PHYSIOLOGICAL RESPONSES OF NEWBORN BOS lndlcus AND BOS lnd/cus x BOS TAURUS CALVES AFTER EXPOSURE TO COLD'J

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1 PHYSIOLOGICAL RESPONSES OF NEWBORN BOS lndlcus AND BOS lnd/cus x BOS TAURUS CALVES AFTER EXPOSURE TO COLD'J R. W. G&ey3, S. D. Smith, M. J. Guthrie, R. L. Stanko4, D. A. Neuendorff and R. D. Randel Texas A&M University Agricultural Research and Extension Center, Overton ABSTRACT Brahman (n = 9) and 1/2 Simmental x 1/4 Brahman x 114 Hereford (n = 11) calves were utilized to determine the influence of exposure to cold on the physiology of the neonate. All calves were removed from their dams within 20 min of birth and prior to suckling. Calves were assigned randomly within breed to either a warm (W, 31'C) or cold (C; 4 C) environmental treatment group. Jugular blood samples were collected via indwelling catheters at 20-min intervals for 180 min. At 100 to 120 min of sampling, all calves were given 1.2 liters of colostrum from their dams via stomach tube. At 120 min, C calves were placed in the W environment. Calf vigor score (CVS) and rectal temperature were determined at each time blood was collected. Serum or plasma was analyzed for glucose (GLU), lactate (LAC), blood urea nitrogen (BUN), hemoglobin 0, triglyceride WG), triiodothyronine q3), thyroxine (T& insulin (INS), cortisol (CORT) and nonesterified fatty acid (NEFA) concentration. Rectal temperature was lower (P <.Ol) in C Brahman than in W Brahman and C or W crossbred calves. Crossbred calves had higher (P <.01) CVS than Brahman calves. Calves in W had lower (P <.01) GLU than C calves. Brahman calves had higher GLU, LAC, BUN, TRG, T3, T4 and CORT (P <.05) than crossbred calves. The C Brahman calves had the highest (P <.05) TRG, CORT, T3 and T4 of all groups. Concentration of NEFA were higher (P <.Ol) in C than in W calves. Concentrations of INS and HEM were not different (P >.lo) among breed or temperature. These data indicate that cold-stressed neonatal Brahman calves did not utilize the energycontaining constituents of blood (GLU, LAC, TRG, protein, NEFA) to regulate body temperature as well as crossbred calves stressed by cold. This dysfunction does not appear to be related to insulin but it may be related to or caused by the metabolic hormones cortisol, T3 and T4. Key Words: Neonates, Environment, Bus indicus, Cattle, Hypothermia 'Journal Paper TA 25276, Texas Agric. Exp. Sta. %his study was a contribution to the West. Reg. Res. Proj. W-112, Reproductive Performance in Domestic Ruminants. The authors thank V. Stidham for assistance in manuscript preparation. 'Present address: Center for Reproduction of Endangered Wildlife, Cincionati Zoo and Botanical Garden, Cincinnati, OH Present address: Dept. of Anim. Sci., North Carolina State Univ., Raleigh Received Pebruary 5, Accepted June 7, J. Anim. Sci : Introduction One measure of reproductive efficiency in a beef cattle operation is the number of live calves produced. Many factors can influence the number of calves produced. A major influence on the calf crop is loss during the perinatal period (Bellows et al., 1979). Approximately 8 to 25% of all beef calves born do not survive longer than 5 d (Bull et al., 1978, 1980). One cause of calf death during the 1st wk of life is environmental stress. Beef

2 COLD STRESS IN NEWBORN CALVES 259 cattle management systems often dictate that calving occur at a time of the year when cold, fluctuating temperatures and increased precipitation are prevalent. Exposure to cold, wet weather has been implicated in augmenting the problems observed in Weak Calf Syndrome (WCS) by several researchers (Bull et al., 1978; Olson et al., 1980; Kvasnicka, 1982). In Bos indicus (Brahman) cattle in the southern U.S., symptoms of WCS are amplified in calves born during the cooler times of the year. Presumably, the causes and symptoms of WCS and cold-stressed calves overlap. Brahman calves may be more sensitive to cold stress-induced WCS because Brahman cattle are a tropical breed of cattle and are not as well adapted to colder climates as Bos tuurus cattle (Godfrey et al., 1990a,b). The objective of this study was to determine the effects of cold stress on the physiology of newborn Bos indicus vs Bos indicus x Bos tuurus calves. Materials and Methods Nine newborn Brahman calves and 11 newborn 1/2 Simmental x 1/4 Brahman x 1/4 Hereford calves were utilized. All calves were born during September (average daily temperature of 15 C). Dams of the calves were maintained on Coastal bermudagrass pasture and had body condition scores of six or greater (1 = thin, 10 = fat; Godfrey et al., 1988) through parturition. About 72 to 