Genomic testing of black and white stock bulls

Rhys Davies, Dairy Technical Officer

Many commercial dairy producers often use beef or dairy stockbulls to sweep up any repeats after a period of artificial insemination. Currently bulls are bought either privately or through specialist bull sales and are often set to work on bulling heifers as well as cows. The untried and untested bulls are often bought on parent information along with the look and conformation of the bull itself. However with recent advances in genomic evaluations by AHDB Dairy for the majority of dairy breeds, it is now also possible to select stockbulls on important health and production traits.

Three yearling bulls owned by Richard and Ruth Pilkington from Shordley Hall in Wrexham were genomically tested through Holstein UK and AHDB Dairy’s genomic evaluation service.  These bulls had their genomic proofs returned with reliability for various traits of between 58% and 68%, which doubles that of parental average alone. This information can then be used to select the most appropriate bull to use on their own herd or provide buyers with additional reliable information regarding production, health and conformation potential. Indeed the information would be at the equivalent reliability to that of any young genomic bull semen sold by the various breeding companies.

Table 1. Production, health and conformation traits from the genomic proof of three young bulls bred at Aintree Holsteins

One of the bulls, Aintree Squire would rank in the top 30 genomic young bulls according to the UK genomic type merit index and just inside the top 500 young bulls for £PLI if he was available commercially, also all three bulls have favourable negative somatic cell count values and are above £450 on £PLI. If used on heifers it would be wise to consider the relative average calving ease score of the three bulls before using widely on maiden heifers, with Aintree Wesley being the slightly easier calving of the three.

Fig 1. Example of a genomic bull proof for one of the three tested bulls

With a single test costing around a £100, sellers of black and white stockbulls should consider the possibility of testing and providing buyers with the additional reliability and information that a genomic bull proof will bring. Buyers should consider any feeding costs of stockbulls along with the availability of adequate housing and handling facilities.