Twelve Karan Fries (Holstein × Tharparker) lactating cows in early lactation of 50–70 days were selected from the Institute's herd and divided in two groups of six each. Group 1 cows were kept without mist (control) while group 2 cows were cooled under mist and fan from 11.00 A.M. to 4.00 P.M. daily. Blood samples were collected from both the groups at 3 days intervals throughout the experimental period of 30 days. Average maximum temperature during hot-dry and hot-humid seasons was 40.8 and 33.4°C, respectively. Relative humidity reached >90% during hot-humid season. Plasma thyroxine levels did not vary between the groups and among periods. Plasma cortisol concentration in control group was higher (P<0.01) as compared to experimental group in both the seasons. Milk yield and feed intake were significantly higher in experimental group as compared to control group during hot-dry season. The results indicated that cooling with provision of mist and fan system during hot-dry and hot-humid seasons was beneficial in alleviating the effect of heat stress on crossbred cows.
Lactating cows, Mist cooling system, Hormones, Heat stress
