Holstein UK has recently started publishing the inbreeding coefficient of Holsteins and Friesians on web factsheets. Darren Todd discusses the interpretation and use of this value.Inbreeding is an inevitable consequence of genetic progress in dairy cattle breeding. Popular Al bulls with high genetic merit for economically important traits, can have tens of thousands of daughters and sire sons which are themselves widely used. Hence the genes of potent bulls such as RORA Elevation and Pawnee Farm Arlinda Chief are present in the genetic make-up of most modern Holsteins.rnInbreeding is a problem for two main reasons;rn1) Inbred animals risk inheriting two copies (homozygous) of any particular deleterious gene from the same ancestor (appearing on both paternal and maternal sides of the pedigree). Example of these genes are BLAD, CVM and the recently identified Cholesterol deficiency (CD). These are known as 'lethal genes'and homozygous carriers tend to die in the embryonic stage or as young calves. Inbreeding depression is caused by less harmful genes which affect vigour and fertility when the animal is a homozygous carrier.
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