DSM Nutritional Products, 4303 Kaiseraugst, Switzerland.
School of Environmental and Rural Sciences, University of New England, Armidale, NSW 2351, Australia.
Poult Sci. 2019 Mar 1;98(3):1321-1332. doi: 10.3382/ps/pey456.
A total of 90 male Ross 308 broiler chicks were used in a digestibility and performance bioassay to explore the effect of reduction in dietary protein and digestible amino acids and inclusion of an exogenous mono-component protease on amino acid digestibility, net energy, jejunal gene expression, and bird performance. Four dietary treatments were created by the supplementation, or not, of 2 control diets with a mono-component exogenous protease. The control diets were corn/wheat/soybean meal-based and were formulated to be either nutritionally adequate or reduced in protein and amino acids (around 3%). The 2 control diets were supplemented with xylanase and phytase (2000 FYT). Treatments were therefore arranged as a 2 × 2 factorial design. The reduction in diet nutrient density had no significant effect on various experimental outcomes (including bird performance, amino acid digestibility, and net energy [NE]) that were measured with the exception of a reduction in the expression of aminopeptidase N and glucose transporter 2. However, the addition of exogenous protease resulted in an increase in weight gain and a reduction in feed conversion ratio (around 4%; P < 0.05) and an increase in the digestibility of several amino acids (P < 0.05) and starch (P = 0.06). Protease addition also resulted in an increase in both apparent metabolizable energy (AME) (+73 kcal/kg; P < 0.05) and NE (+107 kcal/kg; P < 0.05). The addition of exogenous protease to the diet also increased the jejunal expression of genes responsible for peptide transport (PepT2; P < 0.01) and starch digestion (sucrase isomaltase; P = 0.06). These results confirm the efficacy of exogenous protease in broiler diets that contain both xylanase and phytase and suggest substantial beneficial effects that extend beyond protein and amino acid nutrition. The effect of exogenous protease on energy partitioning, starch digestibility and the efficiency of nitrogen cycling is an area for further study.
本试验选用 90 只雄性罗斯 308 肉鸡，进行消化率和生产性能生物测定，以研究日粮蛋白和可消化氨基酸降低以及添加单一组分外源蛋白酶对氨基酸消化率、净能、空肠基因表达和鸡生产性能的影响。通过添加或不添加 2 种含有单一组分外源蛋白酶的对照日粮，设置 4 种日粮处理。基础日粮以玉米/小麦/豆粕为主，配制为营养充足或蛋白及氨基酸（约 3%）降低的日粮。2 种对照日粮分别添加木聚糖酶和植酸酶（2000 FYT）。因此，处理组采用 2×2 因子设计。除了降低氨基肽酶 N 和葡萄糖转运蛋白 2 的表达外，日粮营养密度的降低对各种试验结果（包括鸡生产性能、氨基酸消化率和净能[NE]）没有显著影响。然而，添加外源蛋白酶可提高增重和降低料重比（约 4%；P＜0.05），并提高几种氨基酸（P＜0.05）和淀粉（P＝0.06）的消化率。蛋白酶添加还可提高表观代谢能（AME）（+73 kcal/kg；P＜0.05）和净能（NE）（+107 kcal/kg；P＜0.05）。外源蛋白酶添加还增加了负责肽转运（PepT2；P＜0.01）和淀粉消化（蔗糖异麦芽糖酶；P＝0.06）的空肠基因表达。这些结果证实了含有木聚糖酶和植酸酶的肉鸡日粮中外源蛋白酶的功效，并表明除了蛋白和氨基酸营养之外，还具有实质性的有益效果。外源蛋白酶对能量分配、淀粉消化率和氮循环效率的影响是进一步研究的领域。
