Effects Of Folic Acid And Selenium Supplementation On Lactation Performance,Nutrient Digestion,Ruminal Fermentation And Blood Metabolites In Dairy Cows

The study investigated the effects of coated sodium selenite(CSS)and coated folic acid(CFA)on lactation performance,rumen fermentation and blood metabolites in dairy cows.Fourty-four Holstein cows with a body weight(BW)of 635 ± 14.5 kg,days in milk(DIM)of 115 ± 9.6 d and daily milk yield of 33.6±2.4 kg were selected and randomly divided into 4 groups according to BW,DIM and daily milk yield using2×2 factors design.The results showed that:(1)Addition of CSS increased(P < 0.05)yield of actual milk,fat corrected milk and milk protein but decreased(P < 0.05)urea nitrogen and somatic cell number in milk.Supplementation with CFA increased(P < 0.05)yield of actual milk,fat corrected milk and lactose but decreased milk urea nitrogen and somatic cell number.Lower(P < 0.05)feed conversion rate was observed for CSS or CFA group.Addition of CSS increased(P < 0.05)the ratio of saturated fatty acids to unsaturated fatty acids in milk.(2)Digestibility of dry matter,non-fibrous carbohydrate(NFC),neutral detergent fiber(NDF)and acid detergent fiber(ADF)in the total-tract increased(P < 0.05)with CSS or CFA addition.Addition of CFA increased(P < 0.05)total-tract digestibility of organic matter and crude protein.(3)Supplementation of CSS reduced(P < 0.05)ruminal p H,butyric acid proportion,ammonia nitrogen concentration and acetate to propionate ratio(A:P)but increased(P < 0.05)total volatile fatty acids(TVFA)concentration and propionic acid proportion.Supplemented with CFA decreased(P < 0.05)ruminal p H,propionic acid proportion and ammonia nitrogen concentration but increased(P < 0.05)TVFA concentration,proportion of acetic acid,isobutyric acid and isovaleric acid as well as A:P.(4)Activity of pectinase,amylase and protease was higher(P < 0.05)for CSS group and CFA group.Activity of cellobiase and xylanase was higher(P < 0.05)in CFA group.(5)Addition of CSS or CFA increased population of total bacteria,fungi,protozoa,R.albus,R.flavefaciens,B.fibrisolvens and Rb.amylophilus(P < 0.05).Supplementation with CFA increased population of total methanogens and F.succinogenes(P < 0.05)but population of P.ruminicola decreased(P < 0.05)in the CSS group.(6)Supplementation of CSS increased content of total protein,albumin,total cholesterol,glutathione peroxidase,growth hormone and insulin growth factor 1 in serum(P < 0.05)but decreased(P < 0.05)the concentration of urea nitrogen.Serum content of total protein,albumin,folate,growth hormone,insulin and insulin growth factor 1 was increased(P < 0.05)but urea nitrogen,total cholesterol and homocysteine was decreased(P < 0.05)by CFA supplemented.The interaction between CSS and CFA was significant on somatic cell number,total bacteria,R.albus,alpha-amylase and serum insulin concentration(P < 0.05).The results indicated that supplementation of CSS or CFA was beneficial to the growth of rumen microorganisms,nutrient digestibility and lactation performance of cows.