The Role Of Trace Element Nutrition for Sheep Health, Wellbeing and Fertility
Nutrition plays a central role in the health and wellbeing of sheep, particularly when coming into the mating season. In the run up to tupping it can be very important for farmers to understand the nutritional status of their ewes and whether there might be any trace element deficiencies, excesses or interactions which could be affecting health and fertility.Trace elements are sometimes called 'micro-minerals' as they are essential in very small amounts on a regular basis. The most common trace elements to be considered commercially important for sheep are copper, cobalt, selenium, iodine, and zinc. Here we explore the role of these important trace elements in the health and reproduction of adult sheep.
Copper can also be highly toxic to sheep and so supplementation should only be considered where a deficiency is diagnosed. Also, breeds such as Bluefaced Leicester, Charollais, Zwartble and Texel sheep are particularly susceptible to copper toxicity. Boluses which include copper should not be administered prior to housing without evidence of deficiency and advice from a veterinarian or nutritionist.
Iodine is a component of thyroid hormones which regulate the rate of metabolism and control the rate of absorption of carbohydrate from the gastrointestinal tract. Iodine is therefore central to a good food conversion ratio. The utilisation of iodine in the body also depends on selenium, as selenium is critical to thyroid hormone synthesis and activation.
Zinc operates as a co-factor in around 300 enzymes which are involved in immune function, fertility (sexual maturity, reproductive capacity, the onset of oestrus), healthy hooves, bone and cartilage, udder and skin health and wound healing. Like cobalt, ruminants have very little capacity to store zinc.
Trace element status will vary from year to year and from farm to farm. There is no way to know which deficiencies or toxicities exist without carrying out diagnostics. The effects of deficient diets may not be immediately obvious and are considered subclinical.
Forage forms the basis for all ruminant diets and knowing the levels of trace elements in your grass or preserved forages is a good place to start. If you do not know which trace elements are already being supplied, or which are in inadequate supply, then it is impossible to make decisions on what should be used as an additional supplement. Further analyses of water, soil, and animal tissues (blood and/or liver) might also be valuable to enable a diagnosis of deficiency to be made.
Choosing the Right Supplementation
The supplementation of trace elements can be done via many different routes. Trace elements are commonly included in many fertilisers as well in meals and feeds. Trace elements can also be found in oral drenches, lick blocks, injectable products and in oral boluses. Therefore, when reviewing you diagnostic testing it is worthwhile thinking about all the sources of trace elements which your sheep could be ingesting.
A trace element bolus which releases the required trace elements over several months can be a convenient supplementation option. These boluses release trace elements at levels that are compatible with an animal's daily requirements. They are a particularly good option for the supplementation of trace elements such as cobalt and zinc, which cannot easily be stored by ruminants, making a continuous daily supply necessary to address any deficiency.
It is always worthwhile to consult your veterinarian or nutritionist to help review the information, make an informed conclusion, and help choose the correct targeted approach to trace-element management in your flock.
References1. Gould and Kendall. 2011. Nutrition research reviews. Role of rumen in copper and thiomolybdate absorption, 24, 176-182.
2. Grace, Knowles and Sykes. 2010. Managing mineral deficiencies in grazing livestock. New Zealand society of animal production, p203.