Montana State University

Providing sheep with an adequate supply of trace minerals and vitamins is essential for their health and productivity. However, the content of trace minerals and vitamin precursors within plants and harvested forages is variable across locations, seasons, and years. Therefore, it is possible that sheep are deficient in one or more trace minerals and vitamins at some point during the production year, especially in forage-based operations. Past work by our program has discovered zinc and selenium deficiencies in weaned ram lambs throughout Montana. Current work is seeking to identify if deficiencies in trace mineral and vitamin concentrations of ewes during critical production periods (i.e., pre-lambing, weaning, breeding) also exist. If consistent deficiencies are identified, it may be an area of focus as a means of improving disease resistance and performance in lambs and ewes. Producers do have the option of providing a free-choice supplement to help avoid trace mineral and vitamin deficiencies. However, sheep vitamin and mineral packages are rarely specific to a regionís unique soil and forage deficiencies. Furthermore, individual consumption of supplemental vitamin and mineral is highly variable, which can result in inconsistent statuses across animals. The research proposed herein will strive to determine: 1) the efficacy of injectable supplements at increasing serum trace mineral content and 2) the effect of supra-nutritional trace mineral and vitamin administration on ewe and lamb lifetime performance. The results of this work will be presented to sheep producers, industry representatives, and the scientific community and will stress the role of vitamins and trace minerals in maintaining animal health and improving productivity.

The objectives of this research are to determine: 1) the efficacy of injectable supplements at increasing serum trace mineral content and 2) the effect of supra-nutritional trace mineral and vitamin administration on ewe and lamb lifetime performance.
To achieve the project objectives, the participants will design projects utilizing the flock housed at Montana State Universityís Red Bluff Research Ranch. Recently, our research program has identified consistent serum zinc deficiencies in weaned ram lamb populations across Montana. A follow up study was conducted that found that supranutritional supplementation of zinc increased weight gain and staple length in developing yearling Targhee rams. Additionally, preliminary analysis has found that western whitefaced ewes with high milk somatic cell counts (an indicator of subclinical mastitis) had 30% lower serum zinc concentrations than ewes with consistently low somatic cell counts. Therefore, the proposed research will initially focus on the effect of zinc injection to ewes at breeding, pre-lambing, and weaning on ewe and lamb health and productivity. To evaluate this, 80 yearling Targhee ewes will either be administered a subcutaneous injection of zinc oxide (ZnO) or saline (control) prior to being placed in single sire breeding pens. Treatments will be administered again 4 to 6 weeks prior to lambing and at weaning and ewes will remain in their treatment groups for the remainder of their productive life. Blood will be collected at several time points throughout the year to determine the magnitude of serum zinc concentration and lymphocyte phagocytic differences between ZnO and control ewes. Milk will be collected from ewes shortly after parturition (< 5 d post-lambing) and at turn out to summer grazing (4 wk) from which somatic cell count will be quantified. All lambs will be weighed at birth and weaning to determine the effect of ewe treatment on pre- and post-parturition lamb growth. Replacement ram and ewe lambs will be shorn as yearlings and fleece weight, staple length, and fiber metrology traits will be collected. The proposed project will be conducted two years in a row. This work will be part of a graduate studentís thesis research and results will be presented to sheep producers, industry affiliates, and the scientific community at extension events and research conferences. Additionally, a peer-reviewed research article will be written that summarizes our findings. We expect that zinc oxide injection will be a practical and cost effective means of increasing serum zinc concentration. The proposed work could serve as a non-antibiotic treatment to increase ewe and lamb lifetime productivity and health.