Small things make a big difference in growing lambs

To get to the top of this range requires attention to detail.

Ewe condition score and milking ability, pasture quality and quantity, climatic conditions, trace elements and genetics are among the variables farmers need to manage. It only takes one of these ingredients to be missing or to be in short supply to make it difficult for lambs to reach target weights.

Trace elements, though only required in small amounts, are a key part of this big picture. Adequate dietary levels are essential for healthy lamb growth and production. Selenium and cobalt (used to make vitamin B12) are of particular importance in NZ farming systems.

Providing the ewe’s selenium and B12 levels are adequate, her suckling lambs should receive enough of these minerals through to weaning. If the ewe’s mineral levels are not adequate then additional supplementation may be necessary to ensure good lamb growth rates.

The trick is to know whether you need extra supplementation and whether to give this to the ewe or the lamb. If targeting the ewe, then a pre-lamb mineral boost is ideal; if targeting the lamb then docking/tailing is the first ideal opportunity.

Ideal selenium and B12 levels for lambs:

Herbage (mg/kg DM) Liver (nmol/kg) Serum Blood (nmol/L)

Selenium >0.03 >440 >100

Cobalt >0.11 - -

Vitamin B12 - >375 >500

Test to supplement

Herbage samples in the spring, when the grass is growing, can give you an idea whether the pasture will supply adequate amounts of key minerals.

Herbage trace element information should be supported with liver or blood samples, to confirm actual levels for animals and the level for supplementation required.

All stock have different requirements for each trace element, but an animal health professional can help you decide where there may be shortfalls and interpret the results.

There is a range of different options available for boosting animal trace, including mineral amended fertilisers, mineralised drenches, injections, pour-ons, etc.

• Paul McKee is a Ravensdown animal health advisor.