Shuey S A, Birkelo C P, Marshall D M
Department of Animal and Range Sciences, South Dakota State University, Brookings 57007.
J Anim Sci. 1993 Aug;71(8):2253-9. doi: 10.2527/1993.7182253x.
Thirty-three Hereford x Angus first-calf heifers were used to determine the relationship between production efficiency (PE = calf weaning weight/[12-mo dam+calf ME intake]) and nonlactating dam maintenance ME requirement/BW.75 (MEm) and its components, the efficiency of ME use for maintenance (km), and fasting heat production/BW.75 (FHP). Each heifer was kept in drylot from 19 mo of age until weaning of its first calf, during which time individual feed intakes were measured. After the PE phase, heifers were moved to the metabolism facility and indirect respiration calorimetry was used to determine maintenance energy metabolism. Maintenance metabolism of the dam, determined in controlled conditions, contributed little to explaining PE variation (r2 < or = .04). This may have been due to the high plane of nutrition provided and (or) to the physiological state of the heifers during metabolism measurements. Selection for lower MEm, as determined by the procedures used in this study, is unlikely to improve heifer PE if nutrition is not limited relative to requirements. Additionally, MEm was closely related to FHP (r2 = .73), suggesting that it could be used as an indicator of fed maintenance requirements when determined within defined conditions.
选用33头赫里福德×安格斯初产小母牛来确定生产效率（PE = 犊牛断奶体重/[12个月龄的母牛+犊牛的代谢能摄入量]）与非泌乳期母牛维持代谢能需求/体重0.75（MEm）及其组成部分、维持代谢能利用效率（km）和空腹产热/体重0.75（FHP）之间的关系。每头小母牛从19月龄开始一直饲养在干圈中，直至其第一头犊牛断奶，在此期间测量个体采食量。在PE阶段结束后，将小母牛转移至代谢设施处，采用间接呼吸量热法来测定维持能量代谢。在受控条件下测定的母牛维持代谢对解释PE变化的作用不大（r2≤0.04）。这可能是由于所提供的营养水平较高以及（或者）在代谢测量期间小母牛的生理状态所致。如果营养相对于需求而言不受限，那么按照本研究中所采用的程序来选择较低的MEm，不太可能提高小母牛的PE。此外，MEm与FHP密切相关（r2 = 0.73），这表明在规定条件下测定时，它可作为采食维持需求的一个指标。
