Use of an in vitro gas production method to assess differences in microbial fermentation characteristics of feed ingredients and betaine additives for pig nutrition

In this in vitro study, the modified “Hohenheim Gas Test” (HGT) was used to determine fermentation activity of pig's faecal microbial inoculum, when supplementing three different betaine sources, purified as betaine monohydrate or betaine hydrochloride and native as condensed molasses soluble, to different assay substrates. The assay substrates, consisting of a carbohydrate source (inulin, maize starch, potato starch, pectin, cellulose, wheat bran, sugar beet pulp or distiller's wheat grains) were combined with either casein or soybean meal as protein source. Faeces obtained from six grower pigs fed a standard diet were used as microbial inocula. At the end of in vitro fermentation (24 h), total gas production and ammonia concentration were measured. There were differences (P<0.001) in total gas production and ammonia concentration for the different carbohydrate sources, whereas for the two protein sources only differences (P<0.001) in ammonia concentration were observed. Supplementation of betaine as condensed molasses soluble led to higher (P<0.001) total gas production and ammonia concentration, but no effect on fermentation characteristics was observed with betaine monohydrate and betaine hydrochloride. In this study, the modified HGT has proven to be an economic, fast and reliable screening method to evaluate in vitro fermentation characteristics of carbohydrate and protein combinations, and also feed additives which are supposed to support microbial fermentation processes in pigs.