Canario L, Roy N, Gruand J, Bidanel J P
Station de Genetique Quantitative et Appliquée, Institut National de la Recherche Agronomique, 78352 Jouy-en-Josas, France.
J Anim Sci. 2006 May;84(5):1053-8. doi: 10.2527/2006.8451053x.
Genetic parameters of litter traits and their relationships with farrowing kinetics traits were estimated in a Large White population to examine the impact of selection for litter size on perinatal mortality and one of its main determinants, farrowing kinetics. Data were collected on 2,947 farrowings from 1,267 sows between 1996 and 2004. Litter traits included the number born in total (NBT), number born alive (NBA), and the number (NSB) and proportion (PSB) of stillborn piglets. Four farrowing kinetics traits were considered: farrowing duration (FD), birth interval (BI = FD/NBT), heterogeneity of birth intervals (SDNB = SD of the number of piglets born each one-half hour), and birth assistance (BA) during the farrowing process. Genetic parameters were estimated using restricted maximum likelihood methodology. All traits were analyzed using a mixed linear animal model including year x month and parity as fixed effects; the additive genetic value of each animal and the sow permanent environment were treated as random effects. To normalize their distribution, kinetics traits were Box-Cox-transformed. Low heritability estimates were obtained for litter size and mortality traits, which was in agreement with literature results (i.e., 0.10 +/- 0.02, 0.08 +/- 0.02, 0.19 +/- 0.02, and 0.14 +/- 0.02 for NBT, NBA, NSB, and PSB, respectively). Heritability values were also low for kinetics traits: 0.10 +/- 0.02, 0.08 +/- 0.02, 0.01 +/- 0.01, and 0.05 +/- 0.03 for FD, BI, SDNB, and BA, respectively. The genetic correlation between NBT and NBA was strongly positive (ra = 0.90). On both phenotypic and genetic scales, NBT was positively associated with stillbirth (ra = 0.45 +/- 0.11, rp = 0.38 for NSB; ra = 0.46 +/- 0.13, rp = 0.17 for PSB). Conversely, NBA had low correlations with SB and PSB. Number born in total was moderately correlated to FD (ra = 0.34 +/- 0.15) and BI (ra = -0.37 +/- 0.15). A stronger relationship was found between NBA and BI (ra = -0.49 +/- 0.13), whereas the relationship with FD was lower (ra = 0.16 +/- 0.17). Moreover, FD was strongly correlated with stillbirth (ra = 0.42 +/- 0.12 with NSB), whereas BI was nearly independent of stillbirth. Contrary to selection on NBT, selection on NBA appears to be a good way to limit the negative side effects on stillbirth. Moreover, selection on NBA would lead to a small increase in FD and a faster and more regular birth process than would be obtained by selecting on NBT.
在一个大白猪群体中估计了窝产性状的遗传参数及其与产仔动力学性状的关系，以研究窝产仔数选择对围产期死亡率及其主要决定因素之一——产仔动力学的影响。收集了1996年至2004年间1267头母猪的2947窝产仔数据。窝产性状包括总产仔数（NBT）、产活仔数（NBA）、死胎数（NSB）和死胎比例（PSB）。考虑了四个产仔动力学性状：产仔持续时间（FD）、出生间隔（BI = FD/NBT）、出生间隔的异质性（SDNB = 每半小时出生仔猪数的标准差）以及产仔过程中的助产情况（BA）。使用限制最大似然法估计遗传参数。所有性状均使用混合线性动物模型进行分析，该模型包括年份×月份和平胎次作为固定效应；每头动物的加性遗传值和母猪的永久环境作为随机效应。为使动力学性状的分布标准化，对其进行了Box-Cox变换。窝产仔数和死亡率性状的遗传力估计值较低，这与文献结果一致（即NBT、NBA、NSB和PSB的遗传力分别为0.10±0.02、0.08±0.02、0.19±0.02和0.14±0.02）。动力学性状的遗传力值也较低：FD、BI、SDNB和BA的遗传力分别为0.10±0.02、0.08±0.02、0.01±0.01和0.05±0.03。NBT和NBA之间的遗传相关性很强（ra = 0.90）。在表型和遗传尺度上，NBT均与死胎呈正相关（NSB的ra = 0.45±0.11，rp = 0.38；PSB的ra = 0.46±0.13，rp = 0.17）。相反，NBA与SB和PSB的相关性较低。总产仔数与FD（ra = 0.34±0.15）和BI（ra = -0.37±0.15）呈中等相关性。在NBA和BI之间发现了更强的关系（ra = -0.49±0.13），而与FD的关系较低（ra = 0.16±0.17）。此外，FD与死胎密切相关（与NSB的ra = 0.42±0.12），而BI几乎与死胎无关。与选择NBT相反，选择NBA似乎是限制对死胎负面影响的好方法。此外，选择NBA将导致FD略有增加，并且与选择NBT相比，产仔过程更快且更规律。
