Lactobacillus buchneri for Silage Aerobic Stability
by David K. Combs and Patrick C. Hoffman
Department of Dairy Science, University Wisconsin - Madison
Lactobacillus buchneri is a bacterial inoculant approved for use in grass silages, corn silage, legume silage and high moisture grains. Lactobacillus buchneri has been demonstrated to improve aerobic stability of silages by reducing the growth of yeasts. The net result is that silages inoculated with L. buchneri are more resistant to heating at feed out (exposed to air) as compared to untreated silages.
What is Lactobacillus buchneri?
Lactobacillus buchneri was originally isolated from naturally occurring aerobically stable silages. L. buchneri is a heterofermentative bacteria that produces lactic and acetic acid during fermentation. Silages treated with an effective dose (up to 5 x 105 CFU/gram of fresh material) of L. buchneri have higher concentrations of acetic acid and lower levels of lactic acid than untreated silages.
How is L. buchneri different from other bacterial silage inoculants?
Most bacterial silage inoculants produce primarily lactic acid during the fermentation process. The most common lactic acid producing bacteria used in silage inoculants are Lactobacillus plantarum, L. acidophilus, Pediococcus cerevisiae, P. acidilactici and Enterocccus faecium. These organisms have been demonstrated to increase the rate of pH decline during fermentation, decrease losses of silage DM, and in many cases, animal performance is improved. However, silage fermentation products produced by homofermentative bacterial inoculants sometimes can result in silage that is less stable when exposed to air than silages that have not been inoculated. This is possible because lactic acid produced by homofermentative bacteria can be readily metabolized by some species of yeast and mold upon exposure to oxygen.
When applied at the time of ensiling at the rate of up to 5 x 105 CFU per gram of fresh material, L. buchneri has been demonstrated to improve aerobic stability of high moisture corn, corn silage, alfalfa silage and small grain silages relative to untreated controls.
The beneficial impact of L. buchneri appears to be related to the production of acetic acid. Although the precise mechanism has not yet been determined it is likely that aerobic stability is improved because acetic acid inhibits growth of specific species of yeast that are responsible for heating upon exposure to oxygen.
In research trials yeast and mold growth in silage treated with L. buchneri has been lower at feed-out than for untreated control silages. Yeast and mold levels in silage inoculated with L. buchneri also do not increase as rapidly as in untreated controls when exposed to air. As a result, the temperature of silage inoculated with L. buchneri does not readily rise upon exposure to air and tends to remain similar to ambient temperature for several days, even in warm weather.
When would L. buchneri be most effective?
Treating silage with L. buchneri most likely would be beneficial under circumstances where problems with aerobic instability are expected. Corn silage, small grain silage and high moisture corn are more susceptible to spoilage once exposed to air than legume or grass silage, and therefore L. buchneri inoculation may be a benefit. L. buchneri can also be applied to legume silage if aerobic stability is a problem.
It should be remembered that high ambient temperatures, slow filling, improper packing, low surface removal rate and poor feed bunk management are all factors that can decrease aerobic stability of silage. It is likely that L. buchneri would improve aerobic stability in circumstances where untreated silage or silage treated with lactic acid producing bacteria have a history of heating at feed out. It is unlikely that L. buchneri will improve silage quality in situations where silage has a history of being aerobically stable at feed out. In fact, under such circumstances, the potential reduction in silage dry matter recovery due to this organismís heterofermentative fermentation may actually make L. buchneri a less desirable silage inoculant than homofermentative bacterial inoculants.
Does L. buchneri affect feed intake or milk production?
Acetic acid can reduce feed intake in ruminants. It is not clear at this time whether enough acetic acid is produced in silages treated with L. buchneri to affect feed intake. We found in a recently completed lactation trial that feed intake and milk production were similar when cattle were fed total mixed rations containing untreated or L. buchneri inoculated high moisture corn. Corn inoculated with L. buchneri had higher concentrations of acetic acid and was aerobically more stable than untreated corn.
University of Delaware researchers have also reported that acetate levels were elevated in alfalfa silage and barley silage inoculated with L. buchneri compared to untreated controls. Milk production and feed intake were not different when dairy cows were fed TMRís containing either treated or untreated alfalfa silage, or treated or untreated barley silage.
Forages and grains treated with L. buchneri at a rate of up to 5 x 105 CFU/gram of fresh material at ensiling results in silages that have elevated concentrations of acetic acid and lower levels of lactic acid than untreated controls.
Yeast counts tend to be reduced in silage inoculated with L. buchneri. As a result, silage inoculated with L. buchneri resist heating when exposed to air, when compared to untreated silages or silages inoculated with lactic acid producing bacteria.
Research conducted to date has not shown that animal performance is improved when cattle are fed silages inoculated with L. buchneri. Intake and milk production have been similar in trials where cattle have been fed diets containing either L. buchneri treated or untreated high moisture corn, alfalfa silage or barley silage.
It appears that inoculation of silage with L. buchneri has the potential to dramatically improve aerobic stability of ensiled feeds and may significantly reduce feed waste in circumstances where heating and molding of feeds are an ongoing problem. The economic benefit of using this product will depend on how much feed can be saved by reducing losses associated with aerobic instability.
Driehuis, F., W. J. W. H. Oude Elferink, and S. F. Spoelstra. 1999. Anaerobic lactic acid degradation during ensilage of whole crop maize inoculated with Lactobacillus buchneri inhibits yeast growth and improves aerobic stability. J. Appl. Microbiol. 87:583-594.
Kung, Jr., L., and N. K. Ranjit. 2001. The effect of lactobacillus buchneri and other additives on the fermentation and aerobic stability of barley silage. J. Dairy Sci. 84:1149-1155.
Muck, R. E., 1996. A lactic acid bacteria strain to improve aerobic stability of silages. Pages 42-43 in U. S. Dairy Forage Res. Center 1996 Res. Summaries. Madison, WI.
Ranjit, N. K., and L. Kung, Jr. 2000. The effect of Lactobacillus plantarum and L. buchneri on the fermentation and aerobic stability of corn silage. J. Dairy Sci. 83:526-535.
Taylor, C. C., J. M. Neylon, J. A. Lazartic, J. A. Mills, R. M. Tetreault, A. J. Whiter, R. Charley and L. Kung, Jr. 2000. Lactobacillus buchneri and enzymes improves the aerobic stability of high moisture corn. J. Dairy Sci. 83(supplement 1):111.