| The present study was conducted to investigate the effects of different levels of MetaSmart on milk production and blood components and free amino acids in heat-stressed dairy cows to search for a new method to release negative influence of heat-stress.Experiment1:According to age, number of lactations, milk production and days in milk, Thirty six Chinese-Holstein cows were chosen. And they were divided into3groups (12cows per treatment). The cows freed in stalls. Before the experiment started there was a7days adaptation and this study lasted70days. Cows were fed a common TMR containing corn silage, alfalfa hay, grass hay, concentrates and mineral pellet. No2-hydroxy-4-methionine isopropyl was included in diet of control group.2-hydroxy-4-methionine isopropyl was hand-mixed in the TMR at the first and third feeding and consisted of0(Control) and13(Treatment Ⅰ) and30(Treatment Ⅱ) g/cow/day. The results show us that average milk production of the treatment cows were0.59kg/day and0.52kg/day higher than that of the control. The milk fat, protein, lactose, non-fat solids and total solid of treatment I had risen, but the differences were insignificant (P>0.05). The milk composition of treatment II, only lactose has risen, the difference was insignificant (P>0.05). The SCC of treatments was observed by21%and15.2%, the differences were insignificant (P>0.05). Treatments rectal temperature were decreased by0.17℃and0.1℃. MUN was increased by0.12%and13.38%, the difference was insignificant (P>0.05). It is shown that the2-hydroxy-4-methionine isopropyl can improve the milk production and milk composition, reduce rectal temperature and SCC. Supplementation of13g/d is more economic and effective.Experiment2:The design was the same as Experiment one and the blood samples were taken before the trial, and at the fourth and eighth wk, during the trial. Blood plasma was collected for later analysis. Blood T3, T4, cortisol, GSH-Px, SOD, HSP70, LDH, ALP, GLB had a significant increase in treatments which comparing with control (P<0.05). And the T3of treatment II has a high significant increase (P<0.01). MDA, NO, CPK, Glu had significant decrease in treatments than that of control (P<0.05). The2-hydroxy-4-methionine isopropyl has no effect on ALB. It is suggested that2-hydroxy-4-methionine isopropyl could raise the ability of heat-stressed cows of releasinge negative influence of heat-stress.Experiment3:Nine Chinese-Holstein cows were entered the study. The cows were divided into3groups (3cows per treatment) according to the age, number of lactations, milk production and days in milk. No2-hydroxy-4-methionine isopropyl was included in diet of control group.2-hydroxy-4-methionine isopropyl was hand-mixed in the TMR and consisted of Og (Control) and13g (Treatment I) and30g (Treatment II), fed in one time. Four and zero hour before feeding2-hydroxy-4-methionine isopropyl, blood sample was taken each time. After feeding, blood sample was taken by4h per time, last16h. Blood plasma was collected for free amino acid, T3, T4, cortisol, and index of anti-oxidant analysis. It is suggested that before feeding2-hydroxy-4-methionine isopropyl, the control blood methionine was closed to treatments, and supplementing2-hydroxy-4-methionine isopropyl, blood methionine could reach the peak at4h, and at8h it came back to the control level. It has a good ability to make the anti-oxidant enzyme and hormone stabled, decrease the level of NO and MDA. It can not raise the content of lysine and total amino acid in blood. |
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