Ewe scan lifts flock quality
By Jeremy Hunt
RESULTS from annual ultrasound scanning of a Cumbria Swaledale flock are proving a valuable aid to improving carcass conformation.
Three years ago, Maurice Hall of Oak Bank Farm, Barras, near Kirkby Stephen, saw a Signet demonstration of the technique. Now ultrasound scanning – at about £2 a head – is an important element of the breed improvement policy underway in his 500 Swaledale ewes.
Mr Hall has been working to improve the quality of his Swaledale flock, aiming for a slightly larger, longer type with an increase in body weight. He has achieved a 4.5kg improvement in mature weight of ewes in three years.
For the first time in November 1997, just before tupping, the flocks shearling ewes were scanned by Signet. All sheep were weighed and scanning measurements taken for backfat at three locations on the vertebrae and eye muscle depth.
Measurements taken from each ewe were correlated and relationships between the eye muscle depth and weight and also fat depth and weight of individual animals were highlighted by Signet.
"Research carried out by SAC on Scottish Blackface suggests that ewes carrying excess fat, which most farmers believe ewes need to see them through the winter, does not have any real benefit. It does not improve survivability and you actually get a higher lambing percentage if ewes are leaner," says Mr Hall.
He has two average sets of figures – one for the scanned or nucleus flock and the other for the fell flock – on which to base ongoing performance achievements.
Average figures show that bodyweight of ewes in the nucleus flock is 51.6kg, compared with 47kg in the fell flock.
Eye muscle depth, at 4.5mm, is similar in both flocks. But the 23.6mm eye muscle depth in the nucleus flock shows an improvement of almost 1mm on the fell flock in the three years selection has been based on scanning data.
To monitor the breeding performance of individual rams, ewes are ranked according to scanning data. Superior rams are those producing ewes showing a high eye muscle depth in proportion to liveweight.
"One of our 10 rams that we would rate as doing good job is producing female progeny with bodyweights 5% higher than the average and with a fat depth 23% less and eye muscle depth 2% greater.
"That is a ram that is leaving size and good eye muscle depth in his progeny, which is what we want. But we are not just basing everything on the performance of the rams," says Mr Hall, who switches the lowest 20% of ewes, on figures, to the crossing flock.
"I am only breeding from my top 80% of ewes each year. If it hadnt been for the scanning figures I would have been breeding from ewes that were visually appealing but were clearly falling short on carcass quality, something that is only detectable by scanning."
Mr Hall says his aim is to have all ewes at a mature weight of 50kg and with a fat depth of no more than 3mm and an eye muscle depth of 25mm minimum.
"Signet says that the muscle depth figure in millimetres should always be at least half the liveweight in kilos."
Because only shearling ewes are scanned, the total costs involved are about £220 a year.
"I do not consider myself a tup breeder, but scanning is giving me the confidence to take rams through to shearlings knowing that they are of superior conformation because of scanning data. I can use these tups knowing, with a degree of confidence, that they will not allow the flock to deteriorate in terms of carcass quality."
Signet predicted that three years of scanning and selection should achieve 2kg extra weight on finished Swaledale wether lambs. In previous years, wether lambs -about 180 head – have been sold at 28-32kg into the lightweight export trade. This year they were sold during January and February at about 36kg.
"Eventually, improvements should filter through into the Mule via her Swaledale dam. Commercial prime lamb producers are already buying rams on performance data.
"I think we could see a similar trend on the female side. While I do not think we will ever see Mule gimmer lambs sold with a set of figures, I do think Mule buyers will go back to breeders whose ewes have proved themselves as producers of superior prime lambs because they have been bred from Swaledale flocks where conformation scanning is part of overall management," says Mr Hall.
• Scanning shearling ewes.
• Improve flock quality.
• Better carcass conformation.