Review on performance responses of dairy cattle against thermal stress

Abstract

This manuscript is aimed at reviewing the performance responses of dairy cattle against thermal stress resulting from climate change. Climate change is the major factor that largely affects the dairy industry. Thermal stress (TS) is the perceived discomfort and physiological strains associated with exposure to excessive ambient temperature. Temperature and Humidity Index (THI) have been adopted to describe thermal conditions that drive thermal stress in dairy cattle. The effects of TS are devastating in the dairy industry if not managed well. The thermo-neutral zone for dairy cattle and calves in the tropics is THI <72. Milk yield reductions of up to 50% have been reported for Holstein cows due to thermal stress under summer climate conditions. Moreover, thermal stress is associated with alterations in milk composition. TS reduces the length and intensity of estrus manifestation. Moreover, 80% of estrus may be unnoticeable during the summer season in temperate regions, which further reduces fertility. Conception rates of dairy cows may drop up to 20–27% in the summer season. Climate-induced thermal stress resulted in a decrease of 3.5 kg and 25 kg in the birth weight and weaning weight of Fogera calves, respectively. Dry matter feed intake was reduced by 9.6%. Commonly used thermal stress reduction strategies included modification of the physical environment, breeding for heat-tolerant dairy cattle, and nutritional management. The productive and reproductive traits are susceptible to the negative impacts of thermal stress with an increase in THI above 68.0 for Holstein Frisian cattle and their crosses and 72 for tropical cattle under an open shed system. Mitigations of thermal stress by breeding heat-tolerant animals, using a loose house system, and season-based feeding should be considered an integral component of the dairy cattle management system.

Hormonal panel of various breeds of cattle under the conditions of temperature stress

“…Artificial selection was aimed at achieving high results in milk yield and body condition scoring. However, it causes the risk of breeding of less surviving animals with low adaptation abilities [1,2,3].…”

“…High milk productivity of Holstein cattle is connected with lower health quality and reproductive function and immune biological response, as well as with vulnerability to mastitis, and reduction of productive longevity [1,4,5]. Productive longevity of animals is the result of complex of physiologically favorable parameters specific for cattle, and search for their genetic determinants is still in process [2,6].…”

“…Climatic changes, like significant increase of environmental temperature in the summer time, cause the development of thermal stress of animals. The animals with bad adaptation to environmental factors (temperature and humidity) are noted to have lower milk yield, poorer milk quality and lower reproduction function [1,9,10]. One of the strategies aimed at reduction of negative influence of thermal stress is selection of animals, genetically resistant to climatic changes.…”

“…One of the strategies aimed at reduction of negative influence of thermal stress is selection of animals, genetically resistant to climatic changes. However, genetic determinants and biological properties that form this adaptation have yet to be studied [1,11].…”