Gene chip could save dairy industry big bucks

Mastitis, or bacterial infections of the udder, is a AUD$140 million a year problem for Australia's dairy industry. It can cost farmers up to $150 an animal to treat, and affects both milk output and quality.

Some cows don't get mastitis. Others suffer from chronic udder infections, sometimes by particular bacteria, like Escherichia coli and Staphylococcus aureus. Is it just environmental chance, or in the genes?

Researchers with the Cooperative Research Centre for Innovative Dairy Products have identified a number of genes involved in resistance or susceptibility to mastitis.

The adaptive immune system usually deals efficiently with bacteria typically found in the dairy farm environment, like Escherichia coli but contagious bacteria like Staphylococcus aureus. - golden staph - can cause chronic infection.

CSIRO Animal Production biochemist Dr Ross Talbot said the CRC's gene discovery program has employed a new gene-expression chip, developed in-house, called the Bovine Immune Gene Chip.

It has shown that genes involved in the innate immune response are particularly important for resistance to contagious bacteria.

He said some 5000-odd genes are involved directly or indirectly in the innate and adaptive immune responses - "A very large part of the mammalian genome is devoted to protection against disease."

These genes are represented on the gene chip, allowing researchers to rapidly compare expression levels in udder tissues from individual animals.

The chip has identified several innate immune response genes whose level of expression correlates with resistance - or susceptibility. They include genes for cell-signalling molecules like interleukins.

Cows that express these proteins at high levels in udder tissue are more resistant, and low levels correlated with susceptibility.

Talbot said the project offered two routes to improving herd resistance to mastitis. One was to develop genetic markers that would allow breeders to track high-expression alleles in their breeding programs.

Another was to develop drugs to increase expression of infection-fighting genes, boosting resistance in susceptible animals.