Abstract
In order to investigate the effect of different levels of niacin supplementation on physiological and blood biochemical parameters during heat stress period (April to August; 120 days), eighteen crossbred early lactating cows (2nd to 4th lactation; 11.56 +/- 1.74 days in milk) were divided into three groups of six animals each. The basal ration was fed same to all cows (green fodder, straw and concentrate was fed as per NRC, 2001), except the addition of niacin @ 600 and 800 mg/kg dry matter intake (DMI) in T1 and T2 groups, respectively. The temperature humidity index (THI) was calculated at 07: 30 AM and 02: 30 PM daily. Fortnightly physiological parameters were recorded and blood was collected from the jugular vein at day 0 and subsequently at 15-day interval from all the experimental animals to study blood biochemical parameters. The results revealed that animals were in either moderate or severe stress at morning; whereas, during afternoon the animals were in very severe stress during the entire trial. Supplementation of niacin @ 800 ppm decreased significantly skin temperature, respiration rate, cortisol, super oxide dismutase (SOD) and catalase. Plasma NEFA was significantly low in both niacin supplemented groups. Plasma urea was significantly high in T2 in comparison to control (24.90) and T1 (25.37). It is concluded that 800 ppm niacin supplementation to lactating crossbred cows resulted in better stress alleviation as indicated by the improved biomarker values, viz. SOD, catalase, cortisol and skin temperature.