Effects of direct-fed microbial supplementation on digestibility and fermentation end-products in horses fed low- and high-starch concentrates
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This research evaluated the viability of lactic acid bacteria (LAB) intended for in vivo application as direct-fed microbial (DFM) supplements in two experiments during feed processing (Exp. 1) and storage (Exp. 2) and determined the efficacy of DFM on the digestibility and hindgut fermentation of horses during and after an abrupt increase in starch (Exp. 3). In Exp. 1, lactobacilli survived feed processing and a commercial enumeration method was validated. In Exp. 2, viable colony forming units of LAB were assessed and remained viable during 12 weeks of storage. Controls in both experiments had high levels of naturally-occurring bacteria present. In Exp. 3, a high-starch concentrate caused fecal pH to decrease, and fecal propionate and digestibility of many nutrients to increase. The DFM induced minimal improvements in digestibility or fermentation parameters and data provided no clear evidence to support the use of a multiple versus a single strain DFM preparation.