Teores de fibra em detergente neutro em dietas de alto concentrado para cordeiros em terminação

Abstract

Although high concentrate diets are commonly used for finishing lambs, information about the effect of minimum levels of neutral detergent fiber (NDF) on performance is limited. The purpose of this study was to evaluate the effects of increasing dietary fiber levels on performance, feed efficiency and parameters of carcass, blood and rumen of finishing lambs fed high concentrate diet. Twenty four uncastrated male lambs (initial body weight of 24.55 ± 2.2 kg) were randomly assigned to 24 individual pens, in a complete randomized design with three treatments and eight replicates. Treatments were dietary NDF levels of 15, 20 and 25% based on dry matter. Diets were composed of corn, soybean meal, minerals and corn silage, and were offered twice a day with refusals daily measured to determine dry matter intake (DMI). Animals were weighed weekly and slaughtered after 50 d of feedlot, with body weight of 40.48 ± 2.3 kg. Hot and cold carcass weight (HCW and CCW) as well as hot and cold carcass yield (HCY and CCY) were measured. After evisceration, fluid and rumen contents were collected to determine fatty acid short chain and protozoa. Data were submitted to analysis of regression, using the statistical software SAS (version 9.0, 2002). Lambs fed with increasing levels of NDF had a linear efeect on IMS and residual feed intake (RFI). The average daily gain (ADG) and other food efficiency variables were not statistically different between treatments. Increasing levels of NDF in the diet caused a decrease in HCW, HCY and CCY, and there was no significant effect on other carcass variables. Blood and rumen variables were not affected by treatments, suggesting that the diets with high concentrate and different levels of NDF for finishing lambs provided homeostasis animals and adequate environment for rumen fermentation. In general, diets with low NDF did not alter the ADG, but had no effect on RFI, weight and carcass yield increased and did not provide physiological and ruminal changes.