Chr. Hansen's silage inoculants improve quality

By Dr. David Seale, Technical Sales Manager, Chr. Hansen

Silage fermentation: difficult to control

Despite it's importance to the diet of dairy cows, the silage fermentation itself is difficult to control and the outcome both in terms of fermentation and feeding value is highly variable. This variability is caused by several factors such as the forage type, fertilizer application, moisture and sugar content, buffering capacity (resistance to pH fall) of the forage, weather conditions at ensiling, soil contamination, and the number and type of lactic acid bacteria on the forage.

Good management practices such as cutting the forage at the correct stage of maturity, careful fertilizer usage, sufficient chopping, ensiling in good weather, wilting if possible, avoiding soil contamination, rapid ensiling, well maintained silo structures, adequate compaction, efficient sealing with weighted down good quality plastic, and care in removal of silage from the silo during feeding are critical. As in other major fermentation processes such as cheese or beer production, tightly controlling of the starting materials, the microorganisms present and the fermentation conditions can ensure a consistent product.

Inoculants have a major advantage

As a result it is common practice in many countries to use a silage additive to control the silage fermentation. Traditionally acids such as formic or sulphuric have been used to achieve preservation by acidification. Over the past 20 years, however, the use of bacterial inoculants to aid and control the natural fermentation have become increasingly popular and they are now the main type of additive used. Inoculants have a major advantage over acids for the silage maker in that they are safe to handle and do not corrode expensive harvesting machinery.

Twice as efficient

Chr. Hansen's silage additives work by adding lactic acid bacteria to the forage which are twice as efficient at fermenting glucose and six times more efficient at fermenting fructose than the indigenous lactic acid bacteria on the forage, which are largely inefficient. Provided that at least 100,000 living lactic acid bacteria are applied per gram of forage, the inoculated strains should dominate the fermentation and result in a rapid drop in silage pH due to a faster and more efficient production of lactic acid. This is critical in low sugar content forages where all the sugar present needs to be fermented as quickly and efficiently as possible to ensure preservation. Inoculants usually consist of strains of Lactobacillus plantarum on its own or in combination with strains of for example Pediococcus or Enterococcus.

There are many different strains of L. plantarum and these vary greatly in their suitability as silage inoculants. The selection of the best strains is essential and should be based on their safety and their ability to grow over a wide range of dry matter contents, temperatures and pH values, to utilise the sugars found in forages, and their ability to rapidly reduce the number of contaminant bacteria and fungi. It is also essential that inoculants are stable so that the correct level of living bacteria is applied to the forage.

Documented benefits of inoculants

A huge amount of data has been generated over the years documenting the benefits of inoculants. The first effect is a better fermentation caused by a rapid fall in pH. This can be demonstrated against both untreated and formic acid treated silage (Fig. 1). Other fermentation benefits observed include a higher lactic acid and residual sugar content and lower contents of undesirable fermentation products such as acetic and butyric acids, ethanol and ammonia-nitrogen, as well as lower levels of coliform bacteria and clostridia.

Fig. 1. Effect of Chr. Hansen's silage inoculant containing L. plantarum and Pediococcus pentosaceus on the rate of pH fall in 14.6% DM grass silage (Edinburgh School of Agriculture, Scotland).

Reduction in losses in silage

The second benefit is a reduction in dry matter losses in silage, which simply means that there is more silage left for feeding when the fermentation is finished and the silage is opened. There are two main types of in-silo losses; gas losses caused by an inefficient fermentation and effluent losses from juice run-off. Inoculants have been shown to be capable of reducing both dry matter loss(Fig. 2) and effluent loss compared to untreated silages.

Fig. 2. Effect of Chr. Hansen's silage inoculant containing L. plantarum on dry matter losses in 26.8% DM grass silages, mean of 10 studies. (Institute of Crop and Grassland Science, Braunschweig, Germany).

Higher preservation of nutrients

The third benefit is a higher preservation of nutrients in the silage due to a better fermentation and lower losses. This manifests itself in higher organic matter digestibilities (Fig. 3) and higher energy contents (usually expressed as metabolisable energy or net energy of lactation depending on the country).

Fig. 3. Effect of Chr. Hansen silage inoculant containing L. plantarum and P. pentosaceus on invivo digestibility of 42.1% DM grass silage. (Foulum Research Centre, Denmark).

Higher milk production

This author has consistently observed that farm silages treated with inoculants have a distinctive sweeter, more aromatic and more palatable smell than untreated silages. This concurs with the observations of many producers that their cows eat more inoculant treated silages and from research trials which consistently show that the intake of dairy cows and steers fed inoculant treated silages is higher than of those fed untreated silages.

It can be expected that if a dairy cow eats more high digestibility / high energy content silage that she will ingest more energy and produce more milk. Higher milk production has been demonstrated again and again in research institute trials when cows are fed inoculated compared to untreated silages, and is the main reason why dairy producers use silage inoculants. In a trial with 54.8% dry matter lucerne (60% of total diet) at USDA Madison,Wisconsin USA, cows fed inoculant treated silage produced 2.2 kg more milk per cow per day (Fig. 4) and their milk contained 6.3% more protein and 4.7% more fat than cows fed untreated silage. This would result in a large and meaningful return on investment compared to using no additive.

Fig. 4. Effect of inoculant containing L. plantarum on milk production in cows fed 54.8% DM lucerne silage. (USDA, Madison, Wisconsin, USA).

Improves dairy cow performance

In conclusion silage, which is a major constituent of the diet of dairy cows in most main milk producing countries, is a feed that varies greatly in quality, often for reasons outside the silage makers control. The use of Chr. Hansen's silage inoculants can improve the preservation quality of silage, lower in-silo losses, increase silage nutritive value and improve dairy cow performance.