LAUSR

An experiment was conducted to evaluate the effect of supplementing fourteen ruminally cannulated Angus crossbred steers with polyclonal antibody preparations (PAP) from avian origin against ruminal methanogens Methanobrevibacter gottschalkii Ho (PAP-Ho) and M. ruminantium M1 (PAP-M1). Steers were fed bermudagrass hay ad libitum and 2 kg d-1 of corn gluten feed. A randomized block design was used, with a 3 × 2 + 1 factorial arrangement, replicated in three periods. Factors were proportions of PAP against Ho and M1 in the mixture (100:0, 50:50, and 0:100 Ho:M1) and level of supplementation of each mixture (3 or 6 mL d-1). Control steers had no PAP supplementation. Steers were adapted to the feeding regimen for 14 d, with no PAP supplementation, followed by a 21-d treatment period. Ruminal fluid (RF) from each steer (experimental unit) was collected before PAP supplementation (h 0) and every 4 h (for a 24-h period) on d 0, 14, and 21 of treatment period for the determination of ruminal fermentation profile. In addition, RF collected at h 0 was individually mixed with McDougall’s Buffer (1:3 ratio) to inoculate serum bottles and polycarbonate tubes for the determination of methane production and in vitro fermentation profile. Treatment means were evaluated by preplanned, non-orthogonal, single-degree-of-freedom contrasts. There was no effect (P ≥ 0.48) of level of inclusion on ex situ methane production (ESMP). When PAP-M1 was used either alone or in combination with PAP-Ho, ESMP decreased (P ≤ 0.05) compared to control. Ex situ ruminal fermentation profile was not different (P ≥ 0.12) across treatments. In vivo molar proportion of propionate tended to be greater (P = 0.10) with supplementation of PAP-M1, alone or combined, compared with control. Polyclonal antibody preparations against ruminal methanogens have the potential to decrease enteric methane emissions.