In this article, we tell you all about heat stress in cows and how best to deal with it.
Heat stress in cows has major consequences. Not just in the short term (in the form of lower feed intake), but also in the long term (in the form of reduced fertility). People often think that cows give less milk under the influence of heat because of a lower dry matter intake. This is only partly true.
Under warm conditions, the cow's metabolism changes too. Less energy goes into milk production. At the same time, the cow stores a larger proportion of the energy she ingests in muscle tissue, in the form of glucose. This means that the energy is used not for milk production, but to cool down the body and protect against heat.
Consequences of heat stress in cows
Adjustments to the ration
In response to the reduced intake due to heat stress and warm forage, farmers usually increase the energy density of the ration. This is often done by feeding additional concentrates and reducing the proportion of forage. This adjustment needs to be carried out carefully as it may affect the rumen pH. By adding extra rumen-proof glucose during start-up, you support the natural process while leaving plenty of energy available for milk production.
What to do when there is lower rumination activity
A warmer ration combined with the cow's reduced rumen neutralising capacity increases the risk of rumen acidification and therefore an unhealthy rumen. To keep rumen activity up to standard, the rumen bacteria need to be continually stimulated. This can be done by providing amino acids and peptides from yeasts. Keeping the roughage fresh on warm days has a positive effect on dry matter intake.
Besides increasing the energy density, additives such as glycerol and fats are also used to help the cow through heat stress. However, these solutions only pose an additional challenge for the cow. These products will reduce feed intake, and burning fats will increase body heat.
Changes in hormonal balance
On hot days, more energy is needed to cool the body. This changes the cow's hormonal balance. Her metabolism focuses more on maintaining her body, at the expense of the energy needed for milk production and fertility.
Fertility
The production and maturation of the egg cell is energy-controlled. A crucial factor here is the hormone IGF, which is responsible for ovum development. The hormone needs a lot of glucose for this process but, on warm days, the cow uses a lot of energy to cool down her body, at the expense of glucose for IGF.
In this way, hot days can prevent the cow from becoming pregnant. It takes the cow a long time to get her hormone balance back in order following heat stress. This means that the effect is measurable not only on hot days, but in the longer term.
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