AGRICULTURAL RESEARCH COMMUNICATION CENTRE www.arccjournals.com / indianjournals.com Indian J. Anim. Res., 47 (6) : 492-497, 2013 ANTIOXIDANT STATUS, HORMONE LEVELS AND IMMUNITY IN CROSSBRED COWS OF DIFFERENT LEVELS OF PRODUCTION Anjali Aggarwal and Gulab Chandra Dairy Cattle Physiology Division, National Dairy Research Institiute, Karnal- 132 001, India Received: 14-03-2012 Accepted: 27-10-2012 ABSTRACT Twelve crossbred (KF) cows were selected 60 days before expected date of calving for experiment. The animals were grouped on the basis of their milk production as high (> 15 kg/day) and low (< 10 kg/day) producers based on their previous milk yield. Blood samples were collected at days 60, 45, 30, 15 and 7 before calving, on day of calving and 7, 15, 30, 45 and 60 days after calving. Hormones, leptin, insulin and growth hormone have been estimated in plasma samples. Plasma leptin and insulin levels were lower and growth hormone was found to be higher in high yielding cows as compared to low yielding cows. There was significant variation in leptin, insulin and growth hormone levels between groups (P< 0.01) and between days (P< 0.01). Plasma glucose level was lower and plasma NEFA was found to be significantly higher (P< 0.01) in high yielding cows as compared to low yielding cows. Lymphocyte proliferation index was 1.33± 0.11and 1.45± 0.15 in high and low yielding cows, respectively. Average value of total plasma antioxidant activity was 1377.39± 23.00 and 1313.09± 14.99 FRAP value (μM/L) in high and low yielding cows, respectively. The study shows that changes in leptin, insulin, growth hormone, glucose and NEFA play important roles in metabolic adaptation of cows to changes around calving and the levels of these hormones and metabolites vary with level of milk production. Key words: Leptin, Insulin, Growth hormone, Lactating cows, Antioxidant activity, Immunity. INTRODUCTION In high-yielding dairy cows, the onset of lactation increases the total energy requirements by approximately fourfold, reflecting mostly the oxidative and milk precursor needs of the mammary gland (Bauman and Currie, 1980; Bell, 1995). Because the hyperphagia required to meet these additional demands develops slowly, shortfalls are met by mobilization of endogenous reserves and by shifting the pattern of nutrients used by nonmammary tissues (Bauman and Currie, 1980; Bell, 1995). Peripheral mechanisms orchestrating these adaptations involve changes in the concentration and actions of hormones (Vernon and Pond, 1997). Hypoinsulinemia and decreased insulin responsiveness of skeletal muscle and adipose tissue occur simultaneously in early lactation (Bell and Bauman, 1997; Vernon and Pond, 1997) as a result of these adaptations, there is increased availability of glucose for the mammary gland where uptake is independent of insulin (Bauman and Currie, 1980). Calving associated immunodepression has been considered one of the main causes related to the appearance of various pathologies in dairy cows, such as retained placenta or the mastitis (Waldron, 2007). High yielding cow experiences at least one or more diseases after calving. The condition of oxidative stress is the result of an excessive exposure to oxidants and an inadequate availability of antioxidants, or a combination of both. After parturition, dairy cows suffer from an intense energy deficit caused by the onset of copious milk secretion and an inadequate increase in voluntary food intake which contributes to a decline in plasma leptin. This decline mirrors that of plasma insulin but is reciprocal to the profile of plasma growth hormone (GH), suggesting that both hormones may regulate plasma leptin in periparturient dairy cows (Leury, 2003). In addition, the period around calving is particularly important for health and subsequent performance of dairy cows, which are exposed to drastic physiological changes and metabolic stress (Drackley, 1999; Bernabucci et al., 2005) and is characterized by a depleted antioxidant status. The