increased by 16 percentage units through steam hydrolysis, and daily gains of growing calves were doubled (Klopfenstein, 1975~. Wheat and Other Small Grains Straws from small-grain production tend to be bulkier and are lower in quality than corn residues. Response to pelleting and sodium hydroxide treatment have been quite good (Coombe et al., 1979a; Garrett et al., 1979; Rexen and Thomsen, 19761. Numerous commercial plants in several European countries are producing treated straw pellets. The mode of action and compositional changes caused by sodium hy- droxide treatment are similar to those for corn plant residues (Coombe et al., 1979b; Lesoing et al., 1980b). Pelleting and sodium hydroxide treat- ment each increased rate and efficiency of gains and the effects were essentially additive for both wheat and barley straws (Coombe et al., 1979a,b). Gains of over 0.6 kg/day were obtained with treated, pelleted straws plus protein supplement. Garrett et al. (1979) obtained similar results with rice straw. Straws can also be treated by an on-the-farm system similar to that used for corn residues. Wheat straw treated by this method showed increased digestibility (Hasimoglu et al., 1969; Jared and Donefer, 1970; Lesoing et al., 1980b) and produced increased rate and efficiency of gains (see Table 541. Because of the low protein content of crop residues, the cost of supplemental protein is very important. Nonprotein nitrogen as the only supplemental nitrogen has limited value in treated-residue rations. These same principles were demonstrated with oat straw (Donefer et al., 1969; Saxena et al., 1 97 1 ). Barley straw (Jayasuriya and Owen, 1 975; Mowat and Ololade, 1970; Wilkinson and Santillana, 1978) as well as ryegrass straw (Anderson and Ralston, 1973) shows increased digestibility with chemical treatment. Wheat straw was treated, fed to growing calves, and compared with corn silage and untreated straw (see Table 551. Treatment increased the rate and efficiency of gain compared with untreated straw in diets con- taining 50 percent straw (Lesoing et al., 1980a). Adding potassium, cal- cium, chlorine, and magnesium to diets containing 80 percent treated straw also increased rate and efficiency of gains. This demonstrates that the sodium residue creates a nutritional problem that can be at least partially solved. Calves fed treated straw showed reasonably good performance, but performed considerably less well than they had on diets of corn silage.
Crop Residues 195 TABLE 54 Performance of Lambs Fed Wheat Straw Daily Daily Feed/Gain Organic Matter Rationa Gain (g) Feed (g)b Ratio Digestibility (%)c Straw + SBM ~36 908 25.0 49 Straw + urea -45 636 51 JO NaOH straw + SBM 160 1226 7.6 60 4% NaOH straw + urea 82 999 12.4 59 aDiets were 70 percent straw and 30 percent supplement (soybean meal, urea, wheat, grain, minerals, and vitamins). bDry basis. CDigestibility of straws assuming 90 percent digestibility of the supplements. Soybean meal. SOURCE: Hasimoglu et al. (1969). Treatment of straws for use in beef cow gestating diets shows some promise. Acock et al. (1979) showed that cows gained weight on treated wheat straw plus protein. Ammonia treatment of straws could be accom- plished without grinding and mixing (Garrett et al., 1979; Sundstol et al., 1978). TABLE 55 Effect of Treatment of Wheat Straw and Balancing Minerals for High Sodium Intake on Rate and Efficiency of Gain of Steers Daily Daily Gain Feed Feed/Gain Treatmenta (kg)b (kg)c Ratio Corn silage 1.05 6.14 5.79 50% Untreated wheat straw 0.62 5.53 9.05 50% Treated wheat straw + minerals 0.74 5.83 8.04 80% Treated wheat straw, no minerals 0.54 5.32 9.94 78% Treated wheat straw + minerals 0.65 5.51 8.44 aWheat straw was treated with 3.15 g sodium hydroxide and 1.19 g potassium hydroxide/ 100 g wheat straw dry matter. bSteers were weighed after an overnight shrink on day 109. Steers were fed an equal amount of a standard corn silage diet on days 103 through 108. CDry-matter basis. SOURCE: Lesoing et al. (1980a).
