Avian (IgY) anti-methanogen antibodies for reducing ruminal methane production:: in vitro assessment of their effects

In vitro dry matter disappearance (IVDMD) and production of methane, volatile fatty acids (VFA) and ammonia from an early lactation diet or from freeze-dried alfalfa were assessed in the presence of anti-methanogen antibody treatments in two in vitro ruminal incubations (experiments 1 and 2). In experiment 1, hens were immunised with crude cell preparations of Methanobrevibacter smithii, Methanobrevibacter ruminantium or Methanosphaera stadtmanae and complete Freund's adjuvant (CFA). Semipurified egg antibodies (IgY) prepared from the hens' eggs (alpha-SMICFA, alpha-RUMCFA, or alpha-STAD(CFA), respectively) were dispensed into 24 replicate vials (400 mu L per vial) containing 500 mg of an early lactation total mixed ration (18% crude protein; 33% neutral detergent fibre; DM basis). Vials containing an equal volume of semipurified antibodies from eggs of non-immunised hens were included as a control. In experiment 2, hens were immunised with one of the three antigenic preparations combined with Montanide ISA 70 adjuvant. Triplicate vials per time point included 0.6 g of freeze-dried egg powder (alpha-SMIMon, alpha-RUMMon, alpha-STAD(Mon); 19.0 +/- 2.6 mg IgY/g) or a mixture of all three (Combo(Mon)) and 500 mg of freeze-dried alfalfa. Total gas, methane production and pH were measured at intervals over 24 h. After 24 h, samples were analysed for VFA, ammonia and IVDMD. In experiment 1, cumulative CH4 production was similar (P> 0.05) among treatments at each sampling time. At 24 h, average CH4 production across treatments was 27.03 +/- 0.205 mg/g DM. In experiment 2, alpha-SMIMon, alpha-STAD(Mon) and Combo(Mon) reduced methane production at 12 h (P= 0.05) compared with the control, but by 24 h, CH4 levels in all treatments were similar (P> 0.05) to the control. At 24 h, total VFA concentrations were lower (P< 0.05) in alpha-RUMMon and alpha-SMIMon than in the control. The transient nature of the inhibition of methane production by the antibodies may have arisen from instability of the antibodies in ruminal fluid, or to the presence of non-culturable methanogens unaffected by the antibody activity that was administered.