All through the ages, mankind has tried to improve the domesticated animals around him. The results have been varied and fantastic. We now have over 200 breeds of sheep, well over a 100 breeds of cattle and who knows how many breeds of dogs, cats, chickens, goats, pigs etc. Generally speaking, the animals were improved in looks, rather than performance, until about 150 years ago. The Englishman Bakewell, through intensive keeping of records noted what he was actually doing, and improved the English Leicester.
Since then, his methods were copied everywhere else and great improvements in performance were made. Enhancing one trait is relatively easy, depending on the inheritance factor and improving the growth rate in chickens and pigs, and the milk yield in cows occurred fairly rapidly.
Breeding to improve several characteristics, as with multi-purpose sheep, is a lot more difficult and if you try to improve the average flock on more than six traits, you won't make any progress at all, unless you have thousands of animals to choose from.
To help ram breeders in New Zealand, the Ministry of Agriculture developed a computer assisted, performance based recording scheme in 1969. Because only a few Sheep Breeding Societies made it mandatory to use the scheme, the progress in the New Zealand flock as a whole has been limited. The computer inputs required the lambing production, milk yield (by recording lamb weaning weights at 100 days) and growth rates and fleece weights of the lamb at 300 days.
The output produced is called a production index and this has enabled the farmer to make a better informed choice on what animals he/she should keep. Breeding values of the different traits make it possible to put the emphasis where the breeder wants to.
The breeding values have of course a different economic value, depending on the hereditability factor and their worth in dollars and cents.
Fertility, with a factor of only 12%, has more economic value than say fleece weight with a factor of 25% or growth rate at 30%. In other words, some traits are harder to get than others and are worth more.
These Relative Economic Values (REVs) using past and current prices multiplied by the breeding value produces the Estimated Breeding Value, which is the total index, expressed in dollar cents which you see on the 2th selection list.
REVs can be reviewed from time to time to reflect the changing market conditions.
The Coopworth Society uses the following REVs:
Number of lambs born = 500 cents
Number of lambs reared = 600 cents
Weaning weights = 15 cents
Latest weight = 17 cents
Hogget fleece weights = 100 cents
Here I have been trying to improve on five traits and as such, sail very close to wind in the improvement stakes.
These traits are, in order of importance:
Over the past 20 years I made on average 1.2% progress per annum, with a good performance in FE tolerance and fertility, but with less progress in other traits.
If there had been no constraints in my choice of animals, I could have made approx. 2% progress per annum, maximum.
Of course there are always good indexed animals that have faulty feet, jaws, wool faults, not enough size and so on. Knowing so much about an animal sometimes makes the choice more difficult, especially when the faults are minor.
Overall though the recording scheme has had enormous benefits for ram breeders that participated.
Breeding group schemes, where groups of farmers put their best ewes on one farm to eliminate environmental differences and based on population genetics, were popular up to ten years ago, but were superceded by Sire Referencing Schemes.
Copied from the bull referencing scheme that the Dairy Board was running, we now have our own sire referencing schemes.
Every year we select two rams, whose off spring, with the help of artificial insemination, are compared with the descendants of the rams used on the farm in any given year.
The results give you a chance to see how your own rams compare against the best rating rams, it also enables you to get hold of the best available genes.
In my case, with the need to put FE tolerance first, this limits the progress I could be making, since the ram off-spring of the reference sires don't survive the FE test.
Occasionally however an FE tested ram has made it to the top. My aim is to get more FE sires in the reference team in the next few years.
For further reading see: "A guide to Genetic Improvement in sheep" by Ken Geenty, published by Sheep Improvement Limited.