Study On The Interaction Effect Of Energy And Protein On Production Performance And Energy Metabolism Of Mink During Growing-furring Period

In this study,male short-hair black mink in growing-furring period（growing period and winter fur growing period）was used as the research object to prepare diets with different levels of crude protein（CP）and metabolizable energy（ME）.We adopted feeding test,digestion and metabolism test,serum test,slaughter test and indirect respiration calorimetric experiments to determin the optimum CP and ME level in diet,analyze and calculate NE and ME_m requirement of male mink to provide more accurate reference data for mink industry.The paper consists of four parts:Part 1:Study on the optimum level of diatery CP and ME in growing minkOne hundred forty-four healthy male minks at the age of（75±5）days with the similar body weight were randomly allocated into six groups with 24 replicates,which was one mink for each replicate.A 2×3 factorial design was adopted in this study,the mink was fed six experimental diets and the CP and ME levels of each group were group A（31.17%,14.05 MJ/kg）,group B（31.50%,16.61MJ/kg）,group C（32.09%,17.52 MJ/kg）,group D（35.78%,14.91 MJ/kg）,group E（35.14%,16.21MJ/kg）,and group F（35.97%,18.18 MJ/kg）,respectively.The results showed as followed.（1）The final body weight（FBW）,average daily gain（ADG）were significantly increased by the dietary CP or ME levels（P<0.01）.The maxmum of FBW and ADG of mink was observbed in F group.（2）The fat digestibility of mink in 35.63%CP group were significantly higher than those in low dietary CP level（31.59%）group（P<0.05）.The fat digestibility,digestion rate of gross energy（DE/GE）and metabolic rate of gross energy（DE/GE）were significantly increased by the dietary ME levels（P<0.05）.Mink in the F group had higher fat digestibility,nitrogen deposition content and energy utilization than those in other groups.（3）The serum GLU and LDL-C concentration of the mink fed the 35.63%CP or 17.73MJ/kg ME level diet were significantly higher than those in other group（P<0.05）,and the maximum value of serum GLU,LDL and TG concentration was observed in F group.In conclusion,the optimum dietary CP and ME levels were 35.97%and 18.18 MJ/kg respectively,which can improve growth performance,enhance nutrient digestion in growing mink.Part 2:Study on the optimum level of diatery CP and ME in winter fur-growing minkOne hundred and eighty heathy male minks at the age of（145±5）days with the similar weight were randomly assigned into 6 groups with 30 replicates per group and 1 mink per replicate.A 2×3 factorial design was adopted in this study,the mink was fed six experimental diets and the dietary CP and ME levels of each group were group A（CP 30.08%,ME 13.03 MJ/kg）,group B（CP 30.46%,ME 14.80MJ/kg）,group C（CP 30.80%,ME 16.99 MJ/kg）,group D（CP 34.17%,ME 13.19 MJ/kg）,group E（CP34.86%,ME 15.08 MJ/kg）,and group F（CP 34.72%,ME 16.53 MJ/kg）,respectively.The results showed as followed.（1）The FBW,ADG,F/G and fur quality in 30.45%CP group were significantly lower than those in 34.58%CP group（P<0.01）.The ADFI,F/G,body length and fresh fur length of14.94 MJ/kg ME group were significantly higher than those in other groups（P<0.05）.The mink in F group had better growth performance and fur quality than others.（2）The fat digestibility,nitrogen deposition content of mink in the 34.58%CP group was significantly higher than those in 30.45%CP group（P<0.01）.The nitrogen deposition content and nitrogen utilization of mink in C and E group was higher than others,and mink in E group had higher energy utilization than those in other groups.