Inclusão de palma miúda e ureia em substituição ao feno de capim tifton em dietas para ovinos

Abstract

In semiarid regions, providing a roughage adapted to water deficient conditions, such as spineless cactus (SC), associated with a source of physically effective fiber could be a feed alternative for sheep. The aim of this study was to evaluate inclusion effect of 0, 150, 300, 450 and 600 g/kg dry matter (DM) of SC plus urea and ammonium sulfate (UAS; 9:1) replacing Tifton hay on nutrients intake and its digestibility, feeding behavior, water intake, dynamics and ruminal fermentation, nitrogen (N) balance and microbial protein supply (MPS). Five rumen fistulated and cannulated crossbred wether sheep with average body weight of 43.8 ± 5.80 kg, were randomized in 5 × 5 Latin square design. Isonitrogenous diets (14% crude protein; CP) were based on soybean meal, ground corn, common salt and mineral mixture (roughage-to-concentrate ratio, 70:30). Data were submitted to variance and polynomial orthogonal contrasts analyses. Intakes of DM, digestible organic matter and N, as well as N retained, MPS and metabolizable energy intake showed quadratic responses (P<0.05) with maximum values of 1,281.4, 909.8, 30, 14.1, 48.8 g/d and 3.60 Mcal/d, estimated for the levels of SC+UAS 355.5, 413.8, 363,3, 438.3, 418 and 440 g/kg DM, respectively. Neutral detergent fiber (NDF) intake, feed and rumination times, voluntary water intake, NDF degradation and passage rates, pH and ruminal ammonia nitrogen, urinary N excretion, blood urea and ammonia in both plasma and urine reduced linearly (P<0.05) with the inclusion of SC+UAS. Non-fiber carbohydrates intake, water excretion in feces, blood glucose and acetate and propionate ruminal concentrations increased linearly (P<0.05) with the inclusion of SC+UAS. Crude protein intake, CP and NDF digestibility, butyrate concentration, urinary volume and MPS efficiency were not influenced by inclusion of SC+UAS (P>0.05). In sheep diets with roughage:concentrate ratio of 70:30, roughage consisting of SC (with urea+ammonium sulfate) and Tifton hay in a ratio of 41:29 to 44:26, is recommended to maximize energy intake, N retention and MPS.