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DIETS AND FEEDING PRACTICES PELLETE D VS . NO N P E LLE TE D FE E D S Observation of rabbits indicates that they prefer a pel- leted diet to one in a meal form. They will adjust to a meal diet and accept it satisfactorily, but during the adjustment period intake may be very low and feed spillage exces- sive. Some individuals may refuse to consume a nonpel- leted experimental diet. Unless fat or molasses is added to the diet, dustiness may be a problem with meal-type diets, furler contributing to their lack of palatability. Chapin (1965) compared performance of growing rab- bits on a commercial pelleted diet (0.48 x 0.63 cm) with the same diet in the ground form. He also compared performance on a commercial meal-form diet with He same diet pelleted. In each case, growth rate and feed efficiency were significantly better with the pelleted diets. Lebas (1973) also observed improved growth per- formance with pelleted diets, and King (1974) reported . . A- . slm1 ar zinc legs. PARTICLE SIZE AND CRUDE FIBER Physical form and particle size of feed ingredients may be factors to be considered in rabbit diet formulation. Lebas (unpublished observations) has found that the particle size of alfalfa may influence the occurrence of enteritis. Fine grinding (more than 25 percent passing a 0.2~mm screen and 90 percent passing a 1.0-mm screen) tends to promote diarrhea, whereas coarsely ground material does not. The presence of undigestible fiber of large particle size in the cecum and colon may be necessary for mainte- nance of the epithelial tissue of these organs (Lebas, 1975b). Replacement of a poorly digested fiber source, such as alfalfa, with a well-digested fiber source, such as beet pulp, may provoke diarrhea (Lebas, unpublished observations). These observations, as well as un- documented statements of commercial rabbit producers, suggest Hat the presence of undigestible fiber of large particle size is necessary for normal functioning of the rabbit digestive tract, and that the absence of this mate rial, either through fine grinding or the use of digestible sources of fiber (beet pulp), may result in changes in the cellular structure of the digestive tract lining and diarrhea. This aspect of feed preparation warrants consid- erably more study. PURIFIED AND EXPERIMENTAL DIETS Studies involving strictly purified diets for rabbits are few. In most cases, natural materials such as alfalfa or green feed have been included. Gaman et al. (1970) re- ported the composition of a purified diet that gave satis- factory results; rabbits were fed this diet for periods up to 2.5 yr during all stages of growth and reproduction. No problems were encountered; performance was similar to that of control animals fed a commercial diet. Composi- tion of the diet is shown in Table 2. The vitamin mixture used may contain an excess of some of the vitamins, and it includes some vitamins (e.g., ascorbic acid) for which no dietary need has been demonstrated. If possible, purified diets should be pelleted to in- crease their acceptability and to minimize waste. Diets should be kept under refrigeration to avoid rancidity, or an approved antioxidant maY be added. Use of highly basic mineral mixtures should be avoided. Hove and Herndon (1955) found that potassium acetate or potas c, , slum carbonate in a mineral mixture led to rapid deterio- ration of the diet. Cheeke (1972) observed that Torula yeast has potent antioxidant activity and Hat inclusion of 2 percent Tonala yeast in a diet will stabilize it. The use of lard or tallow in place of corn oil is also of assistance in preventing rancidity. Acceptability of feeds by rabbits is a problem in nutri- tion research. Cheeke (1974) has examined feed prefer- ences. While more extensive data are needed, this work suggests some dietary modifications that may be helpful if palatability is a problem. Adult Dutch male rabbits showed a marked preference for a barley-based diet con- taining sucrose over the same diet without sucrose, and preferred the plant proteins, soybean meal and cotton- seed meal, over meat meal and fish meal. A diet with 5 10
