Effect of Different Zinc Sources on Milk Production and Reproductive Performance of Friesian Cows

This study was conducted to evaluate the influence of dietary supplementation of inorganic or organic zinc on milk production and reproductive performance of dairy cows. A 30 Friesian cows were divided into three groups. Cows in the 1st group (control group, G1) were fed a concentrated feed mixture (CFM), corn silage, fresh berseem and rice straw, while cows in G2 were fed CFM supplemented with inorganic zinc (2.4g/day/cow) and cows in G3 were fed CFM supplemented with organic chelated zinc (2.4g/day/cow). Monthly milk production in G2 and G3 was significantly increased during 2, 5 and 6 months of lactation, as compared with G1. Moreover, G3 increased milk production during 1, 3 and 4 months of lactation than G1 and G2. Milk of fat and protein percentages were significantly (P<0.05) increased in G2 and G3 than G1. The G3 had significantly higher protein, albumin, globulin concentrations as compared with G1 and G2. However, G2 and G3 decreased lipid, cholesterol, urea-N concentrations, and increased zinc concentration than G1.Number of estrus cases and ovulatory cycles per cow were decreased in G2 and G3 than in G1. Progesterone (P4) concentration and its peak during the ovulatory cycles in G2 and G3 were significantly increased as compared with G1. The postpartum first estrus and service interval and days open were shorter in G3 than others. The conception rate was significantly higher in G2 and G3 than G1. These findings suggested that supplemented organic zinc improved milk production, reproductive performance and blood metabolites in Friesian cows.