8
Implications of Stress

Stress in regard to beef cattle is defined as a nonspecific response of the body to any demand from the environment (Frazer et al., 1975; Selye, 1976). Stress can alter the steady state of the body and challenge physiological adaptive processes. Nutrition and stress are interactive and consequential in that stress can produce or aggravate nutritional deficiencies and nutritional deficiencies can produce a stress response. The major stresses observed in beef cattle are feed and water deprivation in the market system or during drought, weaning, crowding, and exposure to disease. Other stresses encountered by cattle are weather changes and castration, dehorning, vaccination, dipping, deworming, and other processing procedures. All these stresses can influence nutrient requirements of beef cattle; and because nutrition and stress interrelate as continuous processes, they should be considered as such. Management of stress in cattle has two major components: (1) management of the cause of stress and (2) management of the effects of stress—the quantified changes seen in animals.

One of the first stresses the animal encounters is weaning, a physical stress that is impossible to eliminate; however, preweaning and preconditioning management techniques have been used to decrease weaning stress (Cole, 1982). Though effective, these techniques often cannot be implemented because of cost and/or lack of adequate facilities.

During the marketing process, when the animal is deprived of feed and water, ruminal fermentation processes and capacity are significantly decreased and remain depressed for a few days after refeeding (Cole and Hutcheson, 1985a). Other changes include increased ruminal pH, serum osmolality, glucose, and urea nitrogen; however, once deprivation ceases, these variables return to predeprivation levels within 24 hours (Cole and Hutcheson, 1985b, 1987a). The number of ruminal protozoa and bacteria is lower in steers subjected to fasting and transit stress than in control animals (Galyean et al., 1980; Cole and Hutcheson, 1981), and the number increases more slowly when fasting occurs in conjunction with transit than when fasting is the only stressor. Baldwin (1967) suggests that the number of ruminal protozoa and bacteria decreases sharply following stress such as transportation. These ruminal changes tend to decrease appetite, thereby leading to decreased feed intake.

Feed intake decreases by more than 50 percent in cattle with respiratory disease and fever (Chirase et al., 1991). After the onset of bovine respiratory disease complex (BRDC), it takes as long as 10 to 14 days before feed intake returns to normal; consequently, nutrient demands for maintenance and growth are difficult to meet during periods of disease stress. The findings of a 7-year study of healthy and diseased calves newly arrived at feedlots (Hutcheson and Cole, 1986) are shown in Table 8–1.

ENERGY

Energy deficiency in cattle can severely depress the immune system (Nockles, 1988); however, excess dietary energy can also have detrimental effects. Calves newly arrived at a feedlot and fed a high-energy diet (75 percent concentrate) experienced increased performance, but inci-

TABLE 8–1 Dry Matter Feed Intake of Newly Arrived Calves (% of body weight)

Age, days

Healthy (SD)

Diseased (SD)

0–7

1.55 (0.51)

0.90 (0.75)

0–14

1.90 (0.50)

1.43 (0.70)

0–28

2.71 (0.50)

1.84 (0.66)

0–56

3.03 (0.43)

2.68 (0.68)

NOTE: SD, standard deviation.

SOURCE: Hutcheson, D.P., and N.A.Cole. 1986. Management of transit-stress syndrome in cattle: Nutritional and environmental effects. J. Anim. Sci. 62:555–560.



