Effects of organic and inorganic zinc sources on production, composition and zinc concentration of milk in early lactating Holstein cows

Abstract

Zinc (Zn) is an essential nutrient for animals, functioning largely or entirely in enzyme systems and being involved in protein synthesis, carbohydrate metabolism, and many other biochemical reactions (Miller, 1970). This element is important in maintenance of health and integrity of epithelial tissue, such as skin (teats) and mammary tissue, because of its role in cell division and protein synthesis (Cook-Mills and Fraker, 1993). The most widely used products for zinc supplementation are zinc oxide, zinc sulphate and zinc methionine. Knowledge of organic Zn compounds is still incomplete. In particular, there is a lack of reports on the effect of such compounds in roughage based diets and only a limited number of studies have investigated the importance of Zn methionine in dairy cattle. Some research suggest that supplementing certain organic forms of zinc improve animal-production responses compared with those observed in ruminants that are supplemented with inorganic zinc (Spears, 1996). Therefore, the present study was conducted to compare organic and inorganic zinc supplements effects on production and components of milk. A second objective was to determine effects of different zinc sources on zinc concentration of milk.