Suplementação de Treonina em Dietas de Frangos de Corte, Variando a Energia e as Relações Energia: Proteína Threonine Supplementation in Broiler Diets Varying Energy and Energy: Protein Ratio

Dois experimentos (EXP 1 e 2) foram conduzidos para avaliar relações energia metabolizável:proteína bruta (EM:PB) e a adição de treonina (Thr) em dietas com alta (A) (3.200kcal EM/kg) e baixa (B) (2.900kcal EM/kg) energia, sobre desempenho e composição de carcaças de frangos de corte machos. As relações energia:proteína foram 139 e 160 kcal/%, para as dietas iniciais (1 a 21 dias) (EXP 1) e 160 e 181kcal/%, para as de crescimento (22 a 40 dias) (EXP 2), nos dois níveis de energia. As dietas com ampla relação EM:PB foram suplementadas, ou não, com Thr a fim de iguala-las às dietas com menor EM:PB. Os níveis de Met+Cys e de Lys foram constantes. As aves receberam uma dieta única após (EXP1), ou antes (EXP2) do fornecimento das dietas experimentais. Nos dois EXP as dietas A proporcionaram melhor desempenho: ganho de peso (GP),consumo de ração e conversão alimentar (CA) (p<0,01), ao final de cada período experimental. Porém, no EXP 1, as aves que receberam dietas B tiveram melhor conversão calórica (CC, kcal/kg,) (p<0,01) no período total (1 a 40 dias), indicando um período de crescimento acelerado. Os níveis de Thr (0,74 e 0,69% para A e B respectivamente) das dietas com relação EM:PB ampla não foram limitantes no desempenho das aves. No EXP 2, a EM:PB 181 deprimiu o GP (p<0,08) e piorou a CA (p<0,01), nas energias A e B. Portanto, em dietas práticas iniciais, Thr não foi um aminoácido (AA) limitante. Porém, de 22 a 40 dias, a adição de Thr foi necessária, em dietas com EM:PB 181kcal/%(EXP 2). A suplementação de Thr não influenciou a composição das carcaças nos dois EXP.<br>Two experiments (EXP) were carried out to investigate the metabolizable energy:crude protein ratios (ME:CP) and threonine addition (Thr) in high-energy (H) (3.200kcal ME/kg) and low-energy (L) (2.900kcal ME/kg) diets, on the performance and carcass composition of male broiler chickens. The ME:CP ratios were: 139 and 160kcal/% for starter diets (1 to 21 days of age) (EXP 1) and 160 and 181kcal/% for grower diets (22 to 40 days)(EXP 2), in both energy levels, keeping Met + Cys and Lys constant. Thr was supplemented to equalize its level to the lower EM:PB ratio. All birds received a unique diet after (EXP 1) or before (EXP 2) been fed with the experimental diets. In both EXP feeding H diets resulted in better performance -weight gain (WG), feed intake (FI) and feed conversion (FC) (p<0,01) at the end of each experimental period. However, in EXP 1, birds fed with L diets during the starter period had better caloric conversion (kcal/kg) (CC) in the total period (1 to 40 days), as an indicative of accelerated growth. The lower levels of Thr (0.74 and 0.69% for H and L diets, respectively) were not limiting for birds' performance. On EXP 2, the 181 ME:CP decreased WG (p<0.08) and increased FC (p<0.01) in both energy levels. Thr was not a limiting amino acid in initial practical diets (1 to 21 days of age). On the other hand, Thr supplementation improved performance of birds at 181 E:CP (22 to 40 days) (EXP2). Thr addition did not influence carcass composition in both EXP

Modelling energy utilization for laying type Pullets

Three trials were carried out to determine energy metabolized (EM) requirement model for starting and growing pullets from different strains, at five ambient temperatures and different percentage feather coverage. In Trial I, metabolizable energy requirements for maintenance (MEm) and efficiency of energy utilization were estimated using 64 birds of two different strains, Hy-Line W36 (HLW36) and Hy-Line Semi-heavy (HLSH), from 9 to 13 weeks of age. The effects of ambient temperature (12, 18, 24, 30 and 36ºC) and percentage feather coverage (0, 50 and 100%) on MEm were assessed in the second trial, using 48 birds per temperature per strain (HLSH and HLW36) from 9 to 13 weeks of age. Trial III evaluated ME requirements for weight gain (MEg) using 1,200 birds from two light strains (HLW36 and Hisex Light, HL) and two semi-heavy strains (HLSH and Hisex Semi-heavy, HSH) reared until 18 weeks of age. According to the prediction models, MEm changed as a function of temperature and feather coverage, whereas MEg changed as a function of age and bird strain. Thus, two models were developed for birds aged 1 to 6 weeks, one model for the light strain and one for the semi-heavy strain. Energy requirements (ER) were different among strains from 7 to 12 weeks, and therefore 4 models were elaborated. From 13 to 18 weeks, one single model was produced for semi-heavy birds, since ER between semi-heavy strains were not different, whereas two different models were elaborated for the light layers. MEg of light birds was higher than MEg of semi-heavy birds, independent of age