New genetic technology to boost dairy cow health

Bonnie Mallard
Bonnie Mallard

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

Speaking at this year’s Semex conference, the scientist behind the technology, Professor Bonnie Mallard from the Department of Pathobiology at the University of Guelph, Ontario, Canada, said the new High Immunity Response technology could result in a reduction in disease of between 4 and 8%, 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% is similar to that for milk production traits, and far higher than those for longevity (8-10%), calving ease (6-7%), daughter fertility (4-7%) and mastitis (10%).

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% of sires tested for immune response. Semex, which has exclusive rights to the technology for ten years at least, then chooses the top 10% for its new Immunity+ range of bulls.

Research carried out on 700 cows in the US showed the technology had resulted in 27% fewer cases of mastitis, 17% metritis, and 32% fewer cases of retained placentas, without any adverse production effects. In other studies disease reduction was up to 50%. Mrs Mallard also stated that 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 that the financial benefit of having a High Immune Responder cow, compared to a Low Immune Responder cow would be $124 (c£80) per year. Daughters of High Immune Responder sires will have $80 or so (£50) of added profit contributed because only have 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,” she said. “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.