Banos G, Coffey M P
1Faculty of Veterinary Medicine, Department of Animal Production, Aristotle University of Thessaloniki, GR-54124 Thessaloniki, Greece.
Animal. 2010 Feb;4(2):189-99. doi: 10.1017/S1751731109991182.
The objective of this study was to quantify the genetic association of body energy assessed throughout lactation with a cow's fertility. Nine direct and indirect body energy traits were defined at different stages of lactation. Four were daily records of energy balance, energy content, cumulative effective energy (CEE) and body condition score (BCS) calculated between lactation days 4 and 311. The other five traits included duration of negative energy balance (DNEB), rate of recovery during DNEB (RNEB), sum of negative energy balance (SNEB), nadir of energy content (NEC) and number of days from calving to NEC. Of these traits, energy balance, DNEB, RNEB and SNEB were primarily based on individual cow feed intake and milk yield, and considered direct measures of body energy. The other traits were calculated from body lipid and protein changes, predicted from BCS and live weight profiles, and were considered indirect measures of body energy. Fertility was defined by number of days between calving and commencement of luteal activity (DLA), first observed oestrus (DH) and conception (DC), and number of services per conception. A total of 957 cows in their first four lactations were considered in the study. Genetic models fitted cubic splines to define longitudinal traits (energy balance, energy content, CEE and BCS) and calculate heritability and genetic correlation with fertility. Daily heritability estimate ranges were 0.10 to 0.34, 0.35 to 0.61, 0.32 to 0.53 and 0.24 to 0.56 for energy balance, energy content, CEE and BCS, respectively, and, in most cases, tended to increase towards the middle of lactation and remain relatively stable thereafter. Of the other body energy traits, heritability of NEC (0.44) was the most notable. Statistically significant (P < 0.05) genetic correlations of DH with daily energy balance, energy content, CEE and BCS ranged from -0.16 to -0.28, -0.35 to -0.48, -0.16 to -0.26 and -0.37 to -0.44, respectively. For DC, respective estimates were -0.28 to -0.64, -0.37 to -0.60, -0.30 to -0.48 and -0.29 to -0.53. For DLA, they ranged from -0.47 to -0.56 with energy content and from -0.50 to -0.74 with BCS. Of special interest was the genetic correlation of NEC with DH (-0.54) and DC (-0.48). Results suggest that indirect measures of body energy have the strongest genetic association with cow fertility. NEC and early lactation (circa day 50) BCS and energy content are the most useful traits for selection in terms of the correlated improvement in a cow's capacity to resume her reproductive activity post partum.
本研究的目的是量化整个泌乳期评估的体能量与奶牛繁殖力之间的遗传关联。在泌乳的不同阶段定义了九个直接和间接的体能量性状。四个是泌乳第4天至311天之间计算的能量平衡、能量含量、累积有效能量（CEE）和体况评分（BCS）的每日记录。其他五个性状包括负能量平衡持续时间（DNEB）、DNEB期间的恢复率（RNEB）、负能量平衡总和（SNEB）、能量含量最低点（NEC）以及从产犊到NEC的天数。在这些性状中，能量平衡、DNEB、RNEB和SNEB主要基于个体奶牛的采食量和产奶量，被视为体能量的直接测量指标。其他性状是根据体脂和蛋白质变化计算得出的，通过BCS和体重曲线预测，被视为体能量的间接测量指标。繁殖力由产犊至黄体活动开始（DLA）、首次观察到发情（DH）和受孕（DC）之间的天数以及每次受孕的输精次数来定义。本研究共纳入了957头处于前四个泌乳期的奶牛。遗传模型采用三次样条函数来定义纵向性状（能量平衡、能量含量、CEE和BCS），并计算其与繁殖力的遗传力和遗传相关性。能量平衡、能量含量、CEE和BCS的每日遗传力估计范围分别为0.10至0.34、0.35至0.61、0.32至0.53和0.24至0.56，并且在大多数情况下，倾向于在泌乳中期增加，此后保持相对稳定。在其他体能量性状中，NEC的遗传力（0.44）最为显著。DH与每日能量平衡、能量含量、CEE和BCS的统计学显著（P < 0.05）遗传相关性分别为-0.16至-0.28、-0.35至-0.48、-0.16至-0.26和-0.37至-0.44。对于DC，相应的估计值分别为-0.28至-0.64、-0.37至-0.60、-0.30至-0.48和-0.29至-0.53。对于DLA，它们与能量含量的范围为-0.47至-0.56，与BCS的范围为-0.50至-0.74。特别值得关注 的是NEC与DH（-0.54）和DC（-0.48）的遗传相关性。结果表明，体能量的间接测量指标与奶牛繁殖力的遗传关联最强。就产后恢复繁殖活动能力的相关改善而言，NEC以及泌乳早期（约第50天）的BCS和能量含量是最有用的选择性状。
