Abstract
Simple SummaryThe divergent selection for birth weight variability was previously proven by the difference between the two selected mice lines, but the comparison with a control line made it possible to measure independently the differential response in each of the low and high birth weight variability lines. In conclusion, the genetic response was much higher for the low variability line than for the high variability line. This was extremely satisfactory given that homogeneity provides advantages in terms of animal welfare and robustness.Birth weight (BW) in animal production is an economically important trait in prolific species. The laboratory mouse (Mus musculus) is used as an experimental animal because it is considered a suitable model for prolific species such as rabbits and pigs. Two mouse lines were divergently selected for birth weight variability with a third line of non-selected control population of the same origin as the animals starting the experiment. The objective of this study was, therefore, to compare and evaluate the differential response of each line. The animals were from the 17th generation of both low and high BW variability lines of the divergent selection experiment, including in addition animals from the control line. The dataset contained 389 records from 48 litters of the high line, 734 records from 73 litters of the low line, and 574 records from 71 litters of the control line. The studied traits were as follows: the BW, the BW variance, the BW standard deviation, the BW coefficient of variation within-litter, the weaning weight (WW), the litter size at birth and at weaning, the weight gain, and the preweaning survival. The model included the line effect jointly with the parturition number and its interaction, the linear and quadratic LS as covariates except for the LS trait itself when analyzing litter traits, as well as the pup sex when analyzing individual traits. The low line had a lower BW and WW, but a higher litter size, and greater robustness owing to a higher survival at weaning. As a model of livestock animals, the findings from this experiment led to a proposal of selection for pig production that would combine an increase in litter size with higher survival and welfare. Compared with the control line, a much higher response was observed in the low variability line than in the high line, making it extremely satisfactory given that homogeneity provides advantages in terms of animal welfare and robustness.
Highlights
The genetic control of the environmental variability in the search for a higher homogeneity is becoming important in current animal breeding programs [1,2,3]
The three experimental mice lines included the following: two lines divergently selected for birth weight (BW) environmental variability and a non-selected population used as control population
The selection intensity was lower in later generations than at the beginning, and this loss in the selection intensity was similar in both lines
Summary
The genetic control of the environmental variability in the search for a higher homogeneity is becoming important in current animal breeding programs [1,2,3]. Selection for homogeneity would result in animals that are more robust and better prepared to face any environmental challenges [4]. Enhancing robustness will improve the functional traits while maintaining as much of the high production potential as possible [5]. Some authors have proved that selecting to reduce the environmental variability of a particular trait was possible [6], leading to more robust animals [7]. Other authors reported that animals in heterogeneous litters were more prone to diseases affecting siblings in the same litter [9]
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