The objective of this research was to evaluate the performance, carcass yield and intestinal morphometry of broiler chickens raised under different temperatures that received feed with or without yeast extract and prebiotic in the pre-initial phase. One thousand four hundred and forty one-day old male chicks were used, raised in different climate chambers. Feed with or without the addition of yeast extract and prebiotic was offered only in the pre-initial phase (1 to 7 days). From the eighth day on, every chick received the same feed, readjusted according to usual recommendations. A randomized complete experimental design was used in a 3 × 2 × 2 factorial arrangement, consisting of three environmental temperatures (hot, comfort and cold) and two levels of yeast extract (with or without) and prebiotic (with or without). The performance of the birds was evaluated considering weight gain, feed intake, food conversion and viability at 42 days of age. Carcass yield and intestinal morphometry were also evaluated. Environmental heat impaired performance and carcass yield. Prebiotic inclusion in the pre-initial feed increased weight gain and enhanced food conversion of birds raised under hot conditions. The inclusion of products in the feed of broiler chickens raised in hot and cold environments has beneficial effects on chicken intestinal villi.
carcass yield; heat stress; intestinal morphometry; mannanoligosaccharides; performance; Saccharomyces cervisiae
