Genotypic effects on norepinephrine-induced changes in thermogenesis, metabolic hormones, and metabolites in newborn calves.

摘要: Heat production was measured in newborn Angus-, Brahman-, and Tuli-sired calves born to Angus (n = 20) Brahman 26) dams, before (thermoneutral metabolic rate, TMR) after norepinephrine (NE) infusion (peak PMR), assess genotypic effects on nonshivering thermogenesis brown adipose tissue. Calves were fed pooled colostrum, fitted with jugular catheters, placed a temperature-controlled (37 degrees C) water immersion system. production, determined by indirect calorimetry, tympanic temperature continuously from approximately 3 6 h of age. Blood samples collected at birth 0, 5, 20, 40, 60, 80, 100, 120 min relative NE (35 micrograms.min-1.kg BW-1 for 4 min), plasma analyzed metabolites (glucose, NEFA, urea nitrogen [PUN]) hormones (cortisol, triiodothyronine [T3] thyroxine [T4]). Weight-specific TMR (cal.min-1.kg-1) not affected breed sire or dam, although weight-specific PMR lower (P .25) Angus-sired (4.1%). The PMR:TMR ratio 1.80 2.21 +/- .06 respectively. Peak .6 degree C < .01) rather than dams. At birth, NEFA concentrations higher .001) glucose tended .13) be Cortisol, T3, T4 dams those These results suggest that may have less thermogenically active tissue which contribute the cold intolerance Bos indicus inheritance.