196 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Gestating beef cows were fed 2.7 kg alfalfa hay/day and wheat straw ad libitum (Faulkner et al., 19811. Ammonia-treated bales were consumed in greater quantities than control, liquid supplement, or NaOH-treated bales. Weight gains were 0.4 kg/day on the ammonia-treated straw. Waagepetersen and Thomsen ( 1977) have shown that the rate of reaction of ammonia is increased with increasing temperature. They have developed equipment to be used for on-farm treatment at elevated temperatures. A lamb digestion trial and two lamb growth trials were conducted to compare straw treated with ammonium hydroxide (6 g/100 g straw dry matter), calcium hydroxide (4 or 5 g/100 g straw dry matter), an ensiled mix of 2 g calcium hydroxide and 3 g ammonium hydroxide, or a 50:50 combination of 4 g calcium hydroxide:6 g ammonium hydroxide mixed at feeding time (Asadpour, 19781. Moisture content of straw was 65 percent. Table 56 lists dry-matter, neutral (NDF), and acid-detergent fiber (ADF) digestibilities for the trial. Hydroxide treatments improved all di- gestibilities over the untreated control. However, lambs fed the straw treated with ammonia or the hydroxide combinations averaged greater digestibilities than lambs fed straw containing either 4 or 5 g calcium hydroxide alone. There were no differences between lambs fed straw treated with 6 g ammonium hydroxide or either of the calcium-ammonium . . . com donation mixes. Performance data from two growth trials were pooled and are presented in Table 56. Lambs fed straw diets containing the hydroxides had better daily gains and feed conversions than those fed the untreated control. Lambs fed straw containing only ammonia or a calcium-ammonium mix gained better than did lambs fed straw treated with calcium hydroxide alone. While there did not appear to be any difference in digestibility between the 4 g and 5 g calcium hydroxide-treated diets, there did appear to be an advantage in average daily gain with lambs fed 5 g calcium hydroxide. Pressure treatment with steam has also increased wheat straw digesti- bility (Umunna and Klopfenstein, 19721. Soybean Soybean residues are very high in lignin. Being legumes, they do not respond well to chemical treatment. Little processing research has been conducted (Bottje et al., 19791. Grain Sorghum Grain sorghum residue responds to sodium hydroxide and calcium hy- droxide treatment (Chandra and Jackson, 1971; Koers et al., 1972; Sherrod
197 - : - Cd sit :' en, At: a' 4- Cd ~9 A: o 3 Cal En 4- 3 o Is s ~ ~ o Ct _ ~ Ct 4 ,, ._ .s _ o fi C) ~ of , , . _ - << ~ Ct ~ to, · -4 Cal te · Ct - - . ED V, . ~ _ cats 0.1)'= ~ ~ Cal 3 ~ ~ z ~ ~ - . _ In ~ Ct on oX~ ~5 Ct - - o ') ~_ t_ o0 00 00 . 0000 c ~cr .. .. O U~ 00 .. r~ ~U~ O ~ _ ~_. ~- O - O O O O O O O a~ ~ ~ D v' cn ;^ C ,~ ~i == O ~ ~- + ~ 3= U) ~ ~L ~ o oo ~ a,, ~o Ct - C: ~ ~ 3 Ct ~ ·- c c: C~ ~ ._ ._ t a.~ ^ C) Ct ·- 3 2 ~ ~ {': 3 3 3 ,~: s =.C _ ~,~ ° ~ D~ 3- ~= .O =.° Ct~ U, ~ O c ~ v, oooo ~0 oooo ao __ .... nO- u~v~u~ .. _~ .. 8~o "o ~ ~ _U~ o ~ o ~ ~ _ + o,0 o 3 ~x 2 x ° ~ x '-~ ~ 2= 2 ~ c~ 2 e c E E E E E E E E E 0 ~ ~ ~ ~ ~ ~ ~ ~ on o~ ~ cs~ .. o - ._ 2 ._ ct ~ ct ~ e, v~
198 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS and Summers, 1974) but probably not as well as corn residue or straws. Pelleting did not improve performance (Bolsen et al., 1977) but pelleting along with sodium hydroxide treatment has not been attempted. Little or no research has been conducted with ammonia treatment. Other Residues A feedlot trial with raw and ammoniated rice hulls (approximately 1.5 g/ 100 g dry matter) replacing sorghum at 3, 6, and 9 percent of the diet resulted in no effect on gains, feed efficiency, or carcass characteristics (Tillman et al., 19691. Ammoniation had no effect on organic-matter digestibility or nitrogen retention. Hutanuwatr et al. (1974) increased the in vitro dry-matter digestibility of rice hulls from 22.5 to 40 percent by adding 12 g sodium hydroxide/100 g dry matter followed by washing. Washing was superior to acid neutralization but was accompanied by a 16.6 percent dry-matter loss. McManus and Choung (1976) reported that high levels of sodium hydroxide resulted in extensive solubilization and removal of silica and lignin. Acid-neutralized sodium hydroxide-treated hulls (0, 2.5, 5, 10, and 15 g sodium hydroxide/100 g dry matter) were fed to sheep for 91 days with an equal amount of alfalfa pellets. Sheep receiving rice hulls treated with the three highest levels of sodium hy- droxide maintained or gained weight, while sheep on the lower two levels lost weight (Choung and McManus, 19764. Only the 15 g sodium hy- droxide-treated hull diet had significantly greater organic-matter digesti- bility than the control in an accompanying metabolism trial (52 versus 42 percent). Acid-detergent-fiber digestibility was greatly increased (62 ver- sus 13 percent). Sheep tolerated the high sodium levels, although water consumption increased. An alternative treatment was employed by Daniels and Hashim (19774. Fungal cellulases were added at various levels to a maximum of 1,250 mg/kg. In vitro dry-matter digestibility was highest with 375 mg/kg (30.6 versus 17.3 percent with no added cellulose). In a digestion trial with Holstein steers, addition of cellulase at levels of 250 to 2,000 mg/kg to rice hulls yielded increases in dry-matter, energy, and protein digestibility. Barton et al. (1974) treated peanut hulls with seven compounds: am- monia, sodium hydroxide, a combination of ammonia and sodium hy- droxide, calcium hypochlorite, chlorine, dioxane, and dimethylsulfoxide. Only calcium hypochlorite appreciably improved in vitro dry-matter di- gestibility (40 versus 25 percent). Chemical treatment of sugarcane bagasse has dramatically increased its value as a feed for ruminants. Randel et al. (1971) fed lactating dairy cattle 40 percent bagasse diets (raw, and treated for 24 hours with sodium
