ABSTRACT

1. Four experiments were conducted to determine the 4th limiting amino acid (AA) in maize–soybean meal-based diets.

2. Deletion assay methodology was used to quantify performance and carcase trait responses to potential deficiencies in essential and conditionally essential AA caused by reductions in dietary crude protein of maize–soybean meal-based diets from 202.9 to 186.5 g/kg.

3. The deletion of Val, Phe and Gly + Pro resulted in negative effects on live performance and carcase traits for male broilers, whereas AA deletion only affected wing weights for females with no response on live performance.

4. Further experimentation could not duplicate a response to Phe or Pro in male broilers.

5. Valine was identified as the potential 4th limiting AA in maize–soybean meal-based diets and was not found to be co-limiting with Ile.

 抽象的

1. 进行了四项实验以确定以玉米-豆粕为主的日粮中的第四种限制氨基酸 (AA)。

2. 使用缺失分析方法来量化性能和胴体性状对必需和条件必需 AA 潜在缺陷的反应，这些缺陷是由于玉米-豆粕日粮的日粮粗蛋白从 202.9 克/千克减少到 186.5 克/千克而引起的。

3. Val、Phe和Gly+Pro的缺失对公肉鸡的活体性能和胴体性状产生负面影响，而AA的缺失仅影响母鸡的翅重，对活体性能没有影响。

4. 进一步的实验无法在雄性肉鸡中复制对 Phe 或 Pro 的反应。

5. 缬氨酸被确定为玉米-豆粕为主的日粮中潜在的第四种限制性氨基酸，并且未发现与异亮氨酸具有共同限制性。