author(s)
Gaurav Kumar, Pooja Devi, Nisha Sharma and Yallappa M Somagond

abstract
Thermal stress is one of the major issues affecting the production capacity of dairy cows almost in every area of the globe. Thermal stress lowers feed intake, milk yield, compromised rumination and nutrient absorption and increased respiratory rate and sweating. Thermal stress adversely affects milk production and its composition in dairy animals, especially in animals of high genetic merit. Elevated temperature and humidity affect various components of milk such as fat (%), SNF, protein and fatty acid profile also. Thermal stress was associated with a decline in total protein and fat content. Cow milk has poten¬tial benefit to human health as it contains a large number of fatty acids (FA), including polyun-saturated fatty acids (PUFA) and conjugated linoleic acid (CLA). Milk fat in summer consists of more linoleic acid, lino¬lenic acid, oleic acid and CLA than in winter. Total saturated fatty acids (SFA) content was higher in summer, where as total monounsaturated fatty acid (MUFA), polyunsaturated fatty acid (PUFA) and conjugated linoleic acid (CLA) concentration were lower in summer as compared to winter season. It may be concluded from this review that thermal stress adversely affects both quantity as well as quality of milk in high yielding dairy cows and therefore effective mitigation strategies should be implemented to minimize the negative effects of high ambient temperature and to boost the production performance of high yielding dairy cows.