Effects of different energy and protein levels in the diets on the amount of lactation,milk composition and plasma biochemical indices of Xinong Saanen dairy goats

To select the appropriate energy and protein levels in the diets for lactating goat,the test was designed according to a completely randomized block design with two treatments in two block,sixty lactating goats[(60.00±7.88)kg body weight]were randomly divided into four groups.Two energy levels(12.36 MJ/kg and 12.92 MJ/kg DM) and two protein levels(13.25% and 15.80%) were used in the diets for the goats.The effects of different energy and protein levels in the diets on the amount of lactation,milk composition and plasma biochemical indices were studied.The results showed that there was no significant difference in the milk yield among each treatment(P0.05).The milk yield of the goats in each group began the downward trend from the milk production peak.The smallest decrease in the amount of lactation was found when the energy level in the diets was 12.92 MJ/kg with protein level of 13.25%,it was conducive to maintaining the milk yield.With different energy and protein levels in the diets,there were no remarkable differences in solids non-fat,lactose,density,freezing point depression and acidity between each groups(P0.05).But with the energy level of 12.92 MJ/kg and protein level of 13.25%,the contents of butterfat,milk protein and total solids of the group were lower than that of the other treatments,especially the content of the butterfat was significantly decreased(P0.05).The contents of glucose,triglyceride and choslesterol in the plasma from the two groups with high energy level of 12.92 MJ/kg were higher than those of the other two groups with low energy level 12.36 MJ/kg(P0.05).There was no significant difference between the two protein levels(P0.05).