HEAT STRESS MANAGEMENT: AN ESSENTIAL TOOL IN LIVESTOCK REARING
Dr Pushpendra Singh Rathore
Abstract
Hot environment impairs production (growth, meat and milk yield and quality, egg yield and quality) and reproductive performance, metabolic and health status, and immune response of different livestock. Heat stress is a major source of production loss in the dairy sector, meat sector and other animal husbandry practices. Implementation of scientific strategies to minimize negative effects of heat is the need of the hour. Steps such as proper cooling system, ration adjustments in the diet and changes in reproductive methodologies etc. will help in reducing the production losses and thus will help in improving the economic conditions of dairy farms.
Introduction
When the environmental temperature exceeds than the capacity of animal to lose heat, the animal body is unable to maintain the core body temperature, resulting in hyperthermia, in this humidity also plays significant role in heat stress. Though indigenous breeds of cattle are more thermo tolerant, buffaloes, crossbred and exotic breeds of cattle are highly sensitive to summer stress. In general, the most productive animals (e.g., highest growth rate or milk production) are at greatest risk of heat stress. Increase in temperatures cause severe damage to the physiology, metabolism and to the healthiness of animals.
Economic implications of heat stress
Heat stress lead to loss of productivity, reduced breeding efficiency and even loss of life in extreme cases. Thus it is imperative to manage summer stress in livestock to avoid ill health and production loss.
Factors influencing the severity of heat stress
- Type of Animal
- Breed and Body colour
- Level of production & feed consumed
- Environmental condition and cooling management
- Stage of lactation/Production
General signs in animals under heat stress
- Decreased feed intake
- Increased water intake
- Abnormal metabolic rate
- Changes in blood hormones concentrations
- Elevated heart rate, respiration rate and increased body temperature
- Decreased Production (Milk yield, Meat yield etc.)
- Laboured breathing
- Excessive salivation
- Dull skin, sunken eyeball, dehydration and death in severe cases
- https://www.pashudhanpraharee.com/heat-stress-management-in-dairy/
Adverse Effect on animals
- Impact on reproductive performance of male and female animals-
Male- Disturbed testicular thermoregulation, decreased semen volume and sperm concentration, abnormal sperm, poor semen quality, decreased fertility.
Female- Impaired physiological functions, hormonal imbalances, irregular estrous cycle, decreased sexual behavior, decreased follicular development and poor oocytes, reduced fertility and conception, diminished embryo survival and development.
- High producing dairy cows generate more metabolic heat and are more sensitive to heat stress than low producing dairy cows. Higher temperature causes reduction in milk along with decreased milk fat and milk protein percentage.
- Buffaloes are more prone to this owing to their black skin and fewer sweat glands. Reduction in milk production. Higher temperature causes reduction in milk along with decreased milk fat and milk protein percentage.
- Heat stress also affects ewe and goat milk production.
- Pigs are very sensitive to hot conditions. This is mainly due to the low sweating capacity. High temperatures reduces the piglets survivability, causes depletion in growth, carcass weight and feed intake.
- Heat stress is of major concern for the poultry industry resulting in poor growth performances (lower body weight gain and carcass yield) and high mortality rates. Egg production, egg weight, shell weight and shell thickness are considerably at loss under heat stress.
Strategies to minimize the adverse effects of Heat stress on Animals
The effects of heat stress on livestock can be minimized via adapting suitable scientific strategies comprising physical modifications of the environment, nutritional management, genetic development of breeds that are less sensitive to heat stress, advanced reproductive technologies involving hormonal treatments, timed artificial insemination and embryo transfer, which may reduce the chances of infertility in farm animals.
- Physical modification of environment
Primary means of altering the environment may be categorized into provision of shade and evaporative cooling techniques. The environmental modifications such as shade and cooling systems are critical in arid and semi-arid zones during heat stress to maintain production level of animals. The basics of providing shade are attributed to the efforts in reducing heat load from direct solar irradiation in livestock.
- Proper Summer oriented housing/Shade
Principles for creating an optimum microenvironment within and around the sheds are directed to reduce heat gain and promote heat losses from structure of animals house.
- Orientation- Shed with its long axis running East – West provides a cooler environment than one with a North-South
- Shelter design- Open type of sheds has advantage over closed type shed. Create barriers against hot wind using thatched wall or wet gunny cloth/ gunny bags. Open end of the shed should be covered with thatched bamboo or jute curtains.
- Width and Height of shelter- Slightly more shaded area than the minimum recommended floor space for different species of livestock should be provided in hot dry climate. Minimum roof height should be 10.0 feet to reduce heat load.
- Ventilation- Well ventilated shed with proper standing and resting space must be provided to dairy animals. Open end of the shed should be covered with jute or thatched bamboo or jute curtains. Asbestos or sheet roof may be also being covered with thatch or top of the roof may be painted with white and under surface with dark colour.
- Colour of roof and walls- It should be white out side and coloured inside. Reflectivity of white colour is around 75%. Thatching the roof with materials like paddy straw etc or providing a false ceiling insulation will help provide a cooler environment.
