Feed restriction on growth of mice divergently selected for birth weight environmental variability

Nowadays, the selection for feed efficiency is one of the main aims in animal breeding in order to decrease the production costs. On the other hand selection for less sensitivity with respect to environmental effects, as indicated by a low variation around the optimum trait value, may have benefits in the productivity and in the animal welfare. Therefore, the objective of this work was to analyze the influence of food restriction, understood as an environmental challenge, on weight at different ages in two lines divergently selected for birth weight variability in mice, low variability (LV) and high variability (HV) lines. A total of 40 females (four full-sib females from 10 random different litters from the 12, 13 and 14 generations of selection), were chosen within lines and fed either ad libitum or restricted from 21 to 70 days. Restriction consisted of feeding with 75%, 90% and 85% of ad libitum consume in the respective three studied generations. Weekly weights from 21 to 77 days were analyzed. The model adjusted the diet (restricted or not), the line, the generation and the litter size, including also the interaction between the line, the generation and the diet. ASReml Release 4.1 program was used. Animals fed ad libitum of LV line had similar weights in all generations unlike those of HV line, which presented lower weights. The dietary restriction had a negative effect on the body weight of the animals but the interaction between line and diet was significantly different only after day 35, showing a differential response of the lines to the environmental challenge, animals from LV line were less sensitive to the feed restriction.