Effects of exogenous glucose or colostrum on body temperature, plasma glucose, and serum insulin in cold-stressed, newborn Brahman calves

The effects of ambient temperature and source of exogenous energy (glucose or colostrum) on the ability of newborn Brahman calves to maintain rectal temperature (RT) were determined. All calves were removed from dams within 30 min of birth, before suckling. Calves were catherized and placed in either a warm (25 degrees C) or cold (50 degrees C) environment for 150 min and given either colostrum or glucose. This resulted in four groups (warm colostrum, n = 7; cold colostrum, n = 7; warm glucose, n = 6; cold glucose, n = 6). Blood samples and RT were obtained at 15-min intervals during warm or cold through 150 min, when calves were removed from cold, and at 180, 240, and 300 min. After 60 min, each calf was given either 1 L of colostrum (38 degrees C) from its dam or glucose (38 degrees C) infusion of 750 mg/kg BW. Plasma glucose concentrations were determined by enzymatic techniques and serum insulin concentrations by RIA. Calves exposed to cold or warm air temperatures had similar declines in rectal temperature from 0 to 60 min. Colostrum-fed, cold calves had a greater (P < .07) decrease in RT than did colostrum-fed, warm calves from 75 through 150 min; glucose-infused warm and cold calves had intermediate decreases in RT. Plasma glucose increased (P < .0001) in glucose-infused compared with colostrum-fed calves at 75 min, but glucose-infused calves had lower (P < .02) glucose levels from 180 to 300 min. Higher (P < .05) glucose concentrations were observed in colostrum-fed, cold than in colostrum-fed, warm calves from go though 135 min. Insulin differed (P < .05) between calves given colostrum and those given glucose with an environmental temperature X feeding interaction (P < .05). Colostrum-fed, cold calves were lowest in insulin until ending cold; glucose-infused, cold calves had the highest insulin response at 75 min and glucose-infused, warm calves at 135 min. Glucose-infused, warm calves had the greatest overall insulin response, but insulin in this group decreased to concentrations similar to those of calves given colostrum by 240 min. Yet, insulin- was lowest in glucose-infused, cold calves from the end of cold (150 min) through 300 min. Newborn Brahman calves experience a greater decrease in RT when chilled. Infusion of glucose, but not feeding colostrum, enabled the chilled calves to maintain RT at levels similar to those of both glucose-infused and colostrum-fed, warm calves.