effects of different ideal amino acid ratios on male and female broiler chicks during 21 to 42 d of age

a chick bioassay with chemically defined amino acid (aa) diets was conducted to compare four different aa profiles: the nrc (1994), feed stuff, rhone poulenc animal nutrition (rpan) and illinois ideal chick protein (iicp) aa profiles. this battery study involved male and female chicks during grower (21 to 42 days of age) period. indispensable aas were rationed to lysine according to requirement ratios presented in the four aa profiles. digestible lysine set 0.85 and 0.78 % of diet for male and female, respectively. all diets were kept isonitrogenous (2.28 % n) by varying levels of l-glutamic acid. all diets were checked to have at least 0.3 % of proline and 0.6 % of glycine. all diets contained 3200 kcal me/kg and a positive control diet were used according to nrc (1994) recommendation. four battery pens of five chicks were fed one of four different profiles or positive control diet in both sexes. weight gain, feed intake, feed conversion ratio (fcr), breast meat, abdominal fat and liver weight measured at day 42 posthatch. results indicate that in male chicks, weight gain and fcr with iicp profile were significantly better than all other profiles. in female chicks weight gain and fcr with iicp profile were significantly better than rpan and nrc (1994) profile, but not from feedstuff profile. results of this experiment suggest that ideal ratio of sulfur aa in nrc (1994) profile is probably insufficient for supporting maximum performance.