48 h before calving, the dams were placed in a pen for observation and given ad libitum access to Coastal bermudagrass hay. Visual observations were conducted every 2 h until the initiation of parturition and continuously thereafter until birth. All calves were removed from their dams within 20 min of birth and prior to suckling. Calves were transported.2 km by truck to a building where the experimental treatments were applied. Upon arrival at the building, each calf was weighed and fitted with an indwelling jugular catheter using aseptic procedures. Calves were assigned to one of two treatments based on sex and breed (Table 1). The treatments consisted of placing the calf in 'sigma chemical CO., st. ~ouis, MO. %aco Pure Chemical Industries, Ltd., Osaka, Japan. TABLE 1. DISTRIBUTION OF NEWBORN BRAHMAN AND CROSSBRED CALVES AMONG TREATMENT GROUPS Brahman Crossbred Bulls Heifers Bulls Heifers Colda 3' warmb *Each calf was exposed to a 4T environment for 120 min followed by 60 min in a 31'C environment. beach calf was exposed to a 31'C environment for 180 min. cnumber of calves. a cold (C; 4 C) or warm (W; 31 C) environment for 120 min after catheterization. Blood samples (20 ml) were collected at 20-min intervals for 180 min, with 0 min being the time when the calf went into the respective environmental treatment. Blood volume was replaced with 20 ml of sterile saline (38'C) after each sample was taken. Between 100 and 120 min of treatment, each calf was given 1.2 liters of colostrum from its dam via stomach tube. After 120 min, C calves were placed in W environment for the remaining 60 min of sampling. At the time each blood sample was taken, rectal temperature and calf vigor score were recorded (Table 2). All calves were tattooed and ear-tagged after the last blood sampling and returned to their dam within 30 min. The dam and calf were observed during the subsequent 24-h period to ensure that the calf was accepted by the dam and allowed to nurse. Blood samples were split immediately after collection into two portions. Ten milliliters of blood were allowed to clot at 4 C for 12 h prior to obtaining serum by centrifugation. The remaining 10 ml were placed in a 16-mm x 125-mm tube containing a heparin (1,OOO USP units) and sodium fluoride (1 mg) mixture; plasma was obtained within 45 min Vigor score TABLE 2. DESCRIPTION OF CALF VIGOR SCORES Description Calf is motionless and not attempting to stand Calf is trying weakly to stand Calf is hying vigorously to stand Calf is standine and amears alert

3 260 GODPREY ET AL. by centrifugation. Serum and plasma samples were stored at -2o'C until analysis. Spectrophotometric techniques were utilized to determine metabolite concentrations in plasma samples. Plasma glucose (Kit 635)5, lactate (Kit 726-UV/826-uv)5, triglyceride (Kit 336)5, blood urea nitro en (BUN; Kit 535)5, hemoglobin (Kit 525) s and nonesterified fatty acid (NEFA; Kit )6 concentrations were determined using the protocols and reagents supplied with each kit, after validation in our laboratory for bovine plasma. Serum insulin concentration was determined by a double-antibody RIA (Chung et al., 1985) as modified in our laboratory (Harrison and Randel, 1986). Samples were assayed at a volume of 100 pl in a single assay. purified bovine insulin (615-70N-80)7 containing 26.6 U/mg was used for iodination and as the reference standard. Guinea pig anti-bovine insulin* was used as the lint antibody and goat anti-guinea pig IgG serum9 was used as the second antibody. Sensitivity of the assay was 1.25 pu/tube, and the intra-assay CV was 13.9%. Serum cortisol (Kit 031)'O. triiodothyronine (T3; Kit 008)'O and thyroxine (T4; Kit O07)10 concentrations also were determined by RIA. Assay procedures and reagents were supplied with each kit, and validation of each assay was conducted in our laboratory for bovine serum. Plasma metabolite concentrations, serum metabolic hormone concentrations, rectal temperature and calf vigor score were analyzed as a 2 x 2 factorial using the GLM procedure for ANOVA specific for repeated measures (SAS, 1985). Breed and environmental temperature were used as the main effects. The effect of sex of calf was not included in the analysis due to the low numbers of each sex within each breed and temperature treatment group. b X CQ IC--- 11Y=?Y919YtYW rib - vl +I ti ti u +I ti +I +I ti +I +I u Results Rectal temperature was lower (P <.01) in C Brahman calves than in W Brahman and C or W crossbred calves (Table 3). Even after removal from the C environment and place- 7Lilly Research Laboratory, Greenfield, IN. *Mes ~aboratory, hc., E- IN. 9Antiibodies Inc., Davis, CA. '%antex, Santa Monica, CA.

