Using crystalline amino acids to supplement broiler chicken requirements in reduced protein diets

Abstract

<p>Reducing dietary CP can reduce N pollution. Much research has been reported in corn-based diets; however, the amino acid (<b>AA</b>) profiles of wheat-based diets differ. Poor performance as a result of reduced protein (<b>RP</b>) has been overcome in corn-based diets with essential AA and glycine (<b>Gly</b>) supplementation. The current study examined RP levels and Gly in wheat-based diets. An industry standard protein (<b>SP</b>) diet plus 3 RP diets with and without Gly supplementation, to match the SP treatment at 0.713 and 0.648% digestible Gly for the grower and finisher periods respectively, were fed to male broilers from day 10 of age. Grower CP included 22.5, 20.6, 18.3, and 17.7% (days 10-21) and finisher CP included 19.7, 17.8, 16.2, and 15.5% (days 21-35). Performance, meat yield, N efficiency, water intake, and apparent ileal digestibility of N and AA were measured. No difference in body weight gain (<b>BWG</b>), feed intake, or feed conversion ratio (<b>FCR</b>) were observed at 20% CP compared to the SP treatment. However, further reducing protein reduced BWG (<i>P</i> < 0.001), feed intake (<i>P</i> < 0.001), and increased FCR (<i>P</i> < 0.001). Supplementation of 0.713% Gly in the grower period increased BWG (<i>P</i> < 0.001) and reduced FCR (<i>P</i> < 0.001). Relative meat yield was not affected by dietary protein, however reducing CP increased relative fat pad weight (<i>P</i> < 0.001). Nitrogen efficiency increased with decreased CP in both grower (R² = 0.69) and finisher (R² = 0.80) treatments. Water intake decreased (R² = 0.83) with decreasing CP intake. Apparent ileal digestibility of AA and N were higher in RP diets (<i>P</i> < 0.05). The benefits of reduced water intake and increased N efficiency and the disadvantages of poor performance and increased body fat in RP corn-based diets have been identified in RP wheat-based diets. Furthermore, at 18.5% CP the supplementation of crystalline AA and Gly can maintain BWG and FCR observed in SP diets.</p>