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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 8 Implications of Stress Stress in regard to beef cattle is defined as a nonspecific response of the body to any demand from the environment (Frazer et al., 1975; Selye, 1976). Stress can alter the steady state of the body and challenge physiological adaptive processes. Nutrition and stress are interactive and consequential in that stress can produce or aggravate nutritional deficiencies and nutritional deficiencies can produce a stress response. The major stresses observed in beef cattle are feed and water deprivation in the market system or during drought, weaning, crowding, and exposure to disease. Other stresses encountered by cattle are weather changes and castration, dehorning, vaccination, dipping, deworming, and other processing procedures. All these stresses can influence nutrient requirements of beef cattle; and because nutrition and stress interrelate as continuous processes, they should be considered as such. Management of stress in cattle has two major components: (1) management of the cause of stress and (2) management of the effects of stress—the quantified changes seen in animals. One of the first stresses the animal encounters is weaning, a physical stress that is impossible to eliminate; however, preweaning and preconditioning management techniques have been used to decrease weaning stress (Cole, 1982). Though effective, these techniques often cannot be implemented because of cost and/or lack of adequate facilities. During the marketing process, when the animal is deprived of feed and water, ruminal fermentation processes and capacity are significantly decreased and remain depressed for a few days after refeeding (Cole and Hutcheson, 1985a). Other changes include increased ruminal pH, serum osmolality, glucose, and urea nitrogen; however, once deprivation ceases, these variables return to predeprivation levels within 24 hours (Cole and Hutcheson, 1985b, 1987a). The number of ruminal protozoa and bacteria is lower in steers subjected to fasting and transit stress than in control animals (Galyean et al., 1980; Cole and Hutcheson, 1981), and the number increases more slowly when fasting occurs in conjunction with transit than when fasting is the only stressor. Baldwin (1967) suggests that the number of ruminal protozoa and bacteria decreases sharply following stress such as transportation. These ruminal changes tend to decrease appetite, thereby leading to decreased feed intake. Feed intake decreases by more than 50 percent in cattle with respiratory disease and fever (Chirase et al., 1991). After the onset of bovine respiratory disease complex (BRDC), it takes as long as 10 to 14 days before feed intake returns to normal; consequently, nutrient demands for maintenance and growth are difficult to meet during periods of disease stress. The findings of a 7-year study of healthy and diseased calves newly arrived at feedlots (Hutcheson and Cole, 1986) are shown in Table 8–1. ENERGY Energy deficiency in cattle can severely depress the immune system (Nockles, 1988); however, excess dietary energy can also have detrimental effects. Calves newly arrived at a feedlot and fed a high-energy diet (75 percent concentrate) experienced increased performance, but inci- TABLE 8–1 Dry Matter Feed Intake of Newly Arrived Calves (% of body weight) Age, days Healthy (SD) Diseased (SD) 0–7 1.55 (0.51) 0.90 (0.75) 0–14 1.90 (0.50) 1.43 (0.70) 0–28 2.71 (0.50) 1.84 (0.66) 0–56 3.03 (0.43) 2.68 (0.68) NOTE: SD, standard deviation. SOURCE: Hutcheson, D.P., and N.A.Cole. 1986. Management of transit-stress syndrome in cattle: Nutritional and environmental effects. J. Anim. Sci. 62:555–560.

