A successful breeding strategy is built on a number of core principles. Genetics provides the potential for high performance, but to fully utilise this potential, management practices need to be first rate.
There is generally scope on many farms to increase performance with the genetics on hand.
This statement rings true for litter size and barren rates, which, in turn, directly influences possible levels of output.
Research carried out by Teagasc and many other institutions shows a strong relationship between ewe liveweight/ body condition score (BCS) and subsequent litter size.
Looking at lowland ewes to begin with, each one unit increase in BCS within a range of 2.5 to 4 has the potential to increase litter size by 0.13 lambs per ewe joined.
Where the BCS of ewes is below a score of 2.5 at mating, it will significantly increase barren rates.
Addressing the body condition of ewes starts at weaning. There has traditionally been a tendency to tighten up ewes on bare pasture for long periods of time post-weaning, resulting in some ewes losing significant weight and falling below target BCS.
This strategy is not only a poor use of resources, it also greatly interferes with an animal’s metabolic processes and can take ewes longer to recover when their nutritional intake increases.
It will take eight to 10 weeks on good grass for ewes to gain one condition score (equivalent to 12% to 15% of bodyweight or 10kg to 12kg in lowland breeds with a mature liveweight averaging 80kg), reinforcing the importance of taking swift action.
The ideal strategy is to split ewes into groups based on BCS – ewes which need preferential treatment and ewes which can be worked hard and used to graze out paddocks after lambs.
An intake of 1kg grass DM to 1.1kg grass DM will generally be sufficient to meet maintenance requirements of ewes in optimum BCS at weaning.
Numbers in the preferential treatment group should hopefully be small and in the region of less than 20% of ewes.
Where this is the case, many farmers join these ewes to a batch of weaned lambs once they have been adequately dried off to reduce the number of grazing groups on farm.
Ewes that fail to improve condition, despite an adequate period of preferential treatment, should be culled from the flock
Under the correct management, healthy ewes with a good mouth can gain 1kg to 1.5kg grazing leafy swards. Weight gain will be lower with aged ewes or where ewes are recovering from a low base.
Ewes that fail to improve condition, despite an adequate period of preferential treatment, should be culled from the flock.
Ewes should be monitored closely and moved from groups once they have reach the desired condition or, conversely, if ewes in the maintenance group have lost condition.
The other reason relating to the statement “breeding starts at weaning” refers to the identification of cull ewes.
The cull ewe trade has been running at record levels for heavier-fleshed ewes for much of the year. This should lessen the blow of a hard culling and clearing out problem ewes or poor performers.
The likely higher value of replacements will erode some of this benefit for those purchasing replacements, but it should still leave the system in no worse of a position.
Some farmers who have a performance-recording system in place use it to identify a given percentage of the bottom-performing ewes for culling annually and thereby allowing continuous improvement in the flock by incorporating replacements with better genetic potential.
Research shows the Scottish Blackface breed of sheep is particularly responsive to achieving target BCS and liveweight at joining with rams.
Increasing from a BCS of 2 to 3 has the potential to lift the lambing percentage by some 13.5%, with the potential gains reflected in Table 1.
This is achieved through a combination of an increased litter size and a reduced barren rate, while having hill ewes in the optimum body condition score of 3 to 3.25 will also deliver in tightening the lambing spread. This is detailed in Table 2 with scope to reduce the lambing spread by five to six days.
Work carried out through the Teagasc BETTER farm sheep programme and findings from Teagasc research lists the following weight targets:
Ewes falling behind weight targets should be grouped, where possible, for preferential treatment and access to better quality grazing.
The level of output in a hill ewe flock will have a major bearing on the breeding programme which can be implemented. As reflected in Table 1, where the number of lambs reared is relatively low at 0.8 lambs per ewe joined, then the focus in the flock will need to remain on pure breeding to be in a position to replenish the flock.
If the number of lambs reared is in the region of 1.10 lambs per ewe joined, it provides much more scope to implement a crossbreeding programme if desired or, alternatively, to produce surplus hill replacements, with a strong market also opening up in recent years due to the increase in crossbreeding taking place.
The Teagasc guidelines have been calculated for a hill flock with a replacement rate of about 24%, while also allowing for 10% of any potential ewe lambs to be deemed unsuitable for selection.
The breeding policy should also focus on breeding the type of ewe and progeny that can excel in the terrain in which they are run, as maintaining land to good agricultural and economic condition has a major influence on direct payments and adherence to environmental schemes.
This could become more important in the future, given the changing direction of supports and the fact that up to 25% of a farmer’s basic payment scheme payment could be decided via eco schemes.
For example, there is no point in chasing the crossbreeding market and significantly altering the breeding profile of the flock if it will lead to issues in managing hill vegetation and sustaining a ewe type that is not suited to the environment.
The lambing date should also match the natural trend of spring forage availability.
The article focuses on management of ewes but it is important not to forget about the other 50% of the breeding mix.
Where purchasing rams, they should be sourced well in advance of when they will be required. This will allow sufficient time to implement a robust quarantine and health protocol and, unfortunately for many, an acclimatisation period may be required to adjust rams from an intensive concentrate-based diet to a grass-based diet.
In terms of the ratio of ewes to rams, the general advice is 1:40. Some farmers opt to increase this to 1:80 and even 1:100, while others targeting a condensed breeding period will reduce below the 1:40 ratio.