Nguyen Tuan Q, Knap Pieter W, Simm Geoff, Edwards Sandra A, Roehe Rainer
Department of Agriculture, Horticulture and Engineering Sciences, SRUC (Scotland's Rural College), Roslin Institute Building, Easter Bush Campus, Edinburgh, EH25 9RG, Scotland, UK.
Department of Animal Breeding, Faculty of Animal Science and Veterinary Medicine, Nong Lam University - Ho Chi Minh City, Linh Trung Ward, Thu Duc District, Ho Chi Minh City, 71308, Vietnam.
Genet Sel Evol. 2021 Mar 15;53(1):28. doi: 10.1186/s12711-021-00612-7.
Postnatal piglet survival is important both in economic and animal welfare terms. It is influenced by the piglet's own direct genetic effects and by maternal genetic effects of the dam, associated with milk production and mothering abilities. These genetic effects might be correlated, affected by other non-genetic factors and unfavourably associated with other reproduction traits such as litter size, which makes the development of optimal breeding strategies a challenge. To identify the optimum selection strategy for piglet survival, a selection experiment was carried out to compare responses in survival and reproduction traits to selection on only direct, only maternal, or both genetic effects of postnatal survival. The data of the experiment were recorded from outdoor reared pigs, with first- and second-generation sires selected based on their estimated breeding values for maternal and direct effects of postnatal survival of indoor reared offspring, respectively, with the opportunity to identify potential genotype-by-environment interaction.
A Bayesian multivariate threshold-linear model that was fitted to data on 22,483 piglets resulted in significant (Pr(h > 0) = 1.00) estimates of maternal and direct heritabilities between 0.12 and 0.18 for survival traits and between 0.29 and 0.36 for birth weight, respectively. Selection for direct genetic effects resulted in direct and maternal responses in postnatal survival of 1.11% ± 0.17 and - 0.49% ± 0.10, respectively, while selection for maternal genetic effects led to greater direct and maternal responses, of 5.20% ± 0.34 and 1.29% ± 0.20, respectively, in part due to unintentional within-litter selection. Selection for both direct and maternal effects revealed a significant lower direct response (- 1.04% ± 0.12) in comparison to its expected response from single-effect selection, caused by interactions between direct and maternal effects.
Selection successfully improved post- and perinatal survival and birth weight, which indicates that they are genetically determined and that genotype-by-environment interactions between outdoor (experimental data) and indoor (selection data) housed pigs were not important for these traits. A substantially increased overall (direct plus maternal) response was obtained using selection for maternal versus direct or both direct and maternal effects, suggesting that the maternal genetic effects are the main limiting factor for improving piglet survival on which selection pressure should be emphasized.
仔猪出生后的存活在经济和动物福利方面都很重要。它受到仔猪自身的直接遗传效应以及母猪的母本遗传效应的影响，这些效应与产奶量和育仔能力相关。这些遗传效应可能相互关联，受到其他非遗传因素的影响，并且与其他繁殖性状（如产仔数）存在不利关联，这使得制定最优育种策略成为一项挑战。为了确定仔猪存活的最佳选择策略，开展了一项选择实验，以比较仅针对出生后存活的直接遗传效应、仅针对母本遗传效应或同时针对这两种遗传效应进行选择时，存活和繁殖性状的反应。实验数据记录自户外饲养的猪，第一代和第二代种公猪分别根据其对室内饲养后代出生后存活的母本和直接效应的估计育种值进行选择，从而有机会识别潜在的基因型与环境的相互作用。
对22483头仔猪的数据拟合贝叶斯多变量阈值线性模型，得出存活性状的母本和直接遗传力估计值分别在0.12至0.18之间（显著，Pr(h > 0) = 1.00），出生体重的母本和直接遗传力估计值分别在0.29至0.36之间。对直接遗传效应进行选择时，出生后存活的直接反应和母本反应分别为1.11% ± 0.17和 -0.49% ± 0.10，而对母本遗传效应进行选择时，直接反应和母本反应更大，分别为5.20% ± 0.34和1.29% ± 0.20，部分原因是窝内的无意选择。对直接和母本效应都进行选择时，与单效应选择的预期反应相比，直接反应显著降低（-1.04% ± 0.12），这是由直接和母本效应之间的相互作用导致的。
选择成功提高了产后和围产期的存活率以及出生体重，这表明这些性状是由基因决定的，并且户外（实验数据）和室内（选择数据）饲养的猪之间的基因型与环境的相互作用对这些性状并不重要。通过选择母本效应而非直接效应或同时选择直接和母本效应，获得了显著提高的总体（直接加母本）反应，这表明母本遗传效应是提高仔猪存活率的主要限制因素，应在其上强调选择压力。
