The effects of increasing weaning age in a commercial production system on nursery and finishing performance were evaluated. A total of 1,176 pigs (PIC 337 × Camborough) were used in a 136-d growth trial with 14 and 10 replications/weaning age on the nursery and finishing phases, respectively. Treatments included weaning litters at 19, 22, 25, or 28 d of age. In the nursery, as weaning age increased, initial (5.04, 5.70, 6.52, and 7.26 kg) and final body weight (BW) (18.2, 19.8, 23.0, and 25.1 kg) increased (linear, P < 0.001). Increasing the weaning age reduced (linear, P < 0.001) the prevalence of pigs exhibiting belly nosing (27.6%, 15.0%, 6.5%, and 1.4%) during the first 3 wk. The percentage of pigs losing weight during the first week after weaning (35.1%, 28.7%, 12.4%, and 9.2%) decreased (linear, P < 0.001) as weaning age increased. Average daily gain (ADG; 295, 320, 374, 406 g/d) and average daily feed intake (493, 534, 619, 661 g/d) increased (linear, P < 0.001), while feed efficiency (G:F) (596, 599, 604, and 615) tended to increase (linear, P = 0.081) with weaning age. Removal rate (8.01%, 3.79%, 2.29%, and 1.65%) declined (linear, P = 0.001) as weaning age increased, while there was no evidence of difference (P = 0.463) in mortality rate (0.71%, 0.36%, 0.96%, 1.04%). In the finishing period, BW at 136 d post-weaning (114.9, 117.8, 124.7, and 126.5 kg) and ADG (1.02, 1.04, 1.08, and 1.07 kg/d) improved (linear, P < 0.001). There was no evidence of differences (P > 0.24) in removal (1.5%, 2.4%, 1.0%, and 0.0%) or mortality rates (0.9%, 1.0%, 1.0%, and 1.4%) with changes in weaning age. When performance was analyzed at a common day of life (164 d of age), no effects of weaning age (P > 0.25) were found for BW (125.2, 124.4, 128.0, and 126.5 kg) and lifetime ADG (growth rate from birth to market) (754, 751, 774, and 762 g/d). The BW sold per pig weaned increased (linear, P < 0.001) with weaning age. Even though the slope indicated a linear response, the magnitude of improvement was high until 25 d, before exhibiting diminishing returns from 25 to 28 d. Thus, the study suggests that increasing the weaning age can be an effective strategy to improve the overall performance in a commercial system. Although lifetime performance was not affected by the weaning age range studied, the consistent effect in the nursery and the increment in the number of pigs reaching the market facilitated by the improvement in the removal rate in the nursery phase imply that 25 d is the optimal weaning age.

-Two experiments using Cobb broiler chicks from 8 to 35 days of age were carried out to evaluate the effect of reducing levels of calcium and available phosphorus in diets supplemented with 500 ftu phytase/kg on the performance of the birds, the content of ashes in the tibia, the metabolizable energy of the diet, and the metabolizability of the dry matter and crude protein. It was used 1,404 broiler chicks in the experiment 1 to evaluate feed intake, weight gain, food conversion and percentage of the ashes in the tibia. In the experiment 2, simultaneously carried out with experiment 1, a total of 390 birds were transferred to a metabolism room to determine the metabolizable energy and metabolizability of the dry matter and crude protein. It was used in the two experiments, a complete random design in a 3 × 4 + 1 factorial scheme with three levels of available phosphorus (0.375; 0.325; and 0.275%) and four levels of calcium (0.85; 0.75; 0.65 and 0.55%) in the diets, supplemented with phytase. It was also used a control diet without phytase, based on corn and soybean bran, formulated with 0.425% of available phosphorus and 0.85% of calcium. In the experiment 1, the reduction of levels of calcium and phosphorus did not cause a significant difference on the performance and percentage of bone ashes. The levels of calcium and available phosphorus used in the experiment 2 can be reduced down to 0.65 and 0.325%, respectively, because the effects are similar to those obtained with the currently suggested levels.Key Words: enzyme, minerals, nutritional requirement Níveis de fósforo disponível e de cálcio para frangos de corte de 8 a 35 dias de idade alimentados com rações contendo fitase RESUMO -Dois experimentos com pintos de corte da linhagem Cobb no período de 8 a 35 dias de idade foram realizados para avaliar o efeito da redução dos níveis de cálcio e fósforo disponível (Pdisp) em rações suplementadas com 500 ftu de fitase/kg sobre o desempenho das aves, o teor de cinzas na tíbia, a energia metabolizável (EMAn) da dieta e a metabolizabilidade da matéria seca (MS) e da proteína bruta (PB). No experimento 1, foram utilizados 1.404 pintos de corte para avaliação do consumo de ração, do ganho de peso, da conversão alimentar e da porcentagem de cinzas na tíbia. No experimento 2, conduzido simultaneamente ao primeiro, um total de 390 aves foram transferidas para uma sala de metabolismo para determinação da EMAn e da metabolizabilidade da MS e PB. Nos dois experimentos, utilizou-se delineamento inteiramente casualizado, em esquema fatorial 3 × 4 + 1, com três níveis de fósforo disponível (0,375; 0,325 e 0,275%) e quatro níveis de cálcio (0,85; 0,75; 0,65 e 0,55%) nas dietas, suplementadas com fitase. Também foi usada uma dieta controle sem fitase, à base de milho e farelo de soja, formulada com 0,425% de fósforo disponível e 0,85% de cálcio. No experimento 1, a redução dos níveis de cálcio e fósforo não ocasionou diferença significativa no desempenho e na porcentagem de cinzas ósseas. Os níveis de cálcio e fósfor...

