Designing a Flock Breeding Programme
The number of lambs reared per ewe joined is a key determinant of the overall financial performance of a lowland sheep enterprise. Sheep Specialist Damian Costello outlines the factors to be considered in a flock breeding programme including: culling, ram selection and purchase of breeding stock.
When it comes to profitability of a lowland sheep enterprise it’s a numbers game – number of lambs reared per ewe joined is a key determinant of the overall financial performance of the system. Teagasc research has shown that female progeny from rams known for prolificacy, such as the Belclare breed, have the capacity to wean 1.7 to 1.8 lambs per ewe to the ram. In analysis of data from the Teagasc Research Demonstration Farm, Bohan et al 2017 concluded that increasing weaning rate from 1.5 to 1.8 lambs weaned per ewe to the ram increased net profit by €336/ha on average across all stocking rate groups carried on the farm. Increasing flock prolificacy has the greatest impact on profitability and should be the first priority to change at farm level. Assuming the current level of management and labour availability on a farm allows for increasing prolificacy of the ewe flock, implementing a good breeding policy will result in a higher output flock in 4 to 5 years.
Cull to improve flock performance
The main reasons for culling ewes from the breeding flock include udder problems, teeth, body condition and 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.
Closed flock option
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.
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.
Ram selection to breed own replacements
To produce prolific replacements you will need to select an appropriate ram. 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 carcase 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|