4 - &Id Brahman (SE i_ Warm Brahman ISE i 2) - Warm Crossbred (SE =.21 Ccld Crossbred ise= 2) I I I I I I r I SO Time (min) Figure 1. Rectal temperature of newborn Brahman and crossbred calves after being in a cold (4T) or warm (31'C) environment for 120 & All cold calves were placed in the warm environment at 120 min. The bar indicates the time that 1.2 liters of colostrum were given to each calf. ment into the W environment, rectal temperature of C Brahman calves remained low (Figure 1). No difference (P >.lo) was noted in rectal temperature among W Brahman and W and C crossbred calves during the 180-min sampling period. Crossbred calves had higher (P <.01) calf vigor scores than did Brahman calves during the sampling period (Table 3). No effect (P >.lo) of temperature on calf vigor score was found. Calves in C had higher (P <.01) glucose concentrations than did W calves; Brahman calves had higher (P <.01) glucose concentrations than did crossbred calves (Table 3). Brahman calves had higher (P <.01) lactate and BUN concentrations than did crossbred calves (Table 3). Cold Brahman calves had higher (P <.01) triglyceride concentrations than W Brahman and C or W crossbred calves (Table 3). Concentration of NEFA was higher (P <.01) in C than in W calves (Table 3). Cold Brahman calves had higher cortisol (P <.01), T3 (P <.01) and T4 (P <.05) than did W Brahman and C and W crossbred calves (Table 3). Insulin and hemoglobin concentrations were not different (P >.lo) between breeds or environmental temperatures. Dlscusslon The rectal temperature (RT) of Brahman calves placed in the cold (4'C) environment for 2 h remained low even after the animals were placed in the warm (31'C) environment. This is in contrast to the results of Olson et al. COLD STRESS IN NEWBORN CALVES 261 (1983a), who found that rectal temperatures began increasing immediately in calves placed under heat lamps after they were removed from a cold water bath (16.6'C) that had lowered their core body temperature by 10 C. Possible explanations for this discrepancy may be that Olson et al. (1983a) utilized Holstein calves, warming methods were different and the magnitude of decrease in body temperature prior to warming was much less in the present study. Because Olson et al. (1983a) decreased core body temperature by 10 C and cold Brahman calves in the current study had a decrease in RT of less than 2"C, the calves of Olson et al. (1983a) may have exhibited a greater compensatory increase in body temperature after removal from the cold. Newborn Brahman calves may not be able to recover as rapidly from cold stress as crossbred calves, even after being exposed to a supplemental heat source. Even by 180 min of the treatment period, the RT of cold Brahman calves had not returned to normal. The vigor of the calf during chilling may have played a part in the ability of the crossbred calves to maintain body temperature. The fact that the crossbred calves were more active during the exposure to cold may explain partially how they prevented a drop in RT. The increase in plasma glucose concentration in the Brahman and crossbred calves after exposure to the cold agrees with previous reports dealing with neonatal ruminants (Alexander and Mills, 1968; Alexander et al., 1968, 1972; Olson et al., 1983b). In all these reports, a decrease in body temperature was accompanied by an increase in blood glucose concentration. In the present study, only the Brahman calves exhibited this inverse relationship between body temperature and glucose concentration. Because the crossbred calves had high vigor scores during exposure to cold, perhaps their level of physical activity played a role in their ability to maintain normal body temperature. This could explain why the cold crossbred calves did not exhibit the inverse relationship between body temperature and blood glucose concentration. Shivering was not monitored in the present study, but Alexander and Williams (1968) reported that shivering is an important means of thermogenesis in newborn lambs as well as in cattle and swine. This would indicate that newborn calves are able to generate heat for maintenance of body temperature with muscular activity. Non-