Crop Residues 199 hydroxide), and a control standard diet. Milk production was greater for the control and treated bagasses, than for the raw bagasse (16.5, 17.2, and 12.5 kg/day, respectively). In a digestion trial conducted at restricted intake with bagasse at 40 percent of the diet, TDN was increased from 55.8 to 67.4 when the bagasse was treated with 2 g sodium hydroxide/ 100 g dry matter (Randel, 19721. Bagasse silage, composed of bagasse, molasses, urea, and whole corn, was more acceptable to crossbred steers when the bagasse was treated with 5 g sodium hydroxide/ 100 g dry matter (Andreis and DeStefano, 19781. In a 182-day trial, average daily gain was 0.71 kg with the treated bagasse as opposed to 0.44 with raw bagasse. Feed conversion with treated bagasse was 12.3 versus 18.7 for the un- treated bagasse. Martin et al. (1974) employed both calcium hydroxide and sodium hydroxide at rates ranging from O to 16 g/100 g bagasse. Both in situ and in vitro digestion increased with increasing levels of treatment, but sodium hydroxide was superior to calcium hydroxide. Steam- pressure treatment also increased in vitro digestibility from 28.3 at 4 arm. for 15 minutes to 44.9 at 6 aim. for 30 minutes. In a subsequent study the combination of sodium hydroxide treatment with steam-pressure treat- ment resulted in the largest increase in digestibility (Martin et al., 19761. UTILIZATION SYSTEMS Use of low-quality crop residues has been restricted primarily to ruminants on maintenance rations, such as gestating beef cows. In many parts of the United States, cornstalks and milo stubble can be grazed. This is the most economical system for the use of crop residues (Ward, 19781. There is essentially no energy (fuel) cost and no machinery cost, and nothing of value is removed from the soil. The manure deposited by the cows adds indigestible fiber to the soil, and if the cow is supplemented, more nitrogen and minerals are deposited than were in the crop residue con- sumed. Grazing of cows on crop residues does require good management to obtain the most efficient production. In the Midwest, spring-calving cows are in midgestation during peak stalk or stubble grazing. Calves are generally weaned prior to this time so that the cows' requirements are only slightly above maintenance. Thus, the cows are grazing stalks at the time of lowest nutrient requirements and grazing grass during peak requirements of lactation and breeding. Two problems exist with this system, however. First, the total feed supply is available on the first day cows are allowed to graze stalks or stubble, but because of weathering and other losses and selective grazing, the nutritional value of feed available declines with time. Concurrently, the nutrient requirements are increasing because of fetal growth. The second
200 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS problem is the period of time from the end of residue grazing until green grass is available. This hiatus generally occurs during the calving period when the nutrient requirements of the cow are rather high. A harvested feed is necessary. There is an opportunity for increased use of crop residues during this time period, but the nutritional value must be higher than that of present material to meet the needs of the cow. Another important problem with the grazing of stalks or stubble is the weather. In higher-rainfall areas of the eastern United States the residues deteriorate rapidly, and muddy conditions may prevent continual grazing. In the western Corn Belt and Plains states, adequate grazing can usually be obtained. Snow cover may prevent grazing, however, and some har- vested forage is needed. Harvested crop residues can meet this need rather economically. Ward ( 1978) reported an average of 88 days of crop residue grazing in eastern Nebraska. An average of 250 kg/cow of supplemental stacked residue was fed as well. Cows gained over 0.25 kg/day and were supplied 1 ha corn or milo residue/cow. Feeding straws to cows is of interest because of the availability of wheat straw in many areas. Other residues (corn and grain sorghum) may not be available in these areas. Beef cow/calf production systems are illustrated in Table 57. These systems range from extensive, using grass, to intensive, using only crop residues. Any of these systems can be economical depending upon man- agement and cost of grain and protein. A system of growing and finishing beef calves is shown in Table 58. The calves were allowed to graze cornstalks followed by harvested stalk- lage feeding. Summer grazing of grass preceded a high-grain finishing period. Less than 800 kg grain were needed to finish these animals, about TABLE 57 Cow-Calf Production Intensive Intensive Condition Extensive Corn Residuea Strawa Mid gestation Stalk grazing Stalklageb Treated straw Late gestation Stalkageb.c Stalklageb C Treated straws Early lactation Grass Treated stalklage ~Treated straws and concentrate Mid and late lactation Grass Treated stalklage ~Treated straws aRequires 4 metric tons residue/year and 170 kg protein. bCould be replaced by treated straw. CRequires .04 kg protein/kg residue. Requires .06 kg protein/kg residue.
Crop Residues 201 TABLE 58 Beef Production Systems With Heifers Utilizing Crop Residues Cornstalk grazing, 56 daysa Harvested stalklage, 75 daysb Summer grass, 110 days' High-grain finishing, 93 days 0.52 kg/day 0.02 kg/day 0.70 kg/day 1.34 kg/day aEquivalent of 280 kg residue, 0.06 kg protein needed/kg crop residue. b450 kg residue. CEquivalent of 770 kg residue. Equivalent of 1,600 kg residue. SOURCE: Faulkner and Ward (1981). 1.7 kg/kg beef produced. Forages were emphasized, especially crop res- idues, and compensatory gain was exploited. Alfalfa, which is a good source of supplemental protein and minerals, may be the logical choice to add to sodium hydroxide-treated rations in an attempt to slow the rate of fiber passage, increase the extent of rumen fiber digestion, and equilibrate mineral balance (Paterson et al., 1978a). The additions of various levels of chopped alfalfa hay in sodium hydroxide- treated corncob or cornstalk diets were evaluated in lamb digestion trials. Dry-matter digestibility of the diets was improved from 50 percent for the all-alfalfa diet to 63 percent for the 50:50 alfalfa:NaOH-treated cob diet. However, when the sodium hydroxide-treated cobs composed more than 50 percent of the diet, dry-matter digestibility decreased to approx- imately 60 percent on the all-treated-cob diet. Lambs exhibited large individual fluctuations in digestibility with diets of 100 percent sodium hydroxide-treated cobs. This variation and the decreased digestibility may be a function of sodium load and rate of fiber passage. In vitro dry-matter- disappearance values compared well with the in vivo digestibilities in diets of up to 50 percent treated cobs. The difference in digestibilities for the two diets was approximately 20 percentage units at the all-treated-residue diet. The failure of the in vivo values to correspond with the expected potential digestibility of in vitro values seems to suggest the effects of sodium on rate of passage and fiber digestion. Similar results were found with cornstalks. Hydroxide-treated corncobs were fed along with alfalfa hay to growing steers to evaluate (1) response to chemical treatment and (2) associative effects of alfalfa and hydroxide-treated cobs (Paterson et al., 1978a). Treatment of corncobs with 3 g sodium hydroxide and 1 g calcium hy- droxide/100 g dry matter increased gains of growing calves an equivalent of 0.27 kg/day. Feeding 50 percent alfalfa with treated cobs increased the
