Effects of high dietary levels of silver hake and Atlantic herring on growing-furring performance and blood clinical-chemistry of mink (Mustela vison)

Abstract

An experiment was conducted with a total of 168 mink (Mustela vison) of the standard black genotype to determine the effects of dietary silver hake (Merluccius bilinearis), silver hake silage and herring (Clupea harengus) on the growing-furring performance. There were seven dietary groups. The control diet (CONTROL) contained 40% haddock offal, 8% poultry offal, 15% beef tripe and lungs, 5% corn gluten meal, 12% extruded wheat, 0.4% vitamin-mineral premix, and water. Test diets were made by replacing the fish offal with 15 or 30% hake (HAKE 15, HAKE 30), hake silage (SILAGE 15, SILAGE 30) or with 40% herring (HERRING 40). The last dietary group (HERR/CONT) was fed alternatingly with the CONTROL or the HERRING 40 diets. The animals in the HERRING 40 group developed anorexia after 2 wk on the test diet and were injected with vitamin B complex. The diet was supplemented with thiamin, 25 mg kg−1 feed. This restored appetite and supported normal growing-furring performance. Mink fed HAKE 30 diet had a lower weight gain from weaning until pelting (males 814 ± 58.0 g, females 366 ± 53.6 g) than the CONTROL (males 987 ± 61.9 g, females 429 ± 52.1 g)(P < 0.05). Blood haemoglobin (Hb) values for all groups were on average 178 ± 4.4 g L−1 in September and 184 ± 7.0 g L−1in October, i.e. well above the critical level to prevent the development of cotton fur. However, the total amount of iron stored in spleen and liver was lower for the HAKE 30 (562.1 ± 85.1 µg) and SILAGE 30 (435.9 ± 77.7 µg) groups than in the CONTROL (800.7 ± 77.7 µg) (P < 0.05) possibly indicating impaired absorption. No signs of poor pigment development were seen in the underfur of the winter pelage. Both silver hake and herring show good potential as alternative feedstuffs in growing-furring diets for mink. At high inclusion levels the effects of thiaminase enzyme in herring and the iron-binding trimethylamine oxide in silver hake should be accounted for. Key words: Mink, herring, thiamin, silver hake, fish silage, iron