关键词: 丙三醇, 泌乳性能, 能量平衡, 代谢产物, 泌乳早期, 荷斯坦奶牛

Abstract: Thirty-six multiparous Holstein dairy cows, blocked by lactation number, corrected milk yield in last lactation, and expected calving date, were designated into four treatments in a randomized block experiment. Graded levels (0,100,200, and 300 g·d^-1) of glycerol were supplemented in the four treatments. The effects of graded glycerol supplementation on feed intake, lactation performance, changes of body weight, energy balance, concentration of blood metabolites and urine ketones in early lactation Holstein dairy cows were observed. The results showed that average feed intake, milk yield, milk protein percentage, milk lactose percentage and milk dry matter percentage were not affected significantly by glycerol supplementation (P>0.05). Feed efficiencies of the 200 and 300 g·d^-1 glycerol supplementation treatments were higher than those of the 100 g·d^-1 treatment and the control (P<0.05). Milk fat percentage was significantly depressed in the 300 g·d^-1 treatment compared with those in the control and 100 g·d^-1 treatment(P<0.05). Cows receiving 200 and 300 g·d^-1 glycerol had a higher plasma glucose and lower plasma NEFA than those of the contol (P<0.05), and 300 g·d^-1 glycerol supplementation treatment had lower content of β-hydroxybutyrate than that of control(P<0.05). 200 and 300 g·d^-1 glycerol supplementation decreased the contents of ketones in excreted urine compared with the control (P<0.05). The energy balance was improved in cows receiving the 200 and 300 g·d-1 glycerol supplementation treatments as reflected energy balance calculations, and a lower body weight loss compared with cows receiving the control (P<0.05). Results of the present study indicated that glycerol supplementation was beneficial to early lactating cows in improving their energy balance status.

Key words: glycerol, lactation performance, energy balance, metabolites, early lactation, Holstein dairy cows