202 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS response to chemical treatment and showed positive associative effects (see Figure 13~. Jackson (1978), in an excellent review, has summarized the effects of diluting sodium hydroxide-treated -straws with either concentrates or high- quality forages. Concentrates dramatically reduced the digestibility of the fiber, especially at higher levels. Below 15 percent of the diet, concentrates seemed to have little effect on fiber digestion. High-quality forages, as was shown here with alfalfa, did not reduce digestibility of crop-residue fiber. Obviously, the formulation of the complete diet is very important in realizing the full benefits of crop-residue treatment. POTENTIAL UTILIZATION Crop residues will likely play a very large role in future production of meat and milk by ruminants. Low-cost extensive systems presently make good use of some residues but meet the needs of only a small portion of .70 .60 l - Z .50 - ~ .40 > .30 ~ 3 9 sodium hydroxide and 1 9 / \ jcium hydroxide/100 9 cobs / \ Entreated \\ /\ 1 1 1 .1 25 50 75 100 LEVEL OF ALFALFA REPLACING COB RATION FIGURE 13 Average daily gains of steers fed corncob ration with 0, 50, or 100 percent alfalfa hay addition. SOURCE: Paterson (1979).
Crop Residues 203 the ruminant population. Utilization of crop residues can be increased by cultural and management practices, such as stage of maturity at harvest. The greatest increase in utilization of crop residues will likely come from chemical treatment in combination with improved management prac- tices. Sodium hydroxide has been widely studied as a chemical for crop- residue treatment. While the treatment is effective, concerns about human safety and sodium residues may limit its ultimate usefulness. Probably treatments with ammonia and combinations of chemicals will prove more useful. In addition to feeding systems, systems of harvest, treatment, and stor- age can be developed to optimize the use of residues. ANIMAL AND HUMAN HEALTH PROBLEMS AND REGULATORY ASPECTS There are no special animal or human health problems involved with feeding crop residues or treated residues to ruminants. Any residue stored improperly will likely mold and can potentially produce aflatoxins that can have devastating effects on animals. Most crops that provide residues for feeding have had herbicides or insecticides applied to them. These compounds present no health problems to animals or people as long as label directions are adhered to strictly. Compounds that are cleared for use on crops for silage will obviously be suitable for use when crop residues are harvested. Herbicides are generally not applied near harvest, but on some occasions insecticides might be applied shortly before harvest. The insecticide label will indicate safety for use on forage crops. For some crops, such as cotton, the whole plant is never intended for silage, and clearance for insecticides might not be as straightforward as for forage crops. Herbicide and insecticide residues can present a very real and serious problem for livestock producers. This does not need to be a problem if the correct compounds are used and if they are used in strict accordance with label directions. Sodium hydroxide, calcium hydroxide, and ammonia do not leave any toxic residues in treated feedstuffs. If these chemicals are sold for the purpose of increasing the digestibility of feedstuffs, U.S. Food and Drug Administration approval is probably necessary. Efficacy rather than safety is the primary concern. RESEARCH NEEDS Considerable research has been conducted on crop residues, but much remains to be done. The nutritional value of residues must be improved
204 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS in many instances, and systems of collecting, storing, treating, and feeding must be improved to make increased use economical. Nutritional improvement seems to be possible by plant genetic im- provement, harvest management, chemical treatment, physical treatment, or biological treatment. All of these need further innovative research. SUMMARY The potential for increased use of crop residues in ruminant production is quite impressive, but the extent of usage depends on two important factors: the availability of grain for feeding to ruminants and the amount of research progress made in improving the nutritional value of crop residues. Residues from the various crops vary in nutritional value, physical characteristics, and response to treatment. It is risky to generalize from one residue to another. Because of the low nutritional value of residues, methods of increasing value are of interest. Calcium hydroxide and am- monia treatments have the greatest long-term potential. Livestock production systems can be developed to use large quantities of residues. These systems would not presently replace all of the grains, but would reduce the quantity used. LITERATURE CITED Acock, C. W. 1978. Wheat straw and sodium hydroxide treatment for beef cow maintenance diets. M.S. thesis. Lincoln: University of Nebraska. Acock, C. W., J. K. Ward, I. G. Rush, and T. J. Klopfenstein. 1979. Wheat straw and sodium hydroxide treatment in beef cow rations. J. Anim. Sci. 49:354. Anderson, D. C. 1978. Use of cereal straws in beef cattle production systems. J. Anim. Sci. 46:849. Anderson, D. C., and A. T. Ralston. 1973. Chemical treatment of rye-grass straw: In vitro dry matter digestibility and compositional changes. J. Anim. Sci. 37: 148. Andreis, H. J., and R. P. DeStefano. 1978. Silage made from sugarcane bagasse treated with sodium hydroxide. P. 13 in Sugar J. October, 1978. Asadpour, P. 1978. Utilization of treated wheat straw by sheep. M.S. thesis. Lincoln: University of Nebraska. Barton, F. E., H. Amos, W. J. Albrecht, and D. Burdick. 1974. Treating peanut hulls to improve digestibility for ruminants. J. Anim. Sci. 38:860. Bender, F., D. P. Heaney, and A. Bowden. 1970. Potential of steamed wood as feed for ruminants. For. Prod. J. 20:36. Berger, L. L., J. A. Paterson, T. J. Klopfenstein, and R A. Britton. 1979. Effect of harvest data and sodium hydroxide treatment on the feeding value of corn stalkage. J. Anim. Sci.49:1312. Berger, L. L., T. J. Klopfenstein, and R. A. Britton. 1980. Rate of passage and rate of ruminal fiber digestion as affected by level of NaOH treament. J. Anim. Sci. 50:745.
