Jaelyn Whaley, South Dakota State University Extension Sheep Field Specialist
(Previously published online with South Dakota State University Extension: May 22, 2024)
Minerals
play an integral role in many reactions throughout the body, and they are critical for animal health and performance. Bioavailability, individual animal consumption, individual mineral interactions, and variable plant and soil mineral concentrations make strategic mineral programs challenging. The differences between toxicity and deficiencies are small and can greatly affect sheep production.
Identifying Deficiencies
Precisely supplementing needed minerals begins with identifying potential deficiencies or toxicities of both macrominerals (Ca, P, Na, K, Mg, Cl) and microminerals (Cu, Mn, Zn, Se, Co, I). If your ewes are on pasture, shrub and forb species are generally higher in mineral concentration than grasses. Therefore, forage sampling that is representative of sheep grazing behavior and your pasture serves accurate assessment of mineral consumption. Making sure that vitamins and minerals are evaluated when you are balancing a ration is critical. In most cases, if you have tested your feed and properly balanced your ration, minerals aren’t an issue. However, subclinical deficiencies can still lead to decreased productivity. For example, poor performing rams may be the result of mineral deficiency, because zinc, selenium, and cobalt play a critical role in sperm quality.
Interactions and Consumption
Mineral interactions and individual animal consumption further complicates utilization. Animals consuming high levels of molybdenum or sulfur may be deficient in copper due to interactions binding copper in the rumen. This is where knowing your forage and soil mineral profiles may be helpful. Much of South Dakota has high soil molybdenum levels, which could be a culprit in copper deficiency (as a reminder, sheep do require ~5 ppm dietary copper). High sulfates in water sources can cause issues also, so consider testing your water for livestock suitability with your nearest county office or regional center.
Sheep can also sometimes be picky eaters! Uneven consumption can affect mineral status and animal performance. Approximately 3 to 10% of sheep will be non-consumers. Additionally, ewes in a confinement system are less likely to consume mineral than grazing sheep. Mineral intake is often driven by salt, so free-choice salt should always be provided. This will also aid in animals’ water intake and can help prevent waterbelly (urinary calculi) if you are feeding high grain diets. Additionally, loose minerals generally have greater consumption than a block. Mineral fortified in a supplement can ensure even intake and can also reduce the cost of purchasing both feed and mineral separately.
Cost Considerations
The cost of utilizing a mineral can be a barrier, but it can be lessened with precise management. It is important to track your flock’s mineral consumption and adjust management if needed. If the label recommends that sheep consume 1 ounce per-head, per-day, a 50-pound bag should last 100 ewes 8 days (1 ounce × 100 head = 100 ounces per-day ÷ 16 ounces/pound = 6.25 pounds/day; 6.25 pounds/day ÷ 50-pound bag = 8 days). If your flock is consuming mineral faster than they should be, do not refill the mineral tub until the correct number of days that the mineral should have lasted. Excess minerals in the body have minimal benefit compared to the cost of overfeeding it. Additionally, you may be able to forego a mineral supplement when ewes are in a maintenance diet if their ration contains balanced nutrients. Young ewes also have a lower mineral requirement than older ewes. Zinc, for example, is required at 33 mg per-day for yearling ewes and increases as ewes age up to 48 mg per-day for four-year-olds. Again, this is where knowing what is in your feed is important.
The cost of a mineral supplement also may dictate how bioavailable those ingredients are to the animal. The cheapest (but least-available) minerals are inorganic minerals. If you read your mineral label, these most commonly end with “sulfate” or “oxide” (for example, zinc oxide). Organic (chelated) minerals are bound to an amino acid and have a moderate bioavailability; and the most-available form of mineral are hydroxy trace minerals. These are typically more expensive, but they provide the animal with a form of minerals that can be better utilized in the body. Reading mineral tags can be confusing. For more information, check out Reading The Tag and Bioavailability. It covers all the details on bioavailability and understanding the different forms of minerals.
In Summary
There are a wide array of factors, from environment to plant physiology to animal age, that influence a sheep’s mineral need. Yet these tiny minerals play a large role in promoting the production and profitability of an operation.