New genetic technology to boost dairy cow health

THE incidence of disease in dairy cattle is increasing, and the only way to tackle it has been through management practices and veterinary inputs.

However things are changing according to Prof Bonnie Mallard who explained how new genetic technology will help reduce disease levels because sires can now be tested for their immune response, with the best ones chosen in order to pass their genes on to their daughters.

Prof Mallard from the department of pathobiology at the University of Guelph, Ontario, Canada, said the new high immunity response (HIR) technology could result in a reduction in disease of between 4 and 8 per cent, and bring financial benefits of £50 per cow per generation – equivalent to the amount gained from production related genetic improvement.

The heritability of immune genetics at 25 per cent is similar to that for milk production traits, and far higher than those for longevity (8-10 per cent), calving ease (6-7 per cent), daughter fertility (4-7 per cent) and mastitis (10 per cent).

Immune response

Disease breakdowns occur when an animal’s immune system does not make an adequate response to a pathogen challenge, either through the first defence mechanism, which is within the cell, or through the second mechanism, which is outside of it, she explained. The HIR technology provides a genetic boost to both of those immune mechanisms. An animal’s immune response can be measured through two relatively simple tests involving three farm visits.

High immune responder cows are defined as the top 16-20 per cent of sires tested for immune response. Semex, which has exclusive rights to the technology for 10 years at least, then chooses the top 10 per cent for its new Immunity+ range of bulls.

Research carried out on 700 cows in the US showed the technology had resulted in 27 per cent fewer cases of mastitis, 17 per cent metritis, and 32 per cent fewer cases of retained placentas, without any adverse production effects. In other studies disease reduction was up to 50 per cent.

Zero mastitis

Prof Mallard also said one HIR group of cows had no cases of mastitis after 220 days in milk, in stark contrast to average or low immune response animals. Trials also showed the technology resulted in the cows responding better to vaccines and having higher quality colostrum.

Her conservative estimate was the financial benefit of having a high immune responder cow, compared to a low Immune responder cow would be $124 (£80) per year. Daughters of high immune responder sires will have about $80 (£50) of added profit contributed because only half of their genes will be high immune ones.

“Selection for production has increased the pressure on fertility and health,” she said. “In addition, there are increasing restrictions on antibiotic use in livestock so we need to look for natural alternatives to livestock health. This is one of them.”

The next stage of her research will be to further validate the health of daughters of HIR sires, and to carry out genomic studies into high immune responder technology.

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