Crop Residues 205 Bolsen, K. K., C. Grimes, J. G. Riley, and L. Corak. 1976. Milo stover, forage sorghum and alfalfa silages for growing calves. P. 203 in ASAS Annual Meeting, St. Louis. (Abstr.) Bolsen, K. K., C. Grimes, and J. G. Riley. 1977. Milo stover in rations for growing heifers and lambs. J. Anim. Sci. 45:377. Bottle, W. G., B. L. Miller, L. L. Berger, R. B. Rindsig, and G. C. Fahey. 1979. In vivo and in vitro evaluations of soybean residues ensiled with various additives. P. 93 in ASAS Midwestern Section Meeting, St. Louis. (Abstr.) Brown, W. H., F. M. Whiting, B. S. Daboll, R. J. Turner, and J. D. Schuh. 1977. Pelleted and nonpelleted cottonseed hulls for lactating dairy cows. J. Dairy Sci. 60:919. Brown, W. H., G. D. Halbach, J. W. Stull, and F. M. Whiting. 1979. Utilization of cotton gin trash by lactating dairy cows. J. Dairy Sci. 62:793. Burdick, D., F. E. Barton, and H. E. Amos. 1975. Performance of steers fed peanut hulls as roughages. Weight gains and DDT residues. ARS-S-61. New Orleans: U.S. Depart- ment of Agriculture. Butterworth, M. H. 1962. The digestibility of sugar-cane tops, rice aftermath, and bamboo grass. Emp. J. Exp. Agric. 30:77. Calhoun, M. C., and M. Shelton. 1973. Peanut Hulls and Cottonseed Hulls Compared with Alfalfa Hay as Roughage Sources in High Concentrate Lamb Rations. Tex. Agric. Exp. Stn. Rep. PR-3179. Chandra, S., and M. G. Jackson. 1971. A study of various chemical treatments to remove lignin from coarse roughages and increase their digestibility. J. Agric. Sci. 77:11. Choung, C. C., and W. R. McManus. 1976. Studies on forage cell walls. 3. Effects of feeding alkali-treated rice hulls to sheep. J. Agric. Sci. (Cambridge). 86:517. Clanton, D. C., and L. Harris. 1966. Beet tops: Silage vs. pasturing. P. 12 in Nebraska Beef Cattle Progress Report. Lincoln: University of Nebraska. Colenbrander, V. F., V. L. Lecktenberg, and L. G. Bauman. 1973. Digestibility of feeding value of brown midrib corn stover silage. J. Ani;m. Sci. 37:294. Coombe, J. B., D. A. Dinius, H. K. Goering, and 1~. R. Oltjen. 1979a. Wheat straw urea diets for beef steers: Alkali treatment and supplementation with protein? monensin and a feed stimulant. J. Anim. Sci. 48:1223. Coombe, J. B., D. A. Dinius, and W. E. Wheeler. 1979b. Effect of alkali treatment on intake and digestion of barley straw by beef steers. J. Anim. Sci. 49:169. Corken, R., R. McElroy, H. Taylor, and W. B. Black. 1979. Feasibility and effects of increased use of crop residues in beef cattle rations. Washington, D.C.: Economics, Statistics and Cooperative Service, USDA. Daniels, L. B., and R. B. Hashim. 1977. Evaluation of fungal cellulases in rice hull base diets for ruminants. J. Dairy Sci. 60:1563. Dinusson, W. E. 1969. Straw for Wintering Cows. 20th Annual Research Roundup. Dick- inson, North Dakota: Dickinson Exp. Stn. Donefer, E., I. O. A. Adeleye, and T. A. O. C. Jones. 1969. Effect of urea supplemen- tation on the nutritive value of NaOH-treated oats straw. Pp. 328-339 in Celluloses and Their Applications. Advances in Chemistry Series 95. Washington, D.C.: American Chemical Society. Dronawat, N. W., R. W. Stanley, E. Cobb, and K. Morita. 1966. Effect of feeding limited roughage and a comparison between loose and pelleted pineapple hay on milk production, milk constituents, and fatty acid composition of milk fat. J. Dairy Sci. 49:28. Durham, R. R., and D. D. Hinman 1979. Digestibility and utilization of bluegrass straw harvested on three different dates. J. Anim. Sci. 48:464. Early, R. J., and D. C. Anderson. 1978. Kentucky bluegrass straw composition, digesti- bility and utilization in wintering cow rations. J. Anim. Sci. 46:787.
