HEAT STRESS INDEX FOR CATTLE AND BUFFALOES AS A GUIDELINE FOR DAIRY FARMING IN TROPICAL CLIMATE
Pramod Kumar
Department of Veterinary Physiology & Biochemisry, C.V.Sc. & A.H., NDUAT, Kumarganj-224229, Ayodhya, UP
Email- pihu012013@gmail.com
Mobile no. 9452725105
*Corresponding author
ABSTRACT
Cattle and buffaloes experience different level of stress during summer and hot humid conditions. Thermal stress experienced by livestock may be assessed on the basis of changes in pulse rate, respiratory frequency and rectal temperature. There is no suitable heat stress indicator for livestock species that is able to measure the extent of stress based on displacement of physiological reactions from the normal resting level. Therefore, displacement of physiological reactions (heart rate, body temperature, respiratory frequency, etc.) can help in quantifying the extent of stress. The higher physiological response of animal indicates higher thermal stress. The THI commonly used for assessing heat stress, various THI indices available with different temperature and humidity weightage are suitable for different specific areas
Keywords: Tropical climate, Thermal stress, THI indices, physiological reactions
https://www.pashudhanpraharee.com/guidelines-to-prevent-heat-stress-in-cows/
Our bovine population comes to 233.1 million; out of which 192.49 Million are cattle and 109.85 Million are buffaloes (20th Livestock Census, 2020). India is the world’s largest milk producing nation (around 198.4 million tonnes in 20019-20) (Economic survey, 2020). One of the greatest challenges to production facing dairy farmers in the India is heat stress and the strain that it causes to the lactating dairy cattle and buffaloes. Thus, heat stress is chronic in nature, there is often little relief from the heat during the evening hours, and intense bursts of combined heat and humidity further depress performance. Lactating dairy cattle and buffaloes create a large quantity of metabolic heat and accumulate additional heat from radiant energy (West, 2003).
Heat stress is caused by a combination of climatic factors like air temperature, humidity, solar radiation, wind velocity etc. Majority of studies on thermal stress in livestock have used temperature-humidity index (THI). THI represent the combined effect of air temperature and humidity with level of heat stress. Milk yield and DMI exhibited significant declines when maximum THI reached 77. Later research determined that the critical values for minimum, mean, and maximum THI were 64, 72 and 76 respectively (Igono et al., 1992). The incidence of stress days as measured by THI greater than 80 has increased significantly over the 40 year period (60%) and the climate change scenarios suggested further, substantial increases (138%) in the frequency of such heat stress days. In addition, in the climate change scenario there was a very marked increase in days where animals could no longer thermo regulate by sweating alone (Howden et al., 1997). Different animal species have different sensitivities to air temperature, humidity, solar radiation and wind velocity etc.
The use of these indices at farm level is recommended, as they are capable of indicating environmental and animal stress. Index for cattle and buffaloes will help to generate more proactive responses to avoid excessive thermal stress effects on livestock productivity.
References:
- 20th Livestock Census, 2020
- Economic survey, 2020
- Howden, S.M. & Turnpenny, J. (1997). Modelling heat stress and water loss of beef cattle in subtropical Queensland under current climates and climate change. Modsim ’97 International congress on modeling and simulation proceedings, 8-11 December, University of Tasmania Hobart, pp 1103 -08.
- Igono, M.O., Bjotvedt, G. & Sanford-Crane, H.T. (1992). Environmental profile and critical temperature effect on milk production of Holstein cows in desert climate. J. Biometrol. 36: 77-87
- West, J. W. (2003). Effect of heat-stress on Production in Dairy cattle. Dairy Sci. 86: 2131-2144.