（3）The serum LDL concentration in 30.45%CP group was significantly higher than those in 34.58%CP group（P<0.01）,but serum HDL concentration was significantly lower than those in 34.58%CP group（P<0.01）.Serum Alb,GLU,CHO,TG and HDL concentration in the 13.11 MJ/kg ME group were significantly lower than those in the high ME group（P<0.01）,but the heart index of mink in this group was significantly higher than those in other groups（P<0.05）.The metabolism of protein,sugar and lipid of mink in E and C group was more vigorous,the heart and liver indexes of mink in group A were significantly higher than those in group E（P<0.05）.In conclusion,when dietary CP level is 34.86%and ME level is 15.08 MJ/kg,the mink can get better growth performance,fur quality and higher nutrient digestibility.Part 3:Research of net energy requirement of mink during growing periodBased on the first part of the experiment,the net energy requirement of mink in growing period was measured by using Open circuit respiratory calorimetry with 6 chambers in parallel for fur animal.（Method）Twenty four heathy male minks at（75±5）days of age were fed with the opitumu dietary ME and CP level experimental diet that has been evaluated by the first trial.An adaptation period of 7 d was used to adjust to the new feeding level and then the respiration calorimetric experiment was carried out.The respiration calorimetric test was conducted in 3 phases,with a period of 7 d,3 replicates per period,and 3 mink for each replicate.Before the beginning of each respiration calorimetric experiment,the test animals were weighed and 9 minks were selected from them and each 3 minks were put into one-respiration chambers.There were 1 d for adaptation at day 2 for a 3 d balance trail,and then at day5 followed by a 3 d fasting period.The results showed as followed.（1）The heat production（HP）was530.03 kJ/kg BW^0.75/d,the net energy requirement for growth（NEg）was 766.92 kJ/kg BW^0.75/d during balance trail.Fast heat production（FHP）was 414.87 kJ/kg BW^0.75/d,the total net energy（NE）requirement was 1181.79 kJ/kg BW^0.75/d.（2）The metabolizable energy requirement for maintenance（MEm）and net energy requirement for maintenance（NEm）estimated from the linear relationship between RE and MEI were 518.47 and 436 kJ/kg BW^0.75/d,respectively.The ME_m and NE_m estimated by logarithmic regression of HP on MEI were 529 and 467.98 kJ/kg BW^0.75/d,respectively.In conclusion,the energy requirements of the mink at the growing stage of 1.30～2.58 kg were:ME_m518～529 kJ/kg BW^0.75/d,NE_m 414.87～467.98 kJ/kg BW^0.75/d,NE_g 766.92 kJ/kg BW^0.75/d,NE 1181.79kJ/kg BW^0.75/d,respectively.Part 4:Research of net energy requirement of mink during winter fur-growing periodThe experiment was carried out based on the second part of the study by using Open circuit respiratory calorimetry with 6 chambers in parallel for fur animal.Thirty heathy male minks were fed the diet with opitumu dietary ME and CP level that has been evaluated by the second trial.An adapted period of 7 d was used to adjust to the new feeding level and then the respiration calorimetric experiment was carried out.The respiration calorimetric test was conducted in 3 phases,with a period of 7 d,3 replicates per period,and 2 mink for each replicate.Before the beginning of each respiration calorimetric experiment,the test animals were weighed and 6 minks were selected from them.The results showed as followed:（1）The HP was 526.31 kJ/kg BW^0.75/d,NE_g was 229 kJ/kg BW^0.75/d during balance trail.The FHP was 489.75 kJ/kg BW^0.75/d,the NE requirement was 718.75 kJ/kg BW^0.75/d.（2）The ME_m and NE_m estimated from the linear relationship between RE and MEI were 519.80 and 493.20kJ/kg BW^0.75/d,respectively.The ME_m and NE_m estimated by logarithmic regression of HP on MEI were 521.4 and 474.24 kJ/kg BW^0.75/d,respectively.In conclusion,the energy requirements of the male mink at the growing stage of 1.92～2.40 kg were,ME_m 514～519.80 kJ/kg BW^0.75/d,NE_m 474.24～493.20kJ/kg BW^0.75/d,NE_g 229 kJ/kg BW^0.75/d,NE 718.75 kJ/kg BW^0.75/d,respectively.