Location: Dairy Forage ResearchTitle: The Effect of LAB Silage Inoculants on the Rumen Environment--Current Research Status Author
Submitted to: International Silage Conference
Publication Type: Proceedings
Publication Acceptance Date: 7/13/2009
Publication Date: 7/27/2009
Citation: Weinberg, Z.G., Miron, J., Chen, Y., Muck, R.E., Contrera-Govea, F.E., Weimer, P.J., Filya, I., Kung, L. 2009. The Effect of LAB Silage Inoculants on the Rumen Environment--Current Research Status. In: Broderick, G.A., Adesogan, A.T., Bocher, L.W., Bolsen, K.K., Contreras-Govea, F.E., Harrison, J.H., Muck, R.E., editors. XVth International Silage Conference Proceedings, July 27-29, 2009, Madison, Wisconsin. p. 55-56. Interpretive Summary:
Technical Abstract: Inoculants containing mainly lactic acid bacteria (LAB) are the most common additives used in making silage. Their function is to promote intensive production of lactic acid and rapid decrease in pH and so minimize fermentation losses. Some LAB inoculants reduce aerobic spoilage. In addition, feeding inoculated silages improved animal performance (live weight gain and milk production) by 3 to 5% in about half of reviewed studies. Animal performance effects are often greater than expected from the effects of LAB on the ensiling fermentation. The objective of recent in vitro experiments conducted in Wisconsin, Delaware and Israel was to find out how and under what conditions LAB impart beneficial (possibly probiotic) effects on ruminant performance. The paper summarizes the results obtained so far. Silages treated with various commercial LAB inoculants were prepared in mini-silos. Inoculated and control silages were used in in vitro digestion experiments in which dry matter and NDF digestibility (DMD and NDFD) were measured as well as gas production, total volatile fatty acids (VFA), acetate-to-propionate ratio and microbial biomass yields. LAB silage inoculants survive in rumen fluid. When added directly to rumen fluid, some LAB inoculants resulted in higher pH values as compared with control rumen fluid. LAB silage inoculants and inoculated silages possess anti-bacterial activity that potentially could inhibit detrimental microorganisms in the silage or in the rumen. Some LAB inoculants applied at ensiling or added directly to rumen fluid tended to increase in vitro DMD and NDFD of wheat and corn silages, especially after 24 h of incubation in the presence of starch. However, in other experiments, LAB inoculants did not have any consistent effect on DMD and NDFD of various corn and alfalfa silages. In vitro experiments with wet ground silage samples revealed that some inoculated alfalfa silages (14 inoculant treatments, 2 trials) reduced ruminal gas production, total VFA and acetate-to-propionate ratio as compared with control silages. Reduced gas production in the rumen is associated with higher microbial biomass production. Subsequent trials with four inoculants in alfalfa and corn silages did not show an effect on gas or VFA production at 9 or 48 h but did show an increase in microbial biomass yield estimated by the difference between true and apparent DMD. This might explain the effect of LAB on improved animal performance, but the mechanism for this increase in microbial biomass is uncertain. LAB silage inoculants survive in rumen fluid and may have an effect on the rumen fermentation, but probably, not directly on digestibility attributes. More research is warranted to elucidate possible interactions between LAB inoculants and rumen microorganisms that would shed light on this beneficial phenomenon.