How to manage grass to ensure lambs gain enough weight before weaning

The performance of lambs tends to decline during the last four weeks in advance of weaning, according to Teagasc’s Dr Tim Keady.

The Teagasc Principal Research Officer said the growth rates slow as lambs make the transition from a mostly milk diet to a grass-based diet.

“For lambs reared as singles, twins and triplets the target gain is 340g/day, 295g/day and 290g/day from birth-to weaning.

“During the last four-to-five weeks prior to weaning, lamb growth rate declines to as low as <200g/day, whilst the target is 230-240g/day during this period.

You always get some reduction in lamb performance this time of the year because more of the lambs diet is coming from grass rather than milk.

Grazing management key for lamb performance

However, despite lamb growth rates slowing, Keady said good grazing management is key to getting the best performance from lambs offered a grazed grass diet.

Good grassland management is essential, he said, especially as grass growth has accelerated over the last couple of weeks.

At this stage of the grazing season, he said that farmers should aim to graze their swards to a post grazing sward height of 6cm, while ewes and lambs should enter swards which have a pre-grazing sward height of 10-11cm.

Heavy grass covers tend to contain a high quantity of stem, he said.

Keady also said that stemmy grass has a lower energy content and lower intake characteristics and a a result the lambs energy intake is reduced.

If the pre-grazing swards become too heavy, Keady recommended taking out bales or grazing it with other stock such as cattle.

He also said that post-grazing swards that contain a lot of stem should be topped.

By taking out paddocks for silage you are decreasing the rotation length and thus increasing the quality of grass which will be available for lambs post weaning

Parasite Management Of Lambs

Keady also said that parasite management is key for the performance of growing lambs.

He said that lambs in the Athenry flock are dosed at five weeks of age for Nematodirus, while lambs are dosed at 10 weeks of age to clear up any other parasites they may have.

The Teagasc researcher also said that lambs should be dosed at weaning, to ensure that these animals perform after weaning.