Effects of Saccharomyces cerevisiae fermentation product on in vitro fermentation and microbial communities of low-quality forages and mixed diets1

Abstract

Two experiments were conducted to investigate the effects of a Saccharomyces cerevisiae fermentation product (XP, Diamond V, Cedar Rapids, IA) on in vitro ruminal fermentation of single forage and mixed diets. In Exp. 1, an in vitro test was used to determine the effects of various concentrations (0, 1, 2, and 3 g/L) of XP on ruminal fermentation of the major forage sources of China (rice straw, RS; corn stover, CS; corn silage without grain, CSNG; and corn silage with grain, CSG). Total VFA reached a peak at 1 g/L XP for RS, CSNG, and CSG and increased linearly (P < 0.01) for CS. The molar proportion of acetate decreased and propionate increased linearly (P < 0.01) with an increasing amount of XP for RS, CS, and CSNG. Microbial protein (MCP) increased linearly (P < 0.01) with an increasing level of XP for RS, and it reached peak values at 1 and 2 g/L XP for CSG and CSNG, respectively. Fungi population was increased (P < 0.05) with 1 g/L XP for all forages except CSNG. The population of Ruminococcus flavefaciens increased (P < 0.05) at 1 or 2 g/L XP for RS, CSNG, and CSG. In Exp. 2, the effects of 3 concentrations of XP (0, 1, and 2 g/L) were tested on in vitro ruminal fermentation of 3 mixed diets with various ingredient combinations: 1) CSC (corn:soybean meal:corn stover = 33:22:45), 2) CSCC (corn:soybean meal:corn stover:corn silage = 33:22:22.5:22.5), and 3) CSCCA (corn:soybean meal:corn stover:corn silage:alfalfa = 33:22:19:21:5). Total VFA concentrations were influenced by diets (P < 0.01) and were enhanced linearly by increasing concentrations of XP (P < 0.01). The molar proportion of acetate was reduced (P < 0.01), but the propionate proportion was enhanced with increasing concentrations of XP (P < 0.01). Ammonia N was decreased and MCP was increased by the addition of XP (linear, P < 0.01; quadratic, P < 0.05). The fungi population was greater with XP addition (quadratic, P < 0.01). The percentage of R. albus was affected by diets (P < 0.01), the level of XP (linear and quadratic, P < 0.01), and their interaction (P < 0.01). From these 2 in vitro studies, it is inferred that the addition of XP could improve the rumen fermentation of forages and mixed diets by stimulating the number of fiber-digesting rumen microbes, especially fungi populations.

Effects ofSaccharomyces Cerevisiaeat Direct Addition or Pre-incubation onin VitroGas Production Kinetics and Degradability of Four Fibrous Feeds

“…Paulus et al (2012) and Mao et al (2013) documented the positive effects of S. cerevisiae on ruminal fermentation and microbial activities. A number of specific hypothetical biochemical mechanisms have been developed to explain the stimulatory effects of S. cerevisiae in the rumen (Chevaux and Fabre, 2007).…”

“…For the in vitro model, the substrate amount relative to the rumen liquid volume is much less than in the rumen of a cow (<1 vs 12%). Therefore, when a rumen modulator like S. cerevisiae is supplemented at a different rate, it could change the fermentation rate and cause different substrate depletion, resulting in different response as the fermentation length is changed (Mao et al, 2013). Lila et al (2004) found variable effects of S. cerevisiae on ruminal fermentation when different substrates were used in vitro.…”

“…S. cerevisiae has the ability to decrease methane and ammonia production, and to improve fermentation efficiency to contribute to a reduction in greenhouse gas emissions (Hristov et al, 2013). Moreover, decreasing protein degradation and ammonia production in the rumen (Mao et al, 2013) has the ability to decrease the overall nitrogen excretion by the animal, which would contribute to decreased ammonia emissions from cattle manure.…”

“…These conflicting results on CH4 production are likely due to strain difference of S. cerevisiae and type of diets (Patra, 2012). Supplementing diets with S. cerevisiae were shown to increase total volatile fatty acids (VFA) and propionic acid production (Mao et al, 2013). S. cerevisiae can enhance fungal colonisation of plant cell walls leading for increased DM and NDF digestion (Patra, 2012), increased initial rate of fibre digestion (Williams et al, 1991), improved in situ crude protein (CP) and NDF degradation.…”

“…S. cerevisiae supplementation leads to increase in the number of total anaerobic and cellulolytic bacteria (Newbold et al, 1996;Jouany, 2001). Saccharomyces cerevisiae can provide the rumen with important nutrients and nutritional cofactors in addition to vitamins such as biotin and thiamine, which reported to be required for microbial growth and activity (Callaway and Martin, 1997;Mao et al, 2013).…”