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Nucleus flock

It is not cost effective to include all animals in a breeding programme, on account of measurement and recording costs, and the difficulties of proper control. The solution is to concentrate effort on a few elite breeding animals, referred to as a nucleus flock.

Nucleus flocks are ‘closed’ if only animals from the nucleus flock can contribute to genetic improvement of the nucleus population, and, are ‘open’ if sufficiently competitive animals from the general population are introduced into the nucleus. Open nucleus flocks have less inbreeding, and can benefit from the superior genetic potential of animals from the larger population, thereby yielding faster genetic progress.