Automated Monitoring of Heat Stress in Livestock
Dr. Ayushi Singh
MVSc Animal genetics and breeding, ICAR-NDRI, Karnal (132001)
*Corresponding Author: ayushi61404@gmail.com
Heat stress is a result of an imbalance between heat production within the body and its dissipation. Even, the scientific heat stress modelling study by Thornton et al. (2022) has also predicted decline of milk production of 25 % per tropical livestock unit in India by the end of 21st century. In the current era of climate change, proper recording of climate extreme and their effect on livestock becomes extremely important for cultivators to further ameliorate the effects of heat stress. Conventional recording techniques are manual and direct human interference driven which decreases its accessibility on daily basis. Recently developed automation for collection of temperature, animal behaviour, respiration rate has increased feasibility of effective monitoring of heat stress in animals.
On animal monitoring
Rectal and vaginal probes
Inbuilt thermal sensors such as rectal and vaginal probes enable distant monitoring of animal without affecting its production. Vaginal probe has better utility because of high correlation between vaginal and core temperature. It is very effective in measuring body temperature under grazing conditions in ewe lambs.
Rumen/reticular boluses
Rumen bolus is integrated with temperature loggers consisting of chip and sensors, which measures rumen or reticular temperature as an indicator of core temperature. Real-time data is collected through wireless transmission, and stores data when animal is near receiving antenna. Rumen temperature is an indicator of heat stress which increases with Temperature humidity index (THI).
Subcutaneous temperature sensors and implantable devices
Microchip transponders are implanted under the skin and temperature is recorded on the handheld receiver. These are commonly implanted into the peritoneum region of sheep. The wearable thermometer is attached to the leg of cattle, which gives a fair idea of rectal temperature.
Temperature sensing ear tags
Ear tags has been used to measure the tympanic temperature in ill calves. The hourly collection of temperature under thermoneutral and heat stress conditions have enabled effective monitoring of restricted feeding regime.
Accelerometer
Accelerometer tags are lighted weighted with minimal interference in animal’s natural behaviour. It is placed under lower jaw in sheep to measure grazing behaviour. It also monitors complex behaviour such as rumination, kicking and foot movements which are altered under heat stress.
Respiration Rate monitor
Increased respiration rate is a primary response under heat stress and responsible for 60 % of total body heat loss. Long term respiration rate can be automatically monitored through a differential pressure sensor installed in the halter of cow.
Off-animal sensors
Bioclimatic indices
These indices are calculated on the basics of Temperature humidity index (THI). THI above 74 is considered as an indicator of heat stress. Improved weather indices such as Heat load index (HLI) has been effectively used in cattle. Portable weather devices with Bluetooth connectivity provide prior predictability of stressful conditions.
Depth Imaging, Video Surveillance, and Artificial Intelligence
Depth imaging provides better resolution under different environmental conditions with high accuracy. Video surveillance helps in monitoring of the physiological and behavioural changes of cattle exposed to heat stress. Artificial intelligence tools such as artificial neural network, fuzzy logic and machine learning based techniques are found to be helpful in observation of animal behaviour under stressful environment.
Infrared thermography
Infrared images based on heat emitted by the body provides a fair idea about animal under heat stress. Thermographic images can be used to indicate increased body temperature and changes in blood circulation under stressful conditions.
Limitations and Future Prospective
Automated monitoring of heat stress using advanced technologies lead to increased cost of farm management especially for small farmers. Even the implantation of certain temperature sensors requires expertise. The ear tags and respiration rate halters need to be properly installed in order to avoid being misplaced during the motion of animal. Despite all the limitations, automated technologies for detection of heat stress offers an edge in farm management under the current and future climate change. Customisation as per species, farm size and weather conditions will ultimately increase the utility of automated heat stress detection technologies.
Reference
Thornton, P., Nelson, G., Mayberry, D., & Herrero, M. (2022). Impacts of heat stress on global cattle production during the 21st century: A modelling study. The Lancet Planetary Health, 6(3), e192–e201. https://doi.org/10.1016/S2542-5196(22)00002-X
