DNA testing is starting to become more popular in the sheep and beef breeding industries, but it doesn’t hold all the answers, veterinarian Trevor Cook says.
New technologies just keep coming along and having any understanding of how they work is increasingly impossible. The comforting aspect of this is that these aids can be effectively used with no understanding of how they work. Two technologies that I just cannot get my head around are purely domestic ones. I’m now into electronic books and cannot understand that when I purchase a book through the device it appears on that device just seconds later. Was it waiting outside my window along with the thousands of other options that I could have chosen? In my new kitchen is this cooking top that only gets hot when a particular type of pot is put on it. That defies my logic. What is also becoming common, but is new technology that can be hard to fully understand, is the world of DNA.
The family game for my Christmas gathering was to each do a DNA analysis to see where we came from. Luckily my kids had bits of where both my wife and I came from. I sort of understand this technology but still find it quite remarkable that our early origins can be identified.
This same type of technology is becoming mainstream in our cattle and sheep breeding programmes. A blood sample from a lamb or a calf can be analysed, and the genetic ranking of that animal be determined against a much wider recorded population. Not all breeds of sheep or cattle have a large enough recorded population to enable this but nevertheless the technology is there and is being used.
The parentage capability has been about for a while and is fully understandable. While these are powerful tools for making genetic gain, the environment in which any performance selection is made in must have an influence on how any genetic status is expressed. At a recent genetics meeting it was comforting to hear breeders talk about the importance of a bull or ram buyer driving up the breeder’s driveway.
Animal health inputs, animal health challenges, mob sizes, feeding levels, terrain and climate can all impact on how any animal can perform. How strong is the evidence that, for example, the performance of the offspring of a stud ram coming from a ewe flock that never gets above 250 mob size and lives on a “park” is different than if that ram had come from a ewe flock run in a 1500-ewe mob on hills where the spring does not always come? Intuitively there should be a difference, but I see, not often, performances, particularly on hills that defy the genetic background. This really highlights the number of factors that impact on the performance outcomes of beef herds and sheep flocks. Maybe as long as those four or five key management influences do happen, the impact of those other factors in the list are very diluted. It supports my finding a few years ago when I looked at the ram source of ten highly profitable sheep flocks in New Zealand. Only two shared the same ram source and five sheep breeds were represented.
To bring some credibility to the breeding programmes, progeny testing is being used by at least the sheep industry. While this is not a new technique, its use on a national level has been in place since 2002. The performance of the offspring of sires can be compared in the same environment. Since not all breeders can ever be represented in such tests, the results for comparison are obviously limited to those used. But a big benefit of such a test is that linkages between sheep breeders can be strengthened and so strengthen the validity of any wider published comparisons. Of course, the environment of these progeny test farms comes under scrutiny for exactly the reasons above.
To reinforce my comments above, the day-to-day management of any flock or herd has the biggest impact on its performance. A change of ram or bull source does not necessarily lead to higher performance.
