Importance of minerals for small ruminants
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Just like other nutrient requirements, such as protein and energy, mineral requirements for small ruminants are not static. Mineral requirements for sheep and goats are dependent upon age, sex, stage, and level of production. For example, lambs less than 8 weeks old have an 80 percent efficiency for copper absorption, while lambs with fully functional rumens have only 3 to 5 percent copper absorption efficiency. Minerals are necessary for normal physiological function and body system development. Incorporating minerals into their diet is essential for overall production but also for tissue development, reproduction, and immunity support. Deficiencies in minerals can lead to poor performance, health issues, and physiological function disruption. Often, subclinical deficiencies and disease are more problematic than clinical deficiencies. Some deficiencies are more difficult to detect because the symptoms are less apparent, like small reductions in average daily gains or decreased milk production. Minerals are divided into macro-minerals and micro-minerals. The classification of the minerals as macro or micro is determined not by importance of the mineral, but rather the concentration needed to support animal health. Sheep and goats require macro-minerals—such as calcium, phosphorus, and potassium—in larger quantities, while micro-minerals—such as zinc, selenium, and copper—are required in smaller concentrations.
Evaluating a problem
True evaluation of mineral status can be a complicated process and often is not feasible or practical. Live animal blood sampling or post-mortem animal sampling are generally adequate for several minerals. With blood sampling it is important to remember that samples may be altered or fluctuate with feeding times or disease status. Blood sampling and post-mortem evaluations are not always feasible or practical, so we must look to other options for evaluating mineral status. At minimum, monitor your animals’ mineral intake. Put out a set amount in a mineral feeder (enough for a week), then weigh how much remains. Also, be cautious of novelty effects. Something new and tasty may result in quicker consumption, but the newness will wear off in about two weeks. Another approach that should be used is forage analysis. If forage is the primary source of feed for your small ruminants, the forage should be analyzed for mineral status. If we do not know the chemical composition of the forage, how can we know if our animals are meeting mineral requirements? Keep in mind that several factors can affect forage mineral status, such as stage of maturity, forage species, soil conditions, weather and pasture management. However, forage analyses still provide a good indication of whether forages are providing adequate, marginal, or inadequate mineral levels. In general, there is a pattern of mineral concentration in forages that follows the forage species maturation and vegetative growth.
Biologically critical times
As stated above, severe mineral deficiencies can occur but marginal deficiencies are more common. Life events, such as pregnancy, lactation, growth, or stress, can impact marginal deficiencies. For instance, ewes have higher calcium requirements during lactation than during maintenance. Also, production performance responses are not consistent from year to year. Evaluation of pastures and soils annually can help determine the needs of your mineral supplementation program.
Stress: We all experience stress, even our small ruminants. Stress can be induced during transit or handling or even events like parasitism. Significant research indicates that mineral metabolism is affected during stress, and therefore mineral absorption can be hindered. The domino effect begins and marginal deficiencies occur. Heat stress is a good example of this effect. When our animals are heat stressed, decreased dry matter intake occurs. Because they are consuming less dry matter, they are likely not consuming enough nutrients. Also, with heat stress comes increased urination or sweat, which leads to increased mineral excretion. Both economic considerations and animal compassion demand that we address this issue.
Reproduction: Reproduction is the single most important industry trait for small ruminants. Research suggests improved reproductive performance and fertility with certain minerals, specifically selenium and zinc. Failing to provide adequate concentrations of these minerals can translate into production losses and decreased longevity in the herd.
Immune responses: Incorporating minerals into rations has led to improved immune responses and increased disease resistance. Parasites are a costly problem for any small ruminant producer. Parasites cause damage to the digestive tract, which in turn can inhibit or impair mineral absorption.
Supplemental methods: There are several options for incorporating minerals into your nutrition program using both indirect and direct delivery methods. Indirect methods include pasture fertilizations, managing soil pH, and providing forage species with high mineral concentrations. Direct methods include water, oral drenches, injectables, ruminal boluses, ration-mix-in or free-choice. Free-choice is often easiest for producers; however, remember that consumption varies across animals, season, and stage of production. Also, evaluate the practicality and cost effectiveness of the delivery method.
Influencing intake factors: Several factors influence and contribute to forage intake, such as:
- Forage quality
- Dry matter content
- Degree of hunger
Cost analysis: When deciding on your mineral supplementation program, a cost analysis should be performed. It is easier to think in tons because that is how we purchase minerals, but try to think in days. One ton of mineral equals 32,000 ounces. In general, the average mineral intake for one animal is 0.5-1.5 ounces (oz.) per day. The following example is adapted from “With Sheep, The Cheapest Mineral Isn’t” (Fluharty, 2018).
Sheep Mineral = $1,200/ton
Intake = 1.0 oz./head/day
$1,200 ÷ 2,000 lb. = $0.60/lb.
$0.60/lb. ÷ 16 oz. = $0.0375
$0.0375 × 1.0 oz./head/day = $0.0375/day
365 days × $0.0375 = $13.70/animal/year
The takeaway with this example is that incorporating minerals into your nutrition program may not be cost prohibitive and may actually pay off.
Mineral requirements for small ruminants can be very dynamic depending on stage and level of production, age, and season. As producers, it is our responsibility to provide our sheep and goats with adequate nutrition to meet their requirements, including minerals. Failure to meet mineral requirements can result in decreased animal wellbeing, decreased productivity, and increased production losses.