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Nitroethane is a potent inhibitor of ruminal CH 4 production, a digestive inefficiency resulting in the loss of 2-15% of a ruminant's gross energy intake and an important emission source of this greenhouse gas. To assess the effect of nitroethane on methanogenesis and characterize ruminal adaptation observed with low treatment doses to this inhibitor, ruminal microbes were cultured in vitro with supplements of water (controls), 4.5 and 9 mM nitroethane, and 0.09 mM monensin, with or without 9 mM nitroethane. All treatments decreased CH 4 production >78% compared to controls; however, differential effects of treatments were observed on CO 2, butyrate isobutyrate, and valerate production. Treatments did not affect H 2 accumulation or acetate and propionate production. Most probable numbers of nitrometabolizing bacteria were increased with 4.5 and 9 mM nitroethane compared to numbers recovered from controls or monensin-containing treatments, which may explain ruminal adaptation to lower nitroethane treatments.

Se evaluó la producción, calidad y componentes de rendimiento de seis variedades de avena forrajera en Zacatecas. Los experimentos se establecieron en julio de 2011 y 2012 en el municipio de Monte Escobedo. El diseño experimental fue bloques completos al azar con tres repeticiones, la densidad de siembra fue 120 kg ha-1 y dosis de fertilización de 60-40-00 de N, P2O5, K. La cosecha fue en estado fisiológico lechoso-masoso. En 2011 y 2012, La variedad Saía sobresalió (P<0.05) entre cultivares en rendimiento de forraje seco con 3.7 y 5.6 ha-1, altura de planta con 119 y 120 cm, y en componentes de rendimiento acumuló la mayor (P<0.05) proporción de hoja y tallo. La variedad Karma sobresalió en proporción de espiga con 42 y 49 % (P<0.05) en 2011 y 2012, respectivamente. En proteína cruda losresultados fueron similares (P>0.05) entre variedades con un rango de 10.6 a 13.8 %. En los dos años de estudio Karma presentó las mejores características nutricionales: baja acumulación de fibra detergente neutro (51 %) y acida (33.4 y 35.3 %), valores altos en total de nutrientes digestibles (54 y 58 %), digestibilidad de la materia seca (60 y 62 %), valor relativo del forraje (110 y 113) y energía neta para lactación (1.4 y 1.34 Mcal/kg; P<0.05). Las variables asociadas de manera positiva con forraje seco fueron altura de planta (r=0.701), días a cosecha (r=0.685) y proporción de tallo (r=0.629), y negativamente con proporción de espiga (r=-0.629). En calidad nutricional Karma tuvo mejor valor forrajero. Saia es una buena alternativa para incrementar el rendimiento de forraje por hectárea.

Methanogenesis is a metabolic process that allows the rumen ecosystem the ability to maintain the low hydrogen partial pressures needed for proper digestive function. However, rumen methanogenesis is considered to be an inefficient process because it can result in the loss of 4% to 12% of the total energy consumed by the host. Recent studies have shown that some short-chain nitrocompounds such as nitroethane, 2-nitroethanol, 2-nitro-1-propanol, and 3-nitro-1-propionic acid (3NPA) are capable of inhibiting the production of methane during in vitro culture; nevertheless, optimal supplementation doses have yet to be determined. In the present study, in vitro cultures of freshly collected mixed populations of ruminal microbes were supplemented with the naturally occurring nitrocompound, 3NPA, to achieve 0, 3, 6, 9, or 12 mM. Analysis of fermentation products after 24 h of incubation revealed that methane (CH 4) production was reduced in a dose-dependent manner by 29% to 96% (P < 0.05) compared with the amount produced by untreated controls (15.03 ± 0.88 µmol mL −1 incubated liquid). Main effects of the supplement were also observed, which resulted in a reduction (P < 0.05) on amounts of total gas and volatile fatty acids (VFA) produced, as well as in an increase of 0.07 to 0.30 µmol mL −1 on rates of 3NPA degradation. Changes in production of metabolites as CH 4 , hydrogen (H 2), VFA, and NH 3 indicated that the fermentation efficiency was not compromised dramatically by 3NPA treatment in moderate doses of 6 and 9 mM. Results further revealed that the metabolism of the 3NPA by microbial populations is also dose-dependent. The microbes were able to metabolize more than 75% of the added nitrocompound, with the greatest degradation rates in cultures treated with 9-mM 3NPA. Finally, from a practical standpoint, and considering the magnitude of CH 4 reduction, effect on VFA, and percentage of metabolized supplement, the most efficacious dose for 3NPA administration may be between 3 and 9 mM.