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 dence of disease was 57 percent compared with 47 percent when a 25 percent concentrate diet was used (Preston and Kunkle, 1974; Preston and Smith, 1974). Supplementing high-energy diets with hay for 3 to 7 days can overcome the adverse health effects of the high-energy diet (Lofgreen et al., 1981; Lofgreen, 1983, 1988). The source of grain type—corn, grain sorghum, barley or wheat—used in starter and receiving diets did not affect calf health or performance (Smith et al., 1988). Grain type used in receiving diets did not affect calf health or performance. In fact, a better rate of gain was obtained with a mixture of grains (Brethour and Duitsman, 1972; Addis et al., 1975, 1978); however, highly stressed calves seem to have low tolerance for added fat, thus fat should probably not exceed 4 percent of dietary dry matter in receiving diets (Cole and Hutcheson, 1987b). Stressed calves prefer a dry diet compared to a diet high in corn silage, but they adapt to high amounts of corn silage in the diet after 7 to 14 days (Preston and Smith, 1973, 1974; Preston and Kunkle, 1974; Koers et al., 1975; Davis and Caley, 1977). PROTEIN Protein requirements of stressed calves do not seem to be different than those of nonstressed calves. Stressed calves, however, generally decrease their feed intake; therefore the concentration of protein in the diet should be increased for stressed or diseased calves (Cole and Hutcheson, 1990; Hutcheson et al., 1993). Protein concentrations of 13.5 to 14.5 percent on a dry matter basis in receiving diets meet the protein requirements of stressed calves (Embry, 1977; Bartle et al., 1988; Cole and Hutcheson, 1988; Eck et al., 1988; Cole and Hutcheson, 1990). Diseased calves exhibit a hypermetabolic response with increased excretion of nitrogen (Cole et al., 1986). The nitrogen kinetics of virus-infected calves are affected by shifts in the rates of protein metabolism (Orr et al., 1989). Figure 8–1 represents the differences in nitrogen (N) rate constants for infectious bovine rhinotracheitis virus calves. When fed increased protein, hyperurinary excretion of nitrogen during disease is partially alleviated (Boyles et al., 1989). Stressed calves have a lower tolerance for nonprotein nitrogen (urea) than do nonstressed calves. Urea intakes of 30 gm/day or less seem to be tolerated by newly arrived or stressed calves during the first 2 weeks of feeding (Preston and Kunkle, 1974; Gates and Embry, 1975; Cole et al., 1984). Feeding undigestible intake protein (UIP) to stressed calves resulted in increased performance (Preston and Kunkle, 1974; Preston and Smith, 1974; Grigsby, 1981; Phillips, 1984). UIP as 5.4 percent of dietary dry matter, FIGURE 8–1 Changes in nitrogen (N) rate constants for calves with infectious bovine rhinotracheitis virus (IBRV). Infected calves fed an increased amount of protein experienced partial alleviation of hyperurinary excretion of nitrogen (Boyles et al., 1989). at 45 percent of total protein, resulted in increased daily gains and dry matter intake (Preston and Bartle, 1990; Gunter et al., 1993; Hutcheson et al., 1993; Fluharty and Loerch, 1995). MINERALS Research indicates that, in general, mineral requirements for stressed cattle are not different than those for nonstressed cattle (Orr et al., 1990); however, decreased feed intake of stressed cattle suggests that higher concentrations of minerals should be formulated into their diets (Hutcheson, 1987, 1990). Cattle subjected to the stresses of marketing and shipping lose weight—primarily from loss of water from the digestive tract and, subsequently, from body cells. When intracellular water is lost, cellular deficiencies of potassium (K) and sodium (Na) can occur (Hutcheson, 1980). The potassium requirement of stressed calves is 20 percent more than that of nonstressed calves (Hutcheson et al., 1984). Data suggest that 1.2 to 1.4 percent potassium in the diet for 2 weeks is the optimum concentration for newly arrived, stressed calves. Additional potassium may not increase gain response if cattle shrink 2 to 4 percent; but with shrinkage of 7 or more percent, a significant effect may be observed with added potassium. Increasing dietary potassium allows the electrolyte and water balance to return to normal. When potassium is added as potassium chloride (KCl), however, care should be taken to limit salt (NaCl) to 0.25 percent of dietary dry matter so as not to increase chloride intake.

