Nutritional value of methionine hydroxy analogue calcium salt compared with both pure DL- methionine and diluted DL-methionine with 65% purity

Correct use of DL-methionine (DL-Met) and methionine hydroxy analogue calcium salt (MHACa) requires knowledge on their nutritional value which can be determined by multi-exponential regression analysis of dose response data. In order to both examine the biological value of MHACa compared with DL-Met and to validate the mathematical approach a dose-response trial was performed with graded levels of either DL-Met, MHA-Ca or DL-Met-65 the latter being DL-Met diluted to a purity of 65%. It was hypothesised that the biological effectiveness of DL-Met-65 must be about 65% if the regression method is valid. Basal unsupplemented starter, grower and finisher diets contained 0.63, 0.57, and 0.52% Met+Cys, respectively, and were fed to male Ross 308 chicken. Regarding weight gain, feed conversion ration (FCR) and breast meat yield (BMY), broilers responded significantly and non-linearly to either Met source. Biological effectiveness of MHA-Ca compared with DL-Met was on average 60% (gain-65%; FCR-60%; BMY-53%) whilst that of DL-Met-65 was 62% (61%; 62%; 63%). These findings suggest that 1kg MHA-Ca can be replaced by 650g or less DL-Met for achieving the same animal performance. The determined bio-efficiency of DL-Met-65 was close to 65% supporting the mathematical approach to be suitable for bio-efficiency determination.