206 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS Estima, A. L., G. C. Caldas, S. P. Viana, M. F. Cavalcante, A. R. de Carvalho, M. S. Farias, and G. P. Lofgreen. 1967. Molasses, cassava and cottonseed meal as supplements to fresh and ensiled sugarcane tops. IRI Res. Inst. Bull. 32. New York: fRI Research Institute. Faulkner, D. G., and J. K. Ward. 1981. Cornstalk grazing of weanling heifers. Nebraska Beef Cattle Report. EC 80-218. Lincoln: University of Nebraska. Faulkner, D. B., J. K. Ward, T. J. Klopfenstein, and I. B. Rush. 1981. Ammonia treat- ment of wheat straw for cows. Nebraska Beef Cattle Report. EC 80-218. Lincoln: University of Nebraska. Garlich, J. D., D. M. Bryant, H. M. Covington, D. S. Chamblee, and A. E. Purcell. 1974. Egg yolk and broiler skin pigmentation with sweet potato vine meal. Poult. Sci. 53:692. Garrett, W. N., H. G. Walker, G. O. Kohler, and M. R. Hart. 1979. Response of rum- inants to diets containing sodium hydroxide on ammonia treated rice straw. J. Anim. Sci. 48:92. Guggolz, J., G. O. Kohler, and T. J. Klopfenstein. 1971. Composition and improvement of grass straw for ruminant nutrition. J. Anim. Sci. 33:151. Gupta, B. S., D. E. Johnson, and F. C. Hinds. 1978. Soybean straw intake and nutrient digestibility by sheep. J. Anim. Sci. 46:1086. Haines, C. E., H. L. Chapman, and R. W. Kidder. 1959. The Feeding Value and Diges- tibility of Dried Celery Tops for Steers. Everglades Stn. Mimeo. Rep. 59- 13. Gainesville: University of Florida. Hale, W. H., C. Lambeth, B. Theurer, and D. E. Ray. 1969. Digestibility and utilization of cottonseed hulls by cattle. J. Anim. Sci. 29:773. Hasimoglu, S., T. J. Klopfenstein, and T. H. Doane. 1969. Nitrogen source with sodium hydroxide treated wheat straw. J. Anim. Sci. 29:160. Heinemann, W. W. 1976. Bluegrass Straw, Cottonseed Hulls and Wheat Screenings in Steer Finishing Rations. College of Agriculture, Washington State Univ. Bull. 832. Pullman: Washington State University. Holloway, J. W., J. M. Anderson, W. A. Pund, W. D. Robbins, and R. W. Rogers. 1974. Feeding Gin Trash to Beef Cattle. Miss. Agric. For. Exp. Stn. Bull. 818. Horton, G. M. J., and G. M. Steacy. 1979. Effect of anhydrous ammonia treatment on the intake and digestibility of cereal straws by steers. J. Anim. Sci. 48:1239. Hunt, G. C., K. R. Cummings, and J. W. Lusk. 1971. Cottonseed hull-concentrate com- plete rations for lactating cows. J. Dairy Sci. 54:452. (Abstr.) Hutanuwatr, N., F. C. Hinds, and C. L. Davis. 1974. An evaluation of methods for improving the in vitro digestibility of rice hulls. J. Anim. Sci. 38:140. Jackson, M. G. 1977. Review article: The alkali treatment of straws. Anim. Feed Sci. Technol. 2:105. Jackson, M. G. 1978. Treating Wheat Straw for Animal Feeding. FAO Animal Production and Health Paper No. 10. Rome: Food and Agriculture Organization of the United Nations. Jared, A. H., and E. Donefer. 1970. Alkali-treated straw rations for fattening lambs. J. Anim. Sci. 31:245. Jayasuriya, M. C. N., and E. Owen. 1975. Sodium hydroxide treatment of barley straw: Effect of volume and concentration of solution on digestibility and intake by sheep. Anim. Prod. 21:313. Jones, J. H., D. S. Logan, and P. J. Lyerly. 1957. Use of Cotton Gin Trash in Steers' Fattening Rations. Tex. Agric. Exp. Stn. Prog. Rep. 1969. Karn, H. P., and K. S. Hendrix. 1977. Digestibility of alkali-treated and brown corn plant residue. P. 611 in ASAS Annual Meeting. Madison: University of Wisconsin. (Abstr.)
Crop Residues 207 Kellems, R. O., O. Wayman, A. H. Nguyen, J. C. Nolan, C. M. Campbell, J. R. Car- penter, and E. B. Ho-a. 1979. Post-harvest pineapple plant forage as a potential feedstuff for beef cattle: Evaluated by laboratory analyses, in vitro and in vivo digestibility and feedlot trials. J. Anim. Sci. 48: 1040. Kernan, J. A., E. C. Coxworth, and M. J. Moody. 1980. A survey of the feed value of various specialty crop residues and forages before and after chemical processing. Sas- katchewan Research Council Publication No. C-814-F-1-B-80. Saskatoon: University of Saskatchewan. Klopfenstein, T. J. 1975. Pressure treatment of corn cobs. In Nebraska Beef Cattle Report. EC 75-218. Lincoln: University of Nebraska. Klopfenstein, T. J. 1978. Chemical treatment of crop residues. J. Anim. Sci. 46:841. Klopfenstein, T. J., and K. K. Bolsen. 1971. High temperature pressure treated crop residues. J. Anim. Sci. 33:290. Klopfenstein, T. J., V. E. Krause, M. J. Jones, and W. Woods. 1972. Chemical treatment of low quality roughages. J. Anim. Sci. 35:418. Klopfenstein, T. J., R. P. Graham, H. G. Walker, and G. O. Kohler. 1974. Chemicals with pressure treated cobs. J. Anim. Sci. 39:243. Koers, W., W. Woods, and T. J. Klopfenstein. 1970. Sodium hydroxide treatment of corn stover and cobs. J. Anim. Sci. 31:1030. Koers, W., M. Prokop, and T. J. Klopfenstein. 1972. Sodium hydroxide treatment of crop residues. J. Anim. Sci. 35:1131. Lamm, W. D. 1976. Influence of nitrogen supplementation on hydroxide treatment upon the utilization of corn crop residues by ruminants. Ph.D. dissertation. Lincoln: University of Nebraska. Lamm, W. D., and J. K. Ward. 1977. Corn crop residue quality and compositional changes. In ASAS 69th Annual Meeting. Madison: University of Wisconsin. (Abstr. 