| This study was conducted to study the effects of different dietary calcium and phosphorus levels on nutrient digestibility,nitrogen metabolism,serum biochemical indices,tibia quality,growth performance and calcium metabolism and phosphorus metabolism of minks in growth period.The purpose is to screen out the suitable level of calcium and phosphorus for mink in growing period and fur-growing period,and provide the theoretical basis for guiding the actual production.The paper consists of two parts: Part 1: Optimum level of calcium and phosphorus in growing minkNinety healthy female mink at the age of 70-days with the similar body weight were randomly divided into 9 groups with 10 replicates each and 1 mink per replicate.Firstly,setting 3 phosphorus levels:1%,1.4%,1.8%;secondly,setting 3 calcium-phosphorus ratios at the same phosphorus levels:1,1.5,2.The mink in 9 groups were fed experimental diets with calcium and phosphorus supplementation levels of group?(1.02% Ca,0.96% P),group?(1.49% Ca,1.00% P),group ?(1.98% Ca,1.01% P),group ?(Ca1.47%,P1.35%),group ?(2.11% Ca,1.40% P),group ?(2.81% Ca,1.40% P),group ?(1.83% Ca,1.73% P),group ?(2.70% Ca,1.80% P)and group ?(3.59% Ca,1.80% P).The trial lasted for 60 days.The results showed as follows: 1)Phosphorus levels had significant effects on the final weight and average daily gain(P<0.01),and had significant effects on average daily feed intake and feed/gain(P<0.05).The calcium-phosphorus ratios only had significant effects on average daily gain(P<0.01),and had no significant effects on the final weight and feed/gain(P>0.05).The interaction between phosphorus levels and calcium-phosphorus ratios in the average daily gain was significant(P<0.01).the final weight and average daily gain of group ? were the maximum while the feed/gain was the minimum.2)The protein digestibility of each group was different significantly,the protein digestibility of group ?and group ? were higher than others,the group ?was the lowest.Phosphorus levels had significant effects on the protein digestibility(P<0.01),but the calcium-phosphorus ratios had no significant effects on the DM digestibility,fat digestibility and protein digestibility.The fat digestibility had a trend of first increase and then decrease with the increasing of calcium-phosphorus ratios.3)There was no significant difference among all groups in nitrogen intake,urea nitrogen retention,fecal nitrogen(P>0.05).The biological value of protein and net protein utilization were different significantly(P<0.01)and the nitrogen deposition was also different significantly(P<0.05).The calcium-phosphorus ratios had significant effects on biological value of protein and net protein utilization(P<0.01).With the phosphorus levels increasing,the fecal nitrogen began to decline,but the biological value of protein and net protein utilization began to increase.The nitrogen deposition and net protein utilization of group ? were the highest.4)Fecal calcium,fecal phosphorus,calcium digestibility and phosphorus digestibility were all different significantly among all groups(P<0.01).Different levels of phosphorus and calcium-phosphorus ratios in diets had significant effects on fecal calcium,fecal phosphorus,calcium digestibility and phosphorus digestibility(P<0.01).The fecal calcium and fecal phosphorus of group ? were significant higher than other groups(P<0.01).The calcium digestibility of group ?was significant higher than others(P<0.01).The phosphorus digestibility of group? was significant higher than others(P<0.01).5)Calcium,phosphorus levels increased serum calcium content(P < 0.01).Calcium,phosphorus levels increased serum phosphorus content(P < 0.01).Different levels of phosphorus and calcium-phosphorus ratios in diets had significant effects on the content of ALP(P<0.01).With the increasing of phosphorus level,the ALP content increased after an initial decrease(P<0.01).With the increasing of the ratio of calcium to phosphorus,the content of ALP increased first and then decreased(P<0.01).Conclusion : Comparing the growth performance and nitrogen metabolism,dietary 1.4% ~1.8%phosphorus level and calcium-phosphorus ratios from 1.5 to 2 is considered to be an optimal supplemental level for growing minks.Part 2: Optimum level of calcium and phosphorus in winter fur-growing season minkNinety healthy female mink at the age of 130-days with the similar body weight were randomly divided into 9 groups with 10 replicates each and 1 mink per replicate.Firstly,setting 3 phosphorus levels:1%,1.4%,1.8%;secondly,setting 3 calcium-phosphorus ratios at the same phosphorus levels:1,1.5,2.The mink in 9 groups were fed experimental diets with calcium and phosphorus supplementation levels of group?(1.03% Ca,0.97% P),group?(1.47% Ca,0.98% P),group ?