In Vitro Fermentative Capacity of Equine Fecal Inocula of 9 fibrous Forages in the Presence of Different Doses of Saccharomyces cerevisiae

Abstract

This experimentwas conducted to evaluate in vitro effects of equine fecal inocula fermentative capacity on 9 fibrous forages in the presence of Saccharomyces cerevisiae. The fibrous feeds were corn stover (Zeamays), oat straw(Avena sativa), sugarcane bagasseandleaves (Saccharum officinarum), llanero grass leaves (Andropogon gayanus), Taiwan grass leaves (Pennisetum purpureum), sorghum straw (Sorghum vulgare), and steria grass leaves (Cynodon plectostachyus). Fibrous feed samples were incubated with several doses of S. cerevisiae; 0 (control), 1.25 (low), 2.5 (medium) and 5 (high) mg/g dry matter (DM) of a commercial yeast product containing 1 1010/g. Fecal inoculumwas collected from4 adult horseswere fed onanamount of commercial concentrate and oat hay ad libitum. Gas production (GP)was recorded at 2, 4, 6, 8, 10, 12, 24, and 48 hours post inoculation. An interaction occurred between feeds and yeast dose for fecalpH(P<.01), asymptoticGP (b, ml/gDM); rate ofGP (c, /hr); initial delay beforeGP began (L, hours),GPat 4 hours and48 hours (P<.01), andGPat 8 hours (P<.01) andat 24 hours (P<.01). Differences in fecal fermentation capacity between the tropical and template grass (P < .05) occurred for fecal pH, c, and GP during first 12 hours, whereas differences occurred (P< .05) between the agriculture byproducts and the grasses for fecal pH, b, and GP from 8 to 48 hours. Fermentation capacity between straws versus not straws (P <.05) differed for fecal pH, b, and GP after 12 hours between straws versus not straws. Addition of S. cerevisiae to Z. mays stover reduced (P <.01) fecal pH and the c fraction with a higher (P <.01) b fraction versus the other feeds. From4 to 24 hours, S. officinarumbagasse improvedGP tothe highest values versus S. officinarum leaves. After 24 hours, Z. mays stover had the highest GP, whereas C. plectostachyus leaves had the lowest. There were no differences among the yeast doses for all measured parameters with the exception of L values (linear effect; P <.01). The Z. mays stover hadthe highestnutritive comparedtothe otherfibrous feeds.However, additionof S. cerevisiae at 2.5 to 5.0 g/kg DM improved fecal fermentation capacity of low-quality forages