Correcting mineral deficiencies in sheep starts with understanding what is missing from the feed base - but it's easier said than done.

AgriPartner Consulting principal Hamish Dickson said calcium was the most common deficiency sheep producers dealt with, largely because of the grass and cereal base of many farming systems.

Mr Dickson, who is based at Orange, NSW, said cereal crops, hay, straw, grains and stubble were all low in calcium, and many grass pastures could also be short.

At some times of the year a calcium shortage could be accompanied by magnesium problems that were often induced by high potassium in lush winter-spring green feed and grazing cereals.

"High potassium levels in plants can reduce magnesium availability in the rumen, so animals could be functionally deficient even when plants were not extremely low in magnesium," he said.

Once calcium and magnesium were covered, Mr Dickson said attention typically turned to trace elements such as copper, selenium, cobalt, sulphur, manganese and zinc.

However, fertiliser programs, liming, pasture species and soil type now varied so much from farm to farm that old regional "deficiency maps" had become a blunt guide at best.

"We see different mineral deficiency profiles from one farm to the next, even if they're in the same region, and even if they're next door to each other," Mr Dickson said.

"Mineral levels will vary across different pasture species, vary somewhat across the year, and across different soil types on the property."

In the paddock

Wandsworth sheep and cattle producer Ann Shipman uses a supplement to help stock maintain condition.

Ms Shipman and her parents Michael and Sonya moved to their 1010 hectare property west of Guyra, NSW, in 2017.

With a flock of 200 Merino ewes producing superfine wool, high-quality nutrition is vital for maintaining low micron levels and high tensile strength, as well as overall health and growth.

Ms Shipman said soil tests had highlighted deficiencies in several minerals, including phosphorus, which will require a long-term program of applying fertiliser and other amendments to rectify.

In the meantime, they are giving stock a year-round boost with MegaMin SulPhos loose lick.

"They took to it straight away," Ms Shipman said.

"Both the cattle and the sheep, they love it ... I've found it helps them keep condition, even though our pastures were just sort of basic natives and fairly lacking in quality."

Recognising signs

Clinical signs of deficiency depend on the mineral and class of stock. In ewes, low calcium near lambing and early lactation shows up as milk fever or hypocalcaemia.

"You can see ewes that go down and they struggle to get back up on their feet, and that's because calcium is important for muscle control and contraction, so they effectively lose control of muscles," Mr Dickson said.

Severe deficiencies in young growing sheep can lead to bone fractures, and wether lambs on high phosphorus cereal diets can develop urinary calculi, stones that prevent them from passing urine.

Magnesium deficiency was as much a behavioural and welfare issue as a production one.

Mr Dickson said affected animals became more stressed and jittery, leading to tetany when grazing on high potassium lush, green feed.

"Magnesium is one of the minerals that animals don't store well, so they need a regular supply of magnesium throughout the year," he said.

Shortfalls in trace elements such as copper, selenium and cobalt often showed up as poor growth, reduced wool quality, impaired immunity or fertility, and increased lamb losses rather than dramatic single animal events.

Testing and timing

Relying on visual signs alone in sheep was a poor basis for long-term mineral management.

Mr Dickson said he favoured plant tissue testing to understand both primary and secondary deficiencies, caused by interacting minerals, and how they shifted through the year.

Testing of pastures across Victoria and South Australia for a Meat & Livestock Australia copper project found significant deficiencies through summer and early autumn, contrary to conventional wisdom that it was most likely in winter and spring.

To capture seasonal trends, Mr Dickson recommends sampling a range of paddocks at three stages over the year: early growth (winter or early spring), late spring as pastures started to run to head, and a summer-autumn sample of dry, senescent feed.

These three points in different crop and pasture types will show seasonal variation in mineral deficiencies and help target treatments to the right paddocks and timing windows.

"Those tests, whilst you invest a little bit of money in the testing upfront, give you the information to really refine your treatment program and get it spot on to treat the deficiencies that you have for the most cost effective price that you can, because you're only treating the deficiencies you know exist," he said.

"In some situations, we have even been able to significantly reduce the amount of supplements used for the same level of production, as many minerals were unnecessary because sufficient levels were already in the feed."

Fixing deficiencies

Loose licks made up of ground limestone and salt, which acts as an attractant for sheep, were usually the simplest and cheapest option for addressing calcium shortages in summer.

Where magnesium was an issue in lush winter-spring feed or grazing cereals, a typical home-mixed lick might be two parts lime, two parts Causmag and one part salt.

Mr Dickson said trace elements and vitamins required more strategic, targeted use because they cost more and some - especially selenium and copper - had a narrow margin of safety.

Options include:

• Injectable products, such as B12 and selenium combinations, or products containing zinc, manganese and selenium, sometimes with copper.
• Mineralised worm drenches and vaccines that include specific trace elements.
• Commercial loose licks or custom mixes that bundle trace elements with vitamins such as A, D and E.

Pasture vs feedlot

Regardless of whether sheep were grazing on pasture or in confinement lots, Mr Dickson said mineral demand was driven by the class of animal and production level.

The highest demand for calcium was in ewes in late pregnancy and early lactation, followed by growing lambs.

Most feedlot rations were 70-80 per cent cereal grain-based, often with cereal straw and a small proportion of protein grain, which typically resulted in low calcium and generally low trace element levels.

In this situation - especially as the focus is on achieving the maximum growth rate of lambs and it is impractical to be trying to constantly test and rebalance multiple bought-in feeds - he suggests including a broad spectrum mineral and vitamin premix in the feedlot ration.

On pasture, the focus can be more strategic through understanding and tailoring the mineral supplementation program to the farm's deficiencies.

This maximised productivity and minimised supplementation costs.

"Whilst we're often focused nutritionally on making sure we meet energy and protein demands of sheep - and that should be the first and foremost thought - minerals are still incredibly really important to deal with," Mr Dickson said.

"Ultimately, if there is a severe mineral deficiency, it doesn't matter how much energy and protein you throw at an animal, you won't achieve maximum production levels because that mineral deficiency is still holding the handbrake on."

This article appeared in Powering Up Profits and here