Ewe Replacement Policy
As farmers complete the annual health check on their ewe flock to determine soundness for breeding, it is certain many will need replacing. To maintain current ewe numbers 23 to 25% is the average replacement rate for most flocks. Sheep Specialist Damien Costello has advice on replacement policy.
The replacement of ewes due to death or culling comes at a cost to the system. The options to provide replacements fall broadly into three categories:
- Retain homebred ewe lambs
- Buy in replacement ewe lambs
- Buy in replacement ewe hoggets
Cull to improve flock performance
The main reasons for culling ewes from the breeding flock include:
- udder problems
- body condition
- persistent lameness.
Along with these issues, strict culling to remove poorly performing and problem ewes will speed up the improvement of a flocks breeding potential. It is especially important at lambing time to identify problem cases 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. In assessing if a ewe is fit for breeding for another season it is useful to ask the question: Would I buy this ewe for breeding? The answer is based on the usual physical checks as well as any information you have on the previous performance of the ewe. If the answer is no then she has to go.
The preferred option is to produce replacements from within your own flock. There are many advantages to having a closed flock, not least reducing the risk of buying in disease. It will also put you firmly in control of the ewe breed that will make up your flock into the future. The system allows you to breed your best performing ewes from the flock with a high genetic merit maternal sire. Potential ewe lamb replacements should 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.
Ram selection to breed own replacements
To get the maximum benefit from this approach, you should use high genetic merit maternal rams with a view to producing prolific maternal replacements. Typically breeds such as Belclare, Blue-faced Leicester, Llyen or some other prolific breed are chosen. As well as checking the physical soundness of the animal before purchase, pay close attention to the €uro value on the Sheep Ireland index system. As the primary function of this ram is to breed replacements, focus on the replacement index values in particular. Also take note of the accuracy associated with the index values. The higher the accuracy the greater the confidence you can have that the values reflect the animals true performance potential.
Number of ewes to maternal rams to breed adequate replacements
In practice this system means that you will be running at least two groups of ewes during the mating season. One group with a maternal sire breed to produce replacements, the remainder of the ewes will generally be mated with terminal sire breeds with the focus on carcass production. The current weaning rate of your flock will determine what proportion of the ewe flock that needs to be mated to a maternal ram in order to produce enough replacements.
Table 1 below outlines this based on a 23% replacement rate. These calculations are based on the assumption that about 50% of lambs reared will be female and are minimum figures which allows for very little further selection. It is advisable to increase the proportion of ewes mated to maternal rams in order to give you more ewe lambs to choose from and also to allow for stricter culling of underperforming ewes.
Table 1 Lowland Flocks – Minimum % ewes bred to a maternal sire based on current weaning rate to achieve 23% replacement rate
|Number of lambs reared per ewe joined||Percentage of ewes required to produce ewe replacements|
Purchase replacement ewe lambs/hoggets
The big advantage to this system is simplicity – no need worry about these stock until they arrive on the farm. All terminal sires can be used with all progeny leaving the farm as stores or finished lambs. It’s important to understand the risks and potential financial consequences of buying in disease issues as well as the limits to genetic improvement within the flock. If this is the option that best suits the farm it would be prudent to try to establish links with a farmer or breeder group that specialise in producing maternally sired replacements that are sold as either ewe lambs or hoggets. Where the flock health history of the farm of origin is known to be good it can reduce the risk of bringing unwanted disease onto the farm.
Purchase breeding stock - Biosecurity
Where the system is to purchase ewe replacements a comprehensive biosecurity protocol should be drawn to minimise the risk of introducing new disease or resistant parasites to the farm. Veterinary advice should be sought in developing this plan. These measures apply to all new sheep coming onto the farm.
In the following video clip Dr Orla Keane has advice on quarantine treatment for any sheep coming onto the farm to prevent introducing resistant worms onto your pasture.