Microbial inoculant effects on cool- and warmseason grass silage.

Silage has been the preferred method of forage conservation in many regions of the world, primarily due to frequent rainfall during the period of maximum forage growth and limited opportunities to preserve forage as hay. Corn and sorghum are the main forages conserved as silage, but cultivation of annual summer crops is costly and may be risky due to variable climactic conditions. Therefore, livestock producers have relied on perennial grasses as a source of forage for conservation as silage. However, most grasses have undesirable characteristics that reduce the potential of achieving satisfactory fermentation and conservation, such as limited dry matter concentration, and morphological and chemical characteristics. Several management practices have been developed with the objective of improving grass silage fermentation and nutritive value, and microbial inoculants have been among the most used management practices. Nonetheless, most microbial inoculants have been tested and developed for corn silage and later recommended to grass silage with limited scientific evidence for the efficacy of the specific inoculant. The most used grasses as forages are divided into cool- (C3) and warm-season (C4) perennial grasses with notorious differences between them. Cool-season grasses have greater water-soluble carbohydrates and lesser structural carbohydrates concentrations than warm-season perennial grasses, which are desirable traits for better silage fermentation and positive microbial inoculant effects. Warm-season perennial grasses have greater accumulation of starch as non-structural carbohydrate, which does not directly contribute to silage fermentation. In addition to the limitations mentioned previously, warm-season perennial grasses have decreased dry matter concentration and nutritive value, reducing the likelihood of achieving desirable fermentation. A literature review was conducted to evaluate the effects of microbial inoculant on nutritive value and fermentation characteristics (pH, lactic acid, acetic acid, butyric acid, and ammonia concentrations) of grass silage. In addition, the effect of different microbial inoculants (homofermentative vs. heterofermentative) was evaluated. Lastly, results from current research projects testing the effects of microbial inoculants on silage microbiome and gas production were presented. [ABSTRACT FROM AUTHOR]