Studies on the relative bioavailability (RBV) of DL-Methionine (DL-Met) to L-Methionine (L-Met) have produced variable results. An experiment was conducted to determine the RBV of DL to L-Met. A total of 2268 1-day old male chicken were housed in 54 floor pens (42 bird/pen). There were 9 treatments (6 repetitions) including the basal diet (BD). The BD was deficient in Met content with 0.27, 0.26 and 0.25 in the starter, grower and finisher periods respectively. Four levels of experimental diets for each DL-Met and L-Met were created by supplementing 0.05%, 0.10%, 0.15% and 0.20% of DL- or L-Met to the BD. The feeding program consisted of starter (0-14 d, 21% CP and 2900 kcal ME/kg), grower (15 - 28 d, 20% CP and 3000 kcal ME/kg) and finisher period (29 - 37 d, 18.5% CP and 3050 kcal ME/kg). Chickens and feed were weighed at the end of each age period. Regression coefficients of a common plateau asymptotic regression were used to calculate RBV. Birds responded to gradual increase in Met levels, BW, FCR and ADG were significantly (P 0.05) higher in treatment groups as compared to control. Through the study period (37 d), the RBVs of DL-Met for BW and FCR were 89 and 77 respectively.
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