Summer Stress Management in Livestock
Yashovardhan Misra
B.V.Sc. and A.H. Scholar (IInd Year), College of Veterinary Sciences and Animal Husbandry (DUVASU), Mathura
Abstract
This article discusses the various aspects of heat stress management that are essential for the optimum performance and production of livestock during the summer seasons in India. Heat stress is one of the most colossal reasons for the downfall in production of dairy products and low breeding efficiencies of livestock during summers in India.
Ref. Words: Heat Stress, Thermoregulation, Humidity, Metabolism, Milk production, Reproductive efficiency, Management
https://www.pashudhanpraharee.com/summer-stress-management-of-livestock/
India is a tropical country, with humongous variations in temperature ranging from 48°C in summers to 0°C in winters. Being the highest producer and consumer of dairy products with over 300 million bovines, there is an enormous task to manage the livestock during various seasons and yield optimum results from them. Heat stress leads to tremendous loss in quantity of production (around 50%) along with its quality. Milk fat % and SNF% seem to be affected along with breeding efficiencies of dairy animals.
When in their comfort or thermo neutral zone, livestock perform at their peak levels. But as soon as the temperature crosses its upper or lower limits, these animals switch on their temperature regulation mechanism for survival. The upper critical temperature for lactating cows is in the range of 24°C to 27°C. At temperatures above UCT, subcutaneous blood supply increases with animal panting and sweating for evaporative cooling. This leads to wastage of production energy of cattle. Each gram of evaporated sweat utilises about 580 calories of energy which can be channelized into production. Also, cattle consume less feed and water in order to lower down the rumen fermentation activity and decrease heat production. High-yielding cows generate more heat than dry cows, irrespective of ambient temperatures. A cow yielding about 18 litres per day will generate almost 28% more body heat than a dry cow.
High air temperature, humidity, solar radiation and low air movement contribute to increased risk of thermal stress among livestock. The most common index of heat stress called THI OR Temperature humidity index is calculated from temperature and relative humidity. THI above 72 adversely affects dairy animals. High relative humidity decreases evaporation and reduces the cow’s ability to lose heat by sweating and breathing. This leads to failure of thermoregulatory mechanism of the animal and might lead to hyperthermia. If animals are exposed to successive heat stresses, it can cause hyperthermia or even loss of lives.
LIVESTOCK BREEDS AND THERMAL TOLERANCE
Indigenous or zebu cattle are better adapted to these environments and are much more thermo-tolerant than exotic and cross bred cattle. These cattle have greater sweating rates due to higher density and larger perimeter of sweat glands. Their metabolic heat gets quickly transferred to the skin because the tissue and hair coat have a lower resistance to heat loss. Currently, around 9-11% cattle responsible for milk production are crossbred and their management is a mammoth task. Exotic and crossbreeds begin to reduce their feed intake when air temperature is greater than about 21°C, and relative humidity is greater than 70%. This reduces the production of milk. Jerseys are more tolerant to heat than pure exotic with production losses insignificant until 25°C. Buffaloes which contribute about 35% of the country’s milk produce are much more prone to thermal stresses due to their black body colour and lack of sweat glands, resulting in higher absorption of solar radiations.
It has been observed that heat-stressed late gestation cows have shorter gestation periods, calves with lower birth weights, reduced milk production and impaired immune function. Also, heifer calves from heat-stressed cows produce less milk for the first 30 weeks of lactation after freshening. Heat stress results in decreased growth rate, average daily gain and feed intake, oestrus frequency, oestrus duration, calving rate and increased inseminations per conception. So proper management of pregnant livestock is essential.
SIGNS OF HEAT STRESS IN LIVESTOCK
- Rapid breathing and pulse
- Panting and sweating
- Increased rectal temperature
- Unusual Salivation
- Increased water intake and decreased feed intake (NRC predicts that the DMI for a 600 kg cow producing 40 kg milk will decline from 18.7 kg at 200C to 16.7 kg at 350C) (9%).
- Decrease milk production with change in milk composition, e.g. fat % and protein %
- Dizziness and unconsciousness
- Changed behaviour- finding shade, near to water bodies
- Changed metabolic rates of body
If diagnosed at an early stage, the deteriorative effects of heat stress on the livestock can be minimised. Here is a list of certain points that should be taken in consideration while raising a herd in a tropical country like India-
HOUSING
- Open type sheds should be preferred over closed sheds as mean temperature is significantly lower inside the open type sheds.