Nutrient Requirements of Rabbits 11 percent corn oil was strongly preferred over a similar diet with no added corn oil' and a 10 percent level of corn oil was preferred over a 20 percent level. Furler identif~ca- tion of preferences or dislikes of rabbits would aid in formulating acceptable diets. DIET INGREDIENTS AND EXAMPLES OF ADEQUATE RATIONS Rabbits consume many kinds of feeds satisfactorily. The feeds selected for use should be determined by relative costs and regional availability. The following simple classification of feeds will guide the discussion of the merits of individual feed ingre- dients. · Green or succulent feeds. Typically average 70-90 percent of H2O. Growing pasture plants, root crops, cab- bage, etc. · Dry feeds. As fed will average only 10-15 percent of H2O. · Roughages. Those having high fiber content and rela- tively low digestibility and therefore low in energy value. Hay, etc. · Concentrate feeds. Those having low fiber content and relatively high digestibility and therefore high in energy value. · High carbohydrate concentrates. Those relatively high in the more digestible carbohydrates but low in protein content. The cereal grains (corn, wheat, oats, etc.) and their milled by-products as wheat bran, middlings, hominy feed, etc. · Protein supplements. Those that are high in protein. Soybean meal, peanut meal, dried milk by-products, etc. The green feeds are widely fed to rabbits, especially by small producers. They are generally succulent and highly palatable. However, the cost per unit of nutrients is too high for the commercial producer, and He high water content renders them bulky and too low in energy for efficient production of meat or for lactating females. The dry roughages, primarily hay, normally make up about 40-80 percent of the diet for rabbits. While rela- tively low in energy value, the hays are economical sources of many nutrients, notably protein, some vita- mins, and some mineral elements and furnish necessary amounts of fiber for a balanced diet. There are two prin- cipal classes of hay: legume (alfalfa, clovers, etc.) and grass (timothy, bluegrass, orchard grass, etc.~. As a group the legume hays are superior to the grass hays in that they are generally more palatable, are significantly higher in protein and in calcium, and are preferred by the rabbit. In most sections of the country, alfalfa is generally used. The high carbohydrate concentrate feeds are primarily rich sources of energy and, when added to the roughage, increase the energy density of the mixture to the point where it is adequate to meet the higher energy needs of producing rabbits growth, meat production, and lacta tion. These concentrates may be fed as whole grains, ground and fed as a meal, or compressed into pellets. Some whole grains such as flint corn are so hard Hat grinding improves digestibility significantly. Protein supplements are concentrate [Beds that are high in protein, and they are used to increase the level of pro- tein in the total diet to the recommended level. For the most part, protein supplements of most interest to rabbit growers are derived from plants rather than the more ex- pensive animal protein supplements. The most widely used is soybean meal, Tough, in usual feed combinations, linseed meal, peanut meal, and sesame meal may also be used successfully. If cottonseed meal is used, it should be treated for removal of gossypol, and even then it should be limited to no more than about 5-7 percent of the diet. Miscellaneous feeds include a wide variety of ingre- dients that are of little interest to commercial producers but may be of interest to small operators. Table wastes, except meat, fat, or spoiled foods, are acceptable. Milk and milk by-products are excellent but usually are too expensive. In some countries many weeds are used by small producers, and a summary of these is given by Aitken and Wilson (19621. In practice, salt is generally added to a diet at a level of 0.5 percent or provided free choice as a salt block. The example diets in Table 3 are adequate in mineral ele- ments so far as is known. Since He great majority of rabbit breeders, including those raising rabbits in medical and biological lab- oratories, use commercially prepared pelleted feeds, the diets in Table 3 are formulated on the basis of suitabil- ity for pelleting. It should be stressed that many over feed combinations are possible. Certain feeds are of interest because of their detrimen- tal effects. There is evidence that cottonseed meal may have a cumulative toxic effect (Holley, 19551. This, in addition to the high sensitivity of rabbits to gossypol in untreated cottonseed meal, would suggest caution in its use until further research is done. It has been dem- onstrated by several workers Hat the feeding of large amounts of cabbage or rapeseed produces goiter in rab- bits as well as in other species (Yamamoto, 1959; F'edelli-Avanzi and Janella, 1976~. Other toxic feeds are listed by Aitken and Wilson (1962~. GERM-FREE DIETS The nutrient requirements for germ-free rabbits have been subjected to only a few studies, but the require- ments, except for B vitamins, do not appear to be funda- mentally different from those of conventional rabbits. Some differences have been noted in the absorption of iron and copper (Ready et al., 1965). In the absence of intestinal flora, vitamins of the complex must be present in the diet to supply those otherwise synthesized by conventional animals. Nutri- tionally adequate diets for germ-free rabbits have been described by Reddy et al. (1968~.
