Embryo survival and fertility differ in lines divergently selected for birth weight homogeneity in mice

Abstract

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.

Differential patterns in runs of homozygosity in two mice lines under divergent selection for environmental variability for birth weight

“…As a result of the divergent experiment, two divergent lines were created: a high variability line (H‐Line) and a low variability line (L‐Line). The L‐Line presented benefits in production, animal welfare, heritability and traits related with robustness traits such as feed efficiency or longevity (Formoso‐Rafferty et al., 2016b, 2017, 2019, 2022; 2023). Moreover, a higher response to selection was observed in the L‐Line than in the H‐Line (Formoso‐Rafferty et al., 2020).…”

Genomic inbreeding measures applied to a population of mice divergently selected for birth weight environmental variance

“…The experimental mating design avoided sharing grandparents and was optimised as a function of selection criteria in both selected lines ( Formoso-Rafferty et al, 2016b ). The homogeneous line presented advantages in production, animal welfare, response to selection, and traits related to robustness, such as longevity, survival and feed efficiency ( Formoso-Rafferty et al, 2017 ; Formoso-Rafferty et al, 2018; Formoso-Rafferty et al, 2019 ; Formoso-Rafferty et al, 2020 ; Formoso-Rafferty et al, 2022 ; Formoso-Rafferty et al, 2023 ).…”