Mink kit growth performance in the suckling period

Abstract

Records of 4103 scanblack mink kits born in 1989–94 were used to estimate genetic parameters for body weight and body length during the growth season with special emphasis on the suckling period. Maternal additive and direct additive effects and effects of permanent maternal and specific litter environment were estimated, using restricted maximum likelihood (REML) in univariate and bivariate animal models. The maternal additive effect was constant during the first 4 weeks after parturition at h² _m ≈ 0.30 for weight, and decreased thereafter. The heritability estimate for direct additive effect for body weight decreased from h² _a ≈ 0.19 at birth to h² _a ≈ 0.12 at 4 weeks but increased to h² _a ≈ 0.50 in August to December. The maternal permanent environment was important only at 2 and 4 weeks, c² _p ≈ 0.10. The specific environment, common within the litter, increased from c² _s ≈ 0.24 at birth to c² _s≈ 0.40 at 2 and 4 weeks, but decreased thereafter to c² _s ≈ 0.10 in December. Estimates for body length showed a slightly different pattern, h² _a varying from 0.07 to 0.17 in the lactation period, but increased to 0.46 at pelting. The heritability of maternal additive effect (h² _m) for body length varied from 0.17 to 0.24 during the lactation period and decreased thereafter to 0.06 at pelting.

The results indicate that selection for maternal traits should be based on kit body weight, or body length within 4 weeks after birth, or on growth from 2 to 4 weeks. The largest direct response for body weight would be obtained by selection on body weight in August‐December.

Key words:

• additive direct effect
• body length
• body weight
• lactation period
• maternal additive effects
• permanent maternal environment
• specific litter environment