Whit Stewart, Extension Sheep Specialist, University of Wyoming
(Previously published in Barnyards & Backyards, July 2018)
As summer progresses and forage quality declines, we are quick to think of shortfalls in protein and energy in nutritional management yet tend to overlook micronutrients such as trace minerals. Even though these are required in relatively smaller quantities than protein and energy, they are essential for basic physiological functions and should be prioritized.
Essential macro minerals, including calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulfur make up major components of skeletal and nervous systems and are usually expressed as a percentage of the diet. In contrast, micro minerals, or trace minerals, are required in relatively small quantities – parts per million (ppm) or milligrams per kilogram (mg/kg). These include manganese, copper, zinc, selenium, iron, cobalt, iodine, and fluorine. Even though these are required in smaller quantities, they play key roles. For example, cobalt is a precursor for production of vitamin B12 in the rumen, which is essential for proper rumen fermentation – a small but mighty role.
Results from a recent Montana study found that 33% of sheep producers failed to consistently provide a complete trace mineral and many of their flocks were largely deficient or marginally deficient in selenium and zinc. After becoming aware of these trace mineral deficiencies, many of these producers resumed trace mineral supplementation and anecdotally recounted marked improvements in lamb survival, fewer open ewes, increased wool quality, and other benefits.
There is no denying the essentiality of trace minerals, but the extent of production losses can vary across [operations]. Clinical signs of trace mineral deficiency are often visibly noticeable, such as white-muscle disease caused by selenium and vitamin E deficiency, which results in lamb paralysis and failure to stand. Often subclinical signs, such as decreased appetite, decreased immune function, and poor conception are not correctly attributed to a specific trace mineral deficiency and are ignored.
Just because not providing a complete trace mineral doesn’t result in a complete “wreck,” doesn’t mean that production losses aren’t occurring. Furthermore, as sheep genetics improve, it’s important that failure to provide a mineral isn’t limiting the genetic potential of our sheep.
A very real challenge to cost-effective trace mineral supplementation is the reality that sheep will overconsume a mineral if given the opportunity. Research conducted at Montana State University in 2010-2011 showed that whether in a dry-lot or grazing scenario, ewes consumed on average two ounces per head per day instead of the one-fourth ounce target intake recommended on the label. Assuming mineral cost of approximately $1,100/ton, a ewe who overconsumes two ounces a day across 365 days a year will cost $24.82 per head, whereas if she consumes the recommended one-fourth ounce per day, the cost will be $3.10 annually.
One strategy to combat overconsumption is to blend in additional white salt. Standard iodized salt is very cost effective at $200/ton – or less than one cent per ounce – and is effective in limiting mineral intake. Take care to avoid overdiluting trace minerals with white salt; working with a nutritionist can help.
Another option is to limit the frequency of feeding. For example, if ewes consume seven days’ worth of mineral in one day, do not refeed for another seven days, remembering to provide iodized white salt at all times. Instances of consuming mineral rapidly in one standing might be reduced with additional bunk space or mineral feeders. The importance of providing fresh, clean water with all trace mineral supplementation cannot be overestimated.
Evaluating and reevaluating nutritional management is an important practice, given feed-related inputs represent at least half of variable costs on many sheep enterprises. Trace minerals represent a smaller proportion of the cost, but have significant impacts on sheep well-being and productivity.
May the lambs look even better going on the truck this year!
Important Trace Mineral Reminders
- Provide iodized white salt (sodium chloride) year-round. Ewes consume 0.2 – 0.5 oz per day, for of a cost of approximately $1 for 365 days. Inadequate consumption reduces water and feed intake, resulting in decreased milk production and growth.
- Prioritize and optimize trace mineral intake to coincide with physiologically demanding production periods, e.g., breeding season, pregnancy, and early lactation.
- Be aware that as cool-season grasses reach maturity and decline in quality, so do the solubility and overall content of some trace minerals. For example, zinc showed a 50% decline from spring to late summer in many cool-season grasses.
- Monitor consumption. Poor placement of mineral or exposure to weather may result in under-consumption. Place mineral feeder close to water source to enhance visibility and encourage consumption.
- Provide mineral weeks prior to weaning so ewes can teach lambs to consume mineral. This can improve lambs’ trace mineral status in advance of stressful weaning and shipping events.
- Read label information and work with nutritionist/supplier to better achieve target intake of mineral. Under- or overconsumption of mineral is not uncommon and requires fine-tuning.