Heat stress and how we can help you manage it for your clients and producers

Ian Sawyer “ Ruminant Technical Specialist


It is official, we are in an El Nino year, and with that we can expect a long hot summer. Probably with heat kicking in early and a delayed autumn break.

What does this mean for the ruminant livestock we all focus on?

Typically, reductions in both production and increases in health challenges occur as animals experience heat stress! The animal has less nutrients going in, and more draws on the nutrients that are there.

All up, there are easily large milk flow losses (2-5L/day typical) or slowed weight gains (in beef we can easily drop 0.5-1+ kg/day).

What™s driving it?

1- Livestock (dairy /beef/lambs) will reduce feed intake

Lower feed intake means less nutrients in, and less potential production. DRY MATTER INTAKE IS KING! It™s always going to drive or impede your position.

2- Increases in maintenance requirements

They pant and use more energy just to thermoregulate. So, at the same time as nutrient provision goes down, the nutrient requirement goes up.

3- Rumen and intestinal mass is under pressure and leaky gut results

Bodily fluids move to the extremities to dissipate heat. Less blood flows around the digestive viscera. The tissue can get œdehydrated, and we are far more prone to leaky gut and resulting systemic inflammation throughout the body. The physiological mechanisms of the animal tries to hold œhydration in these cells. It uses a lot of energy and glucose to pump Na/K into cells in an attempt to hold cellular hydration. It™s costly and usually only partially effective, so we may still get leaky gut, whilst also losing milk and meat production.

4- More SARA can occur in the rumen

The impact on the rumen is a very important aspect of heat stress. It happens because we move less VFA from the rumen to blood (as less blood flow past the rumen), so VFA stay in the rumen. They are problematic there, and not an energy source till they get into blood. In addition, as animals pant it reduces the efficacy of salivation for rumen buffering. So, at the time of challenge, the natural defences are down. This especially plays badly when we also have leaky gut.

5- Preference for energy as glucose during heat

Part of this is because the leaky gut and SARA means more inflammation which stimulates the immune system. This inflammation sucks up glucose in large amounts. The animal tries to eat to replace it. It tends to avoid fibre and favours fermentable carbs more. This is better for glucose, but not so great for rumen stability.

All of this is what comes together to cost us production, health, welfare and inevitability PROFIT.

Yet we can take simple inexpensive steps with in-feed TOOLS that have proven outcomes in addressing these challenges, helping the stock and helping our bottom lines.



Feedworks has committed over 20 years of research efforts with natural betaine, and be aware that it™s our natural betaine that has the data set! Betaine promotes DMI and holds cellular hydration of the gut viscera, which helps reduce energy cost and occurrence of leaky gut. It™s our most potent tool when things get really tough. We have seen it make a 4L milk difference in the past, and a couple of litres is very common. We suggest 15-20g/day used throughout summer in high challenge regions with consistent heat load.


Acidbuf is by far the most effective rumen stability tool on the market. Nothing else has the data set which demonstrates its incredible reliability in maintaining improved rumen conditions and lowering SARA risk. Acidbuf should be used year-round in any case, but an increased SARA risk in heat increases the imperative need for its use. We suggest Acidbuf is used at 0.4% of total DMI in heat periods. For 18-20kg/day of DMI, that is 70-80g/head/day. In addition, don™t forget the valuable Calcium, Magnesium and trace minerals that the product also provides. University trials show that Acidbuf can easily make a 2L milk difference in trial work. Use it year-round. Top up a touch in heat.


There is an enormous data set for Diamond V in both thermoneutral and heat conditions. In all conditions it demonstrates promotion of DMI, and that is especially crucial in heat periods. In fact, it is the only product available that has a registered FDA claim to promote DMI. What a bonus in heat.

It also shows better rumen outcomes of VFA and microbial protein yields from the rumen, yet lower SARA risk, whilst also reducing pro-inflammatory markers that rob the cow of her glucose. It has fabulous data showing improved fibre digestion, and we all know that is great in summer. More mouthfuls and more nutrients from each of those mouthful.

Diamond V is our suggestion for use through summer in more temperate regions, where extreme heat is more intermittent. Its productivity gains are there every day regardless of heat, but on those heat days, it also kicks in to support against heat stress especially.


Many people rightly associate Availa Zinc with its great benefits in lameness or cell count reduction. In heat stress, Availa Zinc supports the wall of the entire enteric viscera. Therefore, this includes both the rumen and lower gut. When we do this, we limit the leaky gut that is so common and so costly in heat periods. It is effectively putting energy back into the system by reducing systemic inflammation. It™s another great tool that has merit and should be used year-round, but has special benefits in heat periods across consistent or intermittent heat regions.



Promote DMI

Create/Spare Energy Less Leaky gut & Inflammation

Improve Rumen pH Stability

Natural Betaine

Yes Yes Yes


Yes Yes Yes Yes

Diamond V

Yes Yes Yes


Availa Zinc Yes Yes