小母牛衰老与营养控制生长速率对产热的关系。

Freetly H C, Nienaber J A, Brown-Brandl T M

USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.

J Anim Sci. 2003 Jul;81(7):1847-52. doi: 10.2527/2003.8171847x.

The first objective of this study was to test how well a function that was developed to describe heat production (HP) in growing ewes fit HP data in growing heifers. The second objective was to determine the pattern of adaptation of HP to feed restriction and subsequent realimentation of nutrients. At 234.5 +/- 0.5 d of age, HP was determined by indirect calorimetry on 32 Meat Animal Research Center III heifers. Following the first calorimetry measurement, heifers on the High-High (HH) treatment continued to receive ad libitum access to feed, and daily feed offered to the Low-High (LH) heifers was set at 157 Mcal of ME/kg of BW0.75. Feed restriction of LH heifers continued for 84 d. After 84 d of restriction, LH heifers were allowed ad libitum access to feed. Heat production was determined 4 and 11 wk following feed restriction and 2, 5, 12, and 18 wk following realimentation. There was no residual bias when HP in ad libitum-fed heifers was estimated with an equation form developed in growing ewes: [(kcal/d) = f(BW, matBW) = BW (Ae[k(BW/mature BW)])], nor was there a residual bias when HP was predicted with an allometric equation: [(kcal/d) = f(BW) = A(BWk)]. However, there were residual biases when HP was estimated with an allometric equation that set the exponent to 0.75. Heat production per unit of BW of LH heifers was lower than that of HH heifers at 4 wk of feed restriction (P < 0.001), but HP did not differ between treatments at 11 wk of feed restriction (P = 0.87). At 2 (P = 0.002) and 5 wk (P < 0.001) following the increase in feed offered, HP per unit of BW of the LH heifers was greater than that of the HH heifers. Heat production did not differ between treatments at 12 and 18 wk following refeeding (P < 0.17). Our findings demonstrate that the relationship between HP and BW is described equally well by a logistic and allometric function, but applying a generalized interspecies exponent in an allometric equation to growing heifers results in a bias in estimating HP. The equation form developed in ewes can be used to develop a single equation for the prediction of HP across ages in heifers.

本研究的首要目标是测试一个为描述生长母羊的产热（HP）而开发的函数对生长小母牛的HP数据的拟合程度。第二个目标是确定HP对饲料限制及随后营养物质再供给的适应模式。在234.5±0.5日龄时，通过间接量热法测定了32头肉类动物研究中心III代小母牛的HP。在首次量热测量之后，高-高（HH）处理组的小母牛继续随意采食，而低-高（LH）处理组小母牛的每日饲料供给量设定为每千克体重0.75次方157兆卡代谢能。LH处理组小母牛的饲料限制持续84天。在限制84天后，LH处理组小母牛被允许随意采食。在饲料限制后的第4周和第11周以及再供给后的第2周、第5周、第12周和第18周测定产热。当用在生长母羊中开发的方程形式估计随意采食小母牛的HP时：[（千卡/天）= f（体重，成熟体重）=体重（Ae[k（体重/成熟体重）]）]，不存在残留偏差；当用异速生长方程预测HP时：[（千卡/天）= f（体重）= A（体重k）]，也不存在残留偏差。然而，当用将指数设为0.75的异速生长方程估计HP时，存在残留偏差。在饲料限制第4周时，LH处理组小母牛每单位体重的产热低于HH处理组小母牛（P < 0.001），但在饲料限制第11周时，两组处理之间的HP没有差异（P = 0.87）。在增加饲料供给后的第2周（P = 0.002）和第5周（P < 0.001），LH处理组小母牛每单位体重的产热高于HH处理组小母牛。再供给后第12周和第18周，两组处理之间的产热没有差异（P < 0.17）。我们的研究结果表明，逻辑函数和异速生长函数对HP与体重之间关系的描述同样良好，但在异速生长方程中对生长小母牛应用广义种间指数会导致在估计HP时出现偏差。母羊中开发的方程形式可用于开发一个预测小母牛不同年龄阶段HP的单一方程。