RESUMO -Avaliaram-se os níveis de cálcio e fósforo disponível (Pdisp) em rações com fitase para frangos de corte da linhagem Cobb nas fases de crescimento (22 a 35 dias) e final (36 a 42 dias). Utilizou-se um esquema fatorial 3 × 4 + 1, composto de três níveis de Pdisp (0,36; 0,31; 0,26% na fase de crescimento e 0,33; 0,28; 0,23% na final), quatro níveis de cálcio (0,82; 0,72; 0,62; 0,52% para a fase de crescimento e 0,76; 0,66; 0,56; 0,46% para a final) e um nível de suplementação da fitase (500 ftu/kg). As rações controle não foram suplementadas com fitase e continham, respectivamente, os seguintes níveis de Pdisp e cálcio: 0,41 e 0,82% (fase de crescimento) e 0,38 e 0,76% (final). Nos ensaios de desempenho, aos 35 e 42 dias de idade, avaliaram-se o consumo de ração, o ganho de peso, a conversão alimentar e o teor de cinzas na tíbia. Nos ensaios de metabolismo, foram determinados os valores energéticos das rações (EMAn) e os coeficientes de metabolizabilidade da matéria seca (CMMS). Na fase de crescimento, a redução do cálcio e Pdisp para 0,52 e 0,26%, respectivamente, não comprometeu o desempenho, a mineralização óssea, a EMAn e o CMMS. Na fase final, a redução do cálcio e fósforo disponível para 0,56 e 0,28%, respectivamente, não comprometeu o desempenho, a EMAn e o CMMS e melhorou a mineralização óssea. Os níveis de cálcio e fósforo disponível em rações para frangos de corte podem ser reduzidos para 0,52 e 0,26% na fase de crescimento e 0,56 e 0,28% na fase final desde que essa redução seja combinada com a suplementação de fitase no nível de 500 ftu/kg de ração.Palavras-chave: cinzas ósseas, desempenho, enzima, exigência nutricional, metabolismo Calcium and available phosphorus levels in diets supplemented with phytase for broilers in the growing and finishing phases ABSTRACT -Calcium and available phosphorus (aP) levels in diets with phytase for Cobb broilers in the growing (22 to 35 days) and finishing phases (36 to 42 days of age) were evaluated. A 3 × 4 + 1 factorial scheme, with three aP levels (0.36, 0.31, 0.26% in the growing phase and 0.33, 0.28, 0.23% in the finishing phase), four calcium levels (0.82, 0.72, 0.62, 0.52% in the growing phase and 0.76, 0.66, 0.56, 0.46% in the finishing phase), and one level of supplementation of phytase (500 ftu/kg) was used. Control diets were not supplemented with phytase and they contained, respectively, the following levels of aP and calcium: 0.41 and 0.82% (growing phase) and 0.38 and 0.76 (finishing phase). In the performance assays, at 35 and 42 days of age, feed intake, weight gain, feed conversion and the ash content in the tibia were evaluated. In the metabolic assays, the energy values of diets (AMEn) and dry matter digestibility coefficients (DMDC) were determined. In the growing phase, the reduction of the calcium and aP to 0.52 and 0.26%, respectively, did not compromise performance, bone ash, AMEn or MCDM.In the finishing phase, the reduction of the calcium and aP to 0.56 and 0.28%, respectively, did not compromise performance, AMEn or MCDM; in add...

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-This study was conducted in order to evaluate the influence of different levels of metabolizable energy and crude protein in diets formulated according to the ideal protein concept with phytase supplementation on performance and nutrient excretion of broilers from 22 to 42 days age. It was used 1,500 Coob lineage broilers at 22 days of age and with initial weight of 833 ± 7g, distributed in completely randomized design in a 3 × 3 + 1 factorial scheme composed of three levels of correct apparent metabolizable energy (2,950; 3,100 and 3,250 kcal/kg), three levels of crude protein (14, 16 and 18%) and a control treatment, totaling ten treatments with six repetitions of 25 birds each. All diets, with the exception of the control, were supplemented with phytase. For determination of excretion of pollutants, it was used 180 broilers from the same lineage at 35 days of age,placed in metabolic cages, with ten treatments each one with six repetitions and three birds per experimental unit. The protein and energy levels in diets containing phytase influenced feed intake, weight gain, feed conversion and excretion of nitrogen, phosphorus, calcium, potassium, copper and zinc by the birds. The corrected apparent metabolizable energy level in the diets for broilers in the studied period must be increased up to 3,250 kcal/kg of metabolizable energy and the levels of crude protein, calcium and phosphorus must be reduced down to 18, 0.70 and 0.31%, respectively, provided that supplemented with amino acids and phytase to improve the performance and to reduce excretion of pollutants by birds.