Effects of hydroxy trace mineral supplementation on gain and reproductive performance in beef heifers

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 < 0.01) liver Cu than HD heifers (121 mg/kg) at the end of the 68 d feeding period. While liver Zn did not differ among sources (P = 0.40) at the end of the feeding period. Despite differences in liver copper concentrations, gain during and after the mineral source treatment did not differ (P ≥ 0.49) between SULF and HD heifers. Furthermore, no differences (P ≥ 0.92) were observed for AI pregnancy or overall pregnancy. All heifers appeared to have adequate Cu and Zn status at the end of the mineral feeding period which coincided with the beginning of the breeding period; this may explain why trace mineral source had no effects on gains or reproduction.