A number of factors can indicate when lambs should be weaned depending on the season and the decision on when to wean lambs should be determined by ewe body condition, feed availability and lamb growth rates.
Liz Genever, AHDB Beef and Lamb livestock specialist says: “From eight weeks of age a lamb’s energy intake is greater from grass than from milk, so competition for high–quality grass between ewes and lambs reaches a critical point. Grazing management and grass growth will differ year on year, so the ideal weaning date cannot be set in stone; figures from the Stocktake survey suggest lambs are usually weaned between 12 and 14 weeks of age.
“If the grass is growing well and ewes are in good condition, weaning can be delayed without reducing lamb liveweight gain. However, if forage availability is low, lamb growth rates will suffer, as ewes and lambs compete for the same grass. If lamb growth rates are lower than 200g per day, this should trigger weaning and lambs should be moved onto better quality forage.
“If creep feed is being fed, liveweight gain may not decline after eight weeks, so weaning decisions should be based on how long the lambs have until they are finished as well as ewe condition.”
High quality grass with lots of green leaf and limited stem and dead matter will be greater than 11.5 MJ of ME, compared to less than 8 MJ for grass with high degree of dead matter and stem. Dry matter intake is calculated at four per cent of bodyweight, for example, a 30kg lamb consuming 1.2 kg DM per day with access to 11.5 MJ forage will be consuming 13.8 MJ per day and should be gaining more than 250g per day.
Research has shown animals which experience novel feeds, such as red clover, chicory or cereals, when with their mothers, perform better once they are exposed to the feed when weaned. It can take up to three weeks for the rumen to adapt to a new feed, therefore it is important to think about a transition period if the lambs are being weaned onto different feeds, says Dr Genever. Any treatments, such as vaccines or wormers, should be given before weaning as stress can affect the immune response, especially to vaccines, making lambs more susceptible to disease.
Dr Genever says ideally, lambs should be weaned onto a pasture they know, but out of sight and sound of the ewes. Once they have settled, they can be moved to pasture with a known low worm burden or onto a forage crop. The parasite challenge in recently weaned lambs should be checked with faecal egg counts.