(1.98% Ca,0.99% P),group ?(Ca1.45%,P1.37%),group ?(2.08% Ca,1.38% P),group ?(2.79% Ca,1.38% P),group ?(1.81% Ca,1.75% P),group ?(2.70% Ca,1.79% P)and group ?(3.59% Ca,1.80% P).The trial lasted for 77 days.The results showed as follows: 1)Different dietary phosphorus levels and calcium-phosphorus ratios had significant effects on the final weight,average dally gain,interaction was also significant(P<0.01).The final weight and average dally gain in group ? was higher than any other group.2).The DM digestibility,fat digestibility and protein digestibility had a same trend of first increase and then decrease,the group ? was higher than any other group.3)Different dietary phosphorus levels and calcium-phosphorus ratios had no significant effects on nitrogen intake,urea nitrogen retention,fecal nitrogen,biological value of protein,and net protein utilization(P>0.05).4)The content of fecal calcium increased while the dietary phosphorus levels increasing,and the difference was very significant,(P<0.01).The content of fecal calcium in group ?,?were higher than any other group(P<0.01).The content of fecal phosphorus increased with the dietary phosphorus levels increasing(P<0.01).When the ratio of calcium to phosphorus was 2,the content of fecal phosphorus was the lowest,and the difference was very significant(P<0.01).The content of fecal phosphorus in group ? was the highest,the content of fecal phosphorus in group ? was the lowest(P<0.01).Different levels of phosphorus in diets had no significant effects on calcium digestibility(P>0.05).Different calcium-phosphorus ratio had significant effects on calcium digestibility(P<0.01),calcium digestibility increased with calcium and phosphorus ratio increasing.The calcium digestibility of group III was significantly higher than other groups(P<0.01).Different dietary phosphorus levels and calcium-phosphorus ratios had no significant effects on the phosphorus digestibility(P>0.05).5)Phosphorus levels increased serum calcium content(P < 0.01).With the increasing of calcium level,the serum calcium content increased after an initial decrease(P<0.01).Phosphorus levels increased serum phosphorus content(P < 0.01).With the increasing of calcium level,the serum phosphorus content increased after an initial decrease(P < 0.01).With the increasing of the ratio of calcium to phosphorus,the content of ALP increased first and then decreased(P<0.01).The effect of phosphorus level on ALP content was not significant,but with the increasing of phosphorus level,the content of ALP present the trend of first decline then up.6)There was significant difference in bone length between groups(P <0.05).The ratio of calcium to phosphorus had significant effect on the length of mink bone(P <0.05).With the increasing of calcium level,bone weight decreased.Different levels of phosphorus and calcium-phosphorus ratios in diets had no significant effects on the content of Ash(P >0.05).There was significant difference in the content of bone calcium between groups(P <0.01).The content of group ? was significantly higher than that of other groups,and the content of?and ?was significantly lower than that of other groups.The effect of phosphorus and calcium-phosphorus ratios on the calcium content of mink was not significant,but the interaction was significant(P <0.01).The interaction between phosphorus and calcium-phosphorus ratios on the content of bone phosphorus was significant(P <0.01).Different levels of phosphorus in diets had no significant effects on the content of bone phosphorus(P >0.05)while the calcium-phosphorus ratios had significant effects on the content of bone phosphorus(P <0.01).With the increasing of calcium levels,bone phosphorus content decreased.7)Different dietary phosphorus levels and calcium-phosphorus ratios had no significant effects on the body length,pile fur length and fur length on the board(P>0.05).Different dietary phosphorus levels had no significant effects on guard fur length(P>0.05),Different dietary calcium-phosphorus ratios had significant effects on guard fur length(P<0.01).The guard fur length was shortest while calcium-phosphorus ratios was 1.Different dietary phosphorus levels had no significant effects on guard fur length /pile fur length fur length(P>0.05).Different dietary calcium-phosphorus ratios had significant effects on guard fur length /pile fur length fur length(P<0.05).The guard fur length /pile fur length fur length between groups was different(P<0.05).Conclusion:Comparing all quotas,dietary 1%~1.4% phosphorus level and calcium-phosphorus ratios from 1.5 to 2 is considered to be an optimal supplemental level for mink in terms of reducing feed expenses,tibia quality and maintaining growth performance. |
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