INHIBITING METHANE PRODUCTION IN BRAHMAN CATTLE BY DIETARY SUPPLEMENTATION WITH A NOVEL COMPOUND AND THE EFFECTS ON GROWTH

Three experiments were conducted to determine the effects of dietary s upplementation with a novel antimethanogenic compound (AM) on methane production and growth in Brahman (Bos indicus) steers. The compound wa s a chemical complex of bromochloromethane (BCM) and alpha-cyclodextri n, which is chemically stable when added to feed, thus overcoming the highly volatile nature of BCM. In these experiments the AM compound wa s administered to steers as a mixture with different feed supplements. In Expt 1 the effect on in vivo methane production of feeding steers the AM compound was determined using a confinement-type respiration ch amber. Methane production of AM-treated steers (0+/-2.4 mL/min) was lo wer (P < 0.001) than that of control steers (205+/-5.2 mL/min) over 28 days. In Expt 2 we determined the effect of AM treatment over 12 week s on growth of steers fed on a low quality roughage diet. The most mar ked effect of AM treatment was reduced (P < 001) voluntary roughage dr y matter intake (DMI), and reduced (P < 0.01) acetate:propionate molar ratio (A:P) in rumen fluid. Average daily liveweight gain (ADG) (0.22 +/-0.01 kg/day) and feed:gain ratio (F:G) (20.7+/-1.46 kg DMI/kg livew eight) were not significantly affected by AM treatment.In Expt 3 we de termined the effect of AM treatment over 10 weeks on growth of steers fed on a medium quality roughage diet, in steers that were either trea ted or not treated with a hormonal growth promotant (HGP; oestadiol 17 beta). AM treatment reduced (P < 0.05) DMI below that of steers not t reated with AM, whereas DMI was not significantly affected by HGP trea tment. Both AM (P < 0.01) and HGP (P < 0.05) treatments separately red uced A:P ratio in rumen fluid. AM treatment had no significant effect on ADG, whereas ADG of HGP-treated steers was higher (P < 0.05) than t hat of steers not treated with HGP (0.76+/-0.27 v. 0.60+/-0.027 kg/day ). F:G was reduced (P < 001) by HGP treatment. F:G of both HGP-treated steers and those steers not treated with HGP was reduced (P < 0.05) b y AM treatment. We conclude that feeding steers with this novel AM. co mpound enables the potent antimethanogenic properties of BCM to be rea lised under commercial conditions, and that prolonged use over 10-12 w eeks is associated with an improved feed conversion efficiency in stee rs fed on better quality roughage diets.