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Nutrient Requirements of Beef Cattle: Seventh Revised Edition, 1996 Many factors affect immune system response (Nockels, 1988; Hutcheson, 1990). On the other hand, during disease states trace mineral requirements may be affected by immune system response (Hutcheson, 1990). High concentrations of zinc have been shown to be beneficial to the animal’s health during disease (Chirase et al., 1991), and zinc (Zn), copper (Cu), selenium (Se), and iron (Fe) seem to be necessary for immunocompetence (Chandra and Dayton, 1982; Brandt and Hutcheson, 1987; Drobe and Loerch, 1989; Erskine et al., 1989, 1990). VITAMINS Adding B vitamins to receiving rations for stressed calves increased their performance and feed intake in one (Overfield et al., 1976) but not all (Cole et al., 1979, 1982) experiments. Niacin added at 125 ppm seemed to increase average daily gain by healthy calves (Hutcheson and Cummins, 1984); however, diseased calves receiving niacin at 250 ppm seemed to have the best average daily gain. The most significant gains were observed when the cattle received 271 mg/cwt/day (Hutcheson and Cummins, 1984). Vitamin E has been shown to be involved in immune system response; lymphocyte-stimulation indices were highest for calves fed 227.5 mg (250 IU) all-rac-a-tocopherol compared to controls (Cipriano et al., 1982). Increasing vitamin E intake during disease or infection produced varying results, but in general the data indicate that vitamin E is necessary for optimal functioning of the immune system. Vitamin E fed at 400 IU/day in receiving and starting diets of newly arrived feeder calves decreased disease and number of sick days and increased gain (Hicks, 1985). TABLE 8–2 Suggested Nutrient Concentrations for Stressed Calves (dry matter basis) Nutrient Unit Suggested Range Unit/day Daily Nutrient Intake for 250-kg Calfa 0–7 days 0–14 days Dry matter % 80.0–85.0 kg 3.88 4.75 Crude protein % 12.5–14.5 kg 0.48–0.56 0.59–0.69 Net energy of maintenance Mcal/kg 1.3–1.6 Mcal 4.84 4.84 Net energy of gain Mcal/kg 0.8–0.9 Mcal 0.01–0.8 0.6–1.6 Calcium % 0.6–0.8 g 23.0–31.0 29.0–38.0 Phosphorus % 0.4–0.5 g 16.0–19.0 19.0–24.0 Potassium % 1.2–1.4 g 47.0–54.0 57.0–67.0 Magnesium % 0.2–0.3 g 8.0–12.0 10.0–14.0 Sodium % 0.2–0.3 g 8.0–12.0 10.0–14.0 Copper mg/kg 10.0–15.0 mg 39–58 47–71 Iron mg/kg 100.0–200.0 mg 388–775 475–950 Manganese mg/kg 40.0–70.0 mg 155–271 190–332 Zinc mg/kg 75.0–100.0 mg 290–387 356–475 Cobalt mg/kg 0.1–0.2 mg 0.4–0.8 0.5–1.0 Selenium mg/kg 0.1–0.2 mg 0.4–0.8 0.5–1.0 Iodine mg/kg 0.3–0.6 mg 1.2–2.3 1.4–2.9 Vitamin A IU/kg 4,000.0–6,000.0 IU 15,500.0–23,250.0 19,000.0–28,500.0 Vitamin E IU/kg 75–100 IU 291–388 356–475 aIntake levels are based on 1.55% for days 0 through 7 and 1.90% for days 0 through 14 from Table 8–1. Vitamin E fed at 450 IU/day to cattle that experienced more than 10 percent shrink increased gain (Lee et al., 1985). Vitamin E should be fed between 400 and 500 IU per head per day during the receiving and starting period. Calves receiving 125 mg/day (125 IU/day) of all-rac-a-tocopherol acetate consumed more than calves that did not receive additional vitamin E or 500 mg/day (500 IU/day) (Reddy et al., 1985). Table 8–2 gives the suggested nutrient concentrations for receiving diets of stressed cattle. Many of the nutrients are based on the subcommittee’s calculations; some are based on published data (Hutcheson, 1990). Decreased intake during disease stress is the single most common observation. Nutrient amounts recommended in Table 8–2 are for the first 2 weeks after arrival or until the cattle are consuming feed, on a dry matter basis, of 2 percent of body weight or more. Table 8–2 also gives nutrient amounts that would be consumed per day when suggested amounts are calculated: 1.55 percent of body weight, the average amount of feed consumed during the first week; and 1.90 percent of body weight, the average amount of feed consumed during the first 2 weeks—that is, the average of the 2 weeks. REFERENCES Addis, D.G., G.P.Lofgreen, J.G.Clark, J.R.Dunbar, and C.Adams. 1975. Barley vs milo in receiving rations. Calif. Feeders Day Kept. 14:53. Addis, D.G., G.P.Lofgreen, J.G.Clark, C.Adams, F.Prigge, J.R.Dunbar, and B.Norman. 1978. Barley vs wheat in receiving rations for new calves. Calif. Feeders Day Rept. 17:54.

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