Tackling heat stress in feeds and forage

It will be no surprise to dairy farmers that when temperatures start to rise, your cows can begin to feel the effects of heat stress. This is an issue that challenges dairy farms around the world, even those in more temperate climates. Left unchecked, heat stress will drastically impact your herd’s performance and production profitability.  

The first step in tackling this challenge is to assess your current approach. Find out how effectively you are managing dairy heat stress with our Heat Stress Strategy Evaluation. 

As further support, we have put together a series of blogs looking at the five main heat stress risk areas on any dairy farm:  

1. Feed and Forages  

2. Calves 

3. Heifers 

4. Milking cows 

5. Transition cows 

When establishing an effective heat stress management strategy, it is crucial that a dairy farmer considers every part of their operation that can be affected by rising temperatures. This means that not only should you look at the animals but what you are feeding too. Heat can alter the quality of the feed and forage, making it less beneficial and possibly harmful for the animal, making good harvest, storage and silage management imperative.  

But what are the signs that you should be looking out for, and what can you do to ensure you provide the best quality feed and forage to your herd in this stressful time?  

Signs of heat stress  

When it comes to assessing feed and forage for signs of heat stress, you need to observe these resources in two areas: in the field and in the clamp.  

In the field, heat- and drought-stressed plants are aware of how quickly they could die under these conditions. Because of this, they increase lignification in order to produce a seed head more quickly. This process lowers the plant’s digestibility and, therefore, the energy that an animal can take from it.  

When trying to identify heat stress in plants, indicators can include:  

• A faster wilting time. This will lead to the plants having a higher % dry matter (DM).  

• Visible mould and fungus. These can lead to a greater risk of field-formed mycotoxins and aerobic deterioration.  

While harvesting at the appropriate time can help you avoid these issues, heat stress can still affect stored feed and forages. Even throughout the different stages of the harvesting and silage-making processes, these materials can be subjected to temperatures that can cause damage.  

Like in the field, higher temperatures in the clamp lead to increased %DM and fibre, which will cause issues such as:  

• Increased trapped oxygen.  

• Poor consolidation.  

• Poor fermentation.  

• Greater plant and microbial proteolysis.  

• Higher levels of protein damage.  

• Increased fungal growth, leading to aerobic spoilage and mycotoxin risk.  

• Greater risk of caramelisation (Maillard’s reaction), reducing the quality and energy of the silage.  

• Increased ash level  

Some signs to be on the lookout for are:  

• Malodours (caramel/tobacco/vinegar aroma).  

• Silage darkening and leaf spots.  

• Visible mould.  

• Reduced palatability when fed to animals.  

Harvesting and management 

There are many steps that you can take to optimise your forage growth and yield when under the pressure of potential heat stress. For the most part, it is imperative that you get your timing right, for example:  

• Monitor the crop and harvest when you see signs of dying begin to show.  

• Cut grass/cereal early, before the stem is visible, for the desired %DM content.  

• Consolidate well and quickly to avoid further heating and spoilage.  

• Do not roll or sheet up overnight, limiting the air in the clamp.  

• Ensure a rapid feed-out across the clamp face, limiting spoilage.  

Other factors to take into consideration include ensuring your soil has all of the required nutrients, as healthy soil improves drought tolerance, and using homofermentative inoculants or chemical additives in the clamp. These will help to counter aerobic spoilage issues. However, do not use L. buchneri or other heterofermentative lactic acid bacterial inoculants.  

Feeding and nutrition  

Along with managing your harvesting and storage, there are a few steps you can take when feeding the animals to make the most of your silage and avoid issues with heat stress. These include:  

• Feeding in the morning and evening, when temperatures are lower.  

• Pushing up feed 8–10 times a day, ensuring your herd has regular access.  

• Disposing of leftover feed every day, mitigating the risk of your cows eating mouldy feed.  

Alltech also offers a range of products that can aid in combatting issues that arise in feed and forage due to increased temperatures. Mycosorb® can be added to feed as a mycotoxin binder, reducing mycotoxin absorption within the animal and the risk factors associated with the damaging effects of mycotoxins on its health. Mold-Zap® can also be used, as it is designed to inhibit mould growth, to retain DM and nutrient content, for less top spoilage, and it is also designed for less deterioration (DM loss).  

For easy access to the information provided in this blog, we have compiled a one-page summary for you to download. Read and download it here.  

Optimising your heat stress strategy is crucial for combatting the effects of rising temperatures on your dairy cows. There are many key risk areas to address, with feed and forage being just one. Fill out our Heat Stress Strategy Evaluation here to learn just how effectively you are tackling heat stress on your farm and what improvements you can make.