Results of pregnancy scanning can be successfully used to investigate breeding performance while also being the starting point in assessing areas where flock performance can be improved.
With this in mind, I examined the pregnancy scan results of 51 mainly February and March 2018 lowland lambing flocks containing 18,156 mature ewes (in Meath, Dublin and Westmeath) through my work as a drystock adviser in Teagasc Meath.
The scan results of 32 of these flocks were also available for the previous year. Only the pregnancy scan results for mature ewes were included. Ewe lambs were not included.
Flock sizes ranged from 50 to 1,150 mature ewes. The average flock size was 356 mature ewes.
In brief, sheep farmers pregnancy-scan for three reasons – to detect barren ewes, to work out late pregnancy feeding and for management at lambing time. However, we greatly undervalue what can be learnt about each flock’s breeding performance from the routine task of ultrasound pregnancy scanning.
Scanning results can provide a lot of information on how successful the breeding season was. Scanning records can also highlight the potential lambs lost on your farm, ie the number of lambs found at scanning compared to the weaning rate. Scanning results may also highlight the lambs that were never there to start with.
Measure of breeding success
Pregnancy-scanning results are the best measure of an individual flock’s breeding performance. Scan rate is very specific because it’s taken two and a half to three months after ram turnout. So scan rate gives you a very clear picture of your breeding season’s success.
Why farm scan results were examined:
To understand what’s happening on farms.To examine each flock’s scan results.To compare yearly scan results.To highlight % of ewes barren.To highlight practices to improve scan rates.To make individual flock recommendations based on facts.To estimate lambs lost between scanning rate and weaning rate.What does pregnancy scanning rate mean?
Here, the pregnancy scanning rate is the number of lambs found at pregnancy scanning divided by the number of mature ewes put to the ram.
Why is pregnancy scanning rate important?
New Zealand and Irish research indicates that about 80-85% of the lambs found at scanning survive to weaning. Each 0.10 increase in the scanning rate increases the weaning rate by 0.08. This 0.08 increase in the weaning rate adds roughly €7 to output per ewe. A profitable ewe depends on a high weaning rate, which depends on a high pregnancy scan rate.
What does barren rate mean?
Here the barren rate equals number of barren mature ewes found at scanning divided by the number of mature ewes put to the ram.
Percentage of ewes barren
The percentage of ewes barren at scanning is critical. The examination of these scan records showed that flocks found it very hard to have a high scan rate when they have a high barren rate.
There are 13 flocks in the top 25% for scan rate. Only one of these had a barren rate above 3%. Of the 13 flocks in the bottom 25% for scan rate, 11 had a barren rate higher than 3%. The barren rate at scanning must be below 3%. Barren rates higher than 3% at scanning are signs of an underlying problem.
As 32 flocks had scan results for two years, it was possible to see the difference in an individual flock’s own scan results for 2016 compared to 2017. The average variation within a flock from one year to the next was on average a difference of 0.10 in the scan rate, eg from 1.75 (in 2016) to 1.85 (in 2017) or 1.80 (2016) to 1.70 (2017). This was surprisingly small. To me, this indicates a tendency for individual flocks to repeat the same practices each year, resulting in very similar outcomes.
Key drivers
In my opinion, it’s unlikely that most low scan rates are due to mineral deficiencies or disease. However, where there are high barren rates the possibility of mineral deficiency or disease should be investigated.
The key driver of the scan rate is body condition. Breed, age and length of breeding season are also important. As key events like weaning date, culling, breeding season, late pregnancy, lambing and lactation arrive, the shepherd’s practices will influence the outcomes.
Top flocks might not body-condition-score in a formal manner but they do cull persistently thin ewes and have a plan that builds condition for two months before breeding.
Most crossbred lowland ewe types can achieve a scan rate of 1.90. Most of the top 25% of flocks looked at here used either Belclare or Lleyn cross ewes. Only flocks that achieve a scan rate of 1.90 should go on to use these prolific ewe types like the Belclare, which can scan 2.10 to 2.4 lambs per ewe joined.
What is the best scan rate?
Determining what is the best scan rate is a topic of discussion often debated. From talking to those who provided their scan results, some farmers with scan rates of 1.80 or slightly below felt that a scan rate of 1.9 would best suit them. Most farmers with scan rates of 2.00 to 2.30 lambs felt that 2.00 to 2.10 lambs was ideal.
The general view from these farmers was that going much beyond 2.10 meant too much additional labour and cost. My own view is that for most commercial lowland flocks the target scan rate should be from 1.90 to 2.10. Go higher if you really want to and if you have the skill, labour and facilities but start from at least 1.90 lambs, the lowest scan rate for the top 25% of these farmers.
Lambs lost between scanning rate and weaning rate
The plan here is to go on and look at the relationship between scanning rate and weaning rate on these farms, ie if 100 ewes went to the ram and had a scan rate of 1.59 or 2.05, what will their weaning rate be? A good weaning rate begins with a good scan rate.
National and regional annual
scanning records
Having a representative sample of national and regional scan records annually for lowland flocks would:
Set a standard for flocks to compare to.Improve understanding of key breeding targets in this area.Give a clear picture of what’s happening each year.Establish the relationship between scan rate and weaning rate.Highlight if improvements are made.Overall, what I have done here is a very crude examination of a simple record. The main conclusions drawn:
Big variations in scanning rates between flocks.Target less than 3% of mature ewes barren at scanning.Target a scan rate of 1.90 to 2.10 for mature ewes.To improve scan rates, flocks below 1.9 must change their practices. Having a national and regional sample of annual scan records would provide valuable information.An excellent exercise for a discussion group.Acknowledgements
Teagasc would like to thank the participating sheep farmers from Meath, Dublin and Westmeath.
