Effect of selection on digestibility and carcass composition in mink

Abstract

In a 5‐generation selection experiment, separate lines of mink (Mustela vison) were selected for litter size at 3 weeks (F‐line) and body weight in September (BS‐line). One unselected line served as a control (C). Nutrient digestibility was studied in a balance experiment with four male kits from each line in the last generation. Carcass composition was determined for four 4th‐generation F‐ and BS‐males each that had been killed on September 21. The feed consumption rate was higher in the BS‐line animals in the balance experiment than in the F‐ and C‐animals (1687 versus 1532 and 1504 kJ/ animal and day). These differences reflected the higher average live weights measured on August 25, of the BS‐males (1831 g versus 1728 and 1619). CP and CHO digestibility were similar in all lines, whereas a numerically small but significant difference in apparent fat digestibility was found between the F‐ and BS‐lines (95%) and the C‐line (93%). Average body weights of animals in the carcass composition evaluation were 2607 g (BS‐line) and 2023 g (F‐line). Retained protein, fat, and energy were significantly affected by line. The amount of protein retained per kg metabolic weight (kg^0.75) was nearly equal in the two lines, indicating that the animals’ genetic capacity for protein retention was similar and probably utilized to its full extent. Retained fat and energy per kg^0.75 were higher in the BS‐line, indicating that the animals had been selected for fat deposition rather than for body size. Hence, selection for body size in mink should be performed by using a selection criterion with which the negative effects of increased fat deposition on reproductive performance can be avoided.

Key words:

• Body weight
• Litter size
• Feed consumption
• Nutrient retention
• Energy retention