Growth performance and carcass yield of broiler chickens in response to carbohydrases and its association with phytase / Desempenho e rendimento de carcaça de frangos de corte em resposta à associação de carboidrase com fitase

An experiment was conducted to evaluate broiler chicken performance and carcass yield in response to carbohydrase supplementation (Xylanase and Betaglucanase; XB) and association of carbohydrase and phytase (PHY). A total of 1,920 day-old male broiler chicks (Cobb 500) were distributed in a completely randomized design with 8 treatments and 8 replicates each, allocated in 64 pens with 30 chicks each. The treatments were: Positive Control (PC); Negative Control (NC): reduced ME [-120kcal/kg (Starter) and -170kcal/kg (Finisher)]; NC + XB [50g/ton]; NC + XB [100g/ton]; NC + XB [150g/ton]; NC + XB [50g/ton] + PHY [100g/ton]; NC + XB [100g/ton] + PHY [100g/ton]; NC + XB [150g/ton] + PHY [100g/ton]. The inclusion of XB (150) and XB (50, 100, and 150) associated with phytase increased feed intake than positive control when considering the total rearing phase. The feed conversion ratio of all broilers fed diets with energy reduction were worse than positive control, even with the addition of enzymes, and did not differ between them. There was no significant effect of treatments on carcass parameters.(AU)

O experimento foi conduzido para avaliar o desempenho e o rendimento de carcaça de frangos de corte em resposta à suplementação de carboidrase (Xilanase e Betaglucanase; XB) e à associação de carboidrase com fitase (PHY). Um total de 1.920 frangos de corte, machos, com 1 dia de idade (Cobb 500), foram distribuídos em um delineamento experimental inteiramente ao acaso, com oito tratamentos e oito repetições, totalizando 64 unidades experimentais (boxes) com 30 aves cada. Os tratamentos foram: controle positivo (PC); controle negativo (NC): redução de EM [-120kcal/kg (fase inicial) e -170kcal/kg (fase final)]; NC + XB [50g/ton]; NC + XB [100g/ton]; NC + XB [150g/ton]; NC + XB [50g/ton] + PHY [100g/ton]; NC + XB [100g/ton] + PHY [100g/ton]; NC + XB [150g/ton] + PHY [100g/ton]. A inclusão de XB (150) e a associação de fitase com XB (50, 100 e 150) aumentaram o consumo de ração em relação ao tratamento controle positivo, considerando-se a fase total de criação. A conversão alimentar de todos os frangos que receberam dietas com redução de energia foi pior que o controle positivo, mesmo com a adição das enzimas, e não diferiu entre elas. Não houve efeito significativo dos tratamentos sobre os parâmetros de carcaça.(AU)

Manipulation of dietary methionine+cysteine and threonine in broilers significantly decreases environmental nitrogen excretion.

The intensification of livestock have increased the emission of pollutants to the environment, leading to a growing interest in seeking strategies that minimise these emissions. Studies have shown that it is possible to manipulate diets by reducing CP levels and thus reducing nitrogen (N) excretion, without compromising performance. However, there is no knowledge of any study that has focused on reducing N excretion and relating this reduction to individual amino acids. This study investigated the effect of dietary methionine+cysteine (MC) and threonine (THR), the two most limiting amino acids for broiler production, on nitrogen excretion (NE) and nitrogen deposition (ND) and determined the efficiency of utilisation of both amino acids for protein deposition. Six trials were conducted to measure the NE and ND in broiler chickens during three rearing phases in response to dietary amino acid. The efficiency of utilisation of the amino acids was calculated by linear regression of body protein deposition and the amino acid intake. Despite the differences between sexes and phases, the efficiency of utilisation was the same, being 0.60 and 0.59 for MC and THR, respectively. The rate of NE behaved exponentially, increasing with amino acid intake, and can exceed 50% of N intake, being higher than ND. On average, for a reduction in intake of each unit of MC or THR (mg) there is a reduction of 0.5% of NE. Although this reduction seems low, considering that it corresponds to changes in one amino acid only, the impact on a large scale would be significant. Knowledge of how animals respond to NE and ND/protein deposition according to amino acid dietary content may represent new efforts towards reducing the impact on environment.

