You are working at a consulting firm that specializes in fermentation technologi

Question

You are working at a consulting firm that specializes in fermentation technologies. You have a client who is expanding their Dairy herd from 500 to 1000 cows. The farm is trying to utilize as much of the farm grown feedstuffs in the cow diets as possible. The corn the farm has to use could not be harvested in a timely manner and ended up standing on the field for 1 extra month while the temperatures dropped below freezing and were very damp. The temperatures s to rise and allowed the corn to be harvested with a high moisture concentration. During storage low levels of mold began to grow. The farmer, your customer, is very concerned that this mold will negatively impact his silage and overall feed. What information can you provide to the farmer about the microorganisms involved in the silage fermentation? How might this mold impact their silage? What is your recommendation for the farmer and why?

Explanation / Answer

When fodder (dried coarse food for cattle) fermented in presence of high moisture and the fermented product used to feed domestic ruminant animals (Like cow, goat, sheep etc), then this type of food is called Silage. The fermentation process is called ensiling. Silage generally prepared form the entire plant of grass crop (like maize, cereals), various weeds are also used to prepare it.

There are some steps to prepare Silage.

·         1st phase: After harvesting of the crop plants are dumped in the sealed silo. As the plant respiration process continued, plant enzymes and aerobic bacteria constantly using stored nutrient by degrading plant proteins and converting sugars into carbon dioxide and water, and as a result of these biochemical reactions heat is also generated..Depending upon the availability of the air supply generated heat increases the silage temperature by 15° to 20°F or more. Until the entire oxygen present inside the silo finished this process continued (generally takes from few hours to 2 days). By harvesting crops at the proper maturity period, chopping to the right length, careful packing the silo tightly and sealing within 12 hours of harvesting are few major things which help to minimizing nutrient losses during this phase.

·         2nd Phase: When oxygen present in silo is finished, anaerobic bacteria begin to ferment plant sugars into organic acids, alcohols, carbon dioxide and nitrogenous compounds. As a result the pH levels drops from 6 to 5 due to production of organic acids. If this pH dropping process occurs at slow rate and moisture concentration of silo is high due to early harvesting, Clostridium bacterial growth founded. They degrade sugars to produce butyric acid, from lactic acid and also releasing strong offensive odors. This group of bacteria can also break down protein to non-protein nitrogen and amines which results dry-matter loss increase and decrease the silage quality.

·         3rd Phase: In silo when Ph level decreased below 5, lactic-acid-producing bacterial (LAB) (Like Lactobacillus, Enterococcus, Pediococcus etc.)Activity increased which reduce the pH to about 4 or 4.5 in well-made silages and haylages. As Lactic acid is more effective than other organic acids at reducing the pH, LAB causes fast pH drop which actually helps to preserve nutrients. Duration of this phase lasts from 3 days to 4 weeks and finished when fermentable sugars are ended.

·         4th phase: At low pH (4 or below 4), the silage becomes stable as o unable to grow at this pH. The quality of the silage can be maintained until its opened or any air penetration event occurred.

When aerobic conditions are restored to silo yeasts and molds those were dormant during the fermentation are revived. They generally use sugars, lactic acid and other nutrients for their growth and as a by-product produce carbon dioxide and heat. Due to excessive heat accumulation denaturation of proteins and other nutrients occurred in the silage which decreases the quality of silage. Molds on the silage may also produce mycotoxins and consumption of them by cattle may leads to various diseases like organic dust toxic syndrome.

Recommendations to maintain better quality Silage:

1.       Harvest crops at the appropriate time when moisture content and maturity stages are proper. Quick filling and properly packing of silages is highly require which has a directly impact the fermentation process and thus the quality. Properly fermented silages result in reduced dry matter losses thus more feed being available for feeding dairy cows. Silage having more lactic acid helps to improve feed intake, milk production etc.

2.       A 3 week period is strongly recommended before feeding new crop silages. Generally a complete fermentation process required 10 days to 3 weeks period. To get the best milk production silages should not be fed before this period.

3.       To increase the silage lives try to minimise the exposure to oxygen as much as possible.

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