Methionine plus Cystine Levels for Light Laying Hens on Growth Phase

The aim of this study was to evaluate the methionine plus cystine levels in the diets of laying hens during the rearing period (13-18 weeks old). The diets included a control diet formulated according to NRC and five other diets with different levels of this digestible methionine plus cystine (0.317, 0.356, 0.396, 0.436 and 0.475%) that have been based on the recommendations of the Brazilian poultry and swine tables. Performance, serological and histological variables were evaluated. There was linear effect on final body weight, weight gain, methionine plus cystine intake and feed conversion, and quadratic effect on the serum albumin levels, serum protein levels and relative spleen weight. The estimated level of digestible methionine plus cystine were 0.361%, 0.346% and 0.398%, for albumin activity, serum protein and relative weight of spleen, respectively. The different formulation bases significantly influenced the histology of the liver, small intestine and magnum. It is recommended the use of levels above 0.475% of digestible methionine plus cystine for light laying hens with 13-18 weeks old, which corresponded to a ratio of digestible methionine plus cystine: digestible lysine of more than 98%.