本试验旨在研究饲粮不同蛋白质水平下添加合成氨基酸对夏季哺乳母猪生产性能及氮排泄的影响。选择120头长白×约克杂交母猪，随机分成3个蛋白质水平组（19.5%、18.5%和17.5%，均添加由赖氨酸、色氨酸、蛋氨酸、缬氨酸和苏氨酸组成的合成氨基酸），每组40个重复，每个重复1头，饲养到仔猪断奶。结果表明：1）18.5%组仔猪断奶窝重和窝增重显著高于17.5%组（P＜0.05），与19.5%组差异不显著（P＞0.05）。蛋白质水平对母猪日均采食量、背膘损失及断奶后发情间隔影响不显著（P＞0.05）；2）18.5%组血浆尿素氮水平显著低于17.5%组（P＜0.05），与19.5%组差异不显著（P＞0.05）；18.5%组血浆部分氨基酸浓度显著低于17.5%组和19.5%组（P＜0.05），乳中部分氨基酸浓度显著高于19.5%组和17.5%组（P＜0.05）；3）各组氮表观消化率无显著差异（P＞0.05）；蛋白质水平每降低1个百分点，粪氮排泄减少6.0%。由结果可知，夏季高温环境下（平均温度为29.5 ℃），哺乳母猪饲粮添加5种合成氨基酸，蛋白质水平为18.5%时哺乳母猪生产性能最佳。

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 (P<0.05), and had no significant differences compared with 19.5% group (P>0.05); no significant differences were found in average daily feed intake, back fat losses and weanling-to-estrus interval of sows among 3 groups (P>0.05); 2) plasma urea nitrogen levels in 18.5% group were significantly lower than those in 17.5% group (P<0.05), and had no significant differences compared with 19.5% group (P>0.05); concentration of partial plasma amino acid in 18.5% group was lower than that in 17.5% group and 19.5% group (P<0.05), while concentration of partial milk amino acid in 18.5% group was higher than that in 17.5% group and 19.5% group (P<0.05); 3) no significant difference was found in apparent N digestibility among different groups (P>0.05); 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 ℃).［Chinese Journal of Animal Nutrition, 2010，22（2）:285-292］