Treating Silages With Bacterial Inoculants Makes Good Cents

By: David W. LaCount, Ph.D.

One of the greatest variables on most dairy operations is forage quality. Stage of maturity, forage hybrid, weather, and harvesting methods are factors that contribute to forage quality. Each of these play a critical role in producing high quality, highly palatable silages that allow cows to maximize their dry matter intake potential. Dry matter intake drives milk yield. The goal of silage production is to maximize the amount of nutrients preserved in a forage in a form appealing to the cow.

Producing a high quality silage requires four basic elements for success. The silage material must be harvested at the appropriate moisture. Alfalfa should be harvested between 60 and 70% moisture for a bunker silo or between 50 and 60% moisture for an upright silo or silage bag. Corn silage should be harvested between 60 and 70% moisture for a bunker silo or between 60 and 65% moisture for an upright or silage bag. In addition, sufficient plant sugars must be available, anaerobic conditions must be established quickly, and an adequate supply of desirable bacteria must be present for the fermentation process to proceed.

There are five phases of silage fermentation. The first phase known as aerobic respiration lasts from the time the crop is ensiled until the oxygen supply is depleted. It is critical to minimize this phase (<48 hours) because plant respiration and mold and yeast growth can occur in the presence of oxygen. Excessive length of Phase I can result in excessive heating, use of plant carbohydrate stores, and lost protein, energy and dry matter.

Phase II begins when oxygen is depleted and anaerobic bacteria take control of the fermentation and produce acetic acid. Production of acetic acid drops the silage pH and eventually inhibits the growth of acetic acid producing bacteria in favor of lactic acid producing bacteria. This phase should be completed in 24 to 72 hours. The greater the availability of the lactic acid bacteria, the quicker this phase will be completed. Phase III begins when the silage pH reaches 5 and is a continuation of anaerobic fermentation through the production of lactic acid. This phase lasts until the pH drops to 4.5 and all bacterial growth is inhibited. This will typically take 1-3 weeks.

Phase IV of silage fermentation is the stable phase. This occurs once pH has dropped to 4.5 or lower. Silage in this phase will keep as long as oxygen and moisture are kept out. Phase V is the feedout phase of silage fermentation. As the silage is being fed, secondary aerobic fermentation can occur on the feedout surface. In addition, dormant yeasts and molds can multiply and compete for substrate and decrease silage quality.

The goal of making good quality silage is to eliminate oxygen from the silage as quickly as possible and decrease the pH of the silage to 4.5 or less. The oxygen content of the silage can be controlled by harvesting at the appropriate moisture and adequately packing the silage to force out as much oxygen as possible. Decreasing silage pH is a function of the bacterial population present on the crop at the time of harvest. There are no guarantees that the crop coming out of the field is populated adequately or with the desired species of bacteria. For this reason bacterial inoculants containing lactic acid producing bacteria often are applied to insure a rapid fermentation producing lactic acid.

Table 1 illustrates the effect of Land O'Lakes silage inoculant on the fermentation of alfalfa silage wilted to 70% dry matter and ensiled for 6 months. Treated silage had a lower pH and 5 percentage units less dry matter loss than untreated silage. Less nonprotein nitrogen as a percentage of total nitrogen and less nitrogen bound to ADF as a percentage of total nitrogen indicate that less protein was destroyed and less heat damage occurred in treated silage. In addition to this study, numerous studies confirm that use of good quality silage inoculant will reduce forage dry matter losses about 5 percentage units.

Effect of inoculant treatment on alfalfa silage quality. Item Control LOL Silage inoculant Silage pH 4.57 4.39 DM recovered, % 84.6 90.4 NPN/total N, % 54.2 52.7 ADF-N/Total N, % 11.4 10.4 J. Buchanan-Smith, 1988, University of Guelph Table 1.

Recent research advances are improving the strains of bacteria used in the next generation of silage inoculants with specific species identified for specific crops. LAND O LAKES Biomax 5 is a silage inoculant designed specifically for corn silage. The product contains two newly isolated strains of Lactobacillus plantarum that have been selected to improve the aerobic stability of corn silage. These two new strains grow rapidly, outcompete other organisms and produce high levels of lactic acid. In addition, one of the strains produces acetic acid which inhibits mold growth. In laboratory tests, the strains of bacteria in Biomax 5 were effective at inhibiting five different strains of yeasts commonly found in problem silages. This silage inoculant is designed to improve dry matter recovery similar to traditional inoculants; however, the product also will reduce the amount of secondary fermentation which occurs on the exposed face of the silo because of the production of acetic acid.

What qualities should you look for in a good quality silage inoculant? First and foremost, the inoculant should be supplied by a reputable company. In the September, 1999 issue of Dairy Herd Management, Limin Kung, professor at the University of Delaware, identified three suppliers that make particularly good quality products. Chr. Hansen BioSystems the manufacturer of Land O'Lakes silage inoculants was one of the three manufacturers cited. In addition, it is important to see animal performance data and make sure that the packaging system is airtight to prevent moisture from reaching the inoculant and killing the bugs. Silage inoculants should be used in dairy operations that are seeking to improve their profitability. Assuming a 5% reduction in DM losses alone, inoculant use will result in at least a 3:1 return on investment, not including benefits of improved forage quality and potential improvements in milk yield.

Land O'Lakes offers three high quality choices of inoculants for your dairy producers:

LAND O LAKES Biomax 5 – formulated specifically for use with Corn Silage. Water soluble or dry form.

LAND O LAKES Biomax A – formulated specifically for use with Alfalfa Haylage. Water soluble or dry form. (Exclusive to Land O'Lakes, Inc.)

LAND O LAKES Biomax MultiDry – formulated for use with both Corn Silage and Alfalfa Haylage (Exclusive to Land O'Lakes, Inc.)