INFLUENCE OF DIET ON LACTATIONAL PERFORMANCE AND DAM AND LITTER WEIGHTS IN LINES OF MICE SELECTED AND UNSELECTED FOR INCREASED 12-DAY LITTER WEIGHT

Abstract

Genotypic and dietary (high energy versus standard) influences on lactational performance and on dam and litter weights were studied in lines of mice selected for increased 12-day litter weight and in unselected control lines. There was no evidence that genotype (either among full-sib families within lines or between selected and control lines) × diet interactions were present for 12-day litter weight or correlated traits. The high energy diet led to significant increases in 5- and 12-day litter weights and milk yield 12 days postpartum, but no change in per cent solids or per cent lipid of the milk. Increased milk yield of dams on the high energy diet was sufficient to account for the larger 12-day litter weights. Increased 12-day postpartum weights of dams fed the high energy diet may be related to the increase in milk yield since there was no diet difference in dam weight at parturition. Litter weights at 5 and 12 days of age were significantly larger in the selected lines. However, there were no significant differences in milk yield, per cent solids or per cent lipid between selected and control dams. Body weights of dams in the selected line were larger at 8 weeks of age, at parturition and at 12 days postpartum.