Heat stress is known to significantly affect lactating dairy cows. When the Temperature-Humidity Index (THI) exceeds 68, cows start to experience discomfort and stress, leading to a reduction in milk production. However, it is not just the lactating cows that are impacted; other animals in the herd can suffer from heat stress as well.
Recent studies have shown that heat stress also affects calves that are in the uterus of pregnant cows. Calves born from heat-stressed cows are typically smaller at birth and have reduced weaning weights. These calves absorb less immunoglobulins (IgG) from colostrum, which makes them more susceptible to diseases and infections.
When comparing the offspring of heat-stressed cows to those of cows that were cooled during the last six weeks of gestation, researchers found significant differences. Calves from heat-stressed mothers produced less milk during their first, second, and third lactations. This reduction in milk production not only affects the immediate generation but has long-term implications for the herd. Most surprisingly, the granddaughters of heat-stressed cows also produced less milk than those from cooled grandmothers. This indicates that the effects of heat stress can transcend generations, impacting overall herd productivity and profitability.
To mitigate these adverse effects, it is crucial to implement cooling strategies for your dry cows during the summer months. Cooling systems such as fans, sprinklers, and shaded areas can help reduce the temperature and alleviate the stress on pregnant cows. Ensuring that cows have access to plenty of clean, cool water is also essential. By taking these steps, you can protect the future milk production potential of your herd, ensuring healthier cows and higher yields for years to come.
Don’t wait until the heat becomes unbearable—start preparing now to keep your cows cool and comfortable throughout the summer. Your cows’ health and productivity depend on it, and so does the profitability of your dairy operation.
Laporta, J., et al. “Late-gestation heat stress impairs daughter and granddaughter lifetime performance.” Journal of dairy science 103.8 (2020): 7555-7568.
Dado-Senn, Bethany, et al. “Early-life heat stress exposure impacts dairy calf feeding and thermoregulatory behavior.” JDS communications 3.1 (2022): 38-43.
Dado-Senn, B., et al. “Methods for assessing heat stress in preweaned dairy calves exposed to chronic heat stress or continuous cooling.” Journal of dairy science 103.9 (2020): 8587-8600.
Ouellet, V., J. Laporta, and G. E. Dahl. “Late gestation heat stress in dairy cows: Effects on dam and daughter.” Theriogenology 150 (2020): 471-479.
