Solutions to overcome heat stress in dairy herd

In the first we can talk about the concept of stress, it is a counteract for any threatening condition , we can also observe imbalance in hormones such as catecholamines and adrenaline.

If we talk about heat stress , it is an imbalance in the heat equilibrium where the equation of heat gain and heat loss is not achieved , simply the cow gain heat mainly from digestion , milk production and from external environment

and loss heat mainly by respiration and evaporation.

So if we have to take in consideration that Temp. should be from -4 to 21 and humidity should be about 50% and there is an index called THI ( Temperature Humidity Index ) considered as

>70% is of no stress

from 70-80 of mild stress

from 80-90 of sever heat stress

we have also to take in consideration the speed of wind and the amount of sun exposure

So Heat stress is of accumulated effect so the new trend is going to measure accumulated heat load unit and heat load index

Signs of heat stress

Increase respiratory rate

increase sweating

Decrease in dry matter intake

physiology of heat stressed cow

Firstly the animal try to go for metabolic adaptation So decreasing rate of digestion and increasing respiratory rate so lose high amount of CO2 and the kidney try to maintain the ratio between CO2 and bicarbonate which is about 1: 20 so try to lose more bicarbonate in urine which lead us to Acidosis so decrease the quality and the amount of saliva which is a main puffer

another point is the circulatory disturbance as the blood go to the periphery for cooling

another syndrome which is leaky gut as the heat stressed cow suffer lose of intestinal integrity which lead to escape of endo toxin ( LPS ) and initiate immune response specially neutrophils which is glucose consuming and the dry matter intake is actually low so increasing stress on the animal and it may end up by protein utilization

If we talk about solutions it is not one solution , We have to look on a different aspect specially managemental aspect and nutritional aspect

Decreasing stocking density

Using efficient cooling system as water sprinkler

high quality water supply

controlling shade direction

from the nutritional aspect we can supply the animal with glutathione as an anti oxidant , we have also to supply it by glucose precursor as propionate and decreasing the amount of degradable proteins to decrease heat gain

Vitamin B supplementation is very important.