Serum mineral concentrations in weaned Montana ram lambs and effects of dietary zinc source and concentration on developing Targhee rams

Abstract

Trace mineral deficiencies exist in livestock operations and can contribute to decreased productivity and profitability. The objective of the first study was to quantify serum trace mineral concentrations in weaned ram lambs, with particular emphasis on Se and Zn. Serum samples (n = 221) were collected from ram lambs at 21 ranches throughout Montana and analyzed for Co, Cu, Fe, Mn, Mo, Se, and Zn concentrations. Additionally, water samples were analyzed for pertinent characteristics. Of ranches surveyed, only 67% provided a complete mineral supplement. Sheep that were provided supplementary trace mineral had greater serum Se concentrations (P < 0.001). Based on serum trace mineral concentration reference ranges, the two most commonly deficient and marginally deficient minerals across Montana were Se (19 and 23.8% of ranches, respectively) and Zn (9.5 and 57.1%, respectively). Of ranches sampled, 40 and 35% of water samples exceeded excessive concentrations in Na and sulfates, respectively. This regional knowledge of serum trace mineral concentrations in a sample of ram lambs can provide information for ranches to evaluate current and future mineral supplementation needs, as well as aid the feed industry in designing formulations for mineral premixes. Based on these results, a second study was designed with the objective to evaluate the effects of dietary Zn source and concentration on serum Zn status, growth performance, wool traits, and reproductive characteristics of developing yearling rams. Forty-four Targhee rams were used in an 84-d completely randomized design and were fed one of three pelleted dietary treatments: 1) a control diet without fortified Zn; 2) a diet fortified with a Zn amino acid complex (ZnAA); and 3) a diet fortified with ZnSO4. Serum samples were collected from each ram at four time periods to quantify serum Zn and testosterone concentrations. ZnSO4 had greater (P < or = 0.03) serum Zn concentrations compared to other treatments. Rams consuming ZnAA had greater (P < or = 0.03) average daily gain than rams in the other treatments. Wool regrowth was greater (P < 0.001) in the ZnSO4 treatment group compared to control. These results indicate that source and concentration of a Zn supplement appears to affect ram development.