Combatting heat stress in calves

When temperatures start to rise, there is one thing on every dairy farmer’s mind: heat stress. The effects that heat can have on your dairy can significantly impact their performance and health, and ultimately your production profitability.  

The first step to addressing this issue is learning where you currently stand. See how well you are managing dairy heat stress on your farm with our Heat Stress Strategy Evaluation. 

To offer further assistance, by using our years of experience and expertise, we have published a series of blogs focussing on the key heat stress risk areas on your dairy farm:  

1. Feed and Forages 

2. Calves  

3. Heifers 

4. Milking cows 

5. Transition cows 

The plight of unchecked heat stress is well-documented, and farmers do not have to look far for advice on tackling the issue in their production animals. However, it is not just the working cows that feel the heat. Calves can also be impacted by heat stress, and while the effects of this may not immediately affect your production and profits, not addressing the issue in early life can have problematic consequences later on.  

So, what are the specific symptoms of heat stress in calves, and what can you do to help combat these effects?  

Signs of heat stress  

Many of the indicators of heat stress in calves can be easily observed without a thorough investigation. General abnormal behaviour can be a cause for concern. Make sure to keep an eye out for signs such as:  

• Increased breathing rate with mouth open.  

• Loss of appetite.  

• Reduced movement.  

• Increased standing time, lying less.  

• Reduced milk intake.  

• Reduced starter grain intake.  

• Increased water consumption.  

These all point to the young animal being under stress. On closer inspection, you may also observe heat-stressed calves having:  

• An elevated respiratory rate above normal, reaching highs of 24–36 breaths per minute.  

• Dehydration.  

• A body temperature rising above 39.5˚C.  

• Reduced weight gain; this is due to both the reduced feed intake but also because the calf is prioritising its energy for body maintenance.  

Without intervention, these issues can drastically impact the health of the young animal. Untreated heat stress in calves will lead to increased cases of:  

• Pneumonia.  

• Scours.  

• Morbidity.  

• Mortality.  

Housing and management 

So, what can be done to help stop heat stress from becoming an issue for your calves? First, you must ensure that the housing you provide is optimised to provide relief from the heat. Often, traditional and commonly used housing and bedding resources can actually exacerbate the risk. For example, many farmers use plastic hutches that are ideal for protecting the young animal from the elements. But, in hot weather, these shelters absorb and retain heat, making them more uncomfortable than being out in the open. Similarly, many farmers use straw for bedding; however, this too retains heat and is undesirable in higher temperatures.  

The key to optimising housing is to prioritise good airflow, which will help to keep the young animals cool and comfortable. Some beneficial adjustments to put in place include:  

• Elevating the plastic hutch off the ground to increase air circulation.  

• Opting for shelters with ample headroom for good aeration.  

• Placing large sheets of cloth above pens to provide shade and block out UV light.  

• Using sand, sawdust (wood shavings) or rice hulls as less heat-absorbent bedding materials.  

• Spacing out single-calf pens/hutches to allow air to move around them.  

• Reducing stocking density in group pens and ensure all animals can rest in the shade.  

• Regularly muck out pens so that calves can rest in a dry space.  

Feeding and nutrition  

As you can imagine, one of the most essential areas of your heat stress management strategy should be hydration. As mentioned above, calves feeling heat stress are likely to be dehydrated and, therefore, increase water intake. To effectively address these issues, you need to make sure that your calves are never left wanting or searching for a drink. Some steps you can apply on your farm include:  

• Providing access to clean and fresh water in shaded areas.  

• Making sure that water is clean and cool.  

• Ensuring that calves consume all of their milk.  

• Offering a midday electrolyte drink for more effective hydration.  

• Providing a fresh starter grain every day.  

When it comes to feeding, timing is everything in high temperatures. Make sure to:  

• Increase the morning feed volume, giving your calves the best possible start to the day.  

• Delay the afternoon feed to the evening when temperatures are lower.  

Additional support can be found through additives incorporated in the feed. Alltech’s Bio-Mos® and Actigen® can both support calf gut function during periods of increased stress, ensuring that the young animal is getting the most out of its feed.  

The advice in this blog is summarised in a useful one-page document, providing you with all the critical information you need to combat heat stress in your calves. Download the summary here. 

Of course, heat stress affects many other areas of your dairy production, and you can never learn too much. With our Heat Stress Strategy Evaluation, you can learn just how effectively you are tackling heat stress on your farm and what improvements you can make. Evaluate your strategy here.