An experiment was carried out to verify the response to the Ca reduction levels of diets with different vitamin D sources on performance, bone mineral deposition, serum concentrations, digestibility, carcass characteristics, and meat quality of broiler chickens in the period from 1 to 42 days reared in thermoneutral environment. A total of 504 male broilers with one day of age and average weight of 43.27±1.08 g were housed in climatic chambers and distributed in a completely randomized design. The study consisted of a 4×2 factorial, with four Ca reduction levels (0, 10, 20, and 30%) and two vitamin D sources (2760 IU of D 3 or 25-OH-D 3). The performance of animals at 21 and 42 days of age was not affected by Ca reduction by up to 30%, regardless of the vitamin source used. Dietary reduction from 10% decreased serum Ca concentrations. The use of vitamin D 3 provided a serum P level greater than the 25-OH-D 3. Calcium reduction decreased serum 25-OH-D 3 levels. No effect of vitamin source or Ca levels on broiler carcass characteristics was observed at 42 days. The vitamin source did not influence meat quality, while Ca reduction of the diet provided lower losses by thawing and cooking and higher initial pH values. The b* color was reduced in diets with lower Ca levels of the diet. Reducing Ca up to 30% does not affect the performance and carcass characteristics, regardless of the vitamin D source used. The quality of broiler meat is improved with the Ca reduction in the diet, but the vitamin used has no effect on such characteristics. We can conclude, based on the results of performance, blood, and bone, that the performance variables are not adequate to determine the actual requirement of Ca, since as it is a priority to maintain performance, bone mineral mobilization occurs, which may compromise the carcass quality of the birds.

-This study was conducted to evaluate the effect of reduction of the available phosphorus (avP) in diets supplemented with 500 FTU/kg phytase on performance, carcass characteristics, and bone mineralization of broilers aged 22 to 42 days kept in a high-temperature environment. A total of 336 Cobb broilers with an average initial weight of 0.883±0.005 kg were distributed in a completely randomized design with six treatments -a positive control (0.354 and 0.309% avP without addition of bacterial phytase for the phases of 22 to 33 and 34 to 42 days, respectively), and another five diets with inclusion of phytase (500 FTU) and reduction of the level of avP (0.354, 0.294, 0.233, 0.173, and 0.112%; and 0.309, 0.258, 0.207, 0.156, and 0.106% for the phases of 22 to 33 and 34 to 42 days, respectively) -eight replicates, and seven birds per cage. The experimental diets were formulated to meet all nutritional requirements, except for avP and calcium. Birds were kept in climatic chambers at a temperature of 32.2±0.4 °C and air humidity of 65.3±5.9%. Phytase acted by making the phytate P available in diets with reduction in the levels of avP, keeping feed intake, weight gain, feed:gain, and carcass characteristics unchanged. Treatments affected ash and calcium deposition and the Ca:P ratio in the bone; the group fed the diets with 0.112 and 0.106%, from 22 to 33 and 34 to 42 days of age, respectively, obtained the lowest values, although the phosphorus deposition in the bone was not affected. Diets supplemented with 500 FTU of phytase, with available phosphorus reduced to 0.173 and 0.156%, and a fixed Ca:avP ratio of 2.1:1, meet the requirements of broilers aged 22 to 33 and 34 to 42 days, respectively, reared in a high-temperature environment.

ResumoConduziu-se este estudo para avaliar os efeitos de níveis de glutamina na ração sobre o desempenho e carcaça de frangos de corte submetidos à ambiente de termoneutralidade no período de 21 a 42 dias de idade. Foram utilizados 168 frangos de corte machos da linhagem Cobb® de 21 a 42 dias de idade, distribuídos em delineamento experimental inteiramente casualizado, com quatro tratamentos, representados pelos níveis de glutamina das rações (0,00; 0,50; 1,00 e 1,50%), sete repetições e seis aves por unidade experimental. Foram avaliados o desempenho, os rendimentos da carcaça, peito, coxa e sobrecoxa e a expressão do mRNA da proteína HSP70. Aos 21 dias e com peso inicial de 900 ± 4,71 g, as aves foram alojadas em câmaras climáticas com temperatura de 23,2 ± 1,77ºC e umidade relativa de 70 ± 5,82% correspondendo ao ITGU calculado de 72 ± 2,75, caracterizando um ambiente de termoneutralidade. Não se observou efeito dos níveis de glutamina sobre o consumo de ração, ganho de peso e conversão alimentar das aves. Os níveis de glutamina não influenciaram os pesos absolutos e os relativos da carcaça, peito, coxa e sobrecoxa das aves. Não se observou efeito dos níveis de glutamina da ração na expressão do mRNA da proteína HSP70. Conclui-se que níveis de glutamina na ração não influenciaram o desempenho e as características de carcaça de frangos de corte dos 21 aos 42 dias de idade mantidos em ambiente termoneutro. Palavras-chave: Ambiente térmico, aves, expressão gênica, HSP AbstractThis study was conducted to evaluate the effects of dietary glutamine levels on performance and carcass traits of broilers kept in thermoneutral environment from 21 to 42 days of age. Hundred sixty eight male broilers Cobb® with 21 days of age and initial body weight of 900 ± 4.71 g were allotted in a completely randomized design with four levels of glutamine (0.00, 0.50, 1.00 and 1.50%), seven replicates with six birds each. Performance, relative weights of carcass, breast, thigh and drumstick and mRNA expression of HSP70 were evaluated. Birds were housed in environmental chambers with temperature of 23.2 ±

