Temperature Humidity Index and Its Relationship with Production Traits of Dairy Cattle and Buffaloes - Review

Abstract

Increased pressure for intensified milk production and simultaneous rise in environmental temperature due
to global warming has increased the thermal load on dairy animals. Elevated environmental temperature
combined with high humidity causes discomfort and escalates the stress level in animals which is reflected
in terms of reduced physiological and metabolic activities that results in reduced growth, drop in
production and reproduction in farm animals. Heat stress is one of the most vital environmental stressor
that has negative impact on milk yield, milk composition (fat%, SNF%, protein % etc). Construction of
Temperature Humidity Index (THI) by combining several climatological parameters like dry bulb, wet bulb
temperature along with relative humidity to quantify the thermal stress is one of the best methods to assess
heat stress on animals. Several research workers have reported that there exists a threshold THI value,
above which the negative effects of heat stress is observed on animals. Mitigation strategies to combat heat
stress includes selection of heat tolerant animals and their breeding, inclusion of heat tolerance as a trait
while constructing selection index, providing balanced nutrition to the animals and implementation of good
ventilation along with suitable cooling system in the farm.