MANAGEMENT OF HEAT STRESS DURING SUMMER IN DAIRY ANIMALS

Heat stress is a major problem faced by dairy animals during summer months which leads to decreased milk production and lower rates of fertility. This post explaines about managements of heat stress, and Strategies to reduce the negative effects of heat stress on dairy cattle

Susceptible animals:-—-

Though indigenous breeds of cattle are more thermo-tolerant, crossbred and exotic breeds of cattle are highly sensitive to heat stress. Buffaloes are more prone to this owing to their black skin that absorbs more solar radiations and fewer sweat glands (only 1/6th that of cattle), compromising heat dissipation through evaporative heat loss.

Signs of heat Stress—-

Common symptoms of heat-stressed animal include

• Animal moves to shade

• Water intake enhanced while feed intake reduced

• Prefers standing than lying down

• Increased respiration rate, body temperature

• Increased production of saliva

Open-mouth panting

· Rapid and weak pulse

· Rapid but shallow breathing

· Abnormal vital parameters: Elevated heart rate, respiration rate, rectal temperature etc.

· Unusual salivation

· Dizziness / unconsciousness

· Skin becomes dull and may be cold too

· In case of heat stroke, body temperature is very high– sometimes as high as 106 – 108°F.

Causes for Heat Stress——

Heat stress occurs when any combination of environmental conditions cause the effective temperature of the environment to be higher than the animal’s thermo neutral (comfort) zone. Four environmental factors influence effective temperature:

• Atmospheric temperature

• Relative humidity

• Air movement

• Solar radiation

Strategies to reduce the negative effects of heat stress—–

Breeding Management—-

As cows exhibit lesser heat symptoms during heat stress zones as compared to thermal comfort periods, it is necessary to adopt a good heat detection program to detect cows with marginal heat symptoms. It is always advisable to continue AI breeding instead of using bulls because in natural breeding both bull and cows suffers infertility due to summer stress. Genetic selection of heat tolerant animals and inclusion of heat tolerance as a trait in selection programme will be a boon to the farms.

Cooling systems in the farm—

Fans in combination with water sprinkling facility provide the best cooling option. Excessive sprinkling should never be practised as it can result into wet bedding making animal prone to mastitis and other diseases. The farm should be well ventilated.

Feeding Management—-

Heat stressed animals are more likely to have lower reproductive and productive performance. Feeding high quality forages and balanced rations will decrease some of the effects of heat stress and will boost performance of the animals. Some nutritional management tips to manage heat stress are:

• Provide high quality feeds like total mixed rations

• Increase the frequency of feedings

• Feed during cooler times of the day

• Keep feed fresh as much as possible

• Provide high-quality forage

• Provide adequate fibre

• Use of by–pass proteins can enhance the milk yield and protein content.

• Intake of sufficient cool water is probably the most important strategy for animals to undertake during heat stress.

Providing natural or artificial shade area——

Plantation around the farm will help in alleviating heat load from the animals. But, in today’s commercial dairy industry, it is not always practicable. Therefore, provision of artificial shade area by shade cloth or a naturally well ventilated structure with open sidewalls can keep the animals away from direct solar radiation.

Selection of heat tolerant animals—–

Genetic Selection of animals based on specific molecular genetic markers for heat tolerance will definitely be a boon to alleviate heat stress in cattle and buffaloes by identifying the heat tolerant animals.

Strategies to minimize the effect of heat stress——

The following factors are important in managing thermal stress

· Ensure that the animals are kept under shades. The most effective source of shade is trees. If shade trees are not available, thatched roof of a minimum height of 9 feet should be provided. Agri-nets with 20% perforation are also useful. If facilities are not available with the individual farmers, facilities available at the village shall be used by the community.

· Thatching the roof with materials like paddy straw etc, painting the roof with white paint or, providing a false ceiling insulation will help provide a cooler environment.

· Create barriers against hot wind using thatched wall or wet gunny cloth/ gunny bags.

· Ensure one ventilator of 3 x 1 feet per cow in covered shed. In these sheds heavy duty fan is best option to facilitate ventilation.

· Misting/Fogging of water in the microenvironment of the animal at least thrice in an hour along with provision of fan is useful in hot dry weather. Auto Mister/ Fugger with mini pumps and cyclic timers are preferable.

· Heat stress can also be managed by spraying/ sprinkling water directly on the body of animalsfor a period of 1 to 5 minutes at an interval of 10- 30 minutes. Fans/ blowers should be used to induce evaporation from the skin of animals. With a provision of fan this method can work both in hot dry and hot humid condition.

· The most effective way of combating heat stress in buffalo is wallowing in the water pond.

Ensure adequate round the clock drinking water to animals, which should be provided under shade.

· 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 have lower dietary heat increment compared to high fibre diets.

