The business of high genetic turnover is not necessarily to do with hybrid
vigour. The standard way of doing things in this part of the world is for
the stud breeders to have the most rapid generation turnover supplying
superior stock to commercial farmers. In this way the farmer is always
about 2 generations "behind" the stud in genetic progress.
The general principle is that there is always a distribution of genetic
potential. To maximise the genetic gain one 1)has maximum selection ie
very few animals at the extremes of performance, out of as large a base as
possible, and 2)shortest generation turnover. The latter partly depends on
what you are selecting for and at what stage in the animal's life this is
These principles are basically statistical and so probably apply whether or
not you are "organic".
The big thing these days is sire referencing where many studs participate
in a scheme where top animals from stud farms are compared. Normally one
cannot directly compare 'top animals' directly for genetic potential
because individual farm conditions have such a great effect on performance.
However, in this scheme, there can be a direct comparison. Also I don't
think it excludes sires who have not already been labelled as 'top' thereby
admitting other genetic material all the time.
As for sustainable agriculture, I feel we have to be careful in asking the
right questions, but I'm not sure I know them. The above description is
glibly based on "performance". What that performance is, is determined by
the breeders. Traditionally it has been production (weight, yield etc) but
with more recent emphasis (at least in NZ) on internal parasite resistance
etc. It is probably important for organic farmers to say we have these
values (xyz) that we want to place this weighting on in the breeding index.
Complicating factors are that many desirable attributes do not have easily
measurable parameters (like disease resistance) and work has to be done to
find good tests or measures. One of these could well be 'production over
lifetime of x years' as opposed to plotting annual production over a short
One quandry is that we can't be best at everything at the same time. If we
want the highest genetic progress, the cost is generation lifetime. This
may not be a desirable feature in sustainable ag. We could say that other
things are more important...welfare issues may say that an animal deserves
an respectable lifetime, in which case the cost is genetic progress and
probably production levels (since production peaks pretty early in an
I hope this prompts a bit more discussion on this topic.