Ensuring lamb growth rates are maintained after eight weeks of age can be a challenge, however worming, and ensuring a continuous supply of good quality grass with the sufficient trace elements will help.

These were just a few of the conclusions from a serious of information webinars conducted by sheep, grassland and veterinary specialists at SAC Consulting and Scotland’s Rural College (SRUC).

Poppy Frater, SAC Consulting's sheep and grassland specialist, told the audience that weighing lambs at eight weeks provides a greater understanding of how well lambs are growing and allows farmers to home in on any management issues if they are not reaching target.

Lamb growth after eight weeks of age typically reduces as the nutrition from milk diminishes while at the same point the lamb is growing, and requires more energy for maintenance as well as growth.

Given the intake from milk reduces at that same point, the quality and quantity of pasture therefore plays a greater role in maximising the lamb’s growth rate. The three main challenges that can hold back growth rates at this stage are: feed quality and quantity, gut worms and trace elements.

Hence, she advised flock masters to weigh in logical groups and lambs of uniform mobs. To prevent gut fill, lambs should be weighed at the same time of day – at least 56 lambs per mob. Scales need to be checked for accuracy too.

“Don’t pick the best, random selection from the mob, e.g., weigh every sixth lamb,” she added.

“Energy drives lamb performance and ewes milk is the best energy when they will receive at 13MJ/kg of ME, therefore make best use of it pre-eight weeks to maximise performance. Post eight weeks, offer the best pasture to ewes and lambs for example, clover pasture +12ME, average ryegrass/clover pasture 10.5-11ME and avoid pastures with stem and dead material in it as this is low energy and will dip growth rates.”

General pasture management tips include:

* Avoid grazing below 5cm

* Graze leafy material and move on

* Legumes and herbs have a quantifiable benefit to growth rates

* Minimise stem and dead material

Those on the webinar were advised that ‘adaptive management is key’ to weaning. Focus on how the lamb is preforming and growing, and how the grass is growing.

“Twelve weeks seems optimal, but if lambs are not thriving, they can be weaned from eight weeks to allocate the best forage to lambs and lean ewes,” Ms Frater added.

“Key to early weaning, is having good quality forage – at least high-quality clover or multi species sward – or if the ewes are fit and loads of grass is available to them, maybe keep them on their mothers depending on condition and the season."

She added that some flockmasters are drawn to premium prices paid for old season lambs the following year. However, such lambs are more expensive to produce, and are costly to the remainder of the business.

“The growth rate for a lamb finished at three months would be 424grams/day, where as a lamb finished at 11 months would be 116grams/day. The dry matter these lambs would require would be 77kg DM (three months) and 261kg DM (11 months), with some 184kg DM difference, this would be one third of a ewe and lamb requirement. Meaning for three long keep lambs, one more ewe could be run by the business.

“Other costs to the system include additional feed, vaccination, labour etc for the 11-month lamb versus the three-month lamb. There are real system benefits to lambs maximising their growth potential when they are younger and most efficient at liveweight gain.”

Heather Stevenson, veterinary investigation officer at SRUC Veterinary Services, highlighted the challenges worms cause.

“Young lambs are very naive to worms, as they have not developed immunity to them, so they produce a large number of worm eggs after eating larvae, which in turn results in challenges from pasture. If they are doing well nutritionally, the challenge should not be as severe, but if they have other issues at the same time such as coccidiosis, then farmers are more likely to see signs of disease.

“Nematodirus in young lambs is typically the first problem you will come across. This is evidenced in scour and deaths in 6-12-week-old lambs, as this is when the grass intake increases. Nematodirus eggs shed in early summer, larvae develop over summer, and then sits there, it likes periods of cold weather before larvae hatches in following spring.

“A lamb-to-lamb disease, eggs hatch once there have been seven consecutive days of 11.5-17degrees centigrade. For this reason, the weather influences when we see outbreaks of nematodirus, usually in May and June in Scotland."

She added: “People can forecast the disease risk through the SCOPS website. Taking grazing history into account, eggs can last for two years in a field, so ideally don’t graze young lambs in the same field every year.”

As temperatures increase into summer, eggs develop more quickly and so at the same time as the lambs are eating more grass, they will eat the larvae which can also be from the previous year, as the larvae can survive through the winter.

Field risks and how to take appropriate action:

* High risk = fields where nematodirus was a problem last year, fields with ewe or store lambs last autumn, ewes and lambs in the spring

* Low risk = cattle only previous year, grazed by non-lactating adult sheep last year, silage

“If you continue to have a problem and you have a high-risk field, then graze with cows, graze with non-lactating ewes for example, weaned ewes, plough and reseed or plant a forage crop,” added Ms Stevenson.