低蛋白日粮添加酪氨酸对育肥猪生长性能和氮代谢的影响

试验选取30头平均体重为(60±0.20)kg杜×长×大三元杂交育肥猪,随机分为3个日粮处理:正常蛋白日粮(对照组,14.52%蛋白),低蛋白日粮添加0.49%丙氨酸(负对照组,12.52%蛋白),低蛋白日粮添加1.0%酪氨酸(试验组,12.52%蛋白)。每组10个重复,每个重复1头猪,试验期为6周。试验结果表明,①饲喂低蛋白日粮对育肥猪平均日增重、平均日采食量和料重比无显著影响(P>0.05)。②与对照组相比,负对照组和试验组摄入氮均显著降低(P<0.05),尿氮排放量和总氮排放量均显著下降(P<0.05),粪氮排放量无显著差异(P>0.05),但在低蛋白日粮中添加酪氨酸可显著提高蛋白质表观生物学价值和净蛋白利用率(P<0.05)。③与对照组相比,负对照组和试验组血清尿素氮含量均显著下降(P<0.05),其余血液生化指标各组间差异不显著(P>0.05)。④与对照组相比,降低日粮蛋白水平对育肥猪胴体重、屠宰率、背膘厚、胴体直长和胴体斜长均无显著影响(P>0.05)。⑤饲喂低蛋白日粮对育肥猪背肌pH45min、pH24h、蒸煮损失和滴水损失与对照组相比均无显著差异(P>0.05),但低蛋白日粮中添加酪氨酸可显著提高肉色红度值(P<0.05)。⑥与对照组相比,饲喂低蛋白日粮对育肥猪血浆激素水平无显著影响(P>0.05)。综上所述,饲喂低蛋白日粮不影响育肥猪生长性能并减少氮排放,补充酪氨酸可提高育肥猪表观生物学价值和净蛋白利用率并改善肉色。试验填补酪氨酸在低蛋白日粮中研究空白,为相关研究提供新思路。

Effect of low protein diets supplemented with tyrosine on growth performance and nitrogen metabolism of finishing pigs

Total 30 finishing pigs(Duroc×Landrace×Yorkshire) with an initial body weights of(60 ±0.20) kg were randomly divided into three diet treatments(10 replicates in each group and one pig in each replicate, and the trial period was six weeks), a normal protein diet(control, 14.52% crude protein),a low protein diet supplemented with 0.49% alanine(negative control, 12.52% crude protein), a low protein diet supplemented with 1.0% tyrosine(test, 12.52% crude protein). Results showed that: ① Finishing pigs fed a low protein diets had no significant effect on ADG, ADFI and F/G of finishing pigs(P>0.05). ② Compared with the control group, the nitrogen intake in negative control group and test group decreased significantly(P<0.05), the emissions of urine nitrogen and total nitrogen were significantly decreased(P<0.05), and there was no significant difference in fecal nitrogen emissions(P>0.05). But supplemented with tyrosine in low protein diets significantly increased the apparent biological value of protein and net protein utilization(P<0.05). ③ Compared with the control group, the serum urea nitrogen levels in negative control group and test group were significantly decreased(P<0.05), and the other plasma biochemical indicators were not significant among three groups(P>0.05). ④ Compared with the control group, finishing pigs fed a low protein diets had no significant effect on the weight, slaughter rate, back fat thickness, carcass straight length and carcass straight length of finishing pigs(P>0.05).⑤ Finishing pigs fed a low protein diets had no significant effect on pH 45 min, pH 24 h, cooking loss and drip loss of longissimus muscle(P>0.05), but supplemented with tyrosine in low protein diets significantly increased the flesh color of redness(P<0.05). ⑥ Compared with the control group, finishing pigs fed a low protein diets had no significant effect on plasma hormone levels(P>0.05). In conclusion,fed low protein diet to finishing pigs had no effect on growth performance and reduced nitrogen emissions, but supplemented with tyrosine in low protein diets increased the apparent biological value of protein and net protein utilization and improved meat color. This study filled the gap of tyrosine in feed industry and provided new insights in low protein diet.