Palma forrageira, bagaço de cana-de-açúcar e uréia : uma alternativa a alimentos conservados

Abstract

The aim was to evaluate the effect of different roughage sources in sheep feeding on intake and digestibility, water intake, ingestive behavior, nitrogen balance, microbial protein synthesis, fiber dynamics and ruminal parameters. Five male crossbred sheep, fistulated and cannulated in the rumen were used, with average initial body weight (BW) of 34.0 ± 3.63 kg, and assigned in a 5 x 5 Latin square. The experimental diets consisted in different roughage sources: cactus Nopalea cochenillifera (L). Salm-Dyck. clododes (Nopalea; NUB) and cactus Opuntia stricta (Haw.) Haw. clododes (Opuntia, OUB) both associated with sugarcane bagasse (SB) and with urea/as, tifton hay (TH) and maize silage (MS) and sorghum silage (SS) also corrected with urea/as. In addition to roughage, the sheep received concentrate composed of corn meal, soybean meal and mineral mixture, with proportion of roughage: concentrate of 69.4: 30.6. The NUB diet promoted higher (P ≤ 0.03) intake of dry matter (1024 g/day), organic matter (OM, 904 g/kg), crude protein (PB, 161 g/day) and digestible organic matter (DOM, 670 g/kg) than the SS. The NUB-based diet provided greater (P <0.01) OM digestibility (741 g/kg) compared with the other diets. Diets containing NUB and OUB registered greater (P ≤ 0.01) digestibility of CP (831 and 806 g/kg, respectively) when compared to the others. The NUB provided greater (P <0.01) water intake via diet (3.02 L/day) and less voluntary water intake, compared to TH. The time spent on rumination was shorter (P <0.01) and the leisure time was longer for animals treated with NUB and OUB (466 and 436; 542 and 578 min/day, respectively), compared to the TH and MS (596 and 598; 542 and 578 min/day, respectively). The highest efficiency of feeding and rumination was registered by the sheep of the treatment with NUB (299; 132 g DM/h), in relation to those that received the diet containing SS (188 and 91 g DM/h, respectively). Higher intake and nitrogen balance were observed (25.7 and 12.5 g/day, respectively), with less nitrogen excretion by feces for NUB; as well as for OUB (P <0.01), in relation to SS (18.7 and 5.3 g/day, respectively). There was no difference for microbial protein synthesis (P = 0.27) between the diets containing the evaluated forages. The TH provided larger pools of DM and NDFi (593.2 and 177.8 g) in relation to diets composed of OUB, MS and SS (407.6 and 120.8; 448.4 and 96.4; 421.0 and 101.0 g, respectively). Diets composed of OUB and MS provided a higher (P <0.01) rate of DM degradation (0.0584 and 0.0566 h-1, respectively) compared to a diet composed of TH (0.0360 h-1). The animals in the OUB treatment showed lower ruminal pH compared to the TH. There was no interaction between time x treatment for ruminal pH. Depending on the time of collection, the lowest pH value (6.38) was estimated at 3.79 hours after the first feeding. There was an interaction between treatment and time for ruminal ammoniacal nitrogen (NAR) concentrations, with maximum concentrations of 35.4; 41.8; 17.92 and 26.49 (mg NAR/dL) estimated for NUB, OUB, MS and SS treatments, respectively, at 2.02; 2.97; 3.01 and 2.87 hours after morning feeding. There was no effect of time on NAR concentration when TH was used (14.33 mg/dL). There was an interaction (P <0.01) between treatment and collection time on VFA concentrations. The roughage composed of cactus cladodes and sugarcane bagasse and Urea/Ammonia Sulfate (9:1) showed similar nutritional value, mainly with regard to energy intake and efficiency in the use of dietary nitrogen, TH and MS, being superior to SS. The use of cactus cladodes associated with sugarcane bagasse and urea is recommended in sheep diets.