46) Larson, W. E., R. F. Holt, and C. W. Carlson. 1978. Residues for soil conservation. Chap. 1 in Crop Residue Management and System. Madison, Wisc.: American Society of Agronomy. Lau, M. M., and P. J. Van Soest. 1981. Titratable groups and soluble phenolic compounds as indicators of the digestibility of chemically treated roughages. Anim. Feed Sci. Tech- nol. 6:123-131. Leonard, R. O., M. E. Stanley, and D. L. Bath. 1973. Unusual Feedstuffs in Livestock Rations. U. Calif. Agric. Ext. Bull. AXT-1979. Lesoing, G., I. Rush, T. Klopfenstein, and J. Ward. 1980a. Wheat straw in growing cattle diets. J. Anim. Sci. 51:257. Lesoing, G., T. Klopfenstein, I. Rush, and J. Ward. 1980b. Chemical treatment of wheat straw. J. Anim. Sci. 51:263. Livingston, A. L., R. E. Knowles, J. Page, D. D. Kuzmicky, and G. O. Kohler. 1972. Processing of cauliflower leaf waste for poultry and animal feed. J. Agric. Food Chem. 20:277. Marshall, S. P., and H. H. Van Horn. 1975. Complete rations for dairy cattle. II. Sugarcane bagasse pellets as roughage in blended rations for lactating cows. J. Dairy Sci. 58:896. Martin, P. C., T. C. Cribeiro, A. Cabello, and A. Elias. 1974. The effect of sodium hydroxide and pressure on the dry matter digestibility of bagasse and bagasse pith. Cuban J. Agric. Sci. 8:21. Martin, P. C., A. Cabello, and A. Elias. 1976. The use of fibrous sugarcane by-products by ruminants. 2. Effect of the NaOH pressure combination on the digestibility and chemical composition of bagasse and bagasse pith. Cuban J. Agric. Sci. 10:19. McDonnell, M. L., and T. J. Klopfenstein. 1980. Cornstalk quality as affected by variety and management. In ASAS Annual Meeting. Ithaca, N.Y.: Cornell University. (Abstr.)
208 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS McKee, M., K. G. Kimple, and K. K. Bolsen. 1977. Crop residues for wintering beef cows in dry lot. In ASAS Annual Meeting. Madison: University of Wisconsin. (Abstr. 314) McManus, W. R., and C. C. Choung. 1976. Studies on forage cell walls. 2. Conditions for alkali treatment of rice straw and rice hulls. J. Agric. Sci. (Cambridge) 86:453. National Research Council. 1971. Atlas of Nutritional Data on United States and Canadian Feeds. Washington, D.C.: National Academy of Sciences. Noland, P. R., and B. F. Ford. 1954. Rice hulls and rice mill feed. Ark. Farm Res. 3(3). Ololade, B. G., D. N. Mowat, and J. E. Winch. 1970. Effect of processing methods on the in vitro digestibility of sodium hydroxide treated roughages. Can. J. Anim. Sci. 50:657. Otagaki, K. K., G. P. Lofgreen, E. Cobb, and G. G. Dull. 1961. Net energy of pineapple bran and pineapple hay when fed to lactating dairy cows. J. Dairy Sci. 44:491. Pate, F. M., and S. W. Coleman. 1975. Sugarcane Tops for Cattle Feed. Fla. Agric. Exp. Stn. J. Series No. 5509. Pate, F. M., D. W. Beardsley, and B. W. Hays. 1971. Chopped Sugarcane Tops as a Feedstuff for Cattle and Horses. Everglades Exp. Stn. Nlimeo. Rep. EES71-5. Paterson, J. A. 1979. The feeding of hydroxide treated crop residues to growing ruminants. Ph.D. thesis. Lincoln: University of Nebraska. Paterson, J. A., T. J. Klopfenstein, and R. A. Britton. 1978a. The digestibility of sodium hydroxide treatments of roughage on mineral balance and digestibility. J. Anim. Sci. 46:340. (Abstr.) Paterson, J. A., T. J. Klopfenstein, and R. A. Britton. 1978b. Effect of sodium hydroxide treatments of roughage on mineral balance and digestibility. J. Anim. Sci. 46:433. (Abstr. ) Paterson, J. A., M. L. McDonnell, and T. J. Klopfenstein. 1979. Decrease in digestibility of cornstalks after physiological maturity. P. 66 in ASAS Midwest Section Meeting. (Abstr. ) Paterson, J. A., R. Stock, and T. J. Klopfenstein. 1980. Calcium hydroxide treatment of crop residues. Nebraska Beef Cattle Report. EC 80-218:21. Lincoln: University of Ne- braska. Randel, P. F. 1970a. Dairy beef production from mixtures of sugarcane bagasse and con- centrates. J. Agr. Univ. P. R. 54:237. Randel, P. F. 1970b. Ad libitum feeding of either a complete ration based on sugarcane bagasse or a conventional concentrates mixture to dairy cows. J. Agr. Univ. P. R. 54:429. Randel, P. F. 1972. A comparison of the digestibility of two complete rations containing either raw or alkali-treated sugarcane bagasse. J. Agr. Univ. P. R. 56:18. Randel, P. F., A. Ramirez, R. Carrero, and I. Valencia. 1971. Alkali-treated and raw sugarcane bagasse as roughages in complete rations for lactating cows. J. Dairy Sci. 55:1492. Rexen, B. 1977. Enzyme solubility A method for evaluating the digestibility of alkali treated straw. Anim. Feed Sci. Technol. 2:205. Rexen, R., and K. V. Thomsen. 1976. The effect on digestibility of a new technique for alkali treatment of straw. Anim. Feed Sci. Technol. 1:73. Rogers, D. J., and M. Milner. 1963. Amino acid profile of manioc leaf protein in relation to nutritive value. Econ. Bot. 17:211. Ross, E., and F. Q. Enriquez. 1969. The nutritive value of cassava leaf meal. Poult. Sci. 48:846. Rush, I. 1977. Sugar beet by-products-What are they worth? P.481 in Beef Cattle Science Handbook 14. Clovis, Calif.: Agriservices Foundation.
