Digestible lysine: crude protein ratio in diets for broiler chickens. / RelaÃÃo lisina digestÃvel:ProteÃna bruta em dietas para frangos de corte

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Three trials were carried, being two of performance and one of metabolism to evaluate the effect of different digestible lysine: crude protein ratios for broiler chickens in the initial phase (1 to 21 days) and growing phase (22 to 42 days) on the birdsâ performance, carcass and part yield, chemical and physical quality of the breast meat and on the values of apparent metabolizable energy corrected by retained nitrogen (EMAn), coefficients of apparent digestibility of dry matter (CDMS), intake, excretion and coefficient of apparent nitrogen retention (N). in the initial phase, the diets were isonutrient, with exception of the levels of protein and digestible lysine, formulated with three levels of CP and four digestible lysine : crude protein ratios. In the growing phase, the diets were isonutrient, with exception of the levels of protein and digestible lysine, formulated with two levels of CP and five digestible lysine: crude protein ratios. In the trial, the diets were fed to five replicates of 30 birds each and, at 21 days old, feed intake, weight gain, feed conversion and carcass yield were evaluated. Feed intake decreased linearly with the ratios evaluated within the level of the levels of 21.5 % of CP. A linear behavior of weight gain at the ratios of lysine within the levels of 18.5 % and 21.5 % of crude protein was found. Feed conversion was influenced linearly (P<0.01) by the ratios of lysine within the three levels of CP studied. Carcass yield linearly increased at the 15.5% level. In the metabolism trial of 14 to 21 days of age, the digestible lysine : crude protein ratios showed a significant quadratic effect for EMAn, within the three levels of CP, with a quadratic effect at the levels 15.5% and 18.5%, and at the level of 21.5% of CP it showed a linear effect. There were no significant effects on the nitrogen excretion for the levels of 15.5 and 21.5% of CP, whilst within the level of 18.5% of CP, there was a linear increase of nitrogen excretion with increasing ratios. In the trial in the growing phase, 1200 male broiler chicks of the Cobb strain were utilized, which were reared up to 21 days old in an experimental house, being given a corn and soybean meal-based diet with the nutrient levels recommend for this phase. At 21 days old, the birds were uniformized per weight (average weight of 87916g) and distributed into the boxes in order to obtain a uniform distribution of the birds. The birds were distributed to six replicates of 20 birds each. At 42 days, performance characteristics (weight gain, feed intake and feed conversion), when two birds of each plot were slaughtered for determining yield (cuts and abdominal fat) and chemical and physical quality of the breast meat. In feed intake and feed conversion, the ratios evaluated showed a linear behavior for the levels of lysine within the level of 17.0% of CP. There was no significant effect of the different ratios on weight gain, carcass and part yield. No significant effects (P>0.05) of the different levels of studied on the physical characteristics of meat were found. In the chemical characteristics, a significant effect was found, within the level of 19.5% of CP, with a linear increase o protein deposition in the breast meat, there being no significant differences (P>0.05) for the other nutrients. It was concluded that there is not ideal digestible lysine: crude protein ratios which should meet the maximum performance in the several phases of rearing, initial and growing; each level of crude protein presents an ideal ratio for the different variables studied. According to weight gain, the best ratios were 6.8 and 5.9% respectively for the levels of 18.5 and 21.5% of CP in the initial phase and 5.9 and 5.3% for the levels of 17.0 and 19.5% of CP, in the growing phase. The level of protein in the broilerâs diet in the initial phase can be reduced up to 18.5% of CP in the initial phase and 17.0% of CP in the growing phase, without affecting performance, carcass yield and breast meat quality, within the ideal protein concept. The reduction of crude protein in the diet reduces both consumption and nitrogen excretion by the birds in the initial phase by 24%.

ASSUNTO(S)

excreÃÃo de nitrogÃnio monogastric nutrition zootecnia lisina nutritional requirement nitrogen excretion broiler chickens exigÃncia nutricional frango de corte lysine nutriÃÃo de monogÃstrico

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