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Periódicos Brasileiros em Medicina Veterinária e Zootecnia

Narasin inclusion for feedlot lambs fed a diet containing high amounts of ground flint corn

Polizel, Daniel MontanherMarques, Samuel SutilWestphalen, Mariana FontanaGouvea, Vinícius NunesFerraz Júnior, Marcos Vinícius de CastroMiszura, Alexandre ArantesBarroso, José Paulo RomanLimede, Arnaldo CintraFerreira, Evandro MaiaPires, Alexandre Vaz

ABSTRACT: Narasin is an antibacterial agent that may change rumen fermentation. Two experiments were proposed to evaluate the efficiency of narasin inclusion for lambs fed a diet containing high amounts of ground flint corn. Thirty rumen-cannulated wethers were used to evaluate nutrient digestibility, nitrogen balance, and rumen metabolism (Exp. 1); and forty-five lambs were used to evaluate performance (Exp. 2) of animals fed with narasin for high flint corn diets. The experimental diets were: control or basal diet without additives (C); 25 mg of monensin kg1 of dry matter (DM) (M); and inclusion of 5 (N5), 10 (N10), and 15 (N15) mg of narasin kg1 of DM. The statistical analyses were performed using the MIXED procedure of SAS. Monensin increased DM digestibility compared to C ( p = 0.01) and increasing doses of narasin linearly increased DM digestibility ( p 0.01). There was a quadratic effect ( p = 0.10) for molar proportion of acetate peaking at N15. Monensin inclusion increased ( p = 0.07) propionate compared to C; however, it did not differ from narasin. The increasing levels of narasin linearly decreased the total volatile fatty acids concentration in the rumen ( p = 0.02). Monensin and C showed a similar performance. The increasing levels of narasin linearly increased ( p 0.04) average daily gain and feed efficiency. Monensin and narasin changed rumen fermentation and improved overall nutrient digestibility. However, lambs that received narasin showed improved performance when compared with animals that received M.

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