Wool is a fibrous protein that is produced by specialized skin cells known as follicles (Sahoo & Soren, 2011). The amount of wool a sheep can produce is dependent on a various of factors, such as breed, genetics and nutrition. While the sheep’s capacity for production and quality of fibre is determined by its genotype, its ability to express its genetic potential is heavily based on its nutritional intake. Nutrition plays an important role in wool production as it can be used to manipulate the flock’s wool performance and quality.

Wool characteristics are based on the value of the fleece which includes fleece weight, fibre diameter and length of staple. Sheep require an adequate nutrition to increase these characteristics and to encourage wool growth. This is because production of wool is dependent on the supply of nutrients available to the follicles during growth (Sahoo & Soren, 2011). Based on numerous studies, 16 minerals have been found essential to include in diets of sheep. These minerals include the macro-minerals: sodium, chloride, calcium, phosphorus, magnesium, potassium and sulphur. And micro-minerals iodine, copper, iron, manganese, zinc, molybdenum, cobalt, selenium and fluoride. We commonly refer to micro-minerals as trace elements, it is important to note that trace minerals are only required in small quantities by the animal. Some trace minerals are required at a much smaller rate compared to others. For example, in table 1.1 you can see that cobalt and selenium are required in very small quantities compared to zinc, manganese and iron.

Source: Based on data presented by the ARC (1980), Grace (1983), NRC (1978), Underwood (1981) these amounts represent the average requirements for growth, pregnancy or lactation, in grazing livestock.

Minerals have shown to influence and alter the production of wool in sheep by affecting feed intake, altering rumen function and the flow of nutrients from the rumen or by directly disrupting the metabolism of the sheep (Sahoo & Soren, 2011). Trace elements such as copper, zinc, iodine and possibly selenium alter the follicle function and wool growth directly. Cobalt has no direct role to wool growth. However, cobalt is essential for the synthesis of vitamin B12 by rumen microbes (Lee, 1951). Vitamin B12 is also involved in many essential enzyme systems (Lee, 1951).  Therefore, a deficiency in cobalt may alter fibre growth via disrupting the synthesis of vitamin B12.

Copper plays a very important role in maintaining quality wool fibre (Sahoo & Soren, 2011). A deficiency in copper can result in de-pigmentations of the wool. This de-pigmentation is caused due to a low activity of the enzyme tyrosinase which contains copper (Sahoo & Soren, 2011). An inadequacy of copper in the diet will also produce wool that lacks crimp and has low mechanical strength and a lustrous appearance (Sahoo & Soren, 2011). Copper deficiency in sheep occurs when there is a decline of copper reserves within the liver, as a result defects in wool appear (White, 1996).   

Zinc deficiencies result in a marked reduction in wool growth and induces a reduced feed intake. A zinc deficiency causes some wool fibres to shed and fibres that are produced are at a poor quality as they also lack crimp and become brittle. The lack of zinc within the diet can marginally reduce cell division in the follicle bulb (White, et al., 1994), this then limits the number of follicles to produce wool. Low zinc within the diet also affects the keratinization of fibre (White, et al., 1994).

Selenium has also been identified to play a role in wool growth, a deficiency in selenium reduces the growth of wool without a reduction in feed intake (Sahoo & Soren, 2011). While the direct correlation between selenium and wool growth isn’t known, it has been assumed it is based on the relationship with selenoproteins. Selenoproteins have a key metabolic role as antioxidants and affect the redox status of cells (Sahoo & Soren, 2011). A deficiency in selenium may result in oxidative stress caused by an increased concentration of peroxides of hydrogen and lipids (Sahoo & Soren, 2011). Oxidative stress can be responsible for cell and tissue damage and in extreme cases can cause gene repression via alteration of transcription factors (Sahoo & Soren, 2011). A study in Western Australia by Edwards (1982) assessed selenium intake in sheep, he found that on average selenium supplementation increased wool growth by 5% and body weight by 3.9% (Masters, 1996).

A lack of iodine in a sheep’s diet reduces the production of the thyroid hormones, this causes abnormal follicle development in the foetus (Hynd, 1994), long term this will impact the next generation of wool producing flocks. Deficiencies of iron also reduces wool growth and quality in adult wool producing sheep (Hynd, 1994). In extreme cases the follicles of thyroid deficient sheep cease fibre production completely (Hynd, 1994).

