A determination of order of limiting amino acids in a low crude protein diet for laying hens
A team of Brazilian researchers determined the order of limiting amino acids in a low crude corn-soybean meal diet (LCP) compared with normal crude protein (NCP) diet. A total of 324 hens were randomly placed in 54 pens. The NCP diet (16.2% crude protein, 0.71% methionine plus cystine, 0.78% lysine, 0.59% threonine, 0.18% tryptophan, 0.74% valine, 0.59% isoleucine) was compared to a LCP diet (14.2% crude protein, 0.42% methionine plus cystine, 0.60% lysine, 0.48% threonine, 0.15% tryptophan, and 0.60% valine, 0.53% isoleucine) that was supplemented with several amino acids to produce the experimental treatments. The hens were fed for eight weeks and the diets were evaluated for four weeks. The birds fed LCP diet had poorer (P<0.05) feed conversion per egg mass (2.269 vs. 1.922 kg/kg) and lower feed intake (100.9 vs. 111.6 g), egg production (74.7 vs. 89.2%), egg weight (59.6 vs. 65.2 g), and albumen weight (37.4 vs. 42.4 g) than birds fed NCP.
Results indicated that the order of limiting amino acid in the Corn-SBM based LCP diet containing 14.2% CP was methionine (as sulfur amino acid), lysine was the second, threonine was the third, tryptophan was the fourth and an isoleucine-valine mix was the fifth limiting amino acid. Layer hens fed 14.2% crude protein diet had a similar performance that those fed 16.2% when methionine alone or a mixture of methionine, lysine, threonine, tryptophan, valine and isoleucine were supplemented. The daily amino acid requirements of laying hens were determined to be 790 mg of methionine, 870 mg of lysine, 658 mg of threonine and 200 mg of tryptophan, 658 mg of isoleucine and 825 mg of valine.