Although phytase has been researched, new enzymes have been produced, leading to different animal responses. In this scenario, the present study proposes to evaluate the inclusion of a bacterial phytase produced by Escherichia coli in broiler diets based on corn and soybean meal, with or without nutrient reductions, on the performance, nutrient digestibility, phosphorus bioavailability, and bone minerals of those animals and on the economic viability of this practice. A total of 896 male broiler chickens were distributed into 32 experimental units, each housing 28 broilers. The experiment was set up as a completely randomized design with four treatments (Positive Control (PC)-diet meeting the nutritional requirements of the broiler chickens; Negative Control (NC) with reductions of 100kcal/kg of ME, 0.14% av P and 0.11% t Ca; NC + phytase (500 FTU/kg); PC + phytase (500FTU/kg)) and 8 replicates. Phytase increased (p < 0.05) feed intake and body weight gain and improved feed conversion ratio in starter (1 to 21 days) and total (1 to 42 days) phases, respectively, compared with Negative Control diet without supplementation. The Negative Control + phytase diet also led to a feed intake similar to Positive Control in the starter and total phases. The inclusion of phytase without nutrient reductions improved (p < 0.05) feed conversion ratio in the starter phase, compared to Positive Control diet. There was an increase (p < 0.05) in the digestibility of dry matter, crude protein and phosphorus and in apparent digestible energy in the Negative Control + phytase diet compared to the Negative Control diet. Phytase supplementation increased (p < 0.05) the digestibility of crude protein, calcium and phosphorus, and apparent digestible energy compared to Positive Control diet. Ash, phosphorus, and calcium contents were higher in the Negative Control + phytase diet compared with those observed in the Negative Control diet without enzyme (p < 0.05). The Positive Control + phytase diet provided higher ash contents (p < 0.05), but calcium and phosphorus deposition was similar to those obtained with Positive Control diet. Phytase inclusion allows for a reduction in the diet cost per ton of produced feed. In conclusion, dietary supplementation with bacterial phytase produced from Escherichia coli for broiler chickens is recommended, as it provided increases in production performance, nutrient digestibility, and energy metabolizability and a reduction in the diet cost. ResumoEmbora a fitase tenha sido estudada, novas enzimas foram produzidas, levando a respostas animais diferentes. Nesse sentido, o presente estudo teve como objetivo avaliar a inclusão de fitase bacteriana produzida por Escherichia coli em dietas à base de milho e farelo de soja, com ou sem redução de nutrientes sobre o desempenho, digestibilidade dos nutrientes, biodisponibilidade de fósforo, minerais ósseos e viabilidade econômica. Foram distribuídos 896 frangos de corte machos em 32 unidades experimentais, cada unidade constituída por 28 frangos. O delineamento f...

ABSTRACT. This study aimed to evaluate different digestible lysine levels in diets for broilers chickens from different commercial strains, from 49 to 56 days of age, on performance and carcass characteristics. A total of 432 male broilers from 49 days old were used, with an average weight of 3560±250 g. It was used a completely randomized design in a factorial arrangement 3x4, and the birds, from three strains (Cobb 500, Hubbard Flex and Ross 308) were divided into four levels of digestible lysine (0.800, 0.950, 1.100 and 1.250%), with four replicates of 12 birds each. It was evaluated the weight gain, feed intake, feed conversion ratio, carcass yield, breast yield, breast meat yield and the yield of the thigh and drumstick. There was no interaction between lysine levels and commercial strains of broiler chickens. The different lysine levels did not influence (p ≥ 0.05) performance and carcass yield. There are significant differences between strains for feed intake and carcass characteristics. The Cobb 500 strain had higher breast yield and breast meat (p < 0.05), while the Hubbard Flex and Ross 308 strains had higher yield of the thigh and drumstick (p < 0.05).Keywords: amino acids, breast meat, performance, genotypes, carcass yield.Lisina digestível para frangos de corte de diferentes linhagens na fase final de criação RESUMO. Objetivou-se avaliar diferentes níveis de lisina digestível em rações para frangos de corte de diferentes linhagens comerciais na fase de 49 a 56 dias de idade sobre o desempenho e características de carcaça. Foram utilizados 432 frangos de corte machos de 49 dias de idade, com peso médio inicial de 3560±250 g. Utilizou-se o delineamento inteiramente casualizado em arranjo fatorial 3x4, sendo que as aves, oriundas de três linhagens (Cobb 500, Hubbard Flex e Ross 308), foram distribuídas em quatro níveis de lisina digestível (0,800; 0,950; 1,100 e 1,250%), com quatro repetições de 12 aves cada. Avaliou-se o ganho de peso, o consumo de ração, a conversão alimentar, o rendimento de carcaça, o rendimento de peito, o rendimento de carne de peito e o rendimento de coxa e sobrecoxa. Não houve interação entre os níveis de lisina digestível e as linhagens comerciais de frangos de corte. Os diferentes níveis de lisina não influenciaram (p ≥ 0,05) o desempenho e rendimento de carcaça. Existem diferenças significativas entre as linhagens para consumo de ração e características de carcaça. Sendo que a linhagem Cobb 500 teve maior rendimento de peito e carne de peito (p ≤ 0,05), enquanto as linhagens Hubbard Flex e Ross 308 tiveram maior rendimento de coxa e sobrecoxa (p ≤ 0,05).Palavras-chave: aminoácido, carne de peito, desempenho, genótipos, rendimento de carcaça.

The trial was conducted to evaluate the supplementation of E. coli phytase on performance, weight and ash of bones, as well as to determine the bioavailability of P and cost/benefit of its use in diets. A total 1,890 Cobb male day old chicks were assigned to six treatments and seven replicates with 45 birds each, distributed in a completely randomized design. The treatments were: Positive Control; Negative Control (NC1)-reduction of 0.06% av P; Negative Control 2 (NC2)-reduction of 0.12% av P; NC2 + Phytase (120 OTU); NC2 + Phytase (180 OTU); NC2 + Phytase (240 OTU), being 1 OTU equivalent to approximately 2 FTU. With different phytase inclusions, it was possible to verify a gradual increase on body weight gain, feed intake, feed conversion ratio, viability and even the bone characteristics of broilers fed diets containing reduction of P. The closest levels to the highest studied (240 OTU) showed the best results. The replacement of dicalcium phosphate by phytase supplementation is economically viable when the