Sulfur amino acid requirement and cystine replacement value of broiler chicks during the period three to six weeks posthatching. Poultry Sci

ABSTRACT Three experiments were conducted with commercial broiler chicks to determine the SAA require-ment during the growth period 3 to 6 wk posthatching. A 20 % CP corn-peanut meal basal diet (3,200 kcal MEn/ kg) was analyzed to contain 0.23 % Met and 0.28% cystine. True digestibility assessment in cecectomized cockerels revealed that Met and cystine in the basal diet were 81 and 75 % digestible, respectively. Therefore, the basal diet contained 0.19 % digestible Met and 0.21% digestible cystine. When fully fortified with DL-Met, growth rate and feed efficiency of chicks fed the corn-peanut meal diet were equal to that of chicks fed a 20% CP Met-fortified corn-soybean meal diet. In the SAA requirement assay, Ross x Hubbard male chicks were fed graded increments of DL-Met (0.03%) and L-cystin