Metionina+cistina digestível na dieta de poedeiras comerciais e sua influência sobre o desempenho, qualidade e perfil aminoácidico dos ovos e avaliação econômica

The objectives of this study were to evaluate the effects of four levels of digestible met + cis on commercial laying hens diet on productive performance, quality and egg amino acid profile and economic viability. A total of 576 Lohmann LSL-Lite laying hens, 19 weeks old, were weighed and randomly distributed into six replicates of 24 birds for each experimental diet. The experimental design was completely randomized, with four treatments defined by the levels of digestible met + cis of the feed. Experimental diets were formulated to contain 0.515, 0.574, 0.639 and 0.698% digestible met + cis (0.465, 0.540, 0.581 and 0.647% analyzed digestible met + cis, respectively). Productive performance was measured for 30 weeks. Egg quality (34 and 50 weeks of age) and amino acid profile of eggs (43 weeks of age) were evaluated in fixed periods. Throughout the experiment, a positive linear response as the levels of met + cis increased was observed on feed intake, number of eggs / bird housed and consumption of digestible met + cis. The met+cis requirements for egg production, egg weight, egg mass, feed efficiency and weight gain were 0.638, 0.654, 0.647, 0.644 and 0.613% met + cis digestible, respectively, on the basis of a quadratic regression model. At 34 weeks, egg shell thickness linearly reduced as met + cis levels increased and Haugh units had a quadratic response, in which the optimal level found was 0.546% met + cis. At 50 weeks of age, the requirement of digestible met+cis for egg shell thickness and egg percentage were 0.571 and 0.570%, respectively. Increasing dietary met+cis content, percentages of protein, branched chain amino acids (leucine, isoleucine and valine), histidine and proline of the egg (albumen + yolk) linearly decreased. The economic viability varied due to the price of methionine and the levels of met + cis used. Therefore, while higher levels of digestible meth + cis (> 0.630%) favor the good performance of the birds, reduced levels of met + cis, close to 0.570%, improve eggshell quality of laying hens at peak production. The effects of the meth + cis levels on amino acid profile of the eggs need to be better studied. As methionine prices in the market changes, different met+cis levels should be used aiming to achieve better economic efficiency of the egg production system