5 262 GODFREY ET AL. shivering thermogenesis occurs in newborn lambs by metabolism of brown fat (Curtis, 1981), but newborn calves may not possess brown fat. Presumably shivering is the major form of supplemental heat production in neonatal calves exposed to cold (Curtis, 1981). The triglyceride concentrations in cold Brahman calves were elevated compared with the other treatments. This fact, along with the elevated concentrations of glucose, indicates that Brahman calves may not be able to utilize the energy constituents of blood to maintain body temperature. The metabolic hormones T3, T4 and cortisol may play roles in thermogenesis in the newborn calf. The role of insulin appears to be minor, because insulin concentration did not differ among the treatments. However, the cold Brahman calves exhibited a slower postprandial rise (after 120 min) in insulin concentration than the other calves did. This suggests that pancreatic function of these calves was compromised by the cold environment. The insulin concentration of the cold Brahman calves was similar to that of the other calves by 180 min. indicating that the inhibition of pancreatic function was not permanent and could be reversed by warming the calf. Presumably the cold environment was perceived as a stress by the Brahman calves, so they responded with increased cortisol concentration. The elevated thyroid hormone and cortisol concentrations in the cold Brahman calves indicates that they were attempting to increase their metabolic rate. Apparently, this was not adequate because body temperature did not increase in the cold Brahman calves. Newborn lambs are able to raise their metabolic rate to a maximal level within 30 rnin of birth (Curtis, 1981). This may be true in newborn calves as well, if elevated thyroid hormone concentrations are indicative of metabolic rate in the Brahman calves exposed to the cold in the present study. Stallcup et al. (1984) reported T3 concentrations for newborn calves that were similar to those in the newborn calves in the present study. However, concentrations of T4 in newborn calves reported by Stallcup et al. (1984) was approximately 10 times lower than the concentration reported in the current study; Hernandez et al. (1972) reported T4 concentrations that were similar to those in the present study. We do not how why the T3 concentrations were similar when the T4 concentrations were so different between the present study and that of Stallcup et al. (1984). Hernandez et al. (1972) showed that T4 concentration increases in the fetus until the time of parturition. We speculated that the elevated T4 at birth saturated the thyroxine-binding globulin and allowed more free T4 for regulation of metabolism. Curtis (1981) stated that mammals increase their rate of heat production greatly at birth; that implies that metabolism increases. The inability of newborn Brahman calves to maintain body temperature in cold weather may be related to factors other than metabolic rate and thennogenesis. The surface area to mass ratio in young calves is high. Therefore, the calf has a large interface with the environment in relation to its mass, making homeothermy more difficult to achieve (Curtis, 1981; Schmidt-Nielsen, 1984). As the calf grows, this ratio decreases, making homeothermy easier to maintain. Brahman calves, with loose, folded skin characteristic of the breed, may be at a disadvantage compared with the tighter-skinned Bos fuurus calves. The hair coat of crossbred calves in the present study appeared thicker than that of the Brahman calves and also may have played a role in insulating the calf. This role should have been minor because all calves were wet at the time of treatment initiation. The traits of Brahman cattle that aid their adaptability to warm, humid environments (i.e., loose, folded skin) may be a detriment to Brahman calves born in a cold, humid environment. implications Newborn Brahman calves did not adapt to a cold environment as well as Bos tuurus x Bos indicus calves. Thermoregulation of Brahman calves was impaired, and they did not seem to utilize the energy-containing constituents of blood. The problem of weak calves is of interest to many producers, especially producers in the northern areas of the U.S. who are interested in utilizing Bos indicus cattle. If calf survival is low during the cooler times of the calving season in the north and south, management procedures may have to be adapted to provide extra postnatal care for Brahman calves. This fact, in conjunction with previous research that shows Brahman cattle are more susceptible to environmental extremes, may influence management decisions regarding utilization of Brahman cattle in colder climates.

