the effects of dietary methionine and protein levels on growth performance and carcass characteristics of broiler chickens

this study was aimed to determine the effects of different dietary levels of methionine and protein on the growth performance and carcass characteristics of broiler chickens. a total of 240 broiler chicks were distributed into a completely randomized design with a 2 × 3 factorial arrangement. experimental factors were: two levels of protein (20% or 24% for starter and 18% or 22% for grower), and three levels of methionine (standard, 115% standard and 130% standard). the experiment consisted of 6 treatments with four replicates and 10 birds in each replicate. all diets were calculated to be isocaloric for starter (7 to 21 d) and grower (22 to 42 d) periods. birds had free access to feed and water throughout the experimental period. mean body weight (bw) and feed intake were determined at the end of each period. on days 43 two birds were randomly selected from each pen and individually weighed and slaughtered. then, carcass weight and weight of parts (yield of breast and abdominal fat pat) were determined. the results indicated that excessive levels of methionine and dietary protein improved weight gain and feed conversion ratio (fcr) at starter, grower and total periods. feed intake was not affect by the increase in dietary methionine and protein levels. the increase in dietary methionine and protein levels was affective in increasing breast meat yield and decreasing abdominal fat pad. there were no interactions between methionine and protein for bw, fcr or carcass characteristics.