Crop Residues 209 Saxena, S. K., D. W. Otterby, J. D. Donker, and A. L. Good. 1971. Effects of feeding alkali-treated oat straw supplemented with soybean meal or non-protein nitrogen on growth of lambs and on certain blood and rumen liquor parameters. J. Anim. Sci. 33:485. Sherrod, L. B., and C. B. Summers. 1974. Sodium hydroxide treatment of cottonseed hulls and sorghum stubble. In ASAS Proceedings. Western Section. Corvallis, Ore. (Abstr. 388) Singh, M., and M. G. Jackson. 1971. The effect of different levels of sodium hydroxide spray treatment of wheat straw on consumption and digestibility by cattle. J. Agric. Sci. 77:5. Smith, D. H. 1977. Effect of physiological and management factors on yield and quality of grain sorghum residues. Ph.D. thesis. Lincoln: University of Nebraska. Sundstol, F., E. Coxworth, and D. N. Mowat. 1978. Improving the nutritive value of straw and other low-quality roughages by treatment with ammonia. World Anim. Rev. 26:13. Tillman, A. D., R. D. Furr, D. R. Hansen, L. B. Sherrod, and J. D. Word. 1969. Uti- lization of rice hulls in cattle finishing rations. J. Anim. Sci. 29:792. U.S. Department of Agriculture. 1979. Agricultural Statistics. Washington, D.C.: U.S. Government Printing Office. Umunna, N. N., and T. J. Klopfenstein. 1972. Response of lambs fed pressure treated wheat straw. J. Anim. Sci. 35:1136. Umunna, N. N., T. J. Klopfenstein, and K. Bolsen. 1972. Response of lambs fed pressure treated corn cobs. J. Anim. Sci. 35:277. Utley, P. R., and W. C. McCormick. 1972. Level of peanut hulls as a roughage source in beef cattle finishing diets. J. Anim. Sci. 34:146. Van Soest, P. J. 1981. Limiting factors in plant residues of low biodegradability. Agric. Environ. 6: 135- 143. Vetter, R. L. 1973. Evaluation of chemical and nutritional properties of crop residues. In Crop Residue Symposium. Lincoln: University of Nebraska. Vetter, R. L., and M. Boehlje. 1978. Alternative feed resources for animal production. In Plant and Animal Products in the U.S. Food System. Washington, D.C.: National Acad- emy of Sciences. Waagepetersen, J., and K. V. Thomsen. 1977. Effect on digestibility and nitrogen content of barley straw of different ammonia treatments. Anim. Feed Sci. Technol. 2:131. Waiss, A. C., Jr., J. Guggolz, G. O. Kohler, H. G. Walker, Jr., and W. N. Garrett. 1972. Improving digestibility of straws for ruminant feed by aqueous ammonia. J. Anim. Sci. 35:109. Waller, J. C. 1976. Evaluation of sodium, calcium, and ammonium hydroxides for treating residues. M.S. thesis. Lincoln: University of Nebraska. Waller, J. C., and T. J. Klopfenstein. 1975. Hydroxides for treating crop residues. J. Anim. Sci. 41:424. Ward, J. K. 1978. Utilization of corn and grain sorghum residues in beef cow forage systems. J. Anim. Sci. 46:831. Ward, J. K., L. J. Perry, D. H. Smith, and J. T. Schmitz. 1979. Forage composition and utilization of grain sorghum residue by beef cows. J. Anim. Sci. 48:919. White, T. W. 1966. Utilization of ammoniated rice hulls by beef cattle. J. Anim. Sci. 25:25. Wilkinson, J. M., and R. Gonzalez Santillana. 1978. Ensiled alkali-treated straw. I. Effect of level and type of alkali on the composition and digestibility in vitro of ensiled barley straw. Anim. Feed Sci. Technol. 3:117.
2 10 UNDERUTILIZED RESOURCES AS ANIMAL FEEDSTUFFS GLOSSARY TERMS BAGASSE CHAFF CORN HUSK CROP RESIDUE HULLS HUSK HUSKLAGE IN VITRO IN VIVO POD STALK STALKLAGE STOVER STRAW Solid residue remaining after extraction of juice. Husks, hulls, joints, and small fragments of straw that are separated from seed in threshing of small grains. CORNCOBS Fibrous portion of the fruiting head (grain producing portion) of the corn plant, excluding the husk. Fibrous outside cover of the fruiting head (grain producing portion) of the corn plant. Fibrous residue remaining after harvest of the primary product (grain, fruit, etc.). Outer covering of seeds. Outer covering of kernels or seeds, especially when fibrous. Corncobs and husks. Outside the living organism in an artificial environment. Within the living organism. Empty seed vessel. Main stem of a herbaceous plant. Moist, ensiled stalks. Stalks and leaves of corn or sorghum after grain harvest. Plant residue remaining after separation of the seeds by threshing of small grains. STUBBLE Lower parts of plant stems that remain standing in the field after harvest.
