FLOCK FIGURES ADD UP…
FLOCK FIGURES ADD UP…
Selecting solely on indexed
performance has helped a
Kent-based Suffolk nucleus
flock improve lamb
performance and carcass
lean meat content.
Emma Penny reports
PERFORMANCE isnt diluted by cosmetic whims by members of the Wye Suffolk Improvement Group, and its a policy that has paid.
Since the groups nucleus flock was established at Wye College eight years ago, lamb weight at scanning has risen by 4.65kg and muscle depth has improved by 1.99mm – a 10% increase.
According to the colleges senior lecturer in animal production, Geoff Pollott, the policy of selecting on performance only may sound fairly standard, but few breeders do it. "We havent totally ignored looks – we do take functional traits such as legs into account. But we dont select for cosmetic factors."
The group was set up by the college and 11 breeders, each of whom contributed 10 of their best ewes to the nucleus flock with the aim of increasing the speed of genetic progress.
"Starting with high performance stock meant that rapid genetic progress could be made by the nucleus flock. The progeny are passed back to members, so they have a stream of genetically-progressive animals coming back into their own flocks," explains Dr Pollott.
Genetic management has been simplified by the use of a family system, with the flock divided into five families and rams rotated round these groups each year. Five rams are selected annually and used as ram lambs for one year, while five ewe age groups are kept for breeding and the oldest group replaced annually with two-year old ewes.
Selection of superior stock for the nucleus flock is based on index values. The flock was, and still is, recorded under the Signet Sheepbreeder programme, with lambs weighed and scanned at 20 weeks old to obtain growth rate, fat and muscle depths.
"Our objective was to increase carcass lean content, and produce rams for sale to commercial breeders who are finishing lambs."
The emphasis on commercial production has paid off, with average lean weight/carcass increasing by 125g/year, while average fat weight/carcass has only risen by 65g/year.
"Lean and fat contents are highly correlated, so one cant be increased without the other rising. However, we have tried to pick out animals which have high growth rates and muscle content but low fat content, and it has worked."
The four breeders remaining in the group hold an annual ballot to decide which of the ram lambs they take back into their own flocks and the remainder are sold as shearlings.
This year, the nucleus flock is to join the Suffolk Sire Reference Scheme, which will again increase rate of genetic progress, says Dr Pollott.
Results of the Wye flock are better than those of the Suffolk SRS over the same period, which show changes in average EBV of 1.56kg in eight week weight, 3.41kg in 20 week weight, 1.22mm increase in muscle depth and 0.13mm rise in fat depth, combining to produce a 54 point increase in index score for SRS progeny.
But Dr Pollott points out that results of the Wye flock and SRS are not directly comparable as the genetic base between the two is different.
"At the moment, we dont really know whether our lambs are good, bad or indifferent compared with other flocks. However, joining the SRS means 30 of our ewes will be inseminated with two reference sires, and next years MLC data will compare our progeny with those in other scheme flocks."
Dr Pollott says he has no idea how the Wye flock will compare with others. "If we started out with good ewes originally we should come out of it reasonably well. But whatever happens, we will maintain – and even improve – the rate of genetic progress." *
Joining the Suffolk Sire Reference Scheme will allow comparison of genetic progress between SRS flocks and the Wye nucleus flock says senior lecturer Geoff Pollott.
FLOCKIMPROVEMENT
• Scanning weight +4.65kg
• Muscle depth +1.99mm
• Fat depth +0.17mm
Selection of superior stock for the nucleus Suffolk flock at Wye College is based on index values. The main objective is to increase carcass lean content.
Average EBVs for four recorded traits and index score by year of lambing in Wye Suffolk nucleus flock
Year Eight week 20 week Muscle depth Fat depth Index score
weight (kg) weight (kg) (mm) (mm)
1990 0 0 0 0 100
1991 0.559 1.125 0.331 0.012 118
1992 0.697 1.651 0.654 -0.012 131
1993 0.827 1.820 0.749 0.032 132
1994 1.027 2.346 0.741 -0.006 140
1995 1.624 3.556 1.471 0.108 161
1996 1.486 3.243 1.385 0.029 160
1997* 1.690 4.651 1.921 0.120 181
* = Provisional results