How to check for and treat trace deficiencies at lambing

The wet winter could impair trace element availability and affect lamb growth rates this season, warn vets.

Correct trace element supplementation of lambs is vital to ensure they achieve maximum growth rates, with cobalt often having the greatest effect.

Jenny Hull, a beef and sheep vet with Alnorthumbria Veterinary Group, said cobalt could be the most limiting in growth rate and copper deficiency can affect fertility.

When lambs are growing fast on grass, cobalt levels can become low, as it can only be stored in the liver for a maximum of three weeks.

Signs of cobalt deficiency:

• Low appetite
• Increased worm burden
• Cracked and crisp ears due to photosensitisation

To obtain a picture of a farm’s trace element status, blood test ewes before tupping. The cost for testing six sheep for copper, cobalt and selenium is about £150.

Treating on the back of pasture analysis alone is not adequate as high selenium >can lock up copper in the soil, making it unavailable to grazing animals.

See also: How to prevent trace element deficiency in lambs at weaning

If ewes have not been tested before tupping, there is still the opportunity to test lambs if they are not performing and worms have been ruled out.

Vet Mark Thompson from Kingsway Veterinary Group advises: “The best time to test is at weaning, or soon after at 12-16 weeks, when all nutrition is obtained through grass and none through milk.”

Testing six to 10 lambs from ewes that have lambed earliest will give a clue as to whether later-born lambs are at risk, allowing supplementation to begin before signs and symptoms occur.

Choosing the right supplementation

With a variety of supplementation options on offer, choosing the right one can have a significant effect on profitability and free-access minerals uptake can be very variable.

“Some take too much – for example, old ewes, where other younger sheep don’t get a look in. They are also expensive at £400-£450/t,” says Dr Hull.

When deciding to use drenches, cobalt and selenium are the most important active ingredients affecting lamb growth.

“Some seem to have everything, but only cobalt and selenium make a difference. Other vitamins are not necessary. Drenching must be repeated every four weeks. The bit in wormers won’t correct a deficiency,” she warns.

Trial treatments

For sustained release without the need for frequent drenching, Dr Hull recommends cosecure boluses, citing the results of a monitor farm trial carried out four years ago in Northumberland.

It involved 500 Suffolk cross Mule and Texel cross Mule lambs, all twins, grazing on white clover/grass leys, offered no minerals and wormed once at weaning.

The trial took place between July and November, with finished lambs drawn throughout.

Treatments included a control group receiving no additional cobalt supplementation, two different cobalt, selenium and vitamin drenches, a SmartShot cobalt injection, a triple bolus and cosecure copper, cobalt and selenium glass boluses.

With the latter, lamb boluses were given to lambs under 25kg and ewe boluses to those greater than 25kg.

Trial results for lamb weight gain are shown in the table below. “The additional profit [through using cosecure boluses] is worth it,” says Dr Hull.

However, for short-keep lambs it may be worth simply using a 6p-a-head cobalt-selenium drench, she admits.

Administering boluses

When using cosecure boluses it is important to administer them warm to avoid shattering, she warns.

To warm them up place two hot water bottles in a bucket and place the boluses in between them until they need to be administered, she advises.

“Then put them in your pockets. They should be almost hot to touch when you put them in.”

Care should also be taken to minimise bolus gun injuries to sheep’s throats when administering boluses, says Dr Hull.

When administering copper-containing products to sheep it is important to get veterinary advice, particularly for breeds sensitive to copper such as Lleyn, Beltex, Soay, Zwartbles and Texels, warns Dr Hull.