12 Nutrient Requirements of Rabbits ANTIMICROBIAL AGENTS Antibiotics, sulfonamides, and nitrofurans added to the feed or drinking water have been evaluated for their effects upon growth or the control of coccidiosis and enteritis. In general, the antibiotics have not shown con- sistent beneficial ejects upon growth, but in some cases 1 hey have aided in the control of enteritis. Sulfonamides are of value in the control of coccidiosis, and nitrofurans have had limited effect upon enteritis. The research with these agents and the practical aspects of their use have been reviewed by Hagen (19741. The use of antibiotics and other antimicrobial agents is controlled by federal regulations, and readers should consult Me Food and Drug Administration (FDA) regarding the latest rulings on use of feed additives. At present the following agents with amounts and indi- cations for use are permitted in rabbit feeds. Oxytetracy- clene at a level of 10 g per ton is permitted as an aid in stimulating grown and improving feed efficiency. Sul- faquinoxaline, 0.025 percent, continuously for 30 days, 0.025 percent intermittently for 2 days per week, or 0.1 percent for 2 weeks may be included as an aid in control- ling coccidiosis due to Eimeria stiedae. Lawrence and McGinnis (1952) reported no improve- ment in grown of rabbits fed Terramycin in amounts up to 50 mg per kg of diet. Chlortetracyclene (100 mg/kg of diet) and oxytetracyclene (50 mg/kg) had no effect upon grown except in the doe's first litter. The high levels of antibiotic reduced the incidence of enteritis and mortality due to enteritis but had no effect on the young once enteritis had appeared (Casady et al., 1964a). Zinc bacitracin (50 mg/kg of diet) likewise was found to have no effect upon growth but reduced evidence of enteritis (Casady et al., 1964b). No evidence of increased grown was observed by Huang et al. (1954) with Terramycin, Aureomycin, or Aureomycin plus vitamin B ill. Studies in England have indicated beneficial effects of oxytetracyclene, chlortetracyclene, and virginiamycin upon growth, but no effect was noted with penicillin (King, 1962, 1966, 1967, 1974a, 1974b). Flavomycin was observed to decrease feed intake and improve feed eff~- ciency but had no effect upon daily gain (Schlolaut and Lange, 1973~. Sulfamethazine (0.05 to 1.0 percent) in the feed, sul- famerazine (0.02 percent) in the drinking water, and sul- faquinoxaline (0.02 and 0.05 percent) in the drinking water controlled liver coccidiosis. Intestinal coccidiosis was successfully treated with 50 mg of sulfaguanidine per 100 g of diet daily for 2 weeks. Sulfamonomethoxine and sulfadime~oxine (75 mg/kg of body weight) were also effective. Limited studies with ni~ofurans have indicated some effect upon growth and enteritis. Furazolidone (50 giton) increased weaning weight and reduced Me inci- dence of enteritis. Nitrofurazone and furazolidone sepa- rately and in combination did not prevent liver lesions from coccidiosis, but the combination had some detri- mental effect on the life cycle of coccidia (reports on sulfonamides and nitrofurans cited by Hagen, 1974~.
