Since those times we have seen dramatic increases in the productivity of our sheep and beef farms, due partly to improved management of feed and partly through genetic improvement. We should celebrate the remarkable successes some of our ram and bull breeders have achieved in such a short time.
While there is still great potential for further improvement of productivity on a national basis, some traits may be near to their optimum for certain farming systems and environments – for example, commercial farms with lambing percentages heading toward 200%, that are producing heavyweight, lean lambs with low levels of fat.
How does this affect the way genetics should be sourced when this is the case?
Ram and bull breeders in New Zealand make use of selection indexes to rate animals for overall merit. Such indexes put pressure on the component traits to change in the “desired” direction (see table). While individual animals vary in their relative strengths, using indexes to buy rams or bulls will cause a directional change in all traits over time in your flock or herd.
It is implicit that we want to move from where we don’t want to be, to where we do want to be. So what do we do when we get to the objective for one or more traits? Further change is not what we want.
An example in our sheep and beef industries is fatness in some maternal ewe and cow lines. Some people believe that the animal types with optimal level of fatness for lamb and beef carcase production have insufficient fatness as ewes and cows to act as a buffer when feed is short and conditions challenging e.g. through winter and peak lactation.
If you do not want some traits to change in the direction an index favours, these indexes will not identify the best animals for you. You may wish to “hold” traits that are near their optimum or even “reverse” any that have overshot the mark. You will need to work with your ram or bull breeder to find the rams or bulls that will improve performance of your flock or herd. Make your needs known to them with respect to traits that are near an optimum or past that optimum. They can then help identify the best animals for your situation.
Selection indexes are still a powerful tool. Their strength is in assessing overall merit for a basket of traits. Different indexes targeting different users are a feature in NZ, but where individual farms have different needs, not all animals with high overall indexes will be as good at meeting their needs.
How can you help your breeder to address your needs? Provide feedback to them about performance of meat animals you send for slaughter and of your ewe flock or cow herd. Pay attention to things you use to assess performance or that indicate animals are under pressure.
Ram and bull breeders want repeat business, so they will want to help you get what you need. Take the time to identify your needs and inform them before you arrive to buys rams or bulls.
- B+LNZ and SIL are interested in your views. You can send us your thoughts by email to email@example.com or by leaving a phone message on 0800-silhelp (0800-745-435).