Climbing temperatures may be inevitable this time of year, but dairy cow productivity doesn’t have to be a casualty of heat stress. The key to success is minimizing decreases in dry matter intake and keeping rumens – and your herd – operating at peak efficiency.
“Reduced intake can lead to digestive upsets and lowered milk and milk component production,” says Tony Hall, Technical Services – Ruminant, with Lallemand Animal Nutrition. “But investing in heat abatement technology and in your herds’ ration – from dry cows to lactating cows – is crucial. Focusing on quality forages and feedstuffs, plus management changes will help diminish the negative influence heats stress has on feed intakes, your herd and your bottom line.”
As you prepare for the upcoming heat stress season, consider these four factors to overcome its effects and rev up your cows’ rations:
- Focus on rumen function
Heat stress in dairy cows is a function of heat and humidity, along with increased body heat generated during dietary fermentation and digestion. When cows are exposed to heat stress, they often experience a reduction in the diversity of the rumen microbes, leading to digestive disruption.
In short, intakes drop, rumen pH is affected, rumen microbes do not operate at peak efficiency, rumination time decreases and fiber digestion suffers. As do milk production, milk component production and feed efficiency.
“When these rumen changes occur, they result in a reduction and inefficiency of fiber digestion,” says Hall. “This causes perfectly formulated rations to not work as hard as they could or should.”
A study from Penn State University revealed a clear correlation between environmental heat stress levels, rumination time and milk production. With each 10-point increase in the Temperature Humidity Index (THI), daily rumination could be reduced by one hour and milk production by 6 pounds.
For a 1,000-cow herd, that’s 6,000 pounds of milk a day or $930 if milk is $15.50 per hundredweight.
2. Invest in ration performance
There’s a simple, economically attractive solution to overcome these losses and maintain profitability during heat stress. Live yeast probiotics, such as S. cerevisiae CNCM I-1077, help drive rumen function and milk component production during times of heat stress for a return on investment of 5:1 or greater.
Research published in the January 2020 Journal of Dairy Science reinforces the ability of live yeast to drive rumen function and keep it operating at peak performance. Results showed lactating cows supplemented with S. cerevisiae CNCM I-1077 under severe heat stress conditions demonstrated:
- 7.6% higher feed efficiency
- 5.7% increase in energy-corrected milk yield
In fact, more than 20 years of extensive research demonstrates cows exposed to heat stress show improvement in rumination activity, fiber degradation and manure consistency when supplemented with S. cerevisiae CNCM I-1077.,,
Plus, data shows ration inclusion of live yeasts such as S. cerevisiae CNCM I-1077 could result in a return on investment of $0.54/head/day based on milk component improvement alone. A 1,000-cow herd would gain $540/day.
3. Feed high-quality aerobically stable forages
Forage quality is always important, but seldom more so than during periods of heat stress. Aerobically unstable silage can cause the entire ration to heat, leading to lowered intakes and reversing the work you’ve done to optimize rumen function. Additionally, aerobic instability is a sure sign of nutrient loss, as well as an indicator of spoilage, molds and toxins.
“The negative effects of heat-stressed dairy cows offered a hot and aerobically unstable TMR is a disastrous combination,” cautions Hall.
Keeping cows eating can be very expensive to “fix” once these feedstuffs are in the feed bunk. These types of products, such as acids, TMR stabilizers and mycotoxin binders can be costly ration additions, adding as much as $0.15 per cow per day to your feed costs.
Instead, focus on providing lactating cows with the highest quality, most digestible forages and strive to maximize the inclusion of forage neutral detergent fiber (NDF) within the appetite limit of each pen.
Remember the basics
Lastly, don’t forget about these basic heat stress mitigation tips. In addition to normal heat abatement strategies, these nutrition-focused management tips help protect feed consumption and rumen efficiency:
- Provide adequate water
- Alter feeding times to counteract higher temperatures
- Push-up feed frequently
- Prevent sorting
“Cows can continue to perform very well during the summer, despite the complications of heat stress,” concludes Hall. “Paying attention to details, reducing feeding disruptions and investing in effective nutrition solutions pay dividends in ration and cow productivity, even in the face of challenging conditions.”
Help your cows power through heat stress with rations formulated to help protect them against expensive inefficiencies.
Provided by Lallemand Animal Nutrition