| This study was conducted to study the effects of different dietary vitamin D and calcium levels at a fixed ratio of calcium to phosphorus on production performance of mink in growth period(including growing period and fur-growing period).The purpose is to screen out the suitable level of vitamin D and calcium for mink in growing period and fur-growing period which can provide the theoretical basis for guiding the actual production.The paper consists of two parts:Part 1: Optimum level of vitamin D and calcium in growing minkOne hundred and seventeen healthy male minks at the age of(60±5)days with the similar body weight were randomly divided into 9 groups with 13 replicates each and 1 mink per replicate.Nine experimental diets were formulated by using 3 × 3 double factorial experimental design.The level of vitamin D in basal diet was 2 100 IU/kg and the level of calcium was 2.3% and the ratio of calcium to phosphorus was 2:1.The three supplementary levels of VD were 0 IU/kg,2 000 IU/kg and 4 000 IU/kg respectively;The three supplementary levels of calcium were 0%,0.4% and 0.8% respectively.The vitamin D and calcium in nine experimental diets were group ?(2 100 IU/kg×2.3%),group ?(4 100 IU/kg×2.3%),group ?(6 100 IU/kg×2.3%),group ?(2 100 IU/kg×2.7%),group ?(4 100 IU/kg×2.7%),group ?(6 100 IU/kg×2.7%),group ?(2 100 IU/kg×3.1%),group ?(4 100 IU/kg×3.1%),group ?(6 100 IU/kg×3.1%),respectively.The pretrial lasted for 13 days,and the formal trial lasted for 60 days.The results showed as follows:1)Dietary vitamin D and calcium levels had extremely significant effects on the final weight,average daily gain and F/G(P<0.01),and the final weight and average daily gain was the highest in group ?,the lowest in group ?,F/G was just the opposite.2)The fat digestibility in groups ?,? and ? was extremely significantly higher than those in groups ? and ?(P<0.01).The dry matter output of growing mink reached the highest when the dietary calcium supplementary level was 0.8%.The fat digestibility was extremely significantly lower when the dietary supplementary calcium level was 0.8% than that when the dietary calcium supplementary level was 0% and 0.4%(P<0.01).Dry matter output reached the lowest when the dietary vitamin D supplementary level was 2 000 IU/kg.The dry matter digestibility and fat digestibility reached the highest when the dietary vitamin D supplementary level was 2 000 IU/kg.3)Nitrogen retention showed a tendency to increase with the increase of dietary calcium level,and it was the highest at the 0.8% calcium supplementary level.Net protein utilization and protein biological value reached the highest when the dietary vitamin D supplementary level was 2 000 IU/kg.4)Fecal calcium and phosphorus increased with calcium levels(P<0.05).When the supplementary vitamin D level was 2 000 IU/kg,the digestibility of calcium and phosphorus were the highest(P<0.05).5)Serum TP and 25-OH-VD concentration at a VD supplementary level of 2 000 IU/kg was significantly higher than 4 000 IU/kg VD supplementary level(P<0.05).Serum 25-OH-VD concentration at 0% calcium supplementary levels were significantly lower than the other two supplementary levels(P<0.05).Conclusion: Comprehensive analysis of various indicators,under the conditions of this experiment,the diet of VD and calcium with different gradients was prepared.The growth performance,nutrient digestibility,nitrogen metabolism,calcium and phosphorus metabolism,serum biochemistry and other indexes was assayed.The results showed that when the ratio of calcium and phosphorus in the diet was 2:1,the VD level of the diet was 4 100 IU/kg and the calcium level was 3.1%,the growing mink obtained a better production performance.Part 2: Optimum level of vitamin D and calcium in fur-growing minkOne hundred and seventeen healthy male minks at the age of(135±5)days with the similar body weight were randomly divided into 9 groups with 13 replicates each and 1 mink per replicate.Nine experimental diets were formulated by using 3 × 3 double factorial experimental design.The level of vitamin D in basal diet was 2 300 IU/kg,and the level of calcium was 2.0%,the ratio of calcium to phosphorus was 1.7:1.The three supplementary levels of VD were 0 IU/kg?2 000 IU/kg and 4 000 IU/kg respectively;The three levels of calcium were 0%,0.4% and 0.8% respectively.The vitamin D and calcium in nine experimental diets were group ?(2 300 IU/kg×2.0%),group ?(4 300 IU/kg×2.0%),group ?(6 300 IU/kg×2.0%),group ?(2 300 IU/kg×2.4%),group ?(4 300 IU/kg×2.4%),group ?(6 300 IU/kg×2.4%),group ?(2 300 IU/kg×2.8%),group ?(4 300 IU/kg×2.8%),group ?(6 300 IU/kg×2.8%),respectively.The pretrial lasted for 13 days,and the formal trial lasted for 60 days.The results showed as follows:1)There was an extremely significant difference between F/G of mink and the lowest was in group ?(P<0.01).The calcium levels had a significant effect on the F/G(P<0.05),while the vitamin D levels had an extremely significant effect on the F/G(P<0.01).2)The calcium levels had an extremely significant effect on fat digestibility(P<0.01),0.8% calcium supplementary level was significantly lower than 0% and 0.4% calcium supplementary levels(P<0.01).3)The dietary levels of vitamin D and calcium had no significant effect on nitrogen metabolism index of mink(P>0.05).4)0% calcium supplementary level extremely significantly decreased fecal calcium and fecal phosphorus content(P<0.01),and increased calcium and phosphorus digestibility(P<0.01).Vitamin D supplementary levels of 0~2 000 IU/kg significantly increased calcium digestibility(P<0.05),extremely significantly reduced the fecal phosphorus content(P<0.01)and increased the phosphorus digestibility(P<0.01).5)The serum TP concentration significantly increased(P<0.05)and serum TG concentration significantly decreased(P<0.05)when the vitamin D supplementary level was 2 000 IU/kg.When the calcium supplementary level was 0.8%,the serum HDL concentration of mink significantly increased(P<0.05),and the concentration of LDL extremely significantly decreased(P<0.01).6)When the calcium supplementary level was 0%,the skin length of mink significantly increased(P<0.05).7)0.8% calcium supplementary level significantly increased mink heart index,liver index and spleen index(P<0.05),Vitamin D supplementary level of 0~2 000 IU/kg extremely significantly increased mink kidney index(P<0.01).8)when the vitamin D supplementary level in mink diet was 2 000 IU/kg,the relative expression of VDR and DBP genes in duodenum of mink was the highest.Conclusion: Comprehensive analysis of various indicators,under the conditions of this experiment,the diet of VD and calcium with different gradients was prepared.The growth performance,nutrient digestibility,nitrogen metabolism,calcium and phosphorus metabolism,serum biochemistry,organ index and other indexes was assayed.The results showed that when the ratio of calcium and phosphorus in the diet was 1.7:1,the VD level of diet was 2 300~4 300 IU/kg and the calcium level was 2.0%,the mink during fur-growing period obtained a better production performance. |
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