Effect of dietary vitamin E and prey supplementation on semen quality in male black-footed ferrets (Mustela nigripes)

Over the recent years, the captive population of the endangered black-footed ferret (Mustela nigripes; ferret) has experienced a decline in normal sperm (NS) morphology (from 50% to 16%), which may be linked to inbreeding depression or it may have been a dietary change. We examined the role of dietary vitamin E, selenium (SE), and vitamin A on serum levels of vitamin E, SE, and vitamin A and semen quality. Ferrets (n = 55 males) were randomly assigned to one of five diet treatments (n = 11 per treatment): (1) horsemeat diet (control); (2) horsemeat diet + vitamin E (400 IU/kg Dry Matter) daily; (3) horsemeat diet + whole prey; (4) horsemeat diet + vitamin E daily + whole prey; and (5) beef diet. Both blood (prediet and postdiet change) and diets were analyzed for vitamin E, vitamin A, and SE concentrations. Electroejaculates were collected monthly and evaluated for sperm concentration, sperm motility index (includes percent motile and forward progression), and percent NS. Results reveal that the beef and horsemeat diets had comparable (P = 0.05) vitamin E and SE concentrations and all diets met most nutrient requirements for small carnivores; however, the horsemeat diet was excessive in vitamin A and the beef diet was deficient in vitamin A. Vitamin E supplementation increased (χ12=25.83; P < 0.001) serum vitamin E. Ferrets fed the beef diet or prey had improved (H4 = 15.596; P = 0.004) sperm motility index than the horsemeat control group, and ferrets fed the horsemeat diet supplemented with vitamin E had the lowest (H4 = 18.408; P = 0.001) NS. In conclusion, the high levels of vitamin A in the horsemeat diet could compete with vitamin E as evidence by serum levels, which may reduce reproductive success in this endangered species.