Trace mineral deficiencies in grazing sheep are typically common as mineral supplies vary between seasons, soil type/conditions, pasture type and stage of maturity (Masters, 1996). Therefore, it is important for graziers to understand trace mineral content variations for both the production and health of their sheep. The stage of plant maturity and season can influence the concentration of minerals within the pasture. For example, concentrations of phosphorus, sodium, potassium, sulphur, iodine and zinc fall as the plant matures  (Masters, 1996). Poor pasture growth or quality can cause a reduction in wool growth and total fleece yield (Sahoo & Soren, 2011).

Even lush green pastures and pastures in a rapid growth phase are associated with mineral issues. The concentration of cobalt and selenium tend to be at their lowest during these periods.  This is because plants do not require selenium for growth and cobalt requirements are lower compared to the requirements of ruminants (Masters, 1996). The decreased concentration of these minerals is due to the dilution within the plant, consequently deficiencies will occur. Temperate grasses have been found to generally contain less iron, copper, zinc, molybdenum and cobalt (Masters, 1996). As soil pH increases the content of selenium and molybdenum also increase, but copper, zinc, cobalt, iron and manganese decrease (Masters, 1996).

As trace mineral contents fluctuate based on these environmental factors it then alters the availability of minerals for intake, this can then interfere with the absorption and utilisation of other minerals. For example, high intakes of iron interfere with the utilisations of copper (Masters, 1996). Because of this the animal now becomes deficient in copper and begins producing wool with a lack of crimps, poor strength and de-pigmentations. Or high levels of molybdenum form insoluble complexes with copper preventing its absorption which will also cause poor quality wool (McDonald, 2011).  

Across Australia trace mineral deficiencies vary between regions. Copper, cobalt and selenium are deficient in most coastal areas of Australia. Large parts of Queensland and Northern Territory are marginally deficient in zinc. Iodine is regarded as marginally deficient throughout Australia and molybdenum is not regarded as deficient. Majority of forages grown in eastern Australia and South Australia are copper deficient.  

Trace minerals are essential elements for both growth and production. Therefore, it is important to ensure your herd is receiving the correct amount and to replace quantities that are lost during metabolism. Commonly drenches are generally used to overcome trace mineral deficiencies. However, drenches are usually short acting and inconvenient for frequent treatments. DIT offers uTRACE as a water-soluble trace element solution that contains iodine, copper, cobalt, selenium, zinc and manganese. Supplementing uTRACE does not require drenching or needling for administration and can be customised to address specific trace mineral deficiencies. This allows farmers and producers to correct trace mineral content to improve the productivity of livestock, especially during pasture and seasonality changes when trace minerals fluctuate.

uTRACE can be accurately supplemented into the water via the uDOSE. The DIT uDOSE unit proportionally doses our water-soluble supplements into the water line, allowing nutrients to be delivered evenly from the unit straight to the mouth of livestock drinking from troughs. Since animals drink accordingly to their body size, you can ensure that each animal will intake the correct amount of supplement to meet requirements.

Reference list

Hynd, P., 1994. Follicular determinants of the length and diameter of wool fibres. 2. Comparison of sheep differing in thyroid hormone status. Australian Journal of Agricultural Research , 45(6), pp. 1149 – 1157.

Lee, H., 1951. Cobalt and copper deficiencies affecting sheep in South Australia. Journal of Agriculture, South Australia, Volume 54, pp. 1-22.

Masters, D., 1996. Mineral Deficiency Problems in Grazing Sheep: an Overview. Australian Centre for International Agricultural Research, Volume 37, pp. 2-12.

McDonald, P., 2011. Animal nutrition. 7th ed. England: Pearson.

Sahoo, A. & Soren, N. M., 2011. Nutrition for Wool Production. Webmed.

White, C., 1996. Understanding the Mineral Requirements of Sheep. Australian Centre for International Agricultural Research, Issue 16-19.

White, C., Martin, G., Hynd, P. & Chapman, R., 1994. The effect of zinc deficiency on wool growth and skin and wool follicle histology in male Merino lambs. British Journal of Nutrition, Volume 71, pp. 425-435.