How to avoid heat in the TMR?

Heat in feed is a common problem in the summer. 

It’s caused by rapid growth of microorganisms, bacteria, mould and yeast found naturally in silage. These microorganisms break down the feed, causing it to lose energy (feed units/MJ), making it unappetising.

The perfect conditions for growth of bacteria, mould and yeast
The summer months, when feed is harvested and mixed, improve living conditions for microorganisms. The change in temperature, oxygen and humidity levels is perfect for them to breed and multiply. The  temperature at  the cut  face, or under the black plastic is high, improving conditions for microorganisms. The degrading process is already underway as a result. Practical tests and classic composting methods show that temperatures from around just under 20 degrees C cause the degrading process to accelerate. A large part of the cause (fungi and bacteria) thrive best under oxygen-rich (aerobic) conditions, and as soon as the compressed silage expands, oxygen enters. 

A high water content also accelerates the process, as water activity is vital for microorganisms, which is why many farmers experience a significant drop in the longevity of feed when water is added. The pH value in the feed should ideally be below 4 to impair growth. Unfortunately, the pH value rises when protein in the feed is broken down, and the addition of lime and sodium bicarbonate also causes a slight increase, further improving living conditions. 

A combination of dry acids means broad effect
Feed contains millions of microorganisms, bacteria, yeast, mould and spores, the breakdown and quantities of which vary from one silage stack to the next. That means the growth of different microorganisms and varying causes of heat generation. By using a combination of dry acids, it’s possible to impair a wide range of microorganisms.

Propionic acid, formic acid and sorbic acid are all carboxylic acids, with a pH value of between 2-5, which means they are relatively weak acids. Acids can occur in several different ways, and they are naturally present in plants, the 
atmosphere and the body’s own cells. For acids to be able to stabilise heat in feed, the feed has to be relatively acidic itself. 

Propionic acid/calcium propionate is able to impair bacteria, mould and yeast when added to feed. The optimum growth conditions for fungi and yeast cells occur at a pH value of between 4-6.5. Some may be able to survive at pH values right down to 1.5. 

Formic acid/calcium and sodium formiate primarily impair bacteria growth. The optimum growth conditions for bacteria occur at a pH value of between 6-7.5, i.e. neutral pH. Bacteria cannot survive at a pH value under 4.

Sorbic acid/potassium sorbate can impair mould and yeast. Sorbic acids primarily occur in berries, and are used extensively as a preservative in the food industry. 

Test shows effect

Vilomix conducted a practical test in the spring, combined with laboratory analyses. The test was conducted in two Danish dairy herds, mixing in the combination acid product Solvita TMR Cool. The feeds were mixed immediately after each other, and feed samples were taken from the feed line. Eurofins performed analysis of the feed samples for aerobic microorganisms, yeast and mould. The results showed that the number of aerobic microorganisms was halved, when measured as CFU per gram of sample, when 2-3 kg dry acid is added per tonne of feed. Mould growth was 
reduced to 1/10th, compared with the 0-sample, and yeast growth was reduced to 1/5th. That makes it possible to achieve a significant reduction in the growth of microorganisms in feed.

Avoid loss of value in feed

Heat in feed means loss of energy and money, but it can be reduced by good roughage production. High silage quality, hygiene and feed management all reduce the risk of heat generation. Unfortunately, some harvest years are the cause of poor quality, and a hot, humid summer increases the risk of heat in feed. Warm silage does not have the same feed value as analysed, and therefore the cow does not receive the necessary nutrients. An unbalanced feed ration leads to loss of production and is detrimental to health. Meanwhile, mould growth will increase the risk of toxins – all-in-all a dangerous cocktail. The risk is present in all feed rations, but can be kept in check by the right dry acid mix.