Níveis de fibra na ração de crescimento e seus efeitos no desempenho de duas linhagens de poedeiras nas fases de crescimento e postura

Abstract

The experiment was conducted to evaluate the effects of neutral detergent fiber (NDF) levels in the diet of two different laying hens strains on the 7 th to the 17 th week of age on the metabolism of dietary energy, development of digestive and reproductive systems and the subsequent effects on sexual maturity, performance and egg quality in laying phase. A total of 1,296 pullets were used and distributed in a completely randomized design in 2 x 3 factorial arrangement (two strains X 3 NDF levels) with four replicates of 54 birds per treatment. Two laying hens strains, light and semi – heavy – weight were evaluated and NDF levels of 14.5; 16.5 and 18.5% were tested. At the end of the growth phase, the birds were transferred to the laying house, kept at the same experimental design, whit each experimental parcel consisted of 14 birds. There was no significant interaction between factors (NDF levels x strain) on the variables in all phases. In the growth phase, it was observed that the increasing the level of NDF in the diet did not affect the feed intake and organ weights of the reproductive system, however, decreased weight gain and average weight of birds at the end of phase growth, increased feed conversion, reduced of metabolizable energy of the dietary and increase the relative weight of the intestines. In the laying period, it was observed that increasing levels of NDF received by the birds in the growth phase did not affect significantly the variables of performance, the constituents and quality of the eggs. During the growth of the brown birds it was observed that they had higher feed intake, greater weight gain and final body weights, feed conversion, increased relative weight of gizzard, increased weight of the contents of the gizzard and intestines, reduced relative liver weight and ovarian than light birds. In the laying period, birds were precocious, had lower weight and egg mass, lower feed conversion, eggs with a higher proportion of yolk, reduced proportion of albumen, higher specific gravity and lower Haugh units. We conclude that, in spite of lineage, the increased level of NDF in the diets offered to the chickens during 7 th to the 17 th weeks of age until the level of 18.5% may influence the metabolizable energy of the dietary and the development and performance of broilers, resulting in raising pullets weighed less at the end of the growth phase, and these effects do not influence age at sexual maturity, performance and quality of eggs from the birds at the production stage.