Feed intake, methane yield, and efficiency of utilization of energy and nitrogen by sheep fed tropical grasses

Forage allowance impacts dry matter (DM) intake and the use of nutrients by ruminants. The efficient use of protein and energy from pasture is related to better livestock performance and lower environmental impacts. The aims of this study were to evaluate the effect of forage allowance levels on intake, digestibility, nitrogen (N) and energy balance, and methane (CH4) emissions by lambs fed fresh pearl millet [Pennisetum americanum (L.) Leeke]. An indoor trial was performed using lambs in a completely randomized design with four treatments [forage allowance at 1.5, 2.0, 2.5 kg DM/100 kg of live weight (LW), and ad libitum allowing 20% of refusals] and four replicates (lambs). Forage intake, digestibility, total urine and feces excretion, and CH4 emission were measured to calculate N and energy balances. An increase in forage allowance resulted in a linear increase in lamb forage intake, N retention, and metabolizable energy intake. Moreover, lamb CH4 emission (g/day) also increased with greater forage allowance, while CH4 yield decreased linearly as forage allowance increased. Our results indicate that maximizing forage intake improves N and energy use efficiency and mitigates CH4 yield and decreases CH4 conversion factor (Ym) by lambs fed pearl millet forage. Thus, management strategies that optimize intake of tropical forages by ruminants improve the use of nutrients ingested and mitigates negative impacts to the environment.Fil: de Azevedo, Eduardo Bohrer. Universidade Federal do Pampa; BrasilFil: Savian, Jean Víctor. Instituto Nacional de Investigación Agropecuaria ; UruguayFil: Azevedo do Amaral, Gláucia. Universidade Federal do Rio Grande do Sul; BrasilFil: Bitencourt de David, Diego. Universidade Federal do Rio Grande do Sul; BrasilFil: Gere, José Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires. Unidad de Investigación y Desarrollo de las Ingenierías; ArgentinaFil: Kohmann, Marta Moura. University of Florida; Estados UnidosFil: Bremm, Carolina. Universidade Federal do Rio Grande do Sul; BrasilFil: Jochims, Felipe. Santa Catarina Research and Rural Extension Company; BrasilFil: Zubieta, Angel Sánchez. Universidade Federal do Rio Grande do Sul; BrasilFil: Gonda, Horacio Leandro. Swedish University of Agricultural Sciences; SueciaFil: Bayer, Cimélio. Universidade Federal do Rio Grande do Sul; BrasilFil: Faccio Carvalho, Paulo César de. Universidade Federal do Rio Grande do Sul; Brasi