Feeding High-Energy Diets:—-

Low-fibre, high fermentable carbohydrate diets lower dietary heat increment compared to high fiber diets. Although the metabolic energy of dairy buffaloes increases in a hot environment, heat stress depresses feed intake. For this reason, it is important to increase the energy content of the diet of dairy buffaloes, in order to maintain their energy intake under hot conditions. The heat increment, which is an internal heat stressor in hot environments, is lower in highly metabolizable diets. So it is imperative to use fatty feeds, or calcium salts of fatty acids, as the means of improving energy supply for buffaloes in summer. Buffaloes fed on such diets have higher milk yield, and a lower body temperature and respiration rate.

Feeding by-Pass Protein:—–

Dietary protein degradability is also critical under heat stress conditions. It is well known that excessive protein intake increases heat production and decreases reproductive performance. However, the protein requirement of buffalo increases and dry matter intake decreases in a hot environment, consequently, the protein supplied to lactating buffaloes during summer is not always sufficient. By using fish meal, which is a by-pass protein, the milk yield and protein content of buffalo milk increases but the ruminal ammonia production decreases.

. Increase ration potassium.—

Potassium is the main mineral in sweat and as temperatures rise, cows lose more potassium through sweating, panting and urination. Beyond the potassium lost during normal milk production, this nutrient becomes even more critical in hot weather. Ensure your herd receives a high-quality potassium source that is protected from overheating to raise potassium levels to 1.7% of ration dry matter and ration DCAD to +35 to +45 meq/100g ration dry matter and maintain DMI, while meeting increasing nutrient demands.

· Ensure increased mineral supplementation during hot weather to meet the increased demand of minerals. Potassium rich mineral mixture should be preferred.

Most of the below mentioned strategies should be considered during planning and construction phase itself.

• Cattle Shed Design

The shed height should be 15 feet height at the center and 10 feet height at the sides. The longer side of the shed should be from east to west direction. This reduces direct sunlight into the shed.

• Painting the roof white

The outer roof should be painted white using supercem which will reflect sunlight and reduce temperature inside the shed. This is a cheap and effective solution to reduce temperature.

• Planting Trees

Planting trees around the shed will provide shade and protects from direct sunlight. This is a very cheap solution but takes time to produce results.

• Installing Fans

Depending on the design of the shed, either a ceiling fan or an oscilating fan can be installed. An high power wall mounted oscillating fan like Almonard is more effective than ceiling fan.

• Sprinklers and Foggers

Sprinklers are installed on the roof to sprinkle water and foggers/misters are installed inside the shed to produce fine drops of water. I have written a detailed article on sprinklers and foggers, click here to read further. This is not a very a economical solution but can be very effective in reducing temperature.

• Misting Rings

These are rings made of 3/4″ pipe which has misting nozzles. This misting ring has to be attached to an oscillating fan and connected to the direct motor water pipeline. This creates good cooling effect inside the shed and is cheaper than fogging system.

• Washing animals in the afternoon.

Washing animals in the afternoon in addition to morning and evening cycle is effective.

• Fixing Gunny Curtains

You can use the empty dhana gunny bags to stich a curtain which can be hanged on the sides of the shed. These will stop direct sunlight to the shed. And also if you spray water on to these gunny curtains while washing animals, they will produce cooling effect.

MANAGING HEAT STRESS TIPS IN THE DAIRY SHED —

Managing heat stress of dairy animals is a great challenge for dairy farmers. Lot of production is lost due to low feed intake of lactating cows and buffaloes during hot and humid climatic conditions. Below mentioned are few tips to manage summer stress of dairy cattle:-

1. Avoid animals from direct sunlight.

2. Washing animals twice or thrice is a good practice.

3. Try feeding animals early in the morning and late in the evening when temperature is relatively low. It will result is greater feed intake and hence more productivity.

4. Exotic cows like HF may require additional etectrolytes and vitamins. Also, good results are obtained when herbal antistress formulations like RESTOBAL and PHYTOCOOL are administered.

5. Animals should have free access to fresh drinking water.

6. In case of fever/pyrexia which is unresponsive to antibiotics and antiprotozoal drugs, administer ice pack and start fluid therapy immediately. Consult your vet for symptoms of heat stroke and HIS (Heat Intolerance syndrome).

7. Heat intolerance syndrome is a metabolic disorter characterized by sudden rise in body temperature of a cow during summer months. The temperature rises along with environmental temperature for e.g. 102 at 10 o clock, 103 at 12 o clock, 104 at 1 o clock, 105 at 2 o clock, 104 at 5 o clock. It is more common in HF cows. In such cases administration of Iodine injections is helpful as Thermoregulatory functioning of thyroid gland is checked.

8. Control over ectoparasites during this season is very important as they are carriers of various diseases like Anaplasmosis, Red – Water disease, Tick fever, Trypanasomasis, Theleria etc

Treatment:-–

Immediate veterinary aid should be provided to the suffering animal. In the meantime, the animal shall be moved to a cooler place, given bath with cold water or wrapped in wet sheets and provided with fan.

Conclusion—

In hot-humid climates, although dairy animal attempts to acclimatize through physiological changes including cutting down on feed intake and heat production, this does not come without sacrificing part of its productivity. In order to prevent this economic loss to the farmer, there is need to understand and effectively combat heat stress by minimizing its impact on the animal body and its productivity.

Reference-on request