Results of pregnancy scanning can be successfully used to investigate breeding performance while also being the starting point in assessing areas where flock performance can be improved.
With this in mind, I examined the pregnancy scan results of 51 mainly February and March 2018 lowland lambing flocks containing 18,156 mature ewes (in Meath, Dublin and Westmeath) through my work as a drystock adviser in Teagasc Meath.
The scan results of 32 of these flocks were also available for the previous year. Only the pregnancy scan results for mature ewes were included. Ewe lambs were not included.
Flock sizes ranged from 50 to 1,150 mature ewes. The average flock size was 356 mature ewes.
In brief, sheep farmers pregnancy-scan for three reasons – to detect barren ewes, to work out late pregnancy feeding and for management at lambing time. However, we greatly undervalue what can be learnt about each flock’s breeding performance from the routine task of ultrasound pregnancy scanning.
Scanning results can provide a lot of information on how successful the breeding season was. Scanning records can also highlight the potential lambs lost on your farm, ie the number of lambs found at scanning compared to the weaning rate. Scanning results may also highlight the lambs that were never there to start with.
Measure of breeding success
Pregnancy-scanning results are the best measure of an individual flock’s breeding performance. Scan rate is very specific because it’s taken two and a half to three months after ram turnout. So scan rate gives you a very clear picture of your breeding season’s success.
Why farm scan results were examined:
To understand what’s happening on farms.To examine each flock’s scan results.To compare yearly scan results.To highlight % of ewes barren.To highlight practices to improve scan rates.To make individual flock recommendations based on facts.To estimate lambs lost between scanning rate and weaning rate.What does pregnancy scanning rate mean?
Here, the pregnancy scanning rate is the number of lambs found at pregnancy scanning divided by the number of mature ewes put to the ram.
Why is pregnancy scanning rate important?
New Zealand and Irish research indicates that about 80-85% of the lambs found at scanning survive to weaning. Each 0.10 increase in the scanning rate increases the weaning rate by 0.08. This 0.08 increase in the weaning rate adds roughly €7 to output per ewe. A profitable ewe depends on a high weaning rate, which depends on a high pregnancy scan rate.
What does barren rate mean?
Here the barren rate equals number of barren mature ewes found at scanning divided by the number of mature ewes put to the ram.
Percentage of ewes barren
The percentage of ewes barren at scanning is critical. The examination of these scan records showed that flocks found it very hard to have a high scan rate when they have a high barren rate.
There are 13 flocks in the top 25% for scan rate. Only one of these had a barren rate above 3%. Of the 13 flocks in the bottom 25% for scan rate, 11 had a barren rate higher than 3%. The barren rate at scanning must be below 3%. Barren rates higher than 3% at scanning are signs of an underlying problem.
As 32 flocks had scan results for two years, it was possible to see the difference in an individual flock’s own scan results for 2016 compared to 2017. The average variation within a flock from one year to the next was on average a difference of 0.10 in the scan rate, eg from 1.75 (in 2016) to 1.85 (in 2017) or 1.80 (2016) to 1.70 (2017). This was surprisingly small. To me, this indicates a tendency for individual flocks to repeat the same practices each year, resulting in very similar outcomes.
Key drivers
In my opinion, it’s unlikely that most low scan rates are due to mineral deficiencies or disease. However, where there are high barren rates the possibility of mineral deficiency or disease should be investigated.
The key driver of the scan rate is body condition. Breed, age and length of breeding season are also important. As key events like weaning date, culling, breeding season, late pregnancy, lambing and lactation arrive, the shepherd’s practices will influence the outcomes.
Top flocks might not body-condition-score in a formal manner but they do cull persistently thin ewes and have a plan that builds condition for two months before breeding.
Most crossbred lowland ewe types can achieve a scan rate of 1.90. Most of the top 25% of flocks looked at here used either Belclare or Lleyn cross ewes. Only flocks that achieve a scan rate of 1.90 should go on to use these prolific ewe types like the Belclare, which can scan 2.10 to 2.4 lambs per ewe joined.
What is the best scan rate?
Determining what is the best scan rate is a topic of discussion often debated. From talking to those who provided their scan results, some farmers with scan rates of 1.80 or slightly below felt that a scan rate of 1.9 would best suit them. Most farmers with scan rates of 2.00 to 2.30 lambs felt that 2.00 to 2.10 lambs was ideal.
The general view from these farmers was that going much beyond 2.10 meant too much additional labour and cost. My own view is that for most commercial lowland flocks the target scan rate should be from 1.90 to 2.10. Go higher if you really want to and if you have the skill, labour and facilities but start from at least 1.90 lambs, the lowest scan rate for the top 25% of these farmers.
Lambs lost between scanning rate and weaning rate
The plan here is to go on and look at the relationship between scanning rate and weaning rate on these farms, ie if 100 ewes went to the ram and had a scan rate of 1.59 or 2.05, what will their weaning rate be? A good weaning rate begins with a good scan rate.
National and regional annual
scanning records
Having a representative sample of national and regional scan records annually for lowland flocks would:
Set a standard for flocks to compare to.Improve understanding of key breeding targets in this area.Give a clear picture of what’s happening each year.Establish the relationship between scan rate and weaning rate.Highlight if improvements are made.Overall, what I have done here is a very crude examination of a simple record. The main conclusions drawn:
Big variations in scanning rates between flocks.Target less than 3% of mature ewes barren at scanning.Target a scan rate of 1.90 to 2.10 for mature ewes.To improve scan rates, flocks below 1.9 must change their practices. Having a national and regional sample of annual scan records would provide valuable information.An excellent exercise for a discussion group.Acknowledgements
Teagasc would like to thank the participating sheep farmers from Meath, Dublin and Westmeath.
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