5 Heat Stress

Transcript

Welcome! back for the Fluid therapy in cattle.

In the last class, we have seen about the calculation of the bicarbonate requirement in cattle as well as in calves and how careful we have to administer the sodium bicarbonate to the animals otherwise it will go for mortality in the case of animals.

In this class, we are going to see about Heat stress, which is an important thing because it reduces the milk yield and sometimes the death of the animal thereby reducing the economy of the farmer.

Now let us see what is Heat stress: Heat stress is a point where the animal is not able to dissipate the heat and maintain the body temperature. So what are the risk factors for Heat stress:

• one is an abnormal or sudden increase in the environmental temperature,
• the continued high temperature on a particular day,
• high temperature combined with high humidity on a particular day with low wind speed, and
• the wide difference between the day temperature as well as night temperature.

These all are important risk factors for the animal, ultimately leading to Heat stress. The situation like air temperature of 940 F, Humidity of 90%, and animal not provided with effective shade, so what happened the radiation from the sun and there is reduced conduction and convention from the animal, because of the increased environmental temperature the animal is not able to dissipate enough heat, there is reduced evaporation from the animal, all these add to the heat production, which exceeds the net heat loss from the animal, ultimately ending in Heat stress of the animal.

Now, this shows the Temperature Humidity Index(THI);

Temperature Humidity Index(THI) THI = 0.72(Cdb + Cwb) + 40.6

Where Cdb = dry bulb temperature (OC)

Cwb = wet bulb temperature (OC)

There is a formula that gives us THI is equal to 0.72 dry bulb thermometer and wet bulb thermometer. So here the thumb rule is when the THI exceeds 72, the animal is under stress. (showing the chart in the slide)That is beautifully explained by this slide, which shows the chart between the Temperature as well as the Relative Humidity and what is all there in the yellow, which shows the animal is in stress. what is in red color, that shows the animal is already in a heavily stressed condition and going to die.

Now we will see what are the direct effect of Heat stress: The direct effect is:

1. The feeds intake is reduced,
2. there are changes in the behavior and it will become restless, lies down,
3. then there is a metabolic change production loss, and
4. the immunity is going to get reduced and succumb to infection.

Buffalos are more sensitive to Heat stress and what happens is milk yield, growth, fertility, and conception are all going to be reduced because of heat stress, moreover, buffalo is in silent heat, and because of the stress by heat, the silent heat will not be exhibited there will be a prolongation of the inter estral period and that goes for the affection of the economy. This shows the indirect effects of the heat stress on the animal:

• increases severity and the distribution of livestock diseases and parasites,
• there is a spread of disease and the parasites into the new regions, and
• there is an increase in the incidence of the diseases

these are the indirect effect.

(showing pictures in the slide) Now, these photos and this slide indicates the various clinical signs noticed in the heat stress namely :

• the reduced feed intake,
• heavy salivation,
• reduced milk yield,
• open mouth breathing, and
• sometimes goes for recumbency.

you can see the animal with

1. protruded tongue,
2. rapid shallow respiration
3. Depression
4. sometimes goes for comatose and
5. imminent death

Heat stress increases

• the metabolic state
• thereby increasing the oxygen demand
• there is hypoxemia and muscular weakness in addition because of lactic accumulation and the animal becomes weak goes for recumbency
• there is a deterioration of cellular integrity
• going for Disseminated Intravascular Coagulation(DIC)
• GI integrity is lost so endotoxin is absorbed and sometimes there will be bleeding and
• cerebral and cardiac dysfunctions are noticed

Now we will see what are the strategies we can adopt for managing heat stress: very commonly we use:

1. NSAID– the non-steroidal anti-inflammatory drug we commonly use for reducing this hypothermia but none of the NSAID works effectively for the management of heat stress.
2. So what is effective? effective is Fluid therapy; as we discussed in the previous lessons calculate the fluid therapy requirement and then pump IV, thereby we can reduce the temperatures.
3. what else we can do? we can do Anema, do cool water enema two or three times, till the temperature comes down.
4. you can also go for gastric Lavage, again it is a cool gastric lavage, put into the room and lavage room and you do lavage repeatedly you do three or four times.
5. Then provide adequate drinking water to the cattle that also reduces.

But the best method is an effective physical method of cooling; by evaporation from the wet skin. (showing video in the slide) this shows how the pouring of water or rinsing the animal with water effectively cools down the temperature.

We can also do environmental modifications to reduce the heat stress, what are those :

1. we can provide shades, shade can be provided by means of providing trees. one such tree is in a Neem tree which provides adequate shade,
2. you can also increase the ventilation, how to increase the ventilation; you can provide a fan, you can give sprinklers, you can give mist, and you can spray water onto the animal.
3. it is necessary to increase the evaporative cooling by wetting the skin, so you can pour the water onto the animal
4. you can increase misting by spraying the mist onto the animal and also to the environment.
5. kindly increase the wind speed and more than 5 km/hr,
6. provide a fan or
7. you can use a sprinklers

So these are the strategies by which you can environmentally modify the heat stress. So here we are able to see a modification in the protein, fiber, supplementation of potassium, supplementation of sodium, and you can also give antioxidants; like vitamin E and Selenium to the diet. You can give adequate salts, yeasts to the animal and these various strategies effectively control the heat stress.

In this lesson we have seen Heat stress, we have seen what are the various factors that contributed to heat stress, and we have followed the strategies and methods we can control heat stress.

The take-home lesson never uses the non-steroidal anti-inflammatory drug for the management of hypothermia.

Please understand physical methods of cooling are the best method, please use cool water anema and gastric lavage.

Thank you! very much