Selecting replacement ewe lambs
It is critical to not leave the selecting of ewe lambs to later in the year after some of the best lambs have been sent for slaughter or sold for breeding. Damian Costello, Sheep Specialist, Teagasc Athenry, discusses selecting replacement ewe lambs and asks if farmers are culling hard enough.
There are many advantages to running a closed flock, not least reducing the risk of buying in flock health issues. The ultimate goal in breeding replacements from within the flock is to produce future mothers that will improve flock productivity. The heritability of many of the desirable maternal traits varies but mating the best performing ewes in the flock with a high genetic merit maternal sire gives the best chance of producing suitable replacements. As there is a genetic component to many flock health traits it is advisable not to retain replacements from ewes that have had issues such as mastitis, lameness, prolapse etc.
Selection process
With the current particularly strong sheep trade it is important not be tempted to cash in on potential replacement ewe lambs. The selection of ewe replacements should take place at first drafting or weaning whichever comes first. It is critical to not leave the selecting of ewe lambs to later in the year after some of the best lambs have been sent for slaughter or sold for breeding. This is effectively introducing poorer performing animals into the breeding flock. It is beneficial to identify more ewe lambs than you will need at this stage. If 25% is the target replacement rate then selecting 30% to start with allows lambs that fail to perform post weaning or encounter health issues be selected out later in the season.
Ideally, potential ewe lamb replacements are first identified at birth using criteria such as lambs born without assistance, vigorous and up sucking quickly, dam has lots of milk and good mothering ability.
Permanent identification is needed using EID tag, management tag or ear notch. At weaning, this group of potential replacements can be selected from based on lambs that are structurally sound, healthy, have good conformation and well grown for their age. Even on farms where ewe lambs are not identified at birth but there is still potential to identify lambs from high performing ewes. The best grown lambs at weaning have good growth traits and most likely come from ewes with good milk yield characteristics, particularly if reared as a twin. You are also selecting for fertility as the strongest lambs were probably conceived to first service.
Are we culling hard enough?
Some of the primary reasons for culling ewes include udder health, broken mouths and poor body condition. The identification of ewes for culling for other issues requires a simple recording system and this need not be an onerous task. All that is required is management tags to identify potential replacements at birth along with cull tags to identify animals that need to be culled.
Hard culling to remove poorly performing and problem ewes will speed up the improvement of a flock's breeding potential.
It is especially important at lambing time to identify culls with a tag or ear notch. If you can identify the dams of the lightest lambs at weaning, insert a cull tag, they are not up to the job. Participants in the Teagasc Sheep BETTER farm programme are carrying out a high level of flock recording with all lambs being EID tagged at a day old. Many participants in the programme are identifying and culling ewes that produce the lightest lambs at weaning. This policy has significantly reduced the percentage of lowland lambs in these flocks that are under 25kg liveweight at weaning.
Teagasc Athenry Sheep Open day Saturday 18th June 2022
Along with a host of other topics information on Breeding for longevity will be presented at next Saturdays open day. We will have up to date information on maternal genetic index selection for sheep and how replacement strategies and management can impact ewe longevity and output. All are welcome to come along from 10am to 4pm with further details on: https://www.teagasc.ie/sheepopenday/
The Teagasc Sheep Specialists and Researchers issue an article on a topic of interest to sheep farmers on Tuesdays here on Teagasc Daily. Find more on Teagasc Sheep here. For any further information or assistance contact your local Teagasc Office here: Advisory Regions.