Effects of β 1-4 galacto-oligosaccharide (GOS) and Candida kefyr on nitrate-induced methemoglobinemia and methane emission in sheep

4 x 4 latin square trial was carried out to assess the effects of beta 1-4 galacto-oligosaccharide (GOS) and yeast (Candida kefyr Strain: Y8A) culture on methemoglobinemia and alteration in gas exchange and metabolic rate in sheep treated with nitrate. Nitrate (1.3 g NaNO3 kg(-0.75) body weight) with or without GOS and Y8A were administered into the rumen through fistulae as a single dose 30 min after the morning meal. GOS and Y8A were supplemented by sprinkling onto the feed and through rumen fistulae, respectively. Physiological saline was used as the control treatment. In each period, gaseous exchange and metabolic rate were monitored by an open-circuit respiratory system. The administration of nitrate alone induced almost 20% methaemoglobin in total haemoglobin. Consequently, drops in oxygen consumption, carbon dioxide production and metabolic rate were demonstrated as well as a marked reduction in methane production. The simultaneous administration of GOS and GOS mixed with Y8A with nitrate suppressed methaemoglobin formation, and consequently higher rates of the gas exchange and metabolic rate were observed. Thus, the results of this study indicate that GOS and GOS supplemented with Y8A are very likely to suppress methaemoglobinemia and depression of gas exchange and metabolic rate induced by nitrate, respectively.