Nutritive Value, In Vitro Fermentation, and Methane Production of Cactus Cladodes, Sugarcane Bagasse, and Urea

SIMPLE SUMMARY: Cyclical droughts affecting arid and semiarid regions promote direct negative impacts on agriculture, with deficits of water availability for the maintenance of crops destined for human supply and animal production, with direct and indirect socioeconomic effects. Although livestock rearing is one of the few viable economic activities for these regions, forage production in terms of quantity and quality is a critical obstacle to support the herd over the year. Research was developed to find a forage adapted to these climates. Cactus cladodes have been used as a traditional ingredient in ruminant diets in dry areas as a solution to forage scarcity. Many traditionally used sources of forage, fresh or conserved, can be added to diets with cactus. However, the limiting factor to their inclusion would be market availability and price. This study showed that cactus cladodes associated with sugarcane bagasse (a high available crop residue) present the same nutritive value of conserved crops as silages and hay. Cactus (Opuntia and Nopalea) are essential for ruminant production systems in arid and semiarid regions due to the limitation of forage production caused by the low precipitation. ABSTRACT: This study evaluated the effect of different roughages fed to sheep on nutrient and water intake, ingestive behavior, nitrogen balance, microbial protein synthesis, fermentation parameters, and methane production using an in vitro gas production system. The treatments consisted of five diets: cactus cladodes Nopalea (NUB) and Opuntia (OUB), both with the addition of sugarcane bagasse (SB) and urea/ammonium sulfate (urea/as); Tifton hay (TH); corn silage (CS); and sorghum silage (SS), also with added urea/as. The NUB provided greater (p ≤ 0.03) intakes of dry matter (1024 g/d), digestible organic matter (670 g/d), and crude protein (161 g/d) than those on the SS. The NUB provided greater (p < 0.01) dietary water intake (3023 g/d) than TH. The time spent on rumination was shorter (p < 0.01), and the idle time was longer in animals fed NUB and OUB than TH and CS. Microbial protein synthesis was not affected (p = 0.27). The final pH (6.4) of the incubation fluid and the concentration of NH(3)-N (39.05 mg/dL) were greater for NUB and OUB. Ruminal parameters and methane production were little or not affected by tested forages. We recommend using cactus cladodes in combination with sugarcane bagasse and urea/as in sheep diets.