ABSTRACT Apparent calcium (Ca) retention and digestibility coefficients are affected by limestone particle size in the diet of laying hens. This study aimed to determine the apparent retention and digestibility coefficients of Ca in limestone of different particle sizes in laying hens. The study comprised 288 Lohmann Brown laying hens (50 weeks of age; 1,964 ± 98 g) distributed in a completely randomized experimental design with a 3 × 2 factorial arrangement [three Ca concentrations (10, 20, and 30 g kg–1) × two limestone particle sizes (480 and 1,978 µm)] with eight repetitions per treatment and six birds per experimental unit. The experiment included five days for adaptation and five days for total excreta collection. All birds were slaughtered at the end of the ten days to collect the ileal contents. The total or ileal Ca content was plotted against the Ca of diets concentration using linear regression analysis. The regression line slope represented the apparent retention (CaR) and digestibility coefficients of Ca (CaD) in limestone. There was interaction between Ca concentration in the diet and limestone granulometry on CaD (p = 0.001) and CaR (p < 0.001). The CaD and CaR of fine- and coarse-grained limestone increased linearly with increasing Ca concentrations in the diet. The apparent digestibility coefficients estimated for laying hens fed with fine-grained and coarse-grained limestone were 0.72 and 0.35, respectively. The apparent retention coefficients estimated for laying hens fed fine-grained and coarse-grained limestone were 0.96 and 0.47, respectively.

O experimento foi conduzido com o objetivo de avaliar a influência que diferentes relações treonina:lisina digestíveis e suplementação ou não de glicina exercem sobre o desempenho de frangos de corte na fase inicial. Foram utilizados 560 pintos de corte, machos, da linhagem Cobb, distribuídos em delineamento inteiramente casualisado, em arranjo fatorial 3 x 2 +1, sendo três relações de treonina:lisina digestíveis (55; 65 e 75%), suplementados ou não com glicina mais um adicional, que continha proteína de origem animal, com relação treonina:lisina digestíveis de 65%. Utilizaram-se oito repetições e 10 aves por unidade experimental. O consumo de ração, o ganho de peso e a conversão alimentar não foram influenciados pelos níveis de treonina. A suplementação de glicina reduziu o consumo de ração, aumentou o ganho de peso e melhorou a conversão alimentar das aves. Não houve interação entre os níveis de treonina e a suplementação de glicina sobre o desempenho das aves. A suplementação de glicina foi essencial para melhorar o desempenho de pintos de corte. Concluise que a relação de 55% de treonina digestível: lisina digestível (0,631% de treonina digestível), suplementada com glicina é suficiente para atender as exigências de pintos de corte de 8 a 21 dias de idade.

The experiment was conducted with the objective evaluating the different digestible threonine: digestible lysine ratio and supplementation or not of glycine on the performance of broilers in the period from eight to 21 days of age. Five hundred and sixty male broiler chicks of the Cobb strain were used, distributed in a completely randomized design, in a factorial arrangement of 3 x 2 + 1, with three digestible threonine:lysine ratio (55, 65 and 75%), supplemented or not with glycine plus an additional treatment, containing animal protein, with digestible threonine:lysine ratio of 65%. Eight replicates were used per treatment and 10 birds were used per experimental unit. The feed intake, the weight gain and the feed conversion were not influenced by the levels of threonine. The supplementation of glycine reduced the feed intake, increased the weight gain and improved the feed conversion of the birds. There was no interaction between the levels of threonine and the supplementation of glycine on the broilers performance. The supplementation of glycine was essential to improve the broiler chicks performance. The digestible threonine: lysine ratio of 55% (0.631% of digestible threonine), supplemented with glycine is sufficient to meet the requirements of broiler chicks from 8 to 21 days of age.

Este experimento foi realizado para determinar a exigência de treonina para frangos de corte, no período de 1 a 21 dias de idade, e avaliar o efeito de diferentes níveis de treonina sobre a excreção de ácido úrico em frangos de corte. Um mil e duzentos pintos foram distribuídos ao caso em esquema fatorial 6x2, sendo seis níveis de treonina total (0,73; 0,77; 0,81; 0,85; 0,89; e 0,93%) e dois sexos, com cinco repetições de 20 aves cada. Consumo de ração, ganho de peso, conversão alimentar e níveis plasmáticos de ácido úrico foram avaliados. Ensaio biológico usando o método da coleta total de excreta foi realizado para avaliar o efeito dos níveis de treonina sobre a excreção de ácido úrico. Efeito linear positivo e negativo dos níveis de treonina sobre o ganho de peso de machos e fêmeas, respectivamente, e efeito quadrático sobre o consumo de ração e conversão alimentar de machos e fêmeas foram observados. Os níveis de treonina não influenciaram os níveis plasmáticos de ácido úrico nas aves, e não foi observado efeito dos níveis de treonina sobre a excreção de ácido úrico. Os níveis de 0,86 e 0,73% de treonina total e 0,73 e 0,62% de treonina digestível foram suficientes para máximo desempenho de machos e fêmeas, respectivamente.

This experiment was carried out to determine the threonine requirement for broilers chicks from 1 to 21 days of age and to evaluate the effect of different threonine levels on the uric acid excretion in broilers. One thousand and two hundred broiler chicks were randomly allotted to a 6x2 factorial arrangement, being six levels of total threonine (.73, .77, .81, .85, .89, and .93%) and two sexes, with five replicates of 20 birds each. Feed intake, weight gain, feed:gain ratio and plasma uric acid levels were evaluated. A biologic trial using the total collection of feces method was conducted to evaluate the effect of threonine level on the uric acid excretion. There were linear positive and negative effects of the threonine levels on males and females weight gain, respectively, and quadratic effect on feed intake and feed:gain ratio of males and female. The threonine levels did not influence the uric acid plasmatic levels in the birds, and was not observed effect of threonine levels on the uric acid excretion. The levels of .86% and .73% of total threonine and .73% and .62% of digestible threonine were sufficient to maximize performance of males and females, respectively.