Avoiding heat stress in milking cows

It is well known to all dairy farmers that when the weather starts to get warmer, heat stress is never too far away. In both hot and temperate climates, a rise in temperatures can make a significant difference in the productivity of your dairy herd and the money going into your pocket.  

To begin preparing your farm to tackle heat stress challenges, fill out our Heat Stress Strategy Evaluation. 

Next, take a look at the information and guidance we have to offer. Over a series of five blogs, we are outlining the signs and appropriate management methods for heat stress on your farm, pinpointing the key risk areas:  

1. Feed and Forages 

2. Calves 

3. Heifers  

4. Milking cows  

5. Transition cows  

When it comes to the negative impact of heat stress on your farm, an area where you will see it most drastically is in your milking cows. Left unchecked, it can not only lead to a reduction in output and performance but also affect your animals’ health, ultimately causing a drop in your production profitability.  

So, when it comes to heat stress in lactating dairy cows, what signs should you be on the lookout for, and what actions can you put in place to address the problem promptly and effectively?  

Signs of heat stress  

When your milking cows are feeling the heat, there are many signs that can be observed with the naked eye. If you are worried about heat stress in your herd, be sure to be on the lookout for:  

• Increased breathing (>70/hour). This is the cows’ attempt to reduce their body temperatures, but it also decreases the concentration of bicarbonate in the blood.  

• Profuse sweating. While this moisture will cool the body by evaporation, it will also lead to a loss of sodium, potassium and magnesium.  

• A reduction in saliva, resulting from the low levels of bicarbonate in the blood. This in itself leads to low rumen activity, a drop in ingestion by around 10–20% and, subsequently, ruminal acidosis.  

• Prolonged standing and congregating, putting the animals at risk of diseases such as laminitis and lameness.  

When you look a bit closer, you will also notice some further internal effects, such as:  

• Decreased milk production and milk fat.  

• A high loss of bicarbonate in the urine, affecting the pH of the blood.  

• Issues with reproduction and fertility, including silent heat, embryonic death and foetal abortion.  

Housing and management 

The key to managing heat stress in your milking cows is to provide them with the most comfortable surroundings possible. The animals should be housed in an environment that offers everything they need to alleviate the effects of heat stress.  

Hydration is the first challenge that needs to be addressed. Under normal circumstances, your milking cow will drink 3–4 litres of water per litre of milk produced. So, for a cow producing 30 litres of milk, she needs access to 90–120 litres of water per day. However, when it is very hot, water intake can rise to 250 litres. To accommodate this increased need, ensure:  

• Water is consistently available to the cows, providing 10–15 centimetres of frontal space per cow in 2–4 sections of the barn.  

• Troughs are cleaned regularly to improve palatability.  

As excess sweating causes the animals to lose essential minerals, it is important to integrate wetting and drying systems into the housing to simulate the cooling effects of sweating. This can be achieved using showers and fans installed at the holding pen, parlour and feeding bunk that operate in cycles. For these to be most effective, ensure:  

• The cows’ skin is soaked with large water droplets for 30 seconds to 1 minute at a time.  

• Soaking cycles every 5 minutes.  

• Fans blow continuously at 3 metres per second.  

Finally, it is crucial that the cows have a comfortable resting area. Make sure to provide 10 m2 per head, increasing to 12–14 m2 for close-up cows.  

Feeding and nutrition  

A simple yet effective change you can implement to help reduce heat stress is to move feeding times to cooler parts of the day, allowing the cows to be comfortable while they eat.  

When it comes to diet formulation, there are many factors to keep in mind, including:  

• Ensuring uniformity of mixed and delivered rations to minimise feed sorting.  

• Using fresh, palatable, high-quality feed that will help maintain rumen function.  

• Avoiding excess dietary protein.  

• Reviewing the energy density of the feed and maintaining a safe forage:concentrate ratio (70:30) in order to limit NEB.  

• Using fractioned and/or highly digestible fat sources for increasing dietary energy.  

• Selecting highly digestible forages, such as cereal, grass and alfalfa silages.  

• Choosing starch with slow degradation rates (e.g., maize vs. barley).  

• Maintaining dietary sugar levels at 5–6%.  

• Providing minerals lost through sweat at recommended levels: potassium (1.5–1.6%), sodium (0.45–0.6%), magnesium (0.35–0.40%).  

• Ensuring the provision of key vitamins and trace minerals, such as vitamin E, selenium and zinc.  

Alltech also provides products that can be added to your milking cow feed to assist in optimising their performance. Yea-Sacc® helps to stabilise the rumen environment and optimise function, while Optigen® can increase nitrogen use efficiency.  

In order for you to gain quick access to all the information covered in this blog, we have summarised it all in a short, two-page document that you can download. Read and download it here.  

Outside of milking cows, there are many other areas of your dairy farm that can be negatively impacted by heat stress, costing you time and money. Our Heat Stress Strategy Evaluation assesses your current approach and suggests improvements for effectively tackling the issue. Evaluate your strategy here.