14 Nutrient Requirements of Rabbits TABLE 1 Nutrient Reauirements of Rabbits Fed Ad Libitum (Percentage or Amount per kg of Diet) . ~ ~ . ~ . . _ ~ ~ ~ Nutrients5 Grovv~hMaintenanceGestationLaceation Energy and protein Digestible energy (kcal) 2500210025002500 TDN (%) 65555870 Crude fiber (%) 1012b14D10-1201~126 Fat(%) 26262626 Crude protein (%) 16121517 Inorganic nutrients Calcium (%) 0 4c0.4S.0.75b Phosphorus (%) 0.22-'0.3700.5 Magnesium (mg) 300400300 400300 400300~00 Potassium (%) 0.60.60.60.6 Sodium (%) 0.20 ~0.26 ~0.26 ~0.2 Chlorine (%) 0.3D.d0.3D-a0.3 b.d0.3 Copper (mg) 3333 iodine (mg) o.2b0.25o.2bo.2b Iron cccc Manganese (mg) 8.5e2.5e2.5e2.5e Zinc cc_cc Vitamins Vitamin A ('u) 580 >1160c Vitamin A as carotene (mg) 0 g3b.e_l0 83b.e_ Vitamin D ~- gg~ Vitamin E (mg) 40h_c40h406 Vitamin K (mg) ii02 Niacin (mg) 180 Pyridoxine (mg) 39-j-j- Choline (9) 1.2b-j-j- Amino acids (%) Lysine . 0.6599g Methionine + cystine 0.6-O-9-g Arginine 0.69g9 Histid~ne 0.3bD, gg Leucine 1lb-9-99 Isoleucine 0 6bgDg Phenylalanine + tyrosine 1.1 b-9-9-9 Threonine 0.6bggg Tryptophan 0.26g- g-g Valine Q76 Glycine a Nutrients not listed indicate dietary need unknown or not demonstrated. D May not be minimum but known to be adequate. ~ Quantitative requirement not determined, but dietary need demonstrated. d May be met with 0.5 percent NaCI. 'Converted from amount per rabbit per day using an air-dry feed intake of 60 9 per day for a 1-kg rabbit. ~Quantitative requirement not determined. ° Probably required, amount unknown. A Estimated. ' Intestinal synthesis probably adequate. Dietary need unknown.
Nutrient Requirements of Rabbits 15 TABLE 2 Purified Diet for Rabbitsa Ingredient % of Diet Isolated soy protein Purified celluloseb Corn oil Mineral mixtures Vitamin mixtures Choline chloride (70%) Antioxidant (Ethoxyquin) Dr-Methionine c'-Tocopherol acetate Glucose monohydrate Corn dextrin Corn starch Water (for pelleting) 20.0 16.0 5.0 6.6 0.2 0.1 0.025 0.2 50 ~u/kg 15.0 5.0 27.4 5.0 · Garnan and Fisher (1970). DSolka Floe, Brown Co., New York, N.Y. 'Composition (in mglkg): CoCI2~6H2O, 3.5; CuSO4~5H20, 34.6; MnSO4.H2O,81.1; ZnS04, 169; FeC6HsO4. 14H2O, 706.3; (NH4)6MO7o24-4H2o' 22.7; (in g/kg): K2HPO4, 10; KHCO3, to; NaHCO3, 8; NaCI, 5; CaCO3, 12.5; CaHP04, 10. ° Composition (in molly): thiamine-HCI, 25; riboflavin, 16; Ca pantothenate, 20; pyridoxine-HCI, 6; biotin, 0.6; folio acid, 4; menadione, 5; vitamin B,2, 0.02; ascorbic acid, 250; niacin, 150; vitamin A, 10,000 IU; vitamin Do, 600 IU; cr~tocopherol acetate, 10 IU. TABLE 3 Examples of Adequate Diets for Commercial Production Kind of Animal Ingredients % of Total Diets Growth, 0.5 to4 kg Alfalfa hay 50 Corn, grain 23.5 Barley, grain 11 Wheat bran 5 Soybean meal 10 Salt 0.5 Maintenance, does and Clover hay bucks, avg. 4.5 kg Oats, grain Salt 70 29.5 0.5 Pregnant does, Alfalfa hay 50 avg. 4.5 kg Oats, grain 45.5 Soybean meal 4 Salt 0.5 Lactating does, Alfalfa hay 40 avg.4.5 kg Wheat, grain 25 Sorghum, grain 22.5 Soybean meal 12 Salt 0.5 ' Composition given on an as-fed basis.