Management of Dairy Animals during summers

Mokshata Gupta¹ and Tanmay Mondal²

¹Assistant Professor, Department of Animal Nutrition, DUVASU, College of Veterinary Science, Mathura, U.P-281001

²Assistant Professor, Department of Veterinary Physiology and Biochemistry, College of Veterinary Science, Rampura Phul, GADVASU, Punjab-151103

India, the world’s leading milk producer, contributes approximately 26.67% to global milk output. This remarkable achievement stems from extensive dairy infrastructure, genetic improvement through crossbreeding, and improved feeding practices. However, climatic extremities, particularly summer heat stress, remain a formidable challenge in sustaining milk yield, quality, and animal health. In India, summer temperatures frequently exceed 45°C, far beyond the thermal comfort zone of 18–23°C for dairy cattle and buffaloes. Crossbred cows and high-producing buffaloes, due to their higher metabolic heat production, are especially vulnerable to heat stress.

The impact is both quantitative and qualitative. Milk production can decline by 10–30%, with significant reductions in fat, protein, and SNF content, particularly during early and mid-lactation phases. Moreover, nutritional imbalance during this period exacerbates metabolic disorders such as ruminal acidosis, ketosis, mineral deficiencies, etc.

To mitigate such adverse effects, nutritional management during summers becomes essential. Such nutritional approaches, when synchronized with housing and breeding interventions, offers a sustainable pathway to minimize climate-induced productivity losses in the Indian dairy sector.

Signs of Heat Stress in Dairy Ruminants

Heat stress in dairy ruminants leads to a cascade of physiological, metabolic, and behavioral changes. As the core body temperature rises beyond the thermoneutral zone (18–23°C), adaptive responses are triggered to enhance heat dissipation, often at the cost of productivity and health. The clinical signs are as follows:

• Polypnea and open-mouth panting.
• Excessive salivation
• Seeking shade or cooler areas.
• Increased water intake with reduced feed intake
• Standing rather than lying
• Elevated rectal temperature
• Dry mucous membranes and tacky gums
• Sunken eyes and tachycardia
• Increased incidence of silent heat and anestrus

Effect of Heat Stress on Animal Production and Reproduction

Heat stress has emerged as a major limiting factor in dairy production systems, especially in tropical and subtropical regions like India.

1. Impact on Milk Production

Thermal stress significantly suppresses milk yield and quality in dairy animals.

• Early lactation cows experience a 14% decline in milk yield, while in mid-lactation, losses can reach 35%.

• In states like Punjab, Haryana, Rajasthan, and Uttar Pradesh, where summer temperatures often exceed 44°C, milk production drops by 15-20% in crossbred cows and 10–15% in buffaloes during May and June. These losses further increase to 20-25% in cows and 20% in buffaloes during the humid months of July and August.
• Heat stress also alters milk composition, with marked reductions in milk fat, protein, casein, and solids-not-fat (SNF) content.

2. Impact on Reproduction

Heat stress negatively affects reproductive physiology and efficiency in dairy animals, with both male and female fertility being compromised.

• There is an increased incidence of anoestrus and silent heat.
• Altered luteinizing hormone (LH) and follicle-stimulating hormone (FSH) patterns, leading to delayed ovulation and poor estrus expression.
• Oocyte quality, fertilization rates, and early embryonic development are significantly affected. Sperm motility and viability also decrease under prolonged heat exposure.
• Exposure to elevated temperatures during gestation may result in intrauterine growth restriction, delayed placental development, and reduced birth weight of calves.

Overall, heat stress not only reduces conception and calving rates but also impairs long-term herd productivity by affecting the next generation of dairy animals.

Strategies to Mitigate the Harmful Effects of Heat Stress in Dairy Animals

Effective mitigation of heat stress in dairy animals requires an integrated approach combining breeding, housing, and nutritional management strategies.

1. Breeding Management: Heat stress adversely affects estrus behavior, conception rate, and semen quality, making breeding management crucial during summer.

• Reduced estrus expression under heat stress makes it difficult to detect optimal breeding time. Hence, timely heat detection protocols using activity monitors, tail chalking, or pedometers should be implemented.
• Artificial Insemination is preferred over natural mating during summer as both bulls and cows experience thermal infertility.
• Incorporating genetic selection for thermotolerance is a sustainable long-term strategy.
• Selection of animals with shorter, lighter-colored coats, loose skin, and larger sweat glands is practical for field-level farmers aiming to maintain herd productivity under rising temperatures.

2. Animal Housing Management: Proper housing design plays a key role in reducing the thermal load on dairy animals.

• Cooling systems, such as a combination of fans with water sprinklers, significantly lower the ambient temperature inside sheds.
• Buffaloes, due to their darker skin and fewer sweat glands, are more heat-sensitive and must be housed in well-ventilated sheds or provided with water pools or wallowing tanks.
• Animal shelters should be constructed along the east-west axis to minimize sun exposure. Roofs and walls should be painted white to reflect solar radiation.
• Avoid excessive sprinkling that may lead to wet bedding, predisposing animals to mastitis and hoof diseases.
• Use insulating roofing materials and install ridge ventilators to facilitate hot air escape.
• Planting trees around farm boundaries can lower the ambient temperature and improve animal comfort.

3. Nutritional Management: Nutrition plays a central role in alleviating the physiological burden of heat stress.

• Provide energy- and nutrient-dense diets to meet production demands.
• Provide Total Mixed Rations rich in bypass fats, bypass proteins, and low in fiber to reduce heat generation during digestion.
• Schedule feeding during cooler hours (early morning or late evening), and encourage night grazing if feasible.
• Supplement diets with antioxidants (Vitamin E, Vitamin C), trace minerals (Zn, Se, Cr), and immune boosters to counteract oxidative stress and maintain immune function.
• Use rumen fermentation stabilizers like live yeast cultures and ionophores to maintain rumen pH and enhance energy utilization.
• Ensure round-the-clock access to cool, clean drinking water.

Conclusion To combat the rising threat of heat stress in dairy animals, a multi-dimensional management approach is necessary. This includes modifying housing conditions, optimizing feeding practices, promoting heat-resilient genetics, etc. Among these, nutritional interventions are the most immediate and controllable tool available to farmers for minimizing heat-induced losses. With the adoption of scientifically designed strategies, dairy farmers can safeguard herd health and productivity, even during the harshest summer months.