127. Effect of Dietary Inclusion of Bromoform Stabilized in Vegetable Oil Concurrently with Succinate-producing Bacteria on Gas Emissions, Ruminal Fermentation, and Digestibility in Growing Cattle

Abstract Reducing methane (CH4) emissions while improving animal performance and elucidating associated changes in ruminal metabolism remains a challenge in ruminant production. Our objective was to evaluate the concurrent supplementation of bromoform stabilized in vegetable oil (BSO; 10 g bromoform/kg oil) with rumen-native succinate-producing bacteria during a 65-d feeding period on gas emissions and ruminal fermentation. Seventeen growing heifers (body weight (BW) = 320 ± 25.6 kg), blocked by CH4 production (g/d) and yield (g CH4/ kg dry matter intake (DMI)), were individually housed and randomly assigned to 1 of 3 treatments: control (CON; no additives, n = 5), BR (BSO at 1% of DMI; n = 6), or BRB (BR + 5 g/d of succinate-producing bacteria; n = 6). Heifers were fed a corn silage-based diet, and the corresponding treatments were individually mixed. Gas samples were collected pre-trial, on d 34, 36, and 38 (period 1; P1), and d 55, 57, and 59 (period 2, P2) using a mask system; every four hours on a 24-h cycle. Ruminal fluid was obtained via esophageal tubing on d 41 and 42 (P1), and d 62 and 63 (P2) 4-h post-feeding. Dry matter intake was measured daily and BW recorded at the beginning (d 0), interim (d 30), and conclusion of the trial (d 65). Data were analyzed using the PROC GLIMMIX procedure in SAS, with treatment, time, and their interaction as fixed effects, and block as random effect. A treatment by time interaction was observed for DMI (P < 0.01; Table 1). Control heifers exhibited greater DMI compared to BR and BRB heifers for most of the trial, although BRB heifers did not differ from CON during the first 2 weeks. A treatment by time interaction (P < 0.01; Table 1) was observed for CH4 production and yield. Notably, CH4 emissions increased from P1 to P2 in the CON group, whereas they remained unchanged in the BR and BRB groups. Methane production was reduced by ∼99% in both the BR and BRB compared to CON. Acetate concentration in CON heifers’ ruminal fluid was greater (P < 0.01; Table 1) than BR and BRB, while BRB heifers had the greatest propionate concentration (P = 0.04; Table 1). Ruminal succinate concentration (P = 0.01; Table 1) was greater in BR and BRB compared to CON heifers. No differences were detected for butyrate, lactate, or ethanol concentrations (P ≥ 0.20; Table 1). Concentration of ruminal formate in the BR heifers tended to be lower than that of CON heifers (P = 0.07; Table 1). Our results showed that BSO supplementation markedly reduced CH4 emissions, and when combined with succinate-producing bacteria, ruminal fermentation may be optimized by increasing propionate production.