Correlated genetic trends for production and welfare traits in a mouse population divergently selected for birth weight environmental variability

Abstract

The objective of this work was to study the changes that, selecting for environmental variability of birth weight (BW), could bring to other interesting traits in livestock such as: survivability at weaning (SW), litter size (LS) and weaning weight (WW), their variability assessed from standard deviations of LS, standard deviation of WW (SDWW) and also the total litter weight at birth (TLBW) and total litter weight at weaning. Data were registered after eight generations of a divergent selection experiment for BW environmental variability in mice. Genetic parameters and phenotypic and genetic evolution were assessed using linear homoscedastic and heteroscedastic models in which the traits were attributed to the female, except BW and WW that were in some models also attributed to the pup. Genetic correlation between the trait and variability levels was −0.81 for LS and −0.33 for WW. Clear divergent phenotypic trends were observed between lines for LS, WW and SDWW. Although animals were heavier in the high line, TLBW and at weaning was greater in the low line. Despite the negative genetic correlation that was obtained, SDWW was also higher in the high line. Heritabilities were 0.21 and 0.06, respectively, for LS and SW. Both phenotypic and genetic trends showed clear superiority of the low line over the high line for these traits, but inferior for WW. Heteroscedastic model performed similar to the homoscedastic model when there was enough information. Considering LS and survival, the low line was preferred from a welfare point of view, but its superiority from the productivity perspective was not clear. Robustness seemed higher as shown by a low variation and having a benefit to the animal welfare, but this still remains unclear. It was concluded that low variation benefits the welfare of animals.

Feed and reproductive efficiency differences between divergently selected lines for birthweight environmental variability in mice

“…Formoso‐Rafferty et al. (2016b) had already suggested that the low line presented higher robustness and welfare, but not yet demonstrated for a worsening productivity. It was, therefore, necessary to broaden the investigation to include this issue.…”

“…All animal weights in the low line were significantly lower than in the high line but there were minor differences between lines in weight gain (Figure ). Differences in body weight were the consequence of lower birth and weaning weight in low line from the genetically correlated response with the selection criterion (Formoso‐Rafferty et al., 2016b). In addition, the low line had lower weights due to higher litter size at birth and at weaning.…”

“…Furthermore, they showed that this selection criterion had direct implications in other interesting traits in livestock. These are related not only to productivity traits but also with animal welfare (Formoso‐Rafferty, Cervantes, Ibáñez‐Escriche, & Gutiérrez, 2016b). As a result of that experiment, two divergent lines for birthweight environmental variability were created (Formoso‐Rafferty et al., 2016a), where low line presented more benefits in production, welfare, heritability and robustness‐related traits.…”

Selection for environmental variance of litter size in rabbits

“…Estimating the correlation between the mean and the variance of a trait has been the goal of several studies, with various results. A negative relationship between the mean of a trait and its environmental variance was detected for litter size in pigs [11, 34], for litter size and litter weight at birth in mice [14, 39], for weight gain in mice [40], for uterine capacity in rabbits [15], and for body weight in broiler chickens [41]. By contrast, no relationship between mean and environmental variance was found for slaughter weight in pigs [42] or for birth weight in rabbits [21, 43], and a positive correlation between mean and environmental variance was found for body weight in snails [13] and broiler chickens [16] and for body conformation in broiler chickens [16].…”

Eficiencia alimentaria en dos líneas divergentes para variabilidad ambiental del peso al nacimiento en ratones

“…Por lo tanto, considerar los programas de selección por homogeneidad, así como por la eficiencia alimentaria, incide tanto en los aspectos económicos del sector agroganadero como en el bienestar animal. Existen muy pocos resultados exitosos de procesos de selección artificial para modificar la variabilidad ambiental (Formoso-Rafferty et al, 2015;2016).…”