Effects Of Dietary Energy Level In Late Gestation On Milk Composition And Serum Biochemical Indices Of Female Donkeys At Different Postpartum Time

Donkey milk has the characteristics of high lactose and low milk fat,and its nutritional value is close to that of human milk,and it has rich active ingredients,so it has gradually attracted the attention of consumers.In this thesis,the effects of dietary energy levels in late pregnancy on the content of lactose,milk fat,milk protein,total milk solids and non-fat solids content of donkeys at different times after parturition were investigated,and the changes of amino acid and mineral contents and serum biochemical indicators in plasma and milk were studied.The completely two-factor test design was adopted in this study.Twenty-four Texas donkeys with similar age,body weight and pre-delivery days were selected,Factor 1 was prenatal diet energy level(DEL),which was divided into three levels: high energy(HE),medium energy(ME)and low energy(LE),with 8 donkeys in each group and 1 replicate in each group.Litters were fed 10.95%(HE),10.53%(ME)and 9.98%(LE)MJ/Kg diets on 60 d before birth,and the same lactation diet was fed on 30 d after foaling.The experiment lasted for 90 days.The second factor was postpartum time(PT).Blood and milk samples were collected at 11 time points,including 0h,6h,12 h,24h,48 h,3d,5d,7d,14 d,21d and28 d.The experiment was divided into three parts.The experiment 1 mainly studied the effect of dietary energy levels in late gestation on serum biochemical parameters and conventional components in colostrum and standing milk of female donkeys at different times after parturition was investigated.The results showed that: The contents of postpartum milk protein,lactose,total milk solids and non-fat solids in LE and ME groups were significantly higher than those in HE group(P<0.05).Milk fat content in HE group was significantly higher than that in LE and ME groups(P<0.05).The interaction of dietary energy level and time postpartum had a significant effect(P<0.05)on milk composition,mainly in colostrum,i.e.feeding diets with low and medium energy levels in late pregnancy increased the concentration of milk protein,lactose,total solids and non-fat solids in postpartum colostrum,especially at low energy levels.The protein,milk fat,total solids and nonfat solids content of colostrum from 7 d after parturition was higher than that of normal milk from 14 d to 28 d after parturition,and even higher within 6 h after parturition,especially at 0 h after parturition,after which they all decreased significantly with the extension of the postpartum period;the lactose content showed an opposite change,with the lowest at 0 h.The various milk components stabilized from 14 d to 21 d after parturition.This thesis yielded that the ranges of protein,fat,lactose,total solids and non-fat solids in colostrum at 6 h postpartum were 7.64% to 12.54%,1.64% to 2.03%,3.01% to 5.62%,15.02% to 19.70% and 13.17% to 17.79%,respectively;the ranges of standing milk at 14 to 28 d postpartum were 2.0% to 2.43%,0.19%～0.31%,6.36%～7.02%,9.25%～9.88% and 8.94%～9.99% respectively.Postpartum serum ALT,AST,ALP,CRE,CHO,TG,LDL-C,BHBA,GN,INS,PRG and NEFA levels were reduced and TP,ALB,GLU,LEP,FSH and PRL levels were increased in the ME and LE groups compared to the HE group.Compared to the ME group,serum CRE levels were reduced and ALT,AST,ALP activity and UREA,HDL-C,GN and INS levels were increased in the LE group of female donkeys.The experiment 2 mainly studied the effects of dietary energy level in late pregnancy on the contents of amino acids in plasma and milk of female donkeys at different postpartum times.The results showed that: Plasma and milk levels of most single AAs and BCAA,LAA,DAA,FAA and TAA were significantly higher in the LE and ME groups than in the HE group(P<0.05).plasma and milk levels of EAA/TAA and EAA/NEAA were significantly higher in the HE group than in the LE and ME groups(P<0.05).With the prolongation of lactation time,the contents of 17 kinds of single AA in plasma and milk of female donkey showed a decreasing trend at different postpartum times,and the contents were higher at 0h postpartum,decreased rapidly from 6 to 12 h postpartum,and tended to be stable at 21 d postpartum.EAA/TAA and EAA/NEAA in plasma and milk increased with the prolonging of postpartum time.The interaction between dietary energy level and postpartum time during the later stages of pregnancy had a significant effect on plasma and milk AA content and composition,mainly in colostrum,but little effect on regular milk.The experiment 3 mainly studied the late pregnancy diet energy levels in plasma and milk with mare after different time the influence of the mineral content,the results showed that: The donkey milk Ca,Mg,Fe and Zn contents in the HE group were significantly higher than those in the LE group(P<0.05);the donkey milk P and Zn contents in the ME group were significantly higher than those in the LE group(P<0.05);the donkey milk Se contents in the HE and ME groups were significantly lower than those in the LE group(P<0.05);the plasma Ca,Mg and Se contents in the ME group were significantly higher than those in the LE group(P<0.05);the plasma K,Mg and Mn levels in the LE group were significantly higher than those in the HE group(P<0.05);plasma Se and Mo levels in the HE group were significantly higher than those in the LE group(P<0.05).Plasma and milk concentrations of Ca,K,Mg,P,Fe,Cu,Mn,Co,Se,Zn and Mo were higher in the 7d postpartum period than in the 14d～28d postpartum period.In summary,the effect of feeding diets with medium and low dietary energy levels in late pregnancy on postpartum milk composition is mainly reflected in the effect on colostrum,which can increase the content of total solids,non-fat solids,milk protein,lactose and most AA in donkey colostrum,and increase the content of Ca,K,Mg,P,Fe,Cu,Mn,Co,Se,Zn and Mo in colostrum;feeding diets with high energy levels can improve donkey colostrum protein The amino acid balance of colostrum can be improved by feeding a diet with high energy levels.The levels of milk fat,milk protein,AA and minerals in colostrum are all higher than in normal milk,especially in the first6 h after parturition,and decrease rapidly from 12 to 24 h after parturition;the opposite is true for lactose content.