NUTRITIVE VALUE OF RAPESEED FLOUR FOR MINK: EFFECTS ON LIVE PERFORMANCE, NUTRIENT UTILIZATION, THYROID FUNCTION AND PELT QUALITY

Abstract

A trial for testing the replacement value of rapeseed flour (RF) (blend of Brassica napus and campestris) for raw meat was conducted with growing-furring mink. The RF contained 67% crude protein and approximately 1/10 of the quantity of glucosinolates normally found in commercial meal. Forty male pastel mink were fed diets containing 0, 6.5, 13.4 and 20% RF (dry-matter basis) from the end of July to pelting. On a dry-matter basis, the diets contained approximately 41% protein and the percentages of protein as RF protein were 0, 4.3, 9 and 12.4. Initially, the animals ate significantly (P < 0.05) more feed and grew significantly (P < 0.05) faster on the 0 and 6.5% RF diets, but later, weight gain and feed consumption were the same for all groups (P > 0.05). After 70 days on trial, weight gain was less (P < 0.05) on the 20% RF diet compared with the 0 and 6.5% diets. There was a significant (P < 0.05) reduction in the apparent digestibilities of dry matter, gross energy and nitrogen, and in nitrogen retention for the mink receiving the diets containing 13.4 and 20% RF. Mink fed the 20% RF diet showed significant (P < 0.05) thyroid hypertrophy, but at slaughter serum protein-bound iodine level was the same (P > 0.05) for all groups. There was little difference among groups with respect to pelt size and pelt quality.