This experiment was conducted to evaluate the effect of diets with two protein levels (16.5% and 14.5%) and 5 supplemental methionine levels (0%, 0.025%, 0.050%, 0.075% and 0.100%) on postmolt layer performance. Two hundred forty commercial laying hens at 67 wk of age were induced to molt by zinc oxide and fed ten molt experimental diets for 6 wk. At the end of the experiment body weight, feed consumption and feed conversion were significantly higher for the birds fed the 16.5% crude protein diet. Hens fed higher protein level diet returned to egg production faster than those birds fed lower protein diet. Rations with 16.5% of protein determined a significant better egg production until the fifth experimental week, without affecting the egg weight. The methionine supplementation significantly increased egg weight, however did not statistically influence the egg production. Birds fed approximately 300 mg methionine daily (0.050% and 0.075% supplemental methionine levels) produced eggs significantly heavier, however resulting in a low egg shell quality measured by egg specific gravity, shell thickness and shell weight. | O presente experimento foi conduzido no sentido de estudar o efeito de dois níveis de proteína (16,5% e 14,5%) e de 5 teores suplementares de metionina (0%, 0,025%, 0,050%, 0,075% e 0,100%) sobre o desempenho de galinhas poedeiras submetidas a muda induzida com óxido de zinco. Duzentas e quarenta galinhas de linhagem comercial com 67 semanas de idade foram alimentadas por 6 semanas com 10 dietas experimentais para avaliação do desempenho. Ao final do experimento, o consumo e a conversão alimentar foram significativamente melhores para as aves que receberam dietas contendo 16,5% de proteína. Estas mesmas aves retornaram mais precocemente à produção de ovos que aquelas alimentadas com dietas contendo 14,5% de proteína. Rações contendo 16,5% de proteína proporcionaram aumento significativo nos índices de postura das aves até a 5ª semana experimental, sem contudo afetar o peso do ovo. A suplementação de metionina à ração aumentou de forma significativa o peso dos ovos, porém não teve influência estatística na taxa de postura. Aves que consumiram ao redor de 300 mg de metionina por dia (0,050% a 0,075% de metionina na ração) produziram ovos significativamente mais pesados, porém apresentaram baixa qualidade de casca (gravidade específica, espessura e peso da casca).

In the conditions of the Republic of Belarus there was showed the possibility of import substitution of methionine and threonine preparations used for growing poultry birds by a new national developed in Belarus fodder additive L-homoserine. The chemical composition of the new feed additive L-homoserine is the following: amino acid L-homoserine; metabolizable energy; crude protein; crude fat; vitamins (B1; B2; B3; betaine; B5; B6; Bc); macro and trace elements (calcium; phosphorous; natrium; manganese; zinc; iron; copper). In course of the study there was analyzed the dynamics of body weight of broiler chickens; expenses of fodders per live weight gain; dynamics of body weight of replacement growing birds; indexes of second pen-feathers; dimensions of combs). Research results showed that addition of L-homoserine for broiler chickens diets was safe and nontoxic; the preparation showed the same growth promoting indexes as the foreign methionine and threonine preparations.