Effects of dietary fat:Carbohydrate ratio on nutrient digestibility, serum parameters, and production performance in male silver foxes (Vulpes vulpes) during the winter fur-growing period

Abstract

Forty male silver foxes were used to investigate the effects of increasing dietary fat:carbohydrate (F:C) ratio {34:34, 41:28, 48:22, and 55:17 [metabolizable energy basis (ME)]} on growth performance, nutrient digestibility, serum parameters, and pelt quality during the winter fur-growing period. The results showed that average daily feed intake, average daily ME intake, average daily gain (ADG), feed efficiency, and protein digestibility were improved (P < 0.01 or P < 0.05) when dietary F:C ratio ranging from 34:34 to 48:22. However, foxes that received the 55:17 feed had lower (P < 0.05) ADG and protein digestibility than the other groups. The fat digestibility was increased (P < 0.01), and the carbohydrate digestibility was decreased (P < 0.01) with the increasing dietary F:C ratio. In addition, serum triglyceride and low-density lipoprotein cholesterol significantly increased (P < 0.05) as dietary F:C ratio increased. Changing dietary F:C ratio from 34:34 to 48:22 resulted in an increase in pelt quality, but it had negative effects on growth and pelt quality when foxes received 55:17 feed. We conclude that the optimal dietary F:C ratio for silver foxes during the winter fur-growing period was 48:22.