Periparturient cows undergo instance mammary growth, copious synthesis and secretion of carbohydrate, fat and proteins as well as marked accumulation of colostrum and milk. Since colostrum is rich in vitamins A and E, therefore, cows require increased supply of these vitamins prior to parturition. At parturition, due to increased colostrogenesis, there is diversion of zinc from plasma pool towards mammary gland. Decrease in serum zinc level at calving is also associated with an acute phase response due to inflammatory reaction in uterus. Stress at calving induces synthesis of zinc distribution protein metallothionein and zinc
is redistributed from blood pool to other tissues such as liver. During periparturient period when there is significant decrease in
vitamin E level and zinc, the cow’s immunity status and neutrophil functions are depressed. Supplementation of vitamin E maintains proper antioxidant status of animals and improves the ability to resist infections. Zinc is an integral part of immune system. It has been indicated that zinc had an indispensable role in the
development and maintenance of immunocompetence. Zinc is also known to be associated with superoxide dismutase (SOD) which is an important antioxidant enzyme involved in oxidative stress. Also
role of vitamin E and zinc in energy metabolism like increase blood glucose level and decrease NEFA during early lactation
when animals are under negative energy balance. 1345705018.php