Níveis de fibra em detergente neutro na dieta de cordeiros confinados na fase de terminação

Abstract

The study was realized in the Animal Science Department of Federal University of Santa Maria, RS, from August to December 2003, aiming to evaluate the effects of increasing of NDF levels in a diet on the performance, ingestive behaviour and carcass characteristics of lambs in the termination phase. Twenty male lambs, non-castrated from the mixing between the races Ile de France and Texel, weaned in 42 days old averige and distributed randomly in four treatments: 25, 31, 37 and 43% NDF were used. Before starting the experimental period , the animals were submited to an adjustmentperiod (7 days), in which they have received, ad libitum, a diet with 35% NDF with 17% raw protein. The food supply was done twice a day, in set up times at 8AM and 4PM, adjusted to keep the excess in 10% of the total given. The food used was composed ofsorghum silage (Sorghum bicolor (L.) Moench), fragmented corn grain (Zea mays L.) soybean bran (Glycine Max L ) and mineral mixing. The proportion between voluminous and condensate varied to obtain the desired NDF levels.The ration used were calculated to be isoproteinic, with 17% of crude protein (DM).The slaughter ocurred when the animals reached 30Kg living weight. The food intake, the daily averige weight gain (DWG) the food conversion (FC), the amount of days the lambs reach the living weigh for 30 Kg slaughter, the time spent in feeding, rumination, idleness and total chewing, the feeding efficiency (FE) and rumination (RE) of DM and of NDF, the hot carcass weight (HCW), cold carcass weigh (CCW), hot carcass yield (HCY), cold carcass yield (CCY), cooling loss index (BIC), central loin area (CLA), subcutaneous fat thickness (SFT), carcass measurements, weight and proportion of the cuts and bone, muscle and hindquarter fat weigh and proportion of lambs were evaluated. The addition of increasing levels of NDF to the diet reduced linearly the consumption of dry matter (DMI), organic matter (OMI), crude protein (CPI), ethereal extract (EEI), total carbohydrates (TCHOI) and non-structural carbohydrates (NSCI). On the other hand, the increasing in the NDF levels in the diet increased in a linear way the consumption of fiber in neutral detergents (NDFI) and fiber in acid detergent (ADFI). It was verified a linear reduction of DWG and of FC with the increasing of fiber in the ration, which proportined a linear increasing in the amount of days the lambs reached the slaughter weigh. There was no significative effect (P>0.05) of the NDF level of diets on the time spent in feeding, rumination, idleness and total chewing time. There was linear increasing effect on the variables feeding efficiency and NDF rumination. The sheeps have predominantly habit diurnal of feeding and nocturnal of rumination. The incresing of NDF levels in the diets proportioned linear decreasing effect (P< 0.05) in the HCW, CCW, HCY, CCY and rib weight. There was qradratic effect of NDF level on the LL. The other variables analysed were not influenced significatively (P>0.05) by the NDF in the rations.