- Best type of animal shelter has 10-12 mm Hg humidity with 15-25°C temperature.
- Ensure sufficient standing area along with shaded resting areas of about 30-40 square feet per animal.
- Height of the roof should not be less than 10 feet to decrease the heat load.
- In the areas of hot climates “A” shaped roof should be preferred over flat roof.
- Asbestos sheets and false ceiling are a good option for roof construction in order to provide thermal insulation. Traditional materials like hay, straw and wood can also be used.
- Proper ventilation with 2-3 open walls. Poor ventilation can lead to high humidity. Walls and roofs should be painted light outside and coloured inside.
- For protection against hot winds, wet gunny cloths or gunny bags should be installed at openings.
- Provision of cooled potable drinking water should be made by using earthen pitchers. Try to provide at least two waterers for a group of animals.
- The surrounding of shed should be covered with green shady trees as it significantly cools down the environment.
- The long axis of shed should be chosen running east to west direction to avoid exposure to solar radiations.
- Well ventilated sheds with good air flow and timely water forging. Increasing airflow over a cow has a dramatic effect on evaporative heat loss from the skin. The results of research from the USA suggest that airflows as low as 10 km/hour can reduce respiration rates in heat stressed animals by as much as 50%.
COOLING AND WATERING SYSTEM
- Water as a cooling agent is used for spraying roofs, walls and floors to regulate temperature.
- For managing the heat stress, livestock should be sprayed/ sprinkled with water directly on the body for period of 2-4 minutes several times daily to enhance heat loss by evaporative cooling.
- Wallowing arrangements should be provided in the farm to neutralise the heat, especially for buffaloes.
- Fans, air coolers and wet curtains should be provided to help livestock to breathe easily, especially in large dairy farms.
- Water fogging should be done various times a day in microenvironment of livestock to regulate the temperature of the shed.
- Animal cooling systems are very essential parts of management of exotic and cross bred cattle to get optimum results.
- It has been found that cattle residing in cooled sheds have greater breeding efficiency and increased milk production.
FEEDING AND WATERING
- Feeding frequency, nutrient concentration, time of feeding and water requirements should be kept in mind while preparing ration.
- Livestock should be allowed to graze only during early mornings or evenings to avoid heat.
- Feeding routines should be changed with maximum feeds given when sun is absent i.e. night feeding for about 55-60% of ration.
- Ration balance should be modified for optimum results during the summer heats. High fibre diets should be reduced to lower the production of heat of fermentation from rumen.
- Increase the concentrates (soaked in water) in diet along with high quality forages only, for maintenance of all the nutrients in adequate amount in diet.
- Vitamins and minerals supplementation should be used as excretory loss of these increases.
- Feeding buffers such as sodium bicarbonate and magnesium oxide can increase milk yield.
- Avoid overfeeding of feed especially proteins and fats as it produces heat.
- In hot weather, water intakes can increase by 10 – 20% so ensure round the clock clean drinking water.
- Diets should be balanced properly in order to avoid digestive disorders such as acidosis and displaced abomasum.
GENERAL MANAGEMENTAL POINTS
- Selection of heat tolerant animals based on specific molecular genetic markers for heat tolerance will definitely be a boon to alleviate heat stress in cattle and buffaloes.
- Isolate cows most severely affected by heat stress and provide shade and cooling. Suffering animal should be wrapped in wet sheets and provided with cooling fans and drinking water.
- Milk earlier in the morning and later in the afternoon, or consider once-a-day milking.
- Try to minimise handling stress.
- During application of water to livestock around the bedded area, do check for the dryness of the beds as it may lead to mastitis and other infections.
- Vaccination, deworming should be done and ectoparasites infestation should be controlled
- Immediate veterinary assistance should be provided to suffering animals.
- Light and energy rich feed which is palatable, digestible, laxative and properly mixed with right balance of nutrients should be provided.
CONCLUSION
Heat stress management is very crucial for optimum performance of livestock by providing a cool environment and a well-balanced light feed with right production techniques. Using the above methods in your dairy farms will certainly lead to a significant boost in milk production and breeding efficiencies. Good veterinary health assistance, along with animal selection techniques will help the herd to reach their performance pinnacle.
https://www.nadis.org.uk/disease-a-z/cattle/managing-heat-stress-in-dairy-cows/
