As we are about to enter the ram buying and selling season, most articles on the subject are contributed by academics who are not actively involved in the breeding, buying or selling of rams. This perspective therefore could well be different to those who have practical experience in this important activity. Invariably their advice is good in the areas of “objective measurement traits” where they have expertise. Nevertheless, there are some aspects in recorded figures that, in my opinion, are not given sufficient emphasis. For example, environmental factors – disease, parasites etc. – can have a considerable impact on the accuracy of the computer generated indexes. More on this later.
There are many important traits that do not come under the “productive traits umbrella”, but nevertheless have an indirect impact on productivity and longevity. These include structural soundness – especially teeth and feet, wool that is free of serious faults, temperament and udder shape and teat placement. These physical attributes are seldom if ever mentioned, as they fall outside the criteria of objective measurement. It may well be assumed that it is the ram breeder’s responsibility to ensure sound rams are put up for sale.
I purchased my first ram at age 17 when my father, who had heart problems, instructed me to travel to Feilding – by train – and purchase a stud sire. I was not daunted by this as I had attended this sale on several occasions with my parents.
The Feilding Ram Fair was the top venue for selling stud Romney rams. The Romney breed dominated the New Zealand sheep scene being about 80% of all sheep. The high wool prices over the 1950-1970 period ensured unprecedented wealth for sheep farmers and made the New Zealand economy as one of the strongest in the world.
Stud Romney rams were making up to 5,000 guineas - $250,000 in today’s values. There were plenty of sales of more than 1,000 guineas (All stud stock were sold in guineas prior to the change to decimal currency. A guinea was one pound and one shilling – with the stock agent taking the shilling as commission).
Choice of Ram Source
One of the most important decisions a sheep farmer makes is where to buy his rams, because the strengths and weaknesses of the ram breeding flock will be transferred to the purchaser’s flock. One should also make a few discreet enquiries on the subject of the breeder’s integrity and ethics. Sadly, in all walks of life there are those whose standards of honesty are below par. Stud stock agents and wool consultants employed by stock firms have a good knowledge of ram breeders and how they operate. Also be aware that some ram breeders employ consultants, on a commission basis, to sell their rams. To me this is unethical as a farmer may think he is being given unbiased advice.
Now back to performance records
How accurate are the computer indexes. I believe that some ram breeders and buyers of commercial rams see the computer generated records along with their indexes as absolute and should be seen as fact. This is not correct. These indexes are a prediction – or forecast - of how an animal should perform in the traits that are measured. The accuracy of these predictions is dependent on a number of factors. If the data inputs are inaccurate or compromised by environmental circumstances, then the resulting indexes will be inaccurate. Once a young animal has progeny, that are also evaluated, they generate their own indexes. In a perfect world there should be little variation between the forecast indexes and the “real” indexes. However, like weather forecasts, the “real” weather that follows can be very different when unknown factors intervene.
In all animal recording systems, it is assumed that animals are farmed under equal conditions, and have equal health and parasite challenges. In the dairy world this is pretty well achieved as the herd grazes the same pastures most of the year. However, in the stud sheep farming situation this is not the case. Generally ewes will be single mated in different paddocks. At lambing time they will rear their lambs in different paddocks. These paddocks will have variable stocking rates, soil fertility levels, and different levels of fungi that produce toxins. All these variables that cannot be identified will impact on the accuracy of computer predictions and may not indicate an animal’s true genetic value.
However, I believe that in the better sheep farming areas – the southern parts of the North Island and most of the South Island – there will be much less impact of these environmental factors, so the predicted figures and rankings will be reasonably accurate.
In the warmer and more humid regions of the North Island where a range of challenging parasites and fungi abound, the impact on an animal’s performance can be significant (This is particularly the case with the toxin zearalenone, which suppresses ovulation rates. So, a ewe unfortunate enough to ingest high levels of this toxin, instead of producing twins, has a late single or worse still, fails to ovulate altogether, and is dry. The impact on her index will be significant and give a false prediction on her reproductive potential).
Over the years in my environmentally challenging area, I have noted that the predictive index of a two tooth ewe sometimes differs greatly from the index she creates with her lifetime performance. A ram’s 2 tooth index can also be affected.
On one occasion, I sold a physically correct ram with a very low DPO or overall index. This ram was sold two years later when this whole South Island stud was sold. By that time he had generated his own index with two years progeny being evaluated. There was a tenfold increase from his predicted index to his actual index two years later. Purchased for a modest price, this sire subsequently sold for $7,200. This is undoubtedly an extreme case, but shows how environmental factors can affect outcomes
Let me be quite clear, I am not critical of SIL (Sheep Improvement Limited) or those who administer it. Indeed, I believe those who designed these recording systems should take pride in their achievements.
In the future the new DNA system of identifying the traits that an animal possesses, will hopefully eliminate the environmental influences, and allow an animal’s true genetic value to be recognised.
In conclusion, I believe that the computer generated information is an invaluable aid which stud breeders are using. However, the computer is our servant not out master. For ram buyers the computer generated information is a good guide for selection. However, in areas of high environmental challenges, good figures are always a sure bet, but those with poorer figures may be a lot better than the figures indicate. Along with the figures a ram needs to be physically sound to pass this soundness on to his progeny. We need to remember that we have an excellent computer between our ears, which is sadly under used.