The impact of elevated temperatures on quality of dairy feed
Fresh TMR for dairy cows contains yeasts, moulds and bacteria that can reduce the quality of the dairy ration. Growth of these micro-organisms leads to heating and fermentation, which reduces both the palatability and the feeding value of the ration. Particularly the easily fermentable proteins, carbohydrates and starch are fermented into water and CO2 (see Figure 1) reducing the dry matter and therefore nutritional value of the dairy feed.
Figure 1: Effect of fermentation on sugar level and dry matter percentage o an untreated TMR. Sugal level was reduced by 50% over a period of 24 hours.
Growth of micro-organisms and fermentation in TMR of dairy cows starts once the ingredients have been exposed to oxygen in the air and results in an increase of the temperature of the TMR. On a warm day in the summer, increases of more than 20°C are not uncommon. Once environmental temperatures start rising, performance of the dairy herd is under pressure for two reasons. Firstly, dairy cows could potentially suffer from heat stress resulting in a decrease of dry matter intake. Secondly, the reduction of palatability and feeding value resulting from heating of the TMR will lead to a further reduction of dry matter intake of dairy cattle.
How can we reduce the negative impact of yeasts, moulds and bacteria on dairy TMR?
The quality of the initial raw materials has a big impact on the level of yeasts, moulds and bacteria. Contamination at harvesting should be avoided as much as possible, and silages should be closed properly to reduce exposure to oxygen. Growth of micro-organisms can be reduced further by using silage preservation products.
Contamination of the raw material with micro-organisms can never be avoided completely. Once the silage is opened, there will be exposure to oxygen and moisture leading to replication of micro-organisms. Particularly if ingredients with a high moisture content are being used or if water is being added to the TMR, heating can become a serious problem. This is where Selko®-TMR for dairy cows comes in.
