Heat stress and its impact on dairy cows, and the ‘cool nutrient’

Dr. Richard Kirkland, Global Technical Manager at Volac Wilmar, looks at the serious topic of heat stress and reveals how you can use rumen-protected fats to reduce the negative effects of heat stress on the health and productivity of your herd.

Plus, special guest, John Newbold, Professor of Dairy Nutrition at Scotland’s Rural College (SRUC), shares insights on why heat stress is becoming more common and what you can do to prevent it.

Watch the video to discover everything you need to know about:

• What heat stress is and why it happens to dairy cows
• How and why heat stress is becoming more common on dairy farms
• Why heat stress is such a risk factor for cows’ health
• The issues heat stress causes for your herd’s productivity
• Why type of feed offered needs to be considered
• How to use feed fats to help reduce heat stress and maintain yields

Watch the video now, or scroll down to read the full transcript.  Why Feed Fats, Episode 2

 Why Feed Fats, Episode 2 transcript:

“In this episode, we look at the hot topic of heat stress and how we can use rumen-protected fats to improve the ability of dairy cows to withstand heat stress. And we'll also hear from a special guest.

Q1: What is heat stress in cows and why does it happen?

Heat stress is a major issue for dairy cows, and cows can really start to be affected by heat stress at even quite low environmental temperatures, much above 20 to 25°C.

Cows will take practical measures, just like ourselves, to get out of a heat stress situation. Also, their physiology will change and that can have major effects on the level of production of the animal, and that can lead to big problems in terms of animal health as well.

Q2: What issues does heat stress cause for productivity – and why?

Heat stress can have major negative effects on productivity of dairy cows. The first one that will be noticed is a reduction in dry matter intake, which can be 25 to 30% lower compared to thermoneutral cows. That will be part of the reason we see a major reduction in milk yield for cows under heat stress because they're eating less. We also see physiological changes during heat stress, which diverts energy away from milk production, and we will see a major fall off in actual milk volume.

The other big issue will be the risk of acidosis. As cows are eating less, they are generating less saliva meaning we see less bicarbonate coming into the rumen for a buffering effect. We can also see increases in acidosis and associated issues such as lameness, negative effects on fertility, and of course, major reductions in milk fat.

Q3: How can we help reduce the impact of heat stress using feed fat products?

There are many practical things we can do to reduce the direct effects of heat stress in dairy cows, but from a nutritional perspective, we can use rumen-protected fats as a key nutritional tool to help reduce the negative effects of heat stress. We describe rumen-protected fats as ‘cool’ ingredients - the key factor being that unlike other nutrients which are fermented in the rumen, rumen-protected fats are not fermented in the rumen, so they generate very little heat during the processes of digestion and mastication.

They are also very efficiently converted from metabolisable energy to net energy used for maintenance and productive purposes. As we feed higher fat diets in heat stress conditions, there's a lot less metabolic heat produced in the animal which helps to reduce the level of heat stress from within the animal.

Hello. My name is John Newbold, and I'm Professor of Dairy Nutrition at SRUC, Scotland’s rural college.

Q4: How common is heat stress on dairy farms in your experience?

There is a metric that people use to assess the heat load, which is the amount of heat that an animal is experiencing – THI – which is the temperature and humidity index, which combines both temperature and relative humidity. I think there's a new appreciation in the last few years that the THI at which production begins to be compromised is lower than previously thought. In other words, heat stress is more common.

Q5: Why is heat stress such a risk factor for cows?

Cows that are experiencing high heat loads are in a physiological trap. Cows themselves generate a lot of heat during digestion in the rumen, absorption, and metabolism, and if they can't dissipate that heat to the environment because the environment is too hot, they've got really no option other than to produce less of it.

I think important to mention that as climate change increases, the number of days in which the world's dairy cows are exposed to high heat load, then genetic selection of heat-tolerant cows (physiologically heat-tolerant cows) is becoming more important, and will become more important, which is highly relevant to cows in more tropical environments, but increasingly also to cows in temperate locations such as the UK.

Q6: Why do we need to be careful in feeding additional fermentable concentrates when cows are suffering heat stress?

We also know that in heat-stressed animals, the concentration of buffers in saliva and the flow of saliva into the rumen can be reduced, also adding to that risk of acidosis. This makes it very difficult to compensate for the lower feed intake simply by increasing the amount of regular concentrates containing fermentable carbohydrates that are going into the rumen.

Q7: How do Volac Wilmar feed fats help reduce the impact of heat stress in cows?

I think the use of properly rumen inert fat supplements, such as those supplied by Volac Wilmar Feed Ingredients, is highly complementary to other approaches, management approaches, breeding approaches to the mitigation of heat stress so the use of shades, sprinklers, fans, etc. to try to improve the physical environment.

So, short term management of cows exposed to periods of heat stress should include both these management interventions as well as nutritional adaptations.”