Bergsma R, Kanis E, Verstegen M W A, Knol E F
Institute for Pig Genetics (IPG), PO Box 43, 6640 AA Beuningen, the Netherlands.
J Anim Sci. 2008 May;86(5):1067-80. doi: 10.2527/jas.2007-0165. Epub 2008 Jan 11.
The increased productivity of sows increases the risk of a more pronounced negative energy balance during lactation. One possibility to prevent this is to increase the lactation efficiency (LE) genetically and thereby increase milk output for a given feed intake and mobilization of body tissue. The benefits of selection for LE depend on its heritability and the relationships with other traits of interest. The objectives of this study were to estimate genetic parameters for LE, its underlying traits, and to predict the consequences of current selection strategies in dam lines. Data from 4 farms were available to estimate genetic parameters. Heritabilities were estimated by using a univariate repeatability model, and genetic correlations were estimated bivariately. Selection index theory was used to predict the genetic progress by 3 alternative breeding programs: 1) a breeding program that aimed at balanced progress in the total number of piglets born, piglet mortality, and percent prolonged interval from weaning to estrus; 2) extension of this breeding goal with LE; and 3) a breeding goal that included only one selection criterion, litter weight gain, to demonstrate the effect of indirect selection for milk production. The heritability for LE was low (0.12). Body fat mass (0.52) and BW (0.45) of sows at the beginning of lactation showed the greatest heritabilities. Protein mass at the beginning of lactation, protein loss, weight loss, and ad libitum feed intake during lactation showed moderate heritabilities (0.39, 0.21, 0.20, and 0.30, respectively). Low to moderate heritabilities were found for litter weight at birth, within-litter SD in the birth weight of piglets, litter weight gain, fat loss, and restricted feed intake during lactation (0.19, 0.09, 0.18, 0.05, and 0.14, respectively). Within-litter SD in the weaning weight of piglets showed no genetic variability. It was predicted that a breeding goal for dam lines with an emphasis on the total number of piglets born, piglet mortality, and percent prolonged interval from weaning to estrus would not dramatically change BW or body composition at the beginning of lactation, or mobilization of body tissue and feed intake during lactation. Inclusion of LE in the breeding goal will improve stayability, as defined by the first-litter survival of sows and LE itself, without negative consequences for other economically important traits. Nevertheless, it might be worthwhile to design a breeding goal in which LE increases and feed intake remains unchanged.
母猪生产力的提高增加了其在泌乳期出现更明显负能量平衡的风险。预防这种情况的一种可能性是通过基因方式提高泌乳效率（LE），从而在给定采食量和体组织动员的情况下增加产奶量。选择LE的益处取决于其遗传力以及与其他感兴趣性状的关系。本研究的目的是估计LE及其潜在性状的遗传参数，并预测当前母系选择策略的后果。有来自4个农场的数据可用于估计遗传参数。通过使用单变量重复性模型估计遗传力，双变量估计遗传相关性。选择指数理论用于预测3种替代育种方案的遗传进展：1）一个旨在使产仔总数、仔猪死亡率和断奶至发情间隔延长百分比取得平衡进展的育种方案；2）将LE纳入该育种目标；3）一个仅包含一个选择标准即窝增重的育种目标，以证明对产奶量进行间接选择的效果。LE的遗传力较低（0.12）。泌乳开始时母猪的体脂肪量（0.52）和体重（0.45）显示出最高的遗传力。泌乳开始时的蛋白质量、蛋白损失、体重损失以及泌乳期的自由采食量显示出中等遗传力（分别为0.39、0.21、0.20和0.30）。出生时窝重、仔猪出生体重的窝内标准差、窝增重、脂肪损失以及泌乳期的限饲采食量的遗传力较低至中等（分别为0.19、0.09、0.18、0.05和0.14）。仔猪断奶体重的窝内标准差未显示出遗传变异性。据预测，一个强调产仔总数、仔猪死亡率和断奶至发情间隔延长百分比的母系育种目标不会显著改变泌乳开始时的体重或体组成，也不会改变泌乳期的体组织动员和采食量。将LE纳入育种目标将提高留存率，留存率由母猪第一胎的存活率和LE本身来定义，且对其他经济重要性状没有负面影响。然而，设计一个使LE增加而采食量保持不变的育种目标可能是值得的。
