Effects of feed energy and protein level on growth and pelt parameters in blue foxes (Vulpes lagopus) in the late growing-furring period
The aim of the present study was to determine whether a decrease in feed energy content would prevent extreme body weight (BW) gain and fatness in blue foxes in the late growing-furring period, without compromising pelt quality or pelt size. BW gain, body mass index (BMI), body condition score (BCS), and pelt characteristics were studied in 60 blue foxes divided into four equal-sized groups from mid-October until pelting (50 days). Experimental diets in were “high energy – high protein”, “high energy – low protein”, “low energy – high protein”, and “low energy – low protein”. High-energy diets contained 19.3 MJ metabolisable energy (ME) in kg dry matter (DM) and high-protein diets contained digestible crude protein (DCP) 20% of ME. Low-energy diets contained 16.3 MJ ME in kg DM and low-protein diets DCP 17% of ME. Feeding was gradually increased towards ad libitum. Reduced ME intake had no effect on pelt size or pelt quality. High-energy feeds resulted in heavier animals with higher BMI. However, the final BW exceeded 20 kg and BCS was “fat” or “extremely fat” in all groups.