Summer is just around the corner and with it, heat stress. According to a 2019 Foundation for Food and Agriculture Research study, the US dairy industry experiences $1.5 billion in losses annually to heat stress. Higher temperatures can affect herds, and in turn, can decrease performance, production, and profit.

However, heat stress impacts more than just the milking herd. Between calves, dry cows, and milking cows, dairy producers should implement a whole-herd heat stress solution to limit those impacts.

Calves, like cows, are susceptible to heat stress at higher temperatures, which can have a negative impact on both health and performance. High humidity can cause calf respiration rates to increase, potentially leading to dehydration, reduced feed intake, weaker immune system, calf scours, and other impactful issues. One of the first signs of heat stress in calves is dehydration. Calves may double their amount of water intake to combat heat and stay hydrated. Be sure to keep cool, clean water available to them constantly.

When it comes to housing and ventilation, shade, cleanliness, and airflow, these should all be a priority. If calves are in hutches, the hutches should face toward the East with all vents open during the summer months. You should consider elevated hutches, to improve air movement. Increasing ventilation in heifer barns can also be beneficial. It’s important to keep airflow moving. Whether it’s adding more fans or using a positive pressure tube ventilation system, calves need to be kept cool.

The impact of heat stress on milking herds is well-known, but the impact on dry cows – those in the last two months of pregnancy – is less understood. One of the most important things to know is the impact of heat stress doubles with dry cows. It can also affect the calf in utero. When a dry cow experiences heat stress, the body temperature of the unborn calf increases. This alters the calf’s metabolism and gene expression, which can lead to smaller calves being born, along with affecting the calf’s health and performance well beyond birth. To minimize the threat of heat stress, cool your cows with proper shade, water, and airflow. Cooling your dry cow and their fetal calf can lead to a positive impact on production. Research from the University of Florida demonstrated that cows cooled during the dry period:

• Produced 8-14 pounds more milk per day over approximately 280 days
• Maintained better body weight, likely allowing for better performance post-calving

In addition, calves born to cooled dry cows were heavier, healthier, and performed better when they started their first lactation.

When it comes to lactating cows, heat stress has the greatest short-term impact. Use a two-fold approach to help cows survive and potentially thrive during the heat and humidity of summer.

One strategy is to use mechanical cooling by providing fans and soakers in areas where cows congregate. This process should be implemented based on the following priority hierarchy:

• Holding area;
• All dry/pre-fresh animals;
• Fresh cows; and
• Lactating pens, high-to low.

Another strategy is to cool cows internally. Higher temperatures can negatively affect milk production and milk fat yield, due in large part to heat stress-induced pH decreases in the rumen and leaky gut. Although it is vital to provide proper heat abatement strategies, there are also feeding strategies that may assist in decreasing performance lost. By incorporating an immune support feed additive, you could help promote gut health, immune strength, and overall wellness. Healthy cows perform better, and a healthy gut can help cows manage the heat. Ultimately, this can result in greater profitability on the farm.

Summer is fast approaching, which means dairy cows will soon be feeling the heat. Heat stress can have a devastating impact on your animals, and not just those lactating. Between calves, dry cows, and milking cows, implement a whole-herd process for reducing the impact of heat stress, helping your herd stay happy, healthy, and productive.