Broiler responses to digestible threonine at different ages: a neural networks approach.

Three experiments were conducted with broiler chickens to evaluate the effects of digestible threonine (DThr) and crude protein (CP) on their performance at three different phases of age: 1-14, 15-28 and 29-42 days. The measured traits included the following: average daily gain (ADG), feed intake (FI), feed conversion ratio (FCR), carcass crude protein (CCP), body lipid (BL), feather weight gain (FWG), protein deposited in feather (FCP), carcass plus feather protein (CFCP), carcass Thr deposition (CDThr) and nitrogen excretion (NE). A dilution technique was used to create seven diets (with eight replicates) increasing the DThr content from 1.5 to 10 g/kg of diet for phase 1, 1.3-8.9 g/kg of diet for phase 2, and 1.2-8.2 g/kg of diet for phase 3. Data measured were imported into neural networks (NNs) to: (i) predict the measured traits in response to DThr and CP, (ii) rank the importance of DThr and CP on these traits through sensitivity analysis and (iii) find the optimal levels of DThr and CP that lead to the desired (maximum or minimum) responses. For each trait investigated, 50 different random groups of data were generated using a bootstrapping method. These 50 data groups were then used to develop 50 separate NNs which were subsequently combined to construct the final ensemble NN model. In general, accuracy of the models constructed was acceptable, although models of high (ADG, FCR, CFCP, BL, DThr and NE; 0.64 ≤ R(2)  ≤ 0.99) and low (CCP, FWG and FCP; 0.26 ≤ R(2)  ≤ 0.79) accuracy were obtained. All models developed showed the greatest sensitivity to DThr. This may be explained by the dilution technique diet preparation used in these experiments. Optimization results showed decreases in optimal values of DThr and CP with increasing age for all traits. The highest level of DThr was suggested for minimum BL, followed by minimum FCR, maximum ADG, maximum CFCP, minimum NE and maximum CCP respectively. Results showed that the optimal values of DThr for minimum FCR in phases 1-3 were 8.5, 7.4 and 6.4 g/kg of diet, while these values for maximum ADG were 8.2, 7.2 and 6.4 g/kg of diet respectively.

Parâmetros ósseos de frangos de corte alimentados com rações contendo fitase e baixos níveis de fósforo disponível e proteína bruta / Bone parameters for broilers fed diets with phytase and low phosphorus and crude protein levels

Foram utilizados 504 pintos de linhagem comercial (Ag Ross 308) para frangos de corte de um dia de idade, distribuídos em 12 tratamentos com seis repetições. O delineamento experimental utilizado foi de blocos ao acaso em esquema fatorial 2x2x3, com dois níveis de fósforo disponível (0,45 e 0,34%), dois níveis de fitase (0 e 1200 FTU/kg) e três níveis de proteína bruta (22,5; 20,5 e 18,5%). A porcentagem de cálcio e fósforo nas tíbias foi influenciada significativamente pelos níveis de proteína e de fósforo na dieta com o uso da fitase. Os teores de matéria mineral nas tíbias apresentaram efeito linear com o uso da enzima e efeito quadrático com a ausência dela, apresentando maior valor com o nível de 22,5% de proteína na dieta. Já com os maiores níveis de fósforo houve efeito linear entre os níveis de proteína bruta na dieta e os pesos da matéria mineral nas tíbias, ou seja, quanto maior o nível de proteína, menor o peso da matéria mineral.

504 (five hundred four) 1 day old male chicks from a commercial broiler line (Ag Ross 308) were used, distributed in 12 treatments, with 6 replicates per treatment. The experimental design was casually blocked and treatments were organized in a 2x2x3 factorial arrangement: two available phosphorus levels (0.45 and 0.34%), two phytase inclusion levels (0 and 1200 FTU/kg) and three crude protein levels (22.5; 20.5 and 18.5%). Tibia calcium percentage was influenced by protein and phosphorus levels in the diet, when using phytase. Tibia ash levels showed a linear effect when enzymes were added and showed a quadractic effect without it, and the higher value was observed with 22.5% crude protein in the diet. With higher phosphorus levels a linear effect was observed between crude protein in the diet and tibia ash weights, as a higher protein level had lower tíbia ash weight.