Selection for litter size, body weight, and pelt quality in mink (Mustela vison): correlated responses.

In a five-generation selection experiment, separate lines of standard mink (Mustela vison) were subjected to selection for litter size at 3 wk (F line), body weight in September (BS line), underfur density (P line), or combined selection for litter size and body weight (I line). One unselected line served as a control (C line). The present paper focuses on correlated responses to selection regarding fertility and fitness traits, fur quality, and body size traits. Genetic and environmental parameters were estimated with REML (Restricted Maximum Likelihood) techniques using a multi-trait, reduced animal model in a derivative-free way. Genetic and phenotypic correlations were estimated from four subsets of data consisting of 1) female September weight, litter size, and kit mortality; 2) body size traits; 3) September weight and fur traits graded on live mink; and 4) fur traits graded on live mink and skins. September weight was found to be negatively correlated with fertility and fitness traits as well as with fur traits. Selection for underfur density resulted in an improvement in guard hair quality and in general impression of the fur and almost eliminated the fur defect metallic sheen.