Three experiments were carried out to verify the effects of the enzyme phytase, alone or combined with an enzyme complex, in diets deficient in available phosphorus (AP), calcium (Ca), and metabolizable energy (ME) on broiler performance, ME, and dietary amino acid digestibility. A total of 1,538 male Cobb 500 broilers were allocated to the three experiments, each of which consisted of five treatments: positive control (PC; basal ration); negative control 1 (NC1; PC minus 0.15% of AP, 0.16% of Ca, and 68 kcal kg-1 ME); negative control 2 (NC2; PC minus 0.15% of AP, 0.16% of Ca, and 101 kcal kg-1 of ME); NC1 plus phytase; and NC2 plus phytase plus enzymatic complex. Body weight gain (WG) and feed intake were measured from 1-21 days and from 1-42 days, and the corrected feed conversion rate (FCR) for mortality was calculated. In the second and third experiments, the apparent ME corrected for nitrogen balance (AMEn) and standardized digestibility of amino acids, respectively, were determined, for the diets supplemented with phytase and the enzymatic complex. In the first experiment, enzyme supplementation increased (p < 0.05) WG at 21 days and 42 days relative to the negative controls. Phytase inclusion improved (p < 0.05) FCR at the initial phase compared to the NC1 diet. In the second experiment, enzyme supplementation did not affect (p > 0.05) AMEn. In the third experiment, both enzyme treatments improved (p < 0.05) the digestibility of amino acids in the supplemented diets compared to the deficient diets. Supplementation with phytase and carbohydrases preserves the performance of broilers fed diets deficient in AP, Ca, and ME and improves amino acid digestibility.

Foram realizados dois experimentos com o objetivo de avaliar os efeitos da suplementação de fitase ou fitase + complexo multienzimático em dietas, à base de milho e de farelo de soja, com redução de cálcio (Ca), fósforo disponível (Pd) e energia metabolizável (EM) sobre o desem- penho, a retenção de energia e a digestibilidade de aminoácidos em frangos de corte. No total, foram utilizados 3.056 frangos de corte Cobb 500, divididos em dois ensaios de desempenho, dois de metabolismo e dois de digestibilidade. Em cada experimento, um total de 1.528 frangos de corte de 1 a 42 dias de idade foram distribuídos em um delineamento experimental inteira- mente casualizado (DIC) com 5 tratamentos, 10 repetições de 20 aves por unidade experimen- tal. Os tratamentos avaliados no primeiro experimento foram: controle positivo, atendendo às recomendações nutricionais (CP); dois controles negativos (CN) com redução de 0,16% de Ca, 0,15% de Pd, 68 kcal/kg de EM no CN1 e 100 kcal/kg de EM no CN2; CN1 + 500 FTU/kg de fitase (Escherichia coli); e CN2 + 500 FTU/kg de fitase + 15.000 U/kg de xilanase + 2.400 U/kg de β-glucanase + 2.400 U/kg de β-mananase + 1.200 U/kg de celulase + 150 U/kg de α- amilase + 100 U/kg de α-galactosidase + 1.500 U/kg de pectinase +2.500 U/kg de protease. No segundo experimento, os tratamentos foram compostos pelo controle positivo, atendendo às recomendações nutricionais (CP); dois controles negativos (CN) com redução de 0,16% de Ca, 0,15% de Pd, 80 kcal/kg de EM no CN1 e 100 kcal/kg de EM no CN2; CN1 + 1.000 FTU/kg de fitase; e CN2 + 1.000 FTU/kg de fitase + 15.000 U/kg de xilanase + 2.400 U/kg de β-gluca- nase + 2.400 U/kg de β-mananase + 1.200 U/kg de celulase + 150 U/kg de α-amilase + 100 U/kg de α-galactosidase + 1.500 U/kg de pectinase + 2.500 U/ kg de protease. Tanto no pri- meiro quanto no segundo experimento, as reduções nutricionais afetaram negativamente o de- sempenho de frangos de corte e a retenção de energia. A adição de fitase ou fitase mais com- plexo multienzimático às dietas CN restaurou o desempenho das aves aos mesmos níveis da dieta CP. No ensaio de desempenho do primeiro experimento, o menor nível de nutrientes e energia reduziu a digestibilidade dos aminoácidos estudados, o que não foi observado no se- gundo ensaio. Em ambos os experimentos, a inclusão de enzimas melhorou a digestibilidade da maioria dos aminoácidos para níveis superiores aos do CN, e no segundo experimento ela aumentou para níveis acima do CP. A suplementação enzimática aumenta a digestibilidade de aminoácidos e restaura o desempenho de frangos de corte alimentados com dietas contendo níveis nutricionais reduzidos. Palavras-chave: Frangos de corte. Desempenho. Fitase. Metabolismo. Digestibilidade de ami- noácidos. Complexo multienzimático.