With summer comes risk of extreme high-heat events, which can negatively affect animal welfare and productivity — especially in feedyards. Researchers at Colorado State University, Kansas State University and Certified Angus Beef collaborated on a study, funded by the Angus Foundation, into stakeholder perceptions and adoption of current heat-mitigation strategies. Key research findings shine light on industry progress and need for continued work.

“When we think about heat stress, one thing that is missing in the knowledge, research and statistics space is understanding how producers are implementing heat stress mitigation strategies,” says Lily Edwards-Callaway, associate professor at Colorado State University. “There’s very little understanding of that and perceptions of how effective certain heat stress strategies are and how heat stress impacts welfare, health or performance.”

By surveying feedyard operators, veterinarians and nutritionists, the study aimed to understand heat-mitigation strategies currently in use and perceptions, frequency of extreme heat events, and industry needs. A majority of the 56 respondents agreed that heat stress negatively affects cattle health, performance and welfare.

Animals are most comfortable in the thermoneutral zone, the “sweet spot,” says A.J. Tarpoff, associate professor and beef Extension veterinarian at Kansas State University. In that zone, cattle can expend the least energy needed to maintain that comfort level. Outside the zone, animals feel stress on their system. That stress causes physiological and behavioral changes, like cooling themselves down, to meet basic needs.

Adapting to the environment comes at the expense of energy, among other things.

“Whenever we have animals expending more energy to stay comfortable, there’s less energy actually being deposited into the carcass,” Tarpoff says. “So how do some of these situations outside of thermoneutral impact carcass quality? It may take longer days on feed, or potentially impact marbling when that animal hits harvest.”

Heat-mitigation strategies are actively used in feedyards. The following respondents noted use of at least one heat-mitigation strategy:

• 72.7% (16) operators;
• 88.5% (23) veterinarians; and
• 100% (8) nutritionists.

Methods used include changing feed delivery time and feed composition, utilizing sprinklers and/or changing processing and handling times.

In terms of which strategy is most effective, “changing processing and shipping hours” ranked at the top, with 75% of respondents marking “strongly agree” on its effectiveness.

“Generally, heat-mitigation strategies include adding something to the environment, like shade, bedding or extra water, or changing certain management procedures, like adjusting feed delivery or animal handling events,” Edwards-Callaway says. “I think there’s opportunity in that space to explore further handling changes.”

Respondents perceive pen infrastructure (shade, fans) and water/feed management as important considerations. Although most veterinarians and nutritionists surveyed recommend having a written protocol for heat stress mitigation strategies, very few of the responding operators had a written plan in place.

While actual head counts vary greatly, 75% of respondents indicated having experienced some level of death loss due to heat stress events.

Factors of heat stress

• Temperature

• Humidity

• Wind speed

• Solar radiation (cloud cover)

• Cumulative heat load

• Cattle accumulate heat during day

• Animal’s ability to dissipate heat at night

Heat-mitigation strategies

Written protocols recommended

Implement written protocols from a veterinarian and nutritionist for heat stress mitigation. Protocols should include various strategies (e.g., changing processing procedures) with details on when to use the strategy, who is responsible and steps to take. Year-round strategies, like permanent shade structures, may not need to be included. Feedyards should consider prioritizing formalized, written protocols for inclusion in employee training programs.

Adjusting feed

Modify feeding processes before, during and after an extreme heat event. Feed delivery could be moving to evening hours, when temperatures have dropped and heat dissipation is occurring. This also shifts the animal’s maximum internal heat load that is experienced from feed rumination. When feed is delivered in the morning, maximum heat of fermentation occurs in the afternoon during the day’s hottest hours (increasing the heat stress load on an animal). When feed is delivered in the evening, maximum heat of fermentation occurs at night when temperatures have hopefully dropped and nighttime cooling is occurring (decreasing the heat stress on an animal).

Water

Use large droplet sprinklers in overnight hours for pen floor cooling. This improves feed conversion, reduces panting scores, and reduces pen floor temperatures. Increase water-tank availability for cattle consumption as water demands increase. This lowers body temperature, decreases respiration rate and helps maintain feed intake.

Environment modifications

Incorporating shade into feedyard design can substantially reduce heat load, improving cattle performance and reducing mortality rates. Feedyard operators should consider shadow, location of shade, orientation of shade structure and material used.