The objective of this study was to evaluate the effect of diets containing different calcium and phytase levels on the nutritional balance of broilers.A total of 108 male AG Ross 308 broilers were used in each of the replicates phases used in the study: starter (1-21 days), grower (29-35 days) and finisher (36-42 days). A completely randomized experimental design in a 3 x 2 factorial arrangement, with three phytase levels (0, 600 or 1200 FTU/kg) and two calcium levels (0.94 and 0.66%; 0.84 and 0.59%; e 0.78 and 0.54% in the starter, grower, and finisher phases, respectively), totaling six treatments with six replicates each.The experimental feeds also contained reduced available phosphorus levels and minimum crude protein level.The method of total excreta collection was applied to determine dry matter, nitrogen, gross energy, calcium, and phosphorus nutritional balance.Reducing dietary calcium levels to 0.66, 0.59, and 0.54%, and using 0.27, 0.22, and 0.20% available phosphorus, 18.50, 17.50, and 16.00% crude protein, and 600 FTU phytase/kg in the diets of the starter, grower, and finisher phases, respectively, allow higher nitrogen, phosphorus, and calcium retention in broilers.During the grower phase, there was positive linear effect of increasing phytase levels in high-calcium diets on AMEn utilization, and the optimal phytase levels for low-calcium diets was 598.71 FTU/kg.In the finisher phase, the best AMEn utilization was obtained with the high-calcium diets.

RESUMO Este experimento objetivou avaliar o efeito da suplementação de diferentes níveis isolados e associados de vitamina E (Vit E) (0, 12 e 120 mg/kg) e do zinco (Zn) (0, 40 e 400 mg/kg) na dieta sobre o desempenho de frangos de corte até 42 dias de idade. Foram alojados 1.440 pintos de um dia, em 36 boxes com 40 aves cada (metade de cada sexo). A ração e a água foram fornecidas ad libitum. Os frangos receberam dieta inicial (1 a 21 dias), de crescimento (22 a 35 dias) e final (36 a 42 dias). O delineamento experimental utilizado foi inteiramente casualizado, em fatorial 3 x 3, com 9 tratamentos e 4 repetições. O aumento da suplementação de Zn na dieta dos frangos resultou em melhoria significativa (p < 0,05) no ganho médio de peso vivo nas fases inicial e de crescimento e no período total de criação. O consumo de ração pelos frangos foi influenciado pelos níveis de Zn utilizados em todas as fases e no período total de criação dos frangos, observando-se diminuição da ingestão alimentar nos frangos que receberam 400 mg/kg de Zn, exceto na fase final de criação. Os tratamentos utilizados não influenciaram a conversão alimentar.

ABSTRACT This study evaluated the influence of different dietary supplementation levels of vitamin E (Vit E) (0, 12 and 120 mg/kg) and zinc (Zn) (0, 40 and 400 mg/kg) on the performance of broilers during their first 42 days. A total of 1,440 1-day chicks were distributed in 36 floor pens containing 40 birds each (half of each sex). Broilers had free access to feed and water at all time. The broilers were fed start diet (days 1 to 21), growing diet (days 22 to 35) and final diet (days 36 to 42). A completely randomized 3 x 3 factorial design was used, with 9 treatments and 4 replicates. The increase of the supplementation of zinc in the diet of the broilers resulted in significant improvement (p < 0.05) in the average gain of live weight of the chickens in the initial and growth phases and in the total period of raising. The feed consumption for the chickens was influenced by the levels of zinc used in all of the phases and in the total period of raising of the chickens, there being observed a decrease in the feed consumption of the chickens that received 400 mg/kg of Zn, except in the final phase of raising. The treatments studied did not influence the gain feed ratio.

Male broilers were used to evaluate the effects of different energy levels in finisher diets and age of slaughter on performance, production pattern and carcass yield. Experimental design was a 2x3 factorial arrangement: energy level (ME) in the finisher diet (3,200 and 3,600 kcal ME/kg) and age of slaughter (42, 49 and 56 days), resulting in six treatments with four replicates. The finisher diet was fed only in the last week of the growing period. Characteristics evaluated were feed consumption (FC), body weight gain (WG), feed conversion (FC), energy intake (EI), caloric conversion (CC), efficiency production index, production pattern, and carcass yield. The results showed better WG and CC for broilers fed 3,200 kcal ME/kg finisher diet. Broilers slaughtered at 42 and 49 days of age had better performance and higher annual production than broilers slaughtered at 56 days of age. Carcass yield was influenced by slaughter age and better breast yield was seen at 49 and 56 days than at 42 days of age. It was concluded that 3,200 kcal ME/kg induced the best overall performance. Poultry houses were efficiently used when broilers were slaughtered at 42 days of age. Meat:bone ratio was improved for broilers slaughtered at 49 and 56 days of age.