Heat stress is one of the most important aspects in the life of cattle as it brings serious consequences on their health, productivity and product quality. Know how it is presented and its indicators.
INTA researcher Aníbal Fernández Mayer explains that exposure to heat in cattle reduces food intake, affecting meat and milk production. In general, animals begin to feel stressed when several unfavorable parameters occur simultaneously. There are many ways to monitor heat stress today. (read: Do you know the 4 types of stress in cattle?,
There are some conditions that generate heat loss from bovine such as radiation, convection, conduction and evaporation.
when talking about rRadiation refers to the removal of heat from the skin to the environment in the form of infrared radiation., For this to happen, there must be a temperature gradient across the skin about 10–15 mm thick, higher in the skin and lower in the environment.
to understand from Convection, all you need to know is that it is due to the movement of air, while conduction is when heat moves from a hotter system to a colder system, by contact, “How heat is transmitted from the inside of the cow to the skin,” says Fernández Mayer.
in that order of thought, for Evaporation occurs when water from sweat and moisture evaporate from the outer mucous membranes, The passage of water from liquid to vapor uses heat energy from the environment, cooling a few millimeters at the level of the animal’s skin.
This is why there are few indicators of heat stress in cattle, all of which interact with each other in high temperature and humidity environments. Know something:
- Breathing Frequency: The normal rate varies from 26 to 50 breaths or gasps per minute. However, “under heat stress it can vary between 65 and 120 breaths per minute,” says Fernandez Mayer.
- rectal temperature: Normal ranges between 36.5 and 37.5 °C and can exceed 39 °C in stressful environments.
- Dry Matter Intake (DM): As Fernández Mayor points out, with high temperature and humidity, DM consumption “decreases by more than 20%, being able to exceed 50% in extreme conditions of +35 °C temperature and +70% humidity”.
- Effect on Production: In stressful environments, production losses exceed 10%, and in extreme cases can drop to more than 50% in tropical and subtropical regions. The effect of high temperature and relative humidity in these areas reduces the quality of fresh fodder.
- Effects on Fertility Indicators: As a result of thermal stress, a decrease in heat has been observed during the hours of highest temperature, as well as a higher frequency of heat during the night. (read: How long does it take dairy cattle to recover from heat stress?,
“The state of Florida (USA) observed 82%” undetected “heat in summer compared to winter. The presence of a higher percentage of nocturnal heat and the absence of another number of them due to the influence of high temperature and humidity,” says Fernandez Mayor Failure to detect heat produces, affecting reproductive and productive capacity.
In addition, a lower conception rate, a longer interval between calvings, an 8% increase in calving problems, a decrease in conception rate by more than 30%, and a lower content of fat and protein in the milk have been found.
