Submitted to: International Silage Conference
Publication Type: Abstract Only
Publication Acceptance Date: 5/1/2012
Publication Date: 7/2/2012
Citation: Muck, R.E., Weinberg, Z.G., Contreras-Govea, F.G. 2012. Silage extracts used to study the mode of action of silage inoculants in ruminants. In: Kuoppala, K., Rinne, M., Vanhatalo, A., editors. XVth International Silage Conference, 2-4 July 2012, Hämeenlinna, Finland. p. 336-337. Interpretive Summary:
Technical Abstract: Silage microbial inoculants can enhance animal performance, but the mechanisms involved in these effects are not clear. Our hypothesis was that an extractable factor from inoculated silage enhances rumen microbial activity. One alfalfa haylage (58% DM) and two corn silages (30% and 50% DM) were made in mini-silos with two treatments: untreated control and Lactobacillus plantarum MTD/1 (LP). The silages were analyzed for pH, fermentation products, in vitro true dry matter digestibility, in vitro microbial biomass yield (MBY), and standard nutritive characteristics. In addition, 1:1 aqueous and 80% ethanol extracts of control and inoculated silages and suspensions of L. plantarum MTD/1 were prepared to study their effects on in vitro ruminal MBY and gas production (GP). In all three crops, pH was greater in control than in LP. Lactic acid concentration was greater in LP than control in alfalfa, whereas the opposite was true in both corn trials. Silage in vitro digestibility and the volatile fatty acids produced during in vitro digestion were different among crops (P < 0.05), but the crop by treatment interaction was not significant (P > 0.05). Alfalfa silage treated with LP had the highest MBY, greater than the alfalfa control (P < 0.05). However, treatment had no effect on MBY in the two corn silages. The in vitro MBY and GP determined from the water or ethanol silage extracts were different among crops (P < 0.05) and the crop by treatment interaction was also significant (P < 0.10). For alfalfa, the LP extract had reduced MBY in the water extract and higher MBY in the ethanol extract than control. In maize, there was no effect of treatment on MBY from the extracts. LP tended to increase GP in the water extracts whereas in the ethanol extracts LP had higher GP in alfalfa and one of the corn silages. The direct application of LP to the rumen inoculum had the lowest values of MBY and GP. These results indicate that substrate availability limited rumen bacterial growth. In the alfalfa silage where the inoculant affected in vitro MBY, ethanol extracts of inoculated silage increased both MBY and GP, suggesting the ethanol extract may contain the factor in inoculated silage that improves rumen microbial growth.