Effects of Dietary Metabolic Energy and Crude Protein Levels on Production Performance,Nutrient Digestibility,Serum Biochemical Parameters and Organ Index of Male Mink During Winter Fur-growing Period

The experiment was performed to evaluate the effects of dietary metabolic energy (ME) and crude protein (CP) levels on production performance, nutrient digestibility, serum biochemical parameter, and organ indexes in furring male mink. One hundred eighty healthy male mink of (145±5) d were randomly divided into 6 groups with 30 replicates, one mink for each replicate. We adopted a completely randomized 2×3 factorial experiment, and the mink were fed 6 experimental diets with two CP levels (30.45% and 34.58%) and three ME levels (13.11, 14.94 and 16.76 MJ·kg^-1), the feeding experiment was completed from September 29, 2018 to December 10, 2018. The results showed that:1) During 175 to 213 days old, the body weight (BW) of the mink in the 34.58% CP group was significantly higher than those in the 30.45% CP group (P<0.01), and the BW of the mink in the 13.11 MJ·kg^-1 ME group was significantly lower than those in the other ME groups (P<0.01). At the age of 175-190 and 213 days, the BW of the mink in A (CP 30.08%, ME 13.03 MJ·kg^-1) group was significantly lower than those in other groups (P<0.01). At 205 day, the maximum value of BW of mink was observed in E (CP 34.86%, ME 15.08 MJ·kg^-1) group. 2) The fresh skin length and weight of mink in 34.58% CP group were significantly greater than those in the 30.45% CP group (P<0.01), and the fresh skin length of mink in 14.94 MJ·kg^-1 ME group was significantly greater than those in other ME groups (P<0.05).However, the fresh skin weight of mink in the 16.76 MJ·kg^-1 ME group was significantly greater than those in 13.11 MJ·kg^-1 group (P<0.01). The fresh skin length and weight of mink in E (CP 34.86%, ME 15.08 MJ·kg^-1) group was significantly higher than those in A (CP 30.08%, ME 13.03 MJ·kg^-1) and B (CP 30.46%, ME 14.80 MJ·kg^-1) groups (P<0.01). 3) The fat digestibility of mink in the 34.58% CP group was significantly higher than those in the 30.45% CP group (P<0.01). The fat digestibility of mink in the 13.11 MJ·kg^-1 group was significantly lower than those in other groups (P<0.01).The fat digestibility of mink in the group A (CP 30.08%, ME 13.03 MJ·kg^-1) and D (CP 34.17%, ME 13.19 MJ·kg^-1) was significantly lower than those in other groups (P<0.01). 4) The content of serum LDL in 30.45% CP group was significantly higher than those in 34.58% CP group (P<0.01), but the HDL concentration in serum was significantly lower than that in 34.58% CP group (P<0.01).The concentration of serum Alb, GLU, CHO, TG and HDL of mink in the 13.11 MJ·kg^-1 ME group were significantly lower than 16.76 MJ·kg^-1 ME group (P<0.01). The concentrations of serum Alb, GLU of mink in the group C (CP 30.80%, ME 16.99 MJ·kg^-1), E (CP 34.86%, ME 15.08 MJ·kg^-1), and F (CP 34.72%, ME 16.53 MJ·kg^-1) were significantly higher than other groups (P<0.05). The concentration of serum HDL of mink in group E (CP 34.86%, ME 15.08 MJ·kg^-1) and F (CP 34.72%,ME 16.53 MJ·kg^-1) was significantly higher than other groups (P<0.01). 5) The heart and liver indexes of mink in 30.45% CP group were significantly higher than those in 34.58% CP group (P<0.05).The heart index of mink in the 13.11 MJ·kg^-1ME group was significantly higher than those in other groups (P<0.05).The heart and liver indexes of mink in group A (CP 30.08%, ME 13.03 MJ·kg^-1) were significantly higher than those in group E (CP 34.86%, ME 15.08 MJ·kg^-1) (P<0.05). In conclusion, when the dietary CP level was 34.86% and the ME level was 15.08 MJ·kg^-1, mink could obtain better growth performance and fur quality, higher digestibility of nutrients.