Mink dam weight changes during the lactation period I. Genetic and Environmental Effects

Records from 570 scanblack mink dams with 786 lactations in the period 1989–94 were used to estimate genetic parameters for body weight and weight changes during the lactation period from parturition to 6 weeks post‐partum. Direct additive effects and effects of permanent environment were estimated using restricted maximum likelihood (REML) in univariate and bivariate models.

During the first 6 weeks of lactation, the dam lost around 15% (169 g) of the body weight at parturition, the main part, 10% (112 g), during the last 2 weeks. Older dams lost more weight than yearling dams, especially during the late part of the lactation period. Dams fed ad libitum had a higher body weight during the last part of the lactation period. The litter size, the sex of the kits and the litter weight influenced weight loss of the dam, especially in the late part of the lactation period.

The heritability of the direct additive effect was intermediate to high for body weight (h² _a ～ 0.39–0.58), but lower for weight changes (h² _a ～ 0.15–0.38). The permanent environmental effect was important for the total body weight (c² ～ 0.23–0.30) and less important for weight changes (c² ～ 0.13), but still significant. The repeatability for weight changes between parities was intermediate to high (r ～ 0.19–0.52).