Effects Of Different Selenium Sources On Performance,Blood Indexes And Selenium Concentrations In Mid-lactation Dairy Cows

This objective of the present study was to evaluate the effects of hydroxy-analogue of selenomethionine(HMSeBA)on performance,blood biochemical indexes,selenium concentrations in milk and plasma,and apparent nutrient digestibility compared to sodium selenite,which might provide a reference basis for the application of HMSeBA in dairy cow.The specific contents are as follows:Experiment 1: The objective of this study was to evaluate the supplementation of different levels of HMSeBA on performance,blood biochemical indexes,antioxidant indexes and selenium concentrations in milk and plasma of mid-lactation Holstein dairy cows.Sixty mid-lactation Holstein dairy cows with similar milk yield,parity and days in milk were randomly assigned to one of four treatments(n = 15).All treatments were: 1)control group(Control,basal diet without Se supplementation from premix);2)SO-0.1(basal diet supplemented with HMSeBA to achieve 0.1 mg Se/kg DM);3)SO-0.3(basal diet supplemented with HMSeBA to achieve 0.3 mg Se/kg DM);4)SO-0.5(basal diet supplemented with HMSeBA to achieve 0.5 mg Se/kg DM).The experiment lasted for 70 days with a pretrial period of 14 days.Supplementation of different levels of HMSeBA did not influence dry matter intake,milk yield and milk composition(P>0.05),while the percentages of milk fat(P=0.06)and total solids(P=0.05)tended to increase linearly as the doses of supplemented HMSeBA enhanced.Besides,the serum aspartate aminotransferase,alanine aminotransferase,alkaline phosphatase,creatine kinase,cholinesterase,glucose,creatinine,urea and uric acid were not affected by the levels of HMSeBA(P>0.05).The activity of total antioxidant capacity(T-AOC)in serum peaked in SO-0.3 treatment(P<0.05).Dietary supplementation of HMSeBA linearly elevated the activity of glutathione peroxidase(GSH-Px)but decreased the concentration of malondialdehyde(MDA)in serum(P<0.01).No differences were observed in superoxide dismutase with the supplementation of HMSeBA in the four treatments compared to Control.Dietary HMSeBA not only improved the total selenium concentration in plasma linearly(P<0.01),but the concentration of selenium concentration in milk(P<0.01).Experiment 2: The objective of this study was to evaluate the supplementation of different selenium sources on performance,antioxidant indexes and nutrient apparent digestibility of mid-lactation Holstein dairy cows.Forty five mid-lactation Holstein dairy cows with similar milk yield,parity and days in milk were randomly assigned to one of three treatments(n = 15).The cows were fed 3 diets: negative control(Control,basal diet without Se supplementation from premix),organic selenium [SO,basal diet supplemented with HMSeBA to achieve 0.3 mg Se/kg DM],and inorganic selenium(SS,basal diet supplemented with sodium selenite to achieve 0.3 mg Se/kg DM).The experiment lasted for 91 days with a pretrial period of 7 days.Supplementation of selenium did not influence dry matter intake,milk yield and milk composition(P>0.05).Compared with Control,HMSeBA supplementation improved the activity of serum T-AOC and GSH-Px(P<0.01),while decreased the content of MDA significantly(P<0.01).However,there were no differences between Control and SS(P>0.05).Neutral detergent fiber,acid detergent fiber and dry matter apparent digestibility was not affected by treatments(P>0.05).Compared to Control,supplementation with HMSeBA enhanced the apparent digestibility of organic matter,crude protein and ether extract(P<0.05).Besides,supplementation of sodium selenite increased the apparent digestibility of organic matter and crude protein,but there was no difference between Control and SS(P>0.05).These results indicated that selenium did not influence performance of dairy cows.However,compared with the Control,the antioxidant indexes and apparent digestibility were improved by supplementation of selenium and the effect of HMSeBA was better than inorganic selenium.To sum up,according to the effect and cost of HMSeBA,the best recommended dose for the dairy cow was 0.3 mg Se/kg DM,and the effect of HMSeBA was significantly better than that of the sodium selenite.