The summer heat comes around every year, whether we like it or not, and it requires preparation and action to help our animals cope.
We all know about heat stress, but what is it exactly? Heat stress occurs when the total heat gain (combined effects of environmental and metabolic heat factors) exceeds the animal’s heat loss capabilities, leading to increased body temperatures, disrupted behaviors, and impaired physiological functions. The THI (Temperature-Humidity Index) chart notes that heat stress can occur before we think about it, especially if the humidity is quite high.
The thermal neutral zone of cattle has generally been accepted to be between 40 and 70 degrees F. This means that between these temperatures, there is no extra requirement of nutrients needed for maintenance. Several researchers, including those at the University of Arizona, have been talking about the fact that heat stress begins below 70 F. Their new THI shows that heat stress can begin in the 60s for high-producing cows.
Humidity is probably the biggest complicating factor, simply because one of the most basic ways that a cow has to cool herself is the passage of air for evaporative cooling. When the air already contains a lot of moisture (humidity), the ability to evaporate moisture is reduced. Without the full effect of this cooling, heat stress can occur based on our definition of heat stress, where the total heat gain exceeds the animal’s heat loss capability.
When heat stress takes place, we see a number of negative things happen, but one of the most significant is lower dry matter intake (DMI). Unfortunately, this takes place even though maintenance requirements are going up (from heat stress), creating a doubling negative effect. If you want to lose weight, experts will tell you, don’t just stop eating. Why? Because your body says, “Oh no, nothing coming in so I must preserve instead of burning up nutrients.” Similarly, a cow with less dry matter intake quickly says, “Staying alive is more important than producing 100+ pounds of milk,” thus a repartitioning of the energy that she does have takes place.
In quantity, energy is the cow’s second largest nutrient requirement, only behind water. She is getting her energy from the feed she is digesting. During heat stress, in addition to lower DMI, there are other factors are working against us:
- Rumination is slowed for a number of reasons, making it more difficult to pull as much energy from the feedstuff.
- Less saliva is available (lost from drooling and open mouth breathing) for the rumen, which contributes a large portion of the buffering capacity, making rumen pH more volatile.
- Blood flow changes (more being directed to the skin surface during heat stress) also changes rumination and the ability to take up nutrients.
- These changes also effect the VFA (Volatile Fatty Acid) production in the rumen, which needs to be addressed to keep a healthy rumen.
For these reasons, your feed rep will make “summertime” adjustments to your diet to help in times of lower DMI. This includes trying to keep the animals healthy as they are now more prone to acidosis, due to the changes in rumination, and are now likely to be losing weight based on decreased energy availability.
You can help your feed rep with this transition by being sure to have highly digestible forages available for summer feeding (and not in limited supply). The rumen becomes a big furnace as it digests fiber so the more digestible your forages, the less heat that is generated to break down the fiber. This is why your nutritionist begs you to be sure to have enough corn silage to feed all summer. Being able to feed more forage keeps a more stable pH, during a time when pH is quite volatile and helps create VFAs in the correct proportion, lessening the risk of acidosis and upset stomach.
Nutritional Tools to Help Cows Beat the Heat
While no feed additive can replace good heat mitigation practices such as providing adequate shade, fans, sprinklers, and access to clean water, there are products to help cows better cope with the challenges of summer heat.
At Phoenix, our nutritionists work with producers to evaluate each herd’s needs and recommend products that support rumen function, nutrient utilization, and overall performance each season.
Probac-6™
Provides a Novel™ bacteria and yeast package designed to support lower GI health in dairy cattle. Specially formulated to combat clostridial challenges common in the Northeast. By excluding pathogenic bacteria, maintaining acid pH, and interacting with the gut wall, Probac-6™ helps support a healthy immune system and a balanced microbiome.
Diamond V™ Ice Plus
Supports cooling at the cellular level through a unique blend of nutritional ingredients designed to lessen the impact of heat stress on milk production, reproductive health, and overall performance. It is an excellent option for producers looking to help cows stay productive during extended periods of hot, humid weather.
More information here.
Selko Fytera™ Balance
Fytera Balance contains a proprietary concentrated capsicum oleoresin and full-spectrum clove essential oil. Because we use full spectrum, standardized ingredients the product has many actives including polyphenols, flavonoids, and numerous volatile compounds that are protected by fat encapsulation. The product is all about decreasing inflammation and protecting gut barrier function. Balance is not rumen bypass but the fat encapsulation offers significant protection, and both ingredients in the product have a high level of stability in the rumen.
We’re here to help. Contact your feed representative to find the right combination of nutritional strategies to help your herd stay healthy, comfortable, and productive all summer long.