Effects of Dietary Crude Protein Level on Growth,Development and Serum Biochemical Indicators of Laoshan Dairy Goats

This experiment was conducted to determine the effects of dietary crude protein(CP) level on growth,development and serum biochemical indicators of Laoshan dairy goats.Thirty 147-day-old weaned Laoshan dairy goats female lambs with an average body weight of(14.57 ±0.32) kg were used in single-factor randomized design and divided into 3 groups with 10 replicates per group and 1 lamb per replicate.Goats in the three groups were fed diets with different CP levels(10.74%,13.22%,and 15.74%,respectively).The pretest lasted for 14 days,and the test lasted for 162 days.The results showed that with the increase of dietary CP level: the ADG of Laoshan dairy goats was increased,and the growth of body size was speeded up; nitrogen intake and urinary nitrogen excretion were significantly increased(P0.05 or P0.01),while no significant effect was found on fecal nitrogen excretion(P 0.05); the contents of serum total protein and glucose were significantly increased(P0.05),but total cholesterol content,and alanine aminotransferase and aspartate aminotransferase activities in serum were not significantly affected(P0.05).In conclusion,according to the relationship between nitrogen intake(x) and average daily gain(y)(y = 0.258 1x2+15.341x-101.88),the nitrogen intake of the best growth performance obtained in Laoshan dairy goats is 29.72g/d.