Heat Stress Can Be Taxing

Heat Stress Can Be Taxing

Just like tax season comes around every year, whether we like it or not, it requires preparation and action on our part; heat stress also comes around every year, whether we like it or not—and it too requires preparation and action on our part to help our animals cope with the summer heat. While it may still feel like “heat” is months away, it is not too soon to start preparation. Now is a good time to start testing sprinklers and fans but also giving thought to what else you might consider to help your animals this summer.

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. Note from the THI (Temperature-Humidity Index) chart 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 40–70 degrees F. What this means is 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 actually begins below 70 F. Their new THI shows that for high-producing cows, heat stress can actually begin in the 60s.

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 contains a lot of moisture (humidity) already, 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.
Energy, in quantity, is the second largest nutrient requirement by the cow, 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.

CFU (108/ml) at 9 h growth
Ruminococcus flavefaciens Gm + 59.4 67.1 113.0%
Ruminococcus albus Gm + 84.1 118.4 140.8%
Butyrivibrio fibrisolvens Gm – 13.6 18.7 137.5%
Fibrobacter succinogenes Gm – 27 40.2 148.9%

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.

Amaferm is the most researched product on the market for heat stress. Amaferm has two major modes of action: it stimulates the growth of bacteria in the rumen and it stimulates the branching of the rumen fungi. Many products will help with the growth of bacteria in the rumen, but which bacteria?
A few years back, it was discovered that there are four major fiber-digesting bacteria in the rumen; research shows us that Amaferm will stimulate the growth of all four of these fiber-digesting bacteria.

Stimulating the fungi sets Amaferm apart from other products. The role of the fungi is twofold. First, the fungi attach, grow into the fiber cell, physically breaking the fiber open and allowing the bacteria to invade and digest (similar to what we try to do with starch, provide more surface area). Secondly, the rumen fungi produce key enzymes involved in fiber digestion. Note the illustration and the branching that takes place in the presence of Amaferm, without this, the bacteria have no way of getting to, or digesting, a very high percentage of the fiber that you are feeding. They say a picture is worth a thousand words. The pictures below show how Amaferm helps break down the fiber by breaking open the fiber cell and the additional branching, allowing the secretion of more microbial enzymes and the subsequent attachment of more bacteria, leading to a higher percentage of the forage fiber being digested.

Today we can check the actual fiber digestion on your dairy by running an Apparent Nutrient Digestibility test (CVAS). By pulling a TMR and fecal sample, we can marry these results analytically to see exactly what the cows have digested for fiber, starch and protein. This lets us know how much help may be needed and what changes to consider. By feeding Amaferm, we can increase the fiber digestion of the forage by an average of 17%, which provides additional energy to the cow; in turn, she may use this additional energy for maintenance (body condition), milk production, or butterfat.

June, 2016 81.1 3.6 3.0 11.6 164,000 147.6
Oct, 2016 83.9 3.7 3.1 9.6 122,000 130.6
Change +2.8 +.1 +.1 -2 -42,000 -17

A field study from last summer helped us see the advantage of higher energy levels with Amaferm. Twelve dairies in Pennsylvania added Amaferm in June/July of 2016 and DHIA information was collected from June–October, 2016. Below is a summary of that data for the twelve herds:
Amaferm helps the breakdown and digestion of fiber. Higher fiber diets mean more chewing and thus more saliva. Increased saliva helps to increase rumen pH. Amaferm also helps to directly stabilize the rumen by stimulating the bacteria in the rumen that ferment lactic acid. Breaking down more fiber in the rumen, the pH is kept more consistent and the VFA levels are more appropriately balanced, both of which encourage better component production as well as a healthier animal. Amaferm will increase fiber digestion and the rate of passage; this takes more pressure off the rumen, making it more efficient so less heat is produced internally. It can be difficult, at times to put a value on better body condition but the chart helps us see what improvements can be made when we are in a more positive energy status. The chart below also helps show how early lactation cows will partition energy in summer vs. winter. Note that it is beneficial to have Amaferm in both situations but again the cow will decide where the additional energy is utilized.

In summary, a number of research studies from Arizona and Florida shows that Amaferm increases milk production in early lactation animals an average of 5.5% during heat stress, not to mention the rumen health benefits. Depending on your situation, Amaferm can be used to help increase the forage level in the diet or help you reach new levels, where energy is the limiting factor.

Amaferm is an all-natural product from BioZyme, Inc. Biozyme has many different products for all types of animals, from additives to treatments. We are proud to have Phoenix Feeds & Nutrition carry our line of products. Visit with your feed rep to see how you can gain the Amaferm Advantage.

Control Amaferm
Winter Trial
DM Intake 51.50 51.39
Milk Yield 72.03 81.13*
Milk:Feed 1.40 1.58
Wt. Change .46 .49
Control Amaferm
DM Intake 35.27 35.58
Milk Yield 54.26 55.25
Milk:Feed 1.54 1.55
Wt. Change -.42 1.32*