Métodos de debicagem e níveis de fibra bruta para frangas leves de reposição

Abstract

Two experiments were conducted to evaluate the effects of beak trimming method by infrared radiation or hot blade and the inclusion of different fiber levels in the diet on performance and development of the laying hens’ digestive system. In the first study were used 1200 laying hens Hy-Line W 36, one day of age, being 600 submitted to beak trimming by infrared radiation in the incubator, and not submitted to another beak trimming method and 600 chicks were submitted to beak trimming by hot blade method at 10 and 75 days old. The birds were distributed in a completely randomized design with two methods of beak trimming and four fiber inclusion levels in the diet (3.0, 3.5, 4.0 and 4.5%), making eight treatments with six replications of 25 birds during the growing period (1 to 6 weeks). It was used a scheme in plot subdivided in time, factorial 2x4 (beak trimming methods and crude fiber levels) in the plot and the subplot age. In the sixth week, the laying hens were transferred to rearing cage, following the same treatment and experimental design of the previous stage, but with 16 birds in each repetition, totaling 768 laying hens, constituting the growing phase (7 to 16 weeks). In the 16th week, the laying hens were transferred to laying cages, following the same experimental design of the previous step, but with 12 birds in each repetition using 576 laying hens constituting the laying phase (20 to 32 weeks), which was evaluated to check the residual effects of the treatments used during the growing phases. The birds taken out of the first experiment were used in the second study, 432 laying hens during the growing period and 192 in the growing period, following the same design used in the first experiment. A total of four birds per treatment were euthanized, weekly and fortnightly, respectively, in the growing phases, to evaluate the development of the intestines and organs (pancreas, liver and gizzard) and abdominal fat. At the end of each phase was carried out a metabolism assay for determination the nutrient digestibility coefficients (dry matter and crude protein) and gross energy, besides the digestibility of fiber fractions. In the first experiment it was found that the beak trimming method used interfered in the birds’ performance in the growing phases, but no residual effect on egg production. Therefore, the beak trimming method by infrared radiation is an effective substitute for beak trimming by hot blade. Crude fiber levels used were not sufficient to provide changes in the birds performance, being possible to use up to 4.5% crude fiber in the feed of laying hens in the growing phases. In the second experiment it was found that the fiber levels have influenced the development of the intestinal segments whose effect is more pronounced in the growing phase, due to nutrient digestibility have great interference of the fiber at this stage. The beak trimming method influenced the bird organs development in the growing phase.