LAUSR

Abstract The objective of this study was to compare hydroxy to sulfate sources of Cu and Zn, on growth and reproduction in Angus-based beef heifers. Over a 2 year period, 200 Angus-based, spring-born heifers were stratified by previous winter development treatment and BW to pens and fed either hydroxy (HD, Micronutrients, Indianapolis, IN) or sulfate (SULF; Phibro Animal Health, Teaneck, NJ) to provide 7.2 Mg Cu/kg and 12.3 mg Zn/kg of diet for 68 d. Each year there were 4 pens per treatment. The ration consisted of 5.5 kg grass hay, 2.1 kg wet corn gluten feed, and 0.41 kg of a pelleted mineral supplement (DM basis). At the end of the feeding period heifers were synchronized, comingled, and artificially inseminated based on heat detection over a 3 day period. Following this period heifers were exposed to bulls for 60 days while grazing native range. The initial liver Cu and Zn did not differ (P ≥ 0.16) among sources. However, the SULF heifers (208 mg/kg) had greater (P