The best time to strategize about heat stress mitigation is early spring when there is still some frost on the ground in the mornings. Or better yet . . . planning for next summer’s heat abatement plan could be done in the previous fall when the shortcomings of the current cooling strategies are fresh on everyone’s mind. However, that doesn’t mean that when we are in the thick of the summer stress we can’t implement new ideas. The goal during these times may be attempting to maintain feed intake during heat stress.

A place to start

One of the easiest and most concentrated cow cooling efforts is parlor exit cooling. Are your cows wet to the hide when they leave the parlor? If they aren’t, they should be.

Adding very basic sprinklers to drench cows as they leave the parlor is perhaps the easiest way to cool all cows. I have seen very elaborate systems that look a bit like a fancy car wash, and I’ve seen systems that are rigged up after a quick trip to the local hardware store. The lower your humidity, the more effective this will be, but it still helps in all situations. Avoid spraying water directly on the udder. Also, think about the potential impact on parlor exit fly control systems.

Also post-parlor, another effective and very concentrated way to help cows is parlor exit water troughs. Continuing along travel lanes back to the pen, more water troughs are always good. In the summer especially, all cows should have water available on the return to the pen. At times, these can hamper cow flow and may be a problem, but if possible, allowing for a good drink postmilking should enhance intake.

Just prior to milking

Before we leave the parlor, here is one more general thought. Is there a way to keep the cows cooler in the holding pen waiting to be milked? Obviously, fans and lots of water is the big opportunity here, and both are in play in nearly every dairy I visit. Perhaps you have some in place but really need more. Are your fans working with or against the prevailing wind? One untapped potential in some holding pens may be removing side panels to boost airflow in and out of the area. Dairies in the South are mostly totally open, but facilities further north have various side panels that could or should be removed during the summer.

Another small opportunity is arranging alleys and gates, where possible, to have cows walk past feed when returning to their pen. In an open lot dairy, if the shade is between the parlor exit and the feedbunk, they may simply stop there and not make it to the feed. In a freestall arrangement, blocking cows from returning via the back lane might encourage a few bites more before they lay down during extreme heat.

What about the ration?

Let’s start by staying with the water theme. Consider adding water to the ration to enhance intake. In my experience, wetter rations are more readily consumed during heat stress. This seems logical when thinking about a cool salad versus a bowl of dry cereal on a hot afternoon.

There are a few potential drawbacks, however. Raising the moisture content of feed will reduce bunk stability and elevate the risk of heating. Using commercial propionic acid-type products to stabilize the bunk along with more frequent pushouts should minimize the risk. Recommending a simple dry matter percentage of the TMR as a target is probably not as effective as simply trying different levels and seeing how the cows respond and how the heating risk turns out.

Higher hay diets compared to high silage diets will take different amounts of water to be the most palatable at the bunk. Wet ingredients like brewers grains, distillers grains, and gluten can offer help here; however, take care to manage the unsaturated fatty acids in those that can hurt milkfat synthesis. Starting at 50% DM in the ration and evaluating from there is a good recommendation.

One of the ways I think adding water can increase dry matter intake (DMI) is that it simply increases the density of each bite of the ration. Another way to raise the density of the ration is to improve the forage processing of the diet and making it shorter in length. This of course has to be done carefully, taking care to not present a ration with inadequate roughage value and increase the risk of poor rumen health. Using a shaker box (Penn State Particle Separator) to be sure the diets don’t get too short for good cow health will likely allow you to get shorter than you might be comfortable with and still be healthy.

We know that for “short” rations to work well, they need to be higher in digestible fiber from various by-products or very high-end forages. Another way to say this is that very high starch diets might be problematic when finding how short is too short. In many heat stress rations, reducing forage fiber and replacing with ingredients like soybean hulls is a solid strategy.

Where you will get in trouble is when you reduce forage and replace the ration space with corn. In areas where they are available, the seemingly magical cottonseed hull can be part of a summer intake enhancement strategy. With forage replacement abilities documented many decades ago, cottonseed hulls seem to help cows eat more, but at the same time, they dilute both dietary energy and protein. There is room in the remainder of the diet to address this.

Watch the cows

Lastly, there are numerous ration strategies to help cows better handle heat stress. Working closely with a nutritionist to consider the various options is the key. Watch the cows, how they eat, the milk components and flow, and respond appropriately to what you see.

Some nutrients can be concentrated to supply needs in a smaller intake package. Starch, however, is usually not one of these. Shifting energy supply to highly digestible fiber sources like soybean hulls and various sources of safe dietary fat can help meet the cow’s energy needs. It is likely a losing battle overall, but mitigating how bad and how long the cow is severely impacted will offer a quicker recovery when the heat breaks.

The overall guiding principles here are pretty straightforward. Move more air, add more water, and look for smart ration adjustments that can help the cows. Be careful to not break nutrition rules to accomplish short term gains. We need to have healthy cows when the long days of summer are in the rearview mirror.

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(c) Hoard's Dairyman Intel 2022
July 21, 2022
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