Dogfish (Squalus acanthias) and dogfish silage as feed-stuffs in growing-furring diets for mink (Mustela vison)

Abstract

A production trial was carried out with 120 mink (Mustela vison) of standard genotype to demonstrate the effects of dogfish (DF) and dogfish silage (DFS) on growth and fur development from weaning until pelting. The experimental treatments were 1) Control, 2) DF15%, 3) DF30%, 4) DF45%, 5) DFS15%, and 6) DFS30%. The test ingredients were used to replace the haddock-herring (35%:10%) mixture in the Control diet at percentage levels indicated by the diet group designation. The rest of the diet was compounded of 10% beef tripe and lungs, 8% poultry offal, 10% cereal, 5% corn gluten meal, 0–2% vegetable oil, 0.4% vitamin-mineral premix and water. All diets guaranteed the females normal body weight gain during the trial. The males receiving the dogfish test diets had significantly poorer growth compared with the males in the Control group. Two males of the DF30% group also developed rickets. The incidence of cotton fur syndrome in the experimental groups was: Control, 0/20; DF15%, 6/20; DF30%, 7/17; DF45%, 0/19; DFS15%, 2/18; and DFS30%, 3/17 pelts produced. Acid ensiling of dogfish was shown to reduce the incidence of cotton fur in the mink but also produced an increased trend in the occurrence of enteritis in the females. Based on the haematology results and tissue iron store analysis, impaired iron metabolism was demonstrated in the DF15-30% and DFS15-30% groups. It can be concluded that the anti-nutritional factor, trimethylamine oxide (TMAO), present in dogfish reduced iron absorption in most of the experimental groups and resulted in disturbances in the fur development of the mink. The absence of cotton fur in the DF45% group is likely due to greater ammonia formation in the feed thus preventing TMAO degradation by triamine oxidase. The improved iron store status in the mink fed the DF45% diet compared with the Control and other dogfish test groups may be explained by the chelating effect of polyamines on iron consequently enhancing its absorption. Key words: Anaemia, cotton fur, trimethylamine oxide, TMAO, nutrition