At this time of year many sheep farmers will of course be concerned with the upcoming tupping season and the issue of sheep fertility, writes Rachel Mallet, BVM&S MRCVS, a Bimeda Professional Services Veterinarian.

While fertility is a complex issue, with a variety of contributory factors, what is accepted by vets, nutritionists and farmers alike is the critical role that trace element nutrition plays in not only ensuring a successful breeding season, but also ensuring that lambs are born healthy and strong. Some trace elements in particular are hugely important.

Copper, for example, plays a critical role in fertility, but housed sheep and continental breeds are known for copper sensitivity, meaning that copper supplementation can prove fatal in these sheep. It is critical that farmers adopt a scientific approach to supplementation and only supplement animals where a need to do so has been established.

Copper is also vital to prevent the development of swayback in lambs. Mid pregnancy, the lamb’s nervous system develops and if the ewe has insufficient copper the nerve fibres cannot form normally. The lamb will be born with swayback: a damaged nervous system which cannot be reversed.

Other critical trace elements for breeding ewes and unborn lambs are selenium and iodine. While selenium is required for the prevention of white muscle disease, selenium deficiency can also result in impaired reproduction, reduced immunity and reduced milk production.

Iodine is also hugely important, and insufficient iodine can result in poor growth, weight loss, reduced hormone secretion and impaired reproductive health. While adults are often slow to present clinical signs of iodine deficiency, the consequences for the lambs are they carrying can be severe, as ewes will not be able to transfer sufficient amounts of the element to the unborn lamb. This can result in lambs being born weak or dead. Surviving lambs may be hairless, slow to suckle, and suffer from goitre. Often the lamb will suffer from poor growth rates.

Cobalt is also a critical trace element for ewes and lambs, as it required for the production of Vitamin B12, which is important for thrive and fertility. The body has no capacity to store cobalt, therefore cobalt must be continuously supplied. A long-acting soluble glass bolus such as Coseicure or Zincosel Sheep is a good option for the long-term provision of cobalt.

When And How Should Trace Elements Be Supplied?

Any deficiencies within the flock should be identified well in advance of tupping (6-8 weeks ahead). Supplementation should ideally be implemented at least 4 weeks prior to tupping, if required to improve fertility.

Peaks and troughs in supplementation have a negative impact on fertility so it is vital to have a consistent supply of trace elements.

Unfortunately, many of the traditionally-favoured methods of supplementation are not suitable for the required supply of a consistent supply of trace elements. For example free-access systems such as licks and blocks are not ideal as they suffer from variable intakes, with some ewes potentially ingesting no trace elements at all, and others consuming to excess. One study carried out, (Kendal, 1977), showed that 50% of ewes did not consume any trace elements via these free access systems.

Oral drenches can also be problematic and prove inconvenient, as their short-acting nature means frequent dosing is required. Options such as pasture dressing and water supplementation are also less than ideal, and can suffer from variable intakes, which are often related to the weather. For hill sheep, these options can be difficult in practice due to extensive nature of hill sheep production. Supplementation feeding also presents problems; adding significantly to the cost of production for hill sheep due to extensive conditions.

Injections also offer disadvantages, requiring long term storage within the animal or frequent dosing, and only offering one mineral per injection.

A Scientific Approach

Peaks and troughs in supplementation have a negative impact on fertility so it is vital to have a consistent supply of trace elements. Boluses, and particularly the Bimeda Coseicure, Cosecure and Zincosel soluble glass boluses are the ideal method of supplementation in the pre-tupping season.

They supply exactly the same amount of trace elements every single day, so the peaks and toughs of trace elements, which have a negative impact on fertility, do not occur. They last for up to 8 months and the boluses’ trace elements can be transferred via the placenta to the unborn lamb.

Critically, the Cosecure and Coseicure soluble glass boluses are the only boluses to supply rumen-available ionic copper, which is vital to address excess molybdenum levels that can result in infertility.

Cosecure Sheep boluses supply copper, selenium and cobalt. Coseicure supplies these trace elements but also provides iodine. Zincosel provides zinc, cobalt and selenium and is frequently used by breeds or housed sheep which are sensitive to copper toxicity.

For more information, speak to your vet or animal health supplier, or call Bimeda on 01248 725 400.

Alternatively, see cosecureboluses.com

By Rachel Mallet, BVM&S MRCVS, Bimeda Professional Services Veterinarian,