Carstens G E, Mostyn P M, Lammoglia M A, Vann R C, Apter R C, Randel R D
Department of Animal Science, Texas A&M University, College Station 77843-2471, USA.
J Anim Sci. 1997 Jul;75(7):1746-55. doi: 10.2527/1997.7571746x.
Heat production was measured in newborn Angus-, Brahman-, and Tuli-sired calves born to Angus (n = 20) and Brahman (n = 26) dams, before (thermoneutral metabolic rate, TMR) and after norepinephrine (NE) infusion (peak metabolic rate, PMR), to assess genotypic effects on nonshivering thermogenesis in brown adipose tissue. Calves were fed pooled colostrum, fitted with jugular catheters, and placed in a temperature-controlled (37 degrees C) water immersion system. Heat production, determined by indirect calorimetry, and tympanic temperature were measured continuously in calves from approximately 3 to 6 h of age. Blood samples were collected at birth and at 0, 5, 20, 40, 60, 80, 100, and 120 min relative to NE infusion (35 micrograms.min-1.kg BW-1 for 4 min), and plasma was analyzed for metabolites (glucose, NEFA, and urea nitrogen [PUN]) and hormones (cortisol, triiodothyronine [T3] and thyroxine [T4]). Weight-specific TMR (cal.min-1.kg-1) was not affected by breed of sire or dam, although weight-specific PMR (cal.min-1.kg-1) was lower (P < .01) in Brahman-sired calves than in Angus- or Tuli-sired calves and was lower (P < .001) in calves born to Brahman rather than Angus dams. The reduction in weight-specific PMR due to the maternal Brahman influence was sire-breed dependent, and the reduction was largest (P < .01) for Tuli-sired (34.3%), intermediate (P < .05) for Brahman-sired (15.1%), and lowest (P > .25) for Angus-sired calves (4.1%). The PMR:TMR ratio was 1.80 and 2.21 +/- .06 in calves born to Brahman and Angus dams, respectively. Peak tympanic temperature was .6 degree C lower (P < .01) in calves born to Brahman rather than Angus dams. At birth, plasma NEFA concentrations were higher (P < .001) and glucose tended (P = .13) to be higher in calves born to Brahman rather than Angus dams. Cortisol, T3, and T4 concentrations at birth were higher in calves born to Brahman dams than in those born to Angus dams. These results suggest that calves born to Brahman dams may have less thermogenically active brown adipose tissue than calves born to Angus dams, which may contribute to the relative cold intolerance of calves with Bos indicus inheritance.
对安格斯（n = 20）和婆罗门（n = 26）母牛所生的、具有安格斯、婆罗门和图利血统的新生犊牛，在去甲肾上腺素（NE）输注前（热中性代谢率，TMR）和输注后（峰值代谢率，PMR）测量产热，以评估基因型对棕色脂肪组织非寒战产热的影响。给犊牛喂以混合初乳，安装颈静脉导管，并置于温度控制在37摄氏度的水浸系统中。通过间接量热法测定产热，并在犊牛约3至6小时龄时连续测量鼓膜温度。在出生时以及相对于NE输注（35微克·分钟-1·千克体重-1，持续4分钟）的0、5、20、40、60、80、100和120分钟时采集血样，分析血浆中的代谢物（葡萄糖、非酯化脂肪酸[NEFA]和尿素氮[PUN]）和激素（皮质醇、三碘甲状腺原氨酸[T3]和甲状腺素[T4]）。体重特异性TMR（卡路里·分钟-1·千克-1）不受父本或母本品种的影响，尽管婆罗门血统犊牛的体重特异性PMR（卡路里·分钟-1·千克-1）低于安格斯或图利血统的犊牛（P <.01），且婆罗门母牛所生犊牛的体重特异性PMR低于安格斯母牛所生犊牛（P <.001）。由于母本婆罗门血统的影响导致的体重特异性PMR降低取决于父本品种，图利血统犊牛的降低幅度最大（P <.01）（34.3%），婆罗门血统犊牛的降低幅度居中（P <.05）（15.1%），安格斯血统犊牛的降低幅度最小（P >.25）（4.1%）。婆罗门和安格斯母牛所生犊牛的PMR:TMR比值分别为1.8 和2.21±.06。婆罗门母牛所生犊牛的鼓膜温度峰值比安格斯母牛所生犊牛低0.6摄氏度（P <.01）。出生时，婆罗门母牛所生犊牛的血浆NEFA浓度较高（P <.001），葡萄糖浓度有升高趋势（P = 0.13）。婆罗门母牛所生犊牛出生时的皮质醇、T 和T 浓度高于安格斯母牛所生犊牛。这些结果表明，婆罗门母牛所生犊牛的棕色脂肪组织产热活性可能低于安格斯母牛所生犊牛，这可能导致具有瘤牛遗传的犊牛相对不耐寒。
