Effects of dietary different protein levels with supplementation of compound amino acid on performance and N excretion of lactating sows in summer.

The experiment was conducted to study the effects of dietary different protein levels with supplementation of compound amino acid on performance and the N excretion of lactating sows in summer. One hundred and twenty Large White×Landrace multiparous sows were randomly divided into 3 groups based on the concentration of crude protein (19.5%,18.5% and 17.5%),each group containing 40 replicates with 1 sow per replicate. Three diets were all supplemented with compound amino acid including Lys,Val,Thr,Met and Trp. The sows were fed until piglets weanling. The results showed as follows: 1) litter weanling weight and litter gain in 18.5% group were significantly higher than that in 17.5% group (P0.05),and had no significant differences compared with 19.5% group (P0.05); no significant differences were found in average daily feed intake,back fat losses and weanling-to-estrus interval of sows among 3 groups (P0.05); 2) plasma urea nitrogen levels in 18.5% group were significantly lower than those in 17.5% group (P0.05),and had no significant differences compared with 19.5% group (P0.05); concentration of partial plasma amino acid in 18.5% group was lower than that in 17.5% group and 19.5% group (P0.05),while concentration of partial milk amino acid in 18.5% group was higher than that in 17.5% group and 19.5% group (P0.05); 3) no significant difference was found in apparent N digestibility among different groups (P0.05); fecal N excretion decreased by 6.0% per 1% reduction of protein concentration. These results indicated that dietary 18.5% protein level with supplementation of compound amino acids could elevate the performance of sows in summer (average temperature=29.5 ℃).