Exigência nutricional de metionina digestível para frangos de corte machos no semiárido.

Abstract

Methionine, along with cysteine in poultry diets, are the first limiting amino acids; so the adequate concentration of these amino acids is critical to determining that other amino acids are used efficiently in protein synthesis. The objective of this study was to estimate the nutritional requirements of digestible methionine for male broilers reared in the semi-arid region of Paraiba and their possible effects on performance and carcass yield. A ration program was adopted with four breeding phases (1 to 7, 8 to 21, 22 to 33 and 34 to 42 days of age). The diets were formulated based on corn bran and soybean meal. To determine the digestible methionine requirement, a basal diet without supplementation of synthetic methionine with 0.454% digestible methionine for the pre-initial phase (1 to 7 days of age) was used. To compose the other treatments, the experimental rations presented values of 0.481; 0.510; 0.540 and 0.572% DL-methionine (79%), being supplemented in the diet, replacing the corn meal. In the other phases were: initial phase (8 to 21 days of age), 0,408; 0.432; 0.458; 0.485 and 0.514%; growth (22 to 33 days of age), 0.384; 0.407; 0.431; 0.457 and 0.484; final (34 to 42 days of age), 0.359; 0.381; 0.404; 0.428 and 0.454% digestible methionine. The experimental design was completely randomized, using five treatments (five levels of digestible methionine) for each breeding stage, with six replicates and 12 birds per experimental plot, totaling 360 broilers at each breeding stage. The data on weight gain (GP), feed intake (CR), feed conversion (CA) and mortality were calculated weekly for each rearing period (1 to 7, 8 to 15, 16 to 21, 22 to 35 of 36 to 42 days of age). The yield of the noble cuts (chest, thigh and overcoat) was calculated in relation to the weight of the eviscerated carcass (with feet and head) and the relative weight of the edible viscera (heart, liver and gizzard) and abdominal fat was calculated in relation to weight fasting. As well as determination of bird length and biometry of edible organs were calculated at 42 days of age. From the results obtained, it was verified that in the pre-initial phase (1 to 7 days of age) a significant difference was observed for the three analyzed variables CR, GP and CA. Observing the variable CR, it is verified that as the methionine levels in the diet were increased, there was an increase in the CR. On the other hand, the chicks chicks GP decreased according to the different minimum levels of methionine implemented in the diets. In the initial phase (8 to 21 days of age) it was observed that there was significant difference only for the GP variable, noting that the increase of methionine in the diet reflected in the GP increase. For the growth phase (22 to 33 days of age), it was observed that there was a significant difference for the CR and CA variables. It is verified that as the levels of methionine in the diet were increased, there was an increase in CR. As for the CA variable, it was seen that there was a worsening in the results through the increasing levels of methionine in the diet. In the final phase, it was verified that there was significant difference for the CR and CA variables. It was found that CR was increased through dietary methionine levels. Thus, the requirements of male broiler breeders in the pre-initial, initial, growth and final stages are 0.454%, 0.408%, 0.384% and 0.359%, respectively, of digestible methionine. The increasing levels of digestible methionine in the diet of male broilers did not influence the yield data of carcass and edible organs.