Desempenho e morfologia intestinal de frangos de corte suplementados com dietas contendo nucleotídeos

Abstract

Two experiments were conducted to evaluate the effect of dietary nucleotide supplementation and levels of digestible lysine on performance, carcass yield and development of the gastrointestinal tract in broilers. In Experiment 1, 1,350 male Ross 780 chicks were used, 1 to 21 days of age, distributed in 45 boxes (1.85 m2) with 30 birds each. The animals were fed with three levels of crude protein (CP) (18%, 20% and 22%), three levels of nucleotides (0%, 0.1% and 0.2%) and five replications, in a completely randomized design with a 3x3 factorial arrangement. No significant (P≥ 0.05) results were found for the interaction of crude protein (%) with the concentration of nucleotides (%) for the variables: weight (g), intestine length (cm) and relative weight of the body weight (%) with the intestine, liver and bolsa cloacalis. There was a linear decrease of CP (P≤ 0.05) for the villus height in the jejunum (Ŷ=1123.89 - 16.785x; R2=0.65) and linear increase of the nucleotides in villus height in the ileum (Ŷ = 584.44+426.708x; R2 = 0.52). There was a decrease in ileal nitrogen concentration, reaching a minimum with 19.31% CP (Ŷ= 22.65?2.12x + 0.055x2; R2=0.61). In experiment 2, 868 male Cobb broilers were used, 21 to 42 days of age, distributed in negative and positive controls, with 18.80% and 16.86% crude protein respectively, both without nucleotides, and meeting the requirement of 1.062% digestible lysine. Using the low-protein diet, five treatments were devised with the addition of 0.5 kg of nucleotides/ton of feed, with different levels of digestible lysine (1.262%, 1.162%, 1.062%, 0962% and 0.862%), with four replications each, in a completely randomized design. Feed intake (g) decreased linearly (P≤ 0.05) in the period from 20 to 27, 20 to 35, and 20 to 42 days of age; feed intake decreased by increasing levels of lysine in the diet. Feed-to-gain ratio showed a quadratic effect (P ≤ 0.05) for birds of the period from 20 to 27, 20 to 35 and 20 to 42 days of age, decreasing as levels of digestible lysine increased, with minimum levels reaching 1.119%, 1.187% and 1.132% digestible lysine, respectively. The diet with 1.062% of lysine did not differ (P> 0.05) from the negative control for villus height and crypt depth in the duodenum. The results were caused by the improvement in the gut integrity of the birds. Nucleotide supplementation helped the low-protein diet