Uso da levedura de cana-de-açúcar em rações de frangos de corte na fase pré-inicial

Abstract

Two studies were conducted to evaluate the effect of increasing levels of sugar cane yeast (Saccharomyces cerevisiae) in diets of post hatching broilers, from 1 to 8 days. A total of 750 male broiler chickens of Cobb 500 were utilized. A completely randomized experimental design, with five treatments consisting of a reference diet without addition of yeast and four test diets with the inclusion of 1.25, 2.5, 3.75 and 5.0% yeast. In the first study with 300 chicks a day old were housed in metabolism cages located in six replicates of 10 birds each. In this study we evaluated: the digestibility of rations by determining: the apparent metabolizable energy and apparent corrected by nitrogen balance and coefficients of apparent metabolizable dry matter, crude protein and gross energy; the performance: body weight, gain weight, feed intake and feed conversion; retention of body moisture, protein, fat and ash; and the development of intestinal mucosa measurand: villous height, crypt depth and villous:crypt ratio of the duodenum, jejunum and ileum. No effect of yeast on the performance. The apparent metabolizable energy, the corrected apparent metabolizable and coefficients of gross energy decreased with the addition of yeast. The retention of body protein was quadratic and fat increased linearly. In the jejunum there was a linear increase in villous height and villous:crypt, however in the ileum crypt depth was quadratic response. In the second study we used 450 broilers during the period 1 to 8 days old, reared on reused litter, distributed in 6 replicates of 15 birds each. We evaluated the variables of performance: body weight, weight gain, feed intake and feed conversion; of body composition: moisture, crude protein, fat and ash; and of intestinal morphology: villous height, crypt depth and villous:crypt segments of small intestine. The inclusion of yeast caused a linear increase in feed intake and feed conversion and caused a quadratic effect on body composition of ash. There was a quadratic response in the jejunum villous height and in crypt depth in jejunum and ileum.