Farm Ireland

Friday 23 February 2018

Inbreeding worries as Oman rules

Caitriona Murphy

Caitriona Murphy

Concern is mounting about the dominance of Holstein bull O-Bee Manfred Justice (Oman or OJI) and his sons on the ICBF dairy bull listings.

It is understood that the number of Oman sons on the spring active bull list, due to be published tomorrow, is continuing to rise. The autumn 2009 active bull list showed no less than 34 Oman sons, close to half the entire list.

However, the spring 2010 list is expected to show a higher number of his sons than last year.

While the Oman effect so far has been to greatly increase genetic gain within the Irish herd, the long-term effect of his dominance in the bull rankings could be to increase the level of inbreeding in the herd.

According to the ICBF, one of the downsides of genetic gain is that related animals tend to be selected (as sires of sons and bull mothers) within each generation.

Unless this problem is managed inbreeding will result, with harmful effects on overall profit in the longer term.

Oman, which has an EBI of €280.07 in the February 2010 evaluations, is so successful at producing high EBI offspring that his sons are dominating the top rankings.

However, the danger is that when Oman's daughters begin to calve down, there will be no unrelated bulls of high genetic merit to service them.

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A staggering 43 bulls in the top 100 bulls ranked on EBI this month are Oman sons, while their sire heads the rankings.

Dr Andrew Cromie of the ICBF has insisted that, while inbreeding is not an issue in the short term for the Irish herd, it could become a problem within three to four years if the situation is not corrected.

As a result, the ICBF and Teagasc have initiated research to identify "out-cross" sires of sons and bull mothers within the national herd, and suggest matings to these herd owners.

It is anticipated that the resultant male calves, to be born in 2011, will either be picked up as young progeny test sires for Gene Ireland or sold as stock bulls to commercial users.

"In this way, genetic diversity and long-term genetic gain will be managed for our farmers and wider industry," said Dr Cromie. "Prevention is better than cure in this case."

Irish Independent