Effects of dietary supplementation of 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester on productive performance and blood biochemical indexes in dairy cows.

The trial was conducted to study the effects of supplementation of 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester (HMBi) for balancing dietary Lys-Met on productive performance and blood biochemical indexes in dairy cows. Forty-five Holstein dairy cows with 2～3 embryoes in late dry period were selected and assigned randomly into A,B and C group which contained 15 dairy cows. Group A as control group was fed a basal diet during total experimental period; for balancing dietary Lys-Met,group B was fed the basal diet with HMBi supplementation started from calving (1 d post-partum),and the group C was fed the basal diet with HMBi supplementation from 15 d pre-partum. The experimental period was from 15 d pre-partum to 90 d post-partum. The results showed as follows: compared with control group,the milk yields in groups B and C were significantly increased by 3.24 and 3.97 kg/d,respectively (P0.05). The milk fat percentage in group C was significantly higher than that in control group and group B (P0.05),and there was no significant difference between control group and group B (P0.05). The milk fat absolute yields in groups B and C were significantly increased by 0.14 and 0.18 kg/d (P0.05) compared with control group,respectively. Although there was no significant difference in milk protein percentages among groups (P0.05),the milk protein yield of groups B and C was 0.10 and 0.09 kg/d higher than that in control group (P0.05),respectively. There was no significant difference of serum glucose among all groups at day 90 of post-partum (P0.05). HMBi supplementation in dairy cows had no significant effects on milk urea nitrogen (MUN),blood urea nitrogen (BUN) and serum total amino acid (P0.05); however,there was a decreasing tendency in BUN and MUN. The concentrations of serum non-esterified fatty acid (NEFA),triglyceride (TC) and total cholesterol were not significantly influenced by dietary HMBi supplementation (P0.05),but there was a trend to decrease the NEFA and TC. The results indicated that balancing dietary Lys-Met by supplementation with HMBi could improve productive performances,and there was a tendency to improve metabolic conditions.