- Animal Cooling systems
The cooling systems alleviate heat load from livestock by using the principle of evaporation, combining water misting and forced ventilation through use of spray and fans. During summer stress improved cooling and proper ventilation in animal houses are still the most profitable and effective method to improve both milk production and reproduction. Different measures that can be followed are as under-
- The proper plantation should be managed in surroundings so that the environment may be cool and fresh and warm air storm could not enter directly in the shed.
- Fans/ blowers should be used to induce evaporation from the skin of animals. Fans in combination with water sprinkling facility provide the best cooling option in both hot and humid environment.
- On large commercial dairy farms various cooling devices viz. fans, wet curtain or panels, air cooler or conditioners etc. can be used during extreme hot condition.
- Use of water as cooling agent either directly on animal body or for cooling the shelter micro environment is a widely accepted practice. Water splashing, showering, sprinkling and fogging of water on animals, inside the shed 3-4 times during hottest part of the day reduces heat load and enhance productivity due to evaporative cooling. Fogging and misting systems use fine droplets of water, which are immediately dispersed into the air stream by quick evaporation and cool the surrounding environment. It has been observed that milk production and reproductive performance of dairy cattle are improved by the use of an evaporative cooling system.
- Summer stress can be managed by spraying/ sprinkling water directly on the body of animals for a smaller period at regular interval.
- Animals specially buffaloes should be wallowed in clean water ponds during extreme hot weather.
- Nutritional Management
Importance should be given for providing balanced nutrition to ensure optimum production and reproduction in animals.
- Combating the heat stress effects on the metabolism is very essential, as animals subjected to mild to severe heat stress needs to be supplemented with extra maintenance requirements. Consider increasing feeding frequency.
- Proportion of fresh green fodder should be increased whenever possible or silage or hay and fodders must be chopped before feeding. Feeding should be practiced during early morning, evening & night. Prefer grazing during early morning & late evening hours to avoid the scorching heat.
- Ration density may be increased so as to provide same nutrients at reduced dry matter intake. Diets with low-fibre and high fermentable carbohydrate are useful.
- Concentrate mixture containing more than 18% digestible protein and 70% energy contents along with palatable, digestible and laxative fodders should be offered to the animals.
- During summer energy requirements for maintenance increases leading to a decrease in the energy available for milk production so to fulfill the energy requirements, it is essential to enhance the nutrient density by feeding high quality forage, concentrates, fat supplements along with low fiber, high protein diet.
- Dietary mineral, vitamin supplementation and salts should be increased during summer as its excretion under the effect of heat stress increases. Dietary supplements of vitamins, trace elements and minerals can ameliorate the adverse effects of heat stress.
- Vitamins like B2, B6, B12 and Vitamin E have been reported as beneficial in improving body weight.
- Feeding of feed additives stabilizes the distorted rumen environment and also improves the energy utilization.
- Ensure adequate round the clock clean and fresh drinking water to animals, which should be provided under shade.
- Genetic development of heat tolerant breeds
The increased practice of selecting high milk yielding breeds has unfortunately reduced the thermoregulatory range of the dairy animals and this might have resulted in heat stress problems along with other complications like seasonal depression in fertility. So, the identification of heat-tolerant animals within the high-producing breeds can be a useful tactic provided the genetically selected animals are able to maintain high productivity and survivability when exposed to heat stress conditions. It has been reported in research that cattle with shorter hair and lighter coat color are more adapted to hot environments. Genes in animals exist for regulation of body temperature and identification and incorporation of these genes into heat sensitive breeds might be a fascinating thing.
- Advanced reproductive technologies and management
- Silent heat is a common problem in buffaloes in summers, so the identification of estrous at the right time is very essential for successful conception. Always try to follow improved heat detection protocols.
- Routine health check up of non pregnant animals with close monitoring and maintenance of accurate records.
- Provision of cooler environment at the time of artificial insemination.
- Summer infertility may be overcome through advanced reproductive technologies involving hormonal treatments (to induce a programmed recruitment of the ovulatory follicle), timed artificial insemination and embryo transfer, which may enhance the chances for establishing pregnancy in farm animals.
- Avoid breeding underweight animals.
- General health management
Proper de-worming and vaccination schedule must be followed for maintaining the health of animals.
Ecto-parasites, should be controlled properly by using suitable acaricidal spray on animals as well as in shed, especially in corners and crevices.
Conclusion
Under the ever changing climate scenario, elevated temperature and relative humidity will definitely impose heat stress on all the species of livestock and will adversely affect their productive and reproductive ability. For optimum productivity both animal feeding and environment must be considered. Management alternatives, such as the strategic use of shade, wind protection, sprinklers and ventilation in the summer, manipulation of ration energy density and intake may also be beneficial for livestock challenged by heat stress. Opportunities also exist for manipulating animal genetics to develop animals that are more resistant to heat stress.
References
- NDDB website
- Belsare, V.P. and Pandey, V, 2008. Management of heat stress in dairy cattle and buffaloes for optimum productivity. Journal of Agrometeorology (Special issue – Part 2): 365-368.
- https://onlinelibrary.wiley.com/doi/full/10.1111/jpn.13496
Corresponding Author:
Dr Pushpendra Singh Rathore
Veterinary Officer,
Animal Husbandry dept. Rajasthan
Email Id: pushpvet@gmail.com
