Effects of feeding forage and concentrate, separately or as a TMR, on ruminal methane emission, fermentation characteristics, and total tract digestibility

Abstract Text: Very little research is available on the advantages of feeding systems, specifically how forage and concentrate feeding, separately (SF) or as a total mixed ration (TMR) affects methane production from enteric fermentation of ruminant. Three experiments were performed at three different levels of daily feed intake (1.8, 2.1, and 2.6% of BW) to investigate methane production from the different feeding systems by using a quadruplicated 2 × 2 cross-over design. Each experiment was conducted using eight male Holsteins with BW ranging from 230–570 kg. Animals were provided either SF or TMR containing 73% concentrate and 27% forage, with the same ratio of same ingredients and grasses, twice a day. Animals fed SF received the forage first for 30–40 min and then received the concentrate. In experiment 2, the ruminal fermentation characteristics (1.5, 3.0, and 4.5 hr after morning feeding) and indirect total tract digestibilities were evaluated based on rumen fluid and fecal grab samples, respectively. Animals fed TMR in experiment 1 and 2 emitted significantly more methane (169.9 vs. 140.1 ± 6.9 L/d; P < 0.05 and 138.4 vs. 114.19 ± 4.2 L/d; P < 0.01, respectively) and lost more methane energy (7.1 vs. 5.6 ± 0.4%; P = 0.01 and 4.0 vs. 3.4 ± 0.2%; P < 0.01, respectively) compared to those fed SF. No differences (P > 0.1) were observed in methane emissions and methane energy losses for animals fed diets at 2.6% of BW in experiment 3, although those fed TMR emitted slightly more methane than those fed SF. Cattle those received SF exhibited significantly lower (P < 0.05) ruminal pH and higher (P < 0.05) ammonia-N concentration, total VFA and individual VFA production compared to those fed TMR at 4.5 hrs after feeding. A significantly (P < 0.05) lower acetate: propionate ratio (2.2 vs. 2.6) in those fed SF reflected the shift in hydrogen transfer towards the formation of more propionate than in those fed TMR. Significantly higher levels of isobutyrate and isovalerate (P < 0.05) were observed in those fed SF compared to those fed TMR. The total tract digestibilities of CP, NDF, and OM were not affected by the feeding system. Overall, these results indicate that, compared to TMR, SF significantly reduces methane emission from ruminants and increases VFA production without affecting the total tract digestion.

Keywords: methane, rumen, separate feeding