Abstract: The experiment was conducted to study the regularity of digestibility and metabolism of diets with different protein levels in fox at prepare breeding period. 180 blue foxes were randomly divided into 4 groups with 45 replicates and each replicate had 1 fox. The foxes in 4 groups were fed with protein levels of 21.64% (group Ⅰ), 26.21% (group Ⅱ),30.43% (group Ⅲ) and 35.10% (group Ⅳ), respectively. The experiment lasted for 52 days, including preset period for 7 days and test period for 45 days. The results showed as follows: foxes in different groups had no significant difference in dry matter output, protein digestibility, fecal nitrogen (P>0.05); dry matter intake in groups Ⅲ and Ⅳ was significant higher than that in groups Ⅰ and Ⅱ （P<0.05 or P<0.01）; the digestibility of fat in group Ⅲ was significant higher than that in groups Ⅰ, Ⅱ and Ⅳ （P<0.05 or P<0.01）; the nitrogen retention in group Ⅳ was significant lower than that in groups Ⅰ, Ⅱ and Ⅲ（P<0.01）. With the increase of dietary protein levels, nitrogen intake and urine nitrogen were increased (P<0.05 or P<0.01), net protein utilization and biological value of protein gradually decreased (P<0.05 or P<0.01). In conclusion, when the protein level of diet arrived at 30.43%, the nutrient digestibility was optimal, but the diet of 21.64% protein level can satisfy the protein need of the fox at prepare breeding period, and CP utilization efficiency is highest.

Key words: prepare breeding period; protein level; blue fox; digestibility and metabolism