days of natural service. This would certainly be an underestimate as there
would be a tendency for the dams of young bulls to have well-known
fathers. But the actual estimates of the rate of inbreeding in Denmark as
well as considerations of the structure itself would certainly suggest that
there is no reason whatsoever to fear too great a restriction of pedigrees
in an A.l. breeding system.

| have been talking up to now almost entirely about dairy cattle. |
would like to discuss rather briefly the situation in Great Britain in so far
as it affects two other kinds of animals in which A.l. is widely used -
pigs and beef cattle. In pigs, the emphasis in breeding programmes, pri-
marily due to the example of Denmark, has been on progeny testing,
mostly to obtain good evidence on carcass characteristics. A.l. has as
yet not spread widely in pig breeding but we should perhaps ask whether
any inbreeding problems are likely to arise from its use. From the dir-
ection which pig improvement seems to be taking in Great Britain | would
think we do not have a great deal to worry about. The knowledge that
some of the most important economic characteristics in pigs (food conver-
sion and back fat thickness) could be measured on the boar himself and
that appeared to have a high heritability, has led to the conversion of
our progeny testing stations into performance and progeny testing stations.
Each year 5000 boars are tested in the stations in groups of two from each
litter, with at the same time a female and a castrated male which are
slaughtered for carcass measurements. The emphasis is then placed not in
the possibility of progeny testing old sires but in evaluating the probable
breeding merit of the young sires. With 5000 being tested each year,
this would almost certainly mean that the genetic base of the population
will stay very wide.

Up to the present, artificial insemination has made no contribution
to the improvement of our beef cattle for the simple reason that it was
impossible to register animals got by A.l. in most of the beef breeds.
There are signs that this opposition from the pedigree breeders is being
relaxed somewhat and that it will be possible in the near future to re-
gister sons from the best sires already used in A.l. A progeny testing
station for the evaluation of these sires on the basis of the beef char-
acteristics of their crossbred progeny has already been set up and it is
hoped that this information could be used to breed new bulls to be tested
in their turn. In the early stages, at least, this would almost certainly
mean a broadening of the breeding structure as it is likely that the bulls
shown to be good for producing commercial crossbred progeny will not
necessarily completely please the pedigree breeders.

What kind of pattern in the breeding of dairy cattle by A.l. will
we see in the future? In several countries, notably Sweden and Norway,
there is no doubt that breeding programmes closely based on A.l. results
will be developed, stimulated by the work of Professor Skjervold {9). In
the working out of these programmes, he has calculated the optimum

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