Effects of Metal Amino Acid Chelates on Milk Production, Reproduction, and Body Condition in Holstein First Calf Heifers

First calf heifers are still growing through their first lactation and second gestation, and consequently have higher mineral requirements than mature cows. This study demonstrates that first calf heifers produce more milk and milk components with fewer open days (days from parturition to estrus) and better breeding efficiency, along with higher body condition scores, when supplemented with metal amino acid chelates (AACs) than herdmates supplemented with inorganic minerals (IOMs). Two identical groups of Holstein first calf heifers (24 and 22 heifers, respectively) were given supplements containing copper, manganese, zinc, magnesium, and potassium as either IOMs or as metal AACs. Supplementation commenced upon calving and continued for 180 days. The AAC group produced 9.3% more total milk fat (P <. 01) than the IOM group due to greater milk production. Milk protein was 3.01% in the IOM group and 3.06% in