Cold spring makes early weaning a sound option

Cold spring weather is keeping a lid on pasture and lamb growth rates so early weaning a proportion of the lamb crop may be a good option this season.
Monday, 28 October 2019

Farm systems scientist Tom Fraser says despite plentiful rainfall, cold spring temperatures mean pasture growth rates in most regions are well below normal for this time of year and this is impacting on lactation and pre-weaning lamb growth rates.

He says given the time of the year, when ryegrass does come away it will quickly go to seed, as it is daylength rather than soil temperatures that determine when it goes reproductive.

“So rather than being long and seedy it will be short and seedy.”

Anecdotally, farmers are reporting tight feed supplies and this builds a strong case for weaning at least a proportion of the lamb crop early so what high-quality feed is available can be partitioned into lambs.

On a positive note, Tom says the cold spring will favour clover production as competition from ryegrass is reduced. This should help drive strong post-weaning growth rates.

“Pre-weaning growth rates are back but we should see some good post-weaning lamb growth rates.”

While early weaning does give farmers the option of selling annual draft ewes before the end of the year, Tom says given strong ewe prices, farmers might consider using the ewes to groom pastures and put extra weight on them post-weaning.

Trials run at Massey University found lambs over 20kgLW coped best with early weaning (minimum weaning weight was 16kg LW), but it was the quality of the forages on offer that was the greatest determinant of how well lambs grew post-weaning.

Professor Paul Kenyon, who led the early-weaning trials, says early-weaned lambs should be given unrestricted access to legume-based forages such as a herb clover mix at a minimum cover of seven centimetres in height.

If lambs are weaned onto the crop, they should be given time to adjust to a change in feed. Running the ewe and lambs onto the crop a few days before weaning, then running the lambs back onto the crop after weaning will help minimise the weaning check.

He says in late lactation all lambs, but especially multiples, are receiving very little nutrition form the ewe, so when grass-growth is limited the ewes are competing with their lambs for feed, compromising the performance of both.

Early weaning can also be particularly useful in hoggets as it will give them more time to recover body condition between lambing and mating again as a two-tooth.

Partitioning high quality feed into lambs in the last spring early summer period will benefit the whole farm system. It means more lambs can be sold prime before the height of summer- making more feed available for capital stock – and ewe lambs can be grown out to heavier weights early. This means there is flexibility to hold them back later when feed resources are more limited.

Find out more

For more information, go to https://beeflambnz.com/search?term=Early+weaning or listen to Professor Paul Kenyon explain the principles of successful early weaning at https://beeflambnz.com/knowledge-hub/podcast/successful-early-weaning-lambs-professor-paul-kenyon-massey-university