Departamento de Producción Agraria, E.T.S. Ingeniería Agronómica, Alimentaria y de Biosistemas, Universidad Politécnica de Madrid, Madrid, Spain.
Departamento de Producción Animal, Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain.
J Anim Breed Genet. 2023 Sep;140(5):549-557. doi: 10.1111/jbg.12778. Epub 2023 May 7.
The selection of animals for lower environment sensitivity around the optimum trait value can also provide benefits in productivity and welfare. A divergent selection experiment for birth weight environmental variability in mice was successfully conducted over 17 generations. Animals from low variability selected line (L-line) were more robust by having a higher litter size and survival at weaning in a common breeding environment, than those from high variability line (H-line). The objective of this study was to analyze the differences between those divergently selected lines for embryo and fetal survival and for fertility and prolificacy rate. To study embryo survival and ovulation rate, a total of 98 females (34 H-line and 50 L-line) were studied in four generations of the divergent experiment. To analyze fetal survival and fertility rate, 378 female mice (138 H-line and 240 L-line) in 10 generations or the divergent experiment were studied. Ultrasound scans were performed at day 14 of gestation to establish the number of total fetal and the embryo absorptions. Mortality was addressed as the difference between litter size at birth and the number of fetuses at 14 days of gestation. The number of pregnant females in the first 3 days after mating was used to measure fertility. A linear model was also fitted to analyze embryo mortality, litter size, and the number of embryos at 14 days of gestation. A categorical model was then used to study fertility, including line, generation, and its interaction as effects. Despite the fact that there were no significant differences in the ovulation rate, litter size at birth was significantly higher in the L-line than in the H-line (9.82 vs. 8.36 pups, p < 0.001). Moreover, embryo mortality was significantly lower in the L-line than in the H-line (1.39 vs. 2.87 fetuses, p < 0.001). L-line females were more fertile (53.49% vs. 23.26% for the H-line). According to these results, the line selected for low environmental variance would be preferable for robustness and animal welfare.
选择环境敏感性较低的动物围绕最优性状值也可以提高生产力和福利。在老鼠中进行了一项成功的 17 代环境变异性出生体重的分歧选择实验。在常见的繁殖环境中，来自低变异性选择系（L 系）的动物具有更高的窝仔数和断奶存活率，比来自高变异性选择系（H 系）的动物更健壮。本研究的目的是分析那些在胚胎和胎儿存活率以及生育力和繁殖力方面表现出差异的两个选择系。为了研究胚胎存活率和排卵率，共研究了 4 代分歧实验中的 98 只雌性（34 只 H 系和 50 只 L 系）。为了分析胎儿存活率和生育率，共研究了 10 代分歧实验中的 378 只雌性小鼠（138 只 H 系和 240 只 L 系）。在妊娠第 14 天进行超声扫描，以确定总胎儿和胚胎吸收的数量。死亡率是指出生时窝仔数与妊娠第 14 天的胎儿数之间的差异。在交配后第 3 天内怀孕的雌性数量用于衡量生育力。还拟合了线性模型来分析胚胎死亡率、出生时的窝仔数和妊娠第 14 天的胚胎数量。然后使用分类模型研究生育力，包括线、代和它们的相互作用作为效应。尽管排卵率没有显著差异，但 L 系的出生时窝仔数明显高于 H 系（9.82 比 8.36 只幼崽，p<0.001）。此外，L 系的胚胎死亡率明显低于 H 系（1.39 比 2.87 只胎儿，p<0.001）。L 系的雌性更具生育力（53.49%比 H 系的 23.26%）。根据这些结果，选择环境方差较低的系可能更有利于健壮性和动物福利。
