Comparison of the bioavailability of methionine hydroxy analogue in relation to DL-methionine for broilers in the initial phase

Methionine must be supplied in poultry feed to ensure maximum performance of the broilers in the initial phase, since methionine is the most limiting amino acid in corn and soybean meal based diet. Therefore, the objective of this study was to compare the bioavailability from two sources of methionine (methionine hydroxy analogue MHA-Ca and DL-methionine) on the performance of broilers in the initial phase (1 to 21 days). For this trial, 1890 day-old male chicks (Cobb 500) were allotted in a completely randomized design, with nine treatments and seven replicates with 30 birds each. The treatments consisted of one basal diet (deficient and without supplementation of any methionine source) with 0.563% of methionine plus cystine (Met+Cys) and the basal diets supplemented with MHA-Ca (0.06; 0.179; 0.361; 0.599% of MHA-Ca) or DL-Met (0.051; 0.153; 0.309; 0.513% of DL-Methionine) in replacement of the inert to obtain four levels of digestible Met+Cys (0.613; 0.713; 0.863 and 1.063% of digestible Met+Cys). The variables evaluated were body weight gain (BWG) and feed conversion ratio (FCR). The BWG and FCR data were regressed in function of the supplementation of each methionine source using multi-exponential regression model and bioavailability of MHA-Ca was calculated by dividing the slope of the MHA-Ca methionine by the slope of the DL-methionine exponential model. For the analysis, 5% of significance was considered in the adjustments of the non-linear model using SAS 9.0 in order to describe the responses of birds subjected to MHA-Ca in comparison to DL-methionine. Birds fed the supplemented diets with increasing levels of Met+Cys, regardless of source, presented higher BWG and better FCR when compared with those fed the basal diet. The models obtained by exponential regression analysis are: BWG = 593.7 + 277.8* (1- e ^{- (28.075*DL}-methionine + 15.952*MHA-Ca)) and FCR= 1.447 + 0.215* (1- e ^- (16.218*DL-methionine + 10.956*MHA-Ca)). Thus, bioavailability of MHA-Ca in relation to DL-methionine was 50% for BWG and 59% for FCR. The smaller bioavailability value of MHA-Ca compared to DL-methionine for BWG and FCR lead to conclude that MHA-Ca is less effective compared to DL-Methionine in diets for broilers in the phase of 1 to 21 days.