Effect of heat stress on cattle reproduction and its management
Anchal Rana* and V.K Gandotra
Authors Name
Dr. Anchal Rana*
(Assistant Professor, Department of Veterinary Gynaecology and Obstetrics, Khalsa College of Veterinary and Animal Sciences, Amritsar, India)
Email ID – anjlirana02@gmail.com
Dr. V.K Gandotra
(Professor and Head of the Department, Department of Veterinary Gynaecology and Obstetrics, Khalsa College of Veterinary and Animal Sciences, Amritsar, India)
Climate change is exerting substantial effects on farming practices and agricultural productivity worldwide. One of the major challenges emerging from this is heat stress, a condition that occurs when cattle are exposed to high temperatures for prolonged period. Heat stress not only causes discomfort to animals but also negatively affects their reproductive efficiency, milk production and overall health, leading to considerable economic losses for farmers.
What Is Heat Stress?
Heat stress occurs when an animal body produces or absorbs more heat than it can release. In cattle, this becomes a problem when the temperature-humidity index (THI) rises beyond safe levels i.e. 72 and 75 for cattle and buffaloes respectively. The temperature humidity index (THI) is widely used to measure the magnitude of heat stress in animals.
High-producing dairy cows are especially vulnerable because their bodies already generate a lot of heat during milk production. Heat stress causes inappetence, reduced feed intake, decreased milk production, lowered reproductive performance, increased susceptibility to diseases and reduced physical activity in cattle. In severe cases, it may even lead to death, resulting in marked financial losses for farmers.
Impact of Heat Stress on Cattle Fertility
Heat stress has a major negative impact on the reproductive performance of cattle by affecting both, the release of hormones and functioning of reproductive organs. Exposure to high environmental temperatures disrupts the hypothalamic–pituitary–gonadal axis, leading to reduced secretion of reproductive hormones such as follicle-stimulating hormone (FSH) and luteinizing hormone (LH). As a result, normal follicular development and ovulation are adversely affected. Heat-stressed cows also exhibit weak and shorter estrus signs, making heat detection difficult. Reduced mounting activity, silent ovulation and increased incidence of anestrus further decrease the chances of successful breeding and artificial insemination. Even when conception does take place, the risk of embryo death in the early days remains considerably high.
In addition, prolonged exposure to heat stress further results in an extended calving interval, increased incidence of abortion and poor fetal development within the womb. In severe cases, complications during calving may also arise, collectively contributing to significant reproductive losses.
The adverse effects of heat stress are not limited to females alone, bull fertility is also severely affected. High temperatures reduce semen quality by decreasing sperm concentration, sperm motility and total sperm output, ultimately lowering fertilization efficiency and overall reproductive performance in cattle.
How Farmers Can Protect Animals from Heat Stress
To minimize the adverse effects of heat stress, farmers should adopt effective management practices aimed at improving animal comfort and reproductive efficiency. Providing adequate shade, proper ventilation and cooling systems can help reduce heat load in animals. Animal sheds should be constructed in an east-west direction to ensure maximum shaded area throughout the day. To further reduce heat, curtains, screens or sacks should be hung on the walls and roof of the shed and water can be sprinkled on them during the day as needed. The roof should be kept at a height of approximately 12 feet and ventilators near the roof should be provided to allow hot air to escape. Exhaust fans can also be installed in the shed as an additional measure for removing hot air.
When it comes to cooling methods, fans and evaporative cooling systems such as water sprinklers, misters or foggers prove to be quite effective. Fans are especially useful at night, as the airflow they generate causes sweat to evaporate and helps the body feel cooler. Similarly, sprinkling water directly on the skin lowers body temperature through the process of evaporation. The fogging method works by dispersing tiny water droplets into the air, which cool the surrounding environment as they evaporate. Bathing animals three to four times a day or allowing them to sit in a pond are also simple, cost-effective ways to help them cope with the heat.
Regarding water and feed, animals require more water during summer and should therefore be given water four to five times a day. The water tank should be placed in a shaded area and kept stocked with clean, fresh water at all times, ensuring animals can drink from it without any difficulty. Essential elements such as potassium, sodium, manganese and bicarbonate are lost through sweat and urine and can be replenished by mixing mineral powder into the animals daily diet, which also helps improve their appetite and digestive capacity.
In terms of reproduction management, the duration of heat and the visibility of external signs tend to decrease during summer. Animals should therefore be observed three to four times daily to ensure conception occurs at the right time. Animals that fail to come into heat on their own can also be treated with dietary supplements or hormones to address the issue. Regular monitoring of reproductive performance in consultation with veterinarians help farmers to improve overall herd productivity under heat stress conditions.Top of Form
Conclusion
Heat stress is one of the most serious challenges in modern livestock farming and its impact on cattle reproduction is both wide ranging and well documented. High temperatures disrupt hormone balance, reduce egg quality, increase early embryo loss and lower conception rates, all of which directly reduce herd productivity. As global temperatures continue to rise due to climate change, managing heat stress effectively will be essential to keep dairy farming productive and sustainable in the long term..