6 COLD STRESS IN NEWBORN CALVES 263 Literature Cited Alexander,G.,A. W. Bel1andJ.R.S. Hales Theeffect of cold exposure on the plasma levels of glucose, lactate, free fatty acids and glycerol and on the blood gas and acid-base status in young lambs. Biol. Neonate 20:9. Alexander, G. and S. C. Mills Free fatty acids and glucose in the plasma of newly born lambx Effects of environmental temperature. Biol. Neonate 13:53. Alexander, G., S. C. Mills and T. W. Scott Changes in plasma glucose, lactate and free fatty acids in lambs during summit metabolism and treatment with cats cholamines. J. Physiol. 198:277. Alexander, G. and D. Williams Shivering and nonshivering themgenesis during summit metabolism in young lambs. J. Physiol. 198:251. Bellows, R. A., R. E. Short and R. B. Staigmiller Research areas in beef cattle reproduction. In: H. Hawk (Ed.) Beltsville Symp. Agric. Res. 3, Animal Reproduction. pp Allanheld, Osum and Co. Publishers, New York. Bull, R. C., D. P. Olson, M. J. Stoszek and R. M. ROSS Maternal protein restriction and cold stress during rearing on blood composition and pathologic lesions in neonatal calves. Roc. West. Sec. Am. Soc. Anim. Sci. 29:339. Bull, R C.. R. G. Sasser, D. P. Olson, R. J. Williams and C. A. Ruder Calf death losses and reproductive failure as a result of maternal protein deficiency. p California Vet. Med. Assoc., 92nd Annu. Sci. Sem. Chung. C. S., T. D. Etherton and J. P. Wiggin Stimulation of swine growth by porcine growth hormone. J. Anim. Sci. 60:118. Curtis, S. E Neonatal adaptation to thermal environment. In: Environmental Management in Animal Agriculture. pp Animal Environment Services, Mahomet, IL. Godfrey, R. W., D. D. Lunstra, T. G. Jenkins, J. G. Berardinelli, D. A. Neuendorff, C. R Long and R. D. Randel. 19%. Effect of location and season on body and testicular growth in Brahman and Hereford bulls. I. Anim. Sci. 68:1520. Godfrey, R W., D. D. Lunstra, T. G. Jenkins, J. G. Berardinelli, M. J. Guthrie, D. A. Neuendorff, C. R. Long and R. D. Randel. 1990b. Effect of season and location upon semen quality and serum concentrations of luteinizing hormone and testosterone in Brahman and Hereford bulls. J. Anim. Sci. 68:734. Godfrey, R. W., F. M. Rouquette, Jr. and R. D. Randel Influence of cow weight change on cow reproductive performance and calf performance. J. Prod. Ag~ic. 1: 221. Harrison, L. M. and R. D. Randel Influence of insulin and energy intake on ovulation rate, luteinizing hormone and progesterone in beef heifers. J. Anim. Sci. 63:1228. Hernandez, M. V.,K. M.Etta, E. P. Reineke, W. D. Oxender and H. D. Hafs Thyroid function in the prenatal and neonatal bovine. J. Anim. Sci. W780. Kvasnicka, W. G Cooperative project on the weak calf syndrome. Beef Res. Prog. Rep. No. 1. pp R. L. Hruska US. Meat Anim. Res. Center ARM-NC- 21. Olson, D. P., C. J. Papasion and R. C. Ritter The effects of cold stress on neonatal calves. I. Clinical conditions and pathological lesions. Can. J. Comp. Med. M12. Olson, D. P.,P. J. South and K. Hendrix. 1983a. Regional differences in body temperature in hypothermic and rewarmed young calves. Am. J. Vet. Res. 44:564. Olson, D. P., P. J. South and K. Hendrix. 1983b. Serum chemical values in hypothermic and rewarmed young calves. Am. J. Vet. Res. M577. SAS SAS User's Guide: Statistics. SAS Inst., Inc., Gary, NC. Schmidt-Nielsen, K Body temperature and temperahue regulation. In: Scalmg: Why is Animal Size Important? pp Cambridge University Press, New York. Stallcup, 0. T., D. L. bider, V. M. Weiker and J. M. Rakes Anatomical and functional development of the bovine fetal thyroid. pp loth Int. Congr. on Anim. Reprod. and Artif. Insem. Univ. of Illinois at Urbana-Champaign.