BIOLOGICAL EFFICACY OF DL-METHIONINE HYDROXY ANALOG-FREE ACID COMPARED TO DL-METHIONINE IN BROILER CHICKS AS DETERMINED BY PERFORMANCE AND BREAST MEAT YIELD

The effects of graded additions of DL-methionine and DL-methionine hyd roxy analog-free acid (DL-MHA-FA) to a basal diet deficient in methion ine were compared in broilers grown from 10 days to 35 days of age. Th e relative efficacy of DL-MHA-FA versus DL-methionine was determined f rom growth, feed conversion, and breast meat yield responses. In an eq uimolar comparison, the relative efficacy of DL-MHA-FA was estimated a t 89 %, 68 % and 82 %, respectively, based on multi-exponential regres sion analysis of growth, feed conversion, and breast meat yield data. In terms of feed cost per kg breast meat, the equimolar efficacy of DL -MHA-FA was 75 % relative to DL-methionine. In a direct comparison of commercially available products this would correspond to a relative va lue of 66 % for liquid DL-MHA-FA (containing 88 % active substance) co mpared to DL-methionine (containing 99 % active substance).