Freetly H C, Ferrell C L, Jenkins T G
USDA, ARS, U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.
J Anim Sci. 2000 Nov;78(11):2790-6. doi: 10.2527/2000.78112790x.
The objective of this study was to determine the effect of feeding strategies in cows that allowed BW loss followed by BW gain on the efficiency of feed utilization for calf production. The first treatment (H-H-H) was designed to maintain body condition score of mature cows at 5.5 from the second trimester until the subsequent breeding season. The second treatment (L-H-H) was designed such that cows lost body condition during the second trimester and regained it during the third trimester and were equal in weight and body condition scores at parturition to cows assigned to the H-H-H treatment. The third treatment (L-L-H) was designed such that cows lost body condition during the second trimester and gained body condition after 28 d of lactation so that they would be equal to the other two treatments at breeding. Forty-eight cows were assigned to each treatment. Total DMI over the entire study did not differ between the H-H-H and L-H-H treatments (P = 0.23), but intake on both were higher than the L-L-H treatment (P < 0.001). Calf birth weight of the H-H-H treatment did not differ (P = 0.43) from those of L-H-H, but both groups were greater than those of the L-L-H (P < or = 0.002) treatment. At 28 d of age, H-H-H (P = 0.008) and L-H-H (P = 0.007) calves weighed more than the L-L-H calves, but at 58 d of age there was no difference in calf BW among the treatments (P = 0.81). The percentage of cows that were diagnosed pregnant at weaning with their next calf did not differ (P = 0.71) among treatments. We interpret the results of this study to suggest that weight cycling in mature beef cows may be a viable management tool for decreasing food costs.
本研究的目的是确定在奶牛中采用先使体重下降随后再增加体重的饲养策略对犊牛生产中饲料利用效率的影响。第一种处理方式（高-高-高）旨在使成年母牛的体况评分从妊娠中期直至随后的繁殖季节维持在5.5。第二种处理方式（低-高-高）的设计是，母牛在妊娠中期体重下降，在妊娠后期体重恢复，且分娩时的体重和体况评分与采用高-高-高处理方式的母牛相同。第三种处理方式（低-低-高）的设计是，母牛在妊娠中期体重下降，在泌乳28天后体重增加，以便在配种时与其他两种处理方式的母牛相同。每种处理方式分配48头母牛。在整个研究期间，高-高-高处理方式和低-高-高处理方式的总干物质采食量没有差异（P = 0.23），但这两种处理方式的采食量均高于低-低-高处理方式（P < 0.001）。高-高-高处理方式的犊牛出生体重与低-高-高处理方式的犊牛出生体重没有差异（P = 0.43），但这两组犊牛的出生体重均高于低-低-高处理方式的犊牛（P ≤ 0.002）。在28日龄时，高-高-高处理方式（P = 0.008）和低-高-高处理方式（P = 0.007）的犊牛体重比低-低-高处理方式的犊牛重，但在58日龄时，各处理方式的犊牛体重没有差异（P = 0.81）。断奶时被诊断怀有下一胎犊牛的母牛比例在各处理方式之间没有差异（P = 0.71）。我们对本研究结果的解读表明，成年肉牛体重循环可能是降低饲料成本的一种可行管理手段。
