Heat stress can impart significant economic ramifications on your livestock operation. It is estimated that the annual cost of heat stress to the dairy industry is approximately $900 million, while cost estimates for the swine and beef industries are each greater than $300 million.
Based on these estimates, it should come as no surprise that investments in on-farm cooling systems are highly prevalent. However, cooling systems alone may not be sufficient to mitigate the economic impacts of heat stress.
What’s Happening Inside the Animal?
We know that upon the onset of heat stress, animals experience a marked reduction in dry matter intake, which has been hypothesized as a mechanism to help reduce metabolic heat. This reduction in feed intake may only partially explain why animals under heat stress have poorer performance.
Other changes are happening inside the animal to combat heat stress, such as changes in blood flow, and oxygen and energy availability.
When animals are under heat stress, blood flow is diverted from visceral tissue — tissue that lines the blood vessels, stomach, digestive tract and other internal organs — to the skin, which allows for heat dissipation. This reduction in blood flow to the visceral tissue causes a reduction in the amount of oxygen and energy available to the epithelial layer of cells lining the intestinal tract, thus the tight junctions that hold these epithelial cells together can weaken, allowing pathogens and toxins to translocate into the bloodstream, leading to a condition called leaky gut.
Zinc: The Key to Tight Junctions
Several research studies have established that the trace mineral zinc plays a key role in maintaining intestinal integrity by strengthening the tight junctions during challenges. The research has also shown that the form of zinc fed can influence its effectiveness at reducing leaky gut.
Iowa State University conducted a study to demonstrate how heat stress contributes to leaky gut, and how feeding performance trace minerals like Availa® Zn helps alleviate the occurrence of leaky gut in beef cattle.
The study involved forty Holstein steers with a starting weight of 174 kg that were randomly assigned to five treatments:
- Treatment 1 — 75 ppm of zinc from zinc sulfate fed in thermal-neutral conditions
- Treatment 2 — 75 ppm of zinc from zinc sulfate fed in cyclical heat stress conditions for six days to simulate what commonly happens in the production setting
- Treatment 3 — 75 ppm of zinc from zinc sulfate in thermal-neutral conditions, pair-fed to match the feed intake animals under cyclical heat stress conditions
- Treatments 4 and 5 — replaced 40 ppm of zinc from zinc sulfate with Availa-Zn with Treatment 4 being fed in cyclical heat stress for six days, and Treatment 5 in thermal-neutral conditions, being pair-fed to match the feed intake of animals under cyclical heat stress conditions
As anticipated, dry matter intake for heat-stressed steers was lower compared to the thermal-neutral controls. However, control animals — those supplemented with zinc sulfate — had a reduction in feed intake of 22.8% compared to a 14.9% reduction in feed intake for steers fed Availa-Zn during heat stress.
Steers under the heat stress environment had greater rectal temperatures than those in thermal-neutral conditions. However, the steers in Treatment 4 — those fed Availa-Zn in a cyclical heat stress environment — had lower rectal temperatures than steers in Treatment 2 — those fed zinc sulfate under cyclical heat stress condition — after three days of heat stress. This may indicate less inflammation occurring in the steers fed Availa-Zn after sustaining a period of heat stress.
Steers fed Availa-Zn under heat stress conditions had greater intestinal villi height and decreased villi width compared to the steers fed zinc sulfate. In fact, this response was observed in all steers fed Availa-Zn, regardless of environmental conditions. This improvement in gut morphology may be explained by the nutritional effect Availa-Zn had on reducing intestinal permeability.
Heat stress is a widespread issue that cattle producers have to manage, and it’s critical to have a plan in place prior to the onset of hot weather to prevent the long-term effects heat stress can have on an animal. Cooling systems alone may not be enough to mitigate the effect of heat stress. By incorporating performance trace minerals like Availa-Zn, animals are better able to reduce the impact of leaky gut during heat stress conditions.
To learn more about heat stress and its impact on gut health, read this Feedstuffs article written by Zinpro. To learn more about supplementing your beef cattle nutrition program with Availa-Zn, contact your Zinpro representative today.