Scientists look for genetic key to milk production

Agricultural scientists are spending $4 million on feeding trials to find dairy cows which most efficiently convert feed to milk, and to identify the genetic markers for that capability.

Hamilton-based Livestock Improvement Corporation is working with Australian firm Innovative Dairy Products on the biotech project. Each company has received $1 million in Government grants over three years.

The project is expected to lead to significant gains in productivity in dairy cows by genetically selecting the most efficient cows.

Importantly, the project might help researchers not only find the genes controlling how efficiently cows convert feed to milk, but also identify the trait in any cow and enhance it through selective breeding, said Suzanne Bertrand, Livestock Improvement's innovation manager.

Once that was understood, the scientists expected to also be able to advise farmers about the sensitivity of specific sires and breeds to environmental factors such as temperature and oxygen, she said.

By comparing how genetically similar herds performed in different environments, the researchers might be able to distinguish between the effects of genetics and environmental effects.

Feeding systems would also be evaluated.

"The target of the proposal is definitively to understand if there are significant genetic differences in the metabolic conversion efficiency between cows fed in a very similar manner," said Dr Bertrand.

Milk production would be measured to evaluate efficiency, but other traits, such as fertility and health, would also be monitored.

Newly available mapping of the bovine genome would help researchers link production and other traits, she said.

It would be possible to recognise tiny differences in the genetic code, called single nucleotide polymorphisms, or SNPs, which can alter a gene enough to make a cow susceptible or resistant to a specific disease, or to switch on a particular production trait.

"A study such as this one needs a large herd to understand the genetic background of the effect."

The dairy industry's on-farm research arm, Dexcel, and other scientists had tried to understand the effects but were not able to establish strong genetic reliability. The large-scale feeding experiment, with more than 2000 cows, would allow for a strong and accurate discovery of the location of specific characteristics on genes.

Livestock Improvement is a partner with Fonterra's Vialactia subsidiary in their Boviquest joint venture, which was the first biotech firm to identify and license a test for the exact genes relating to milk production in cows.

Dr Bertrand said the collaboration with Australian researchers, as well as scientists from Dexcel and Vialactia, might be able to make greater metabolic efficiency gains than the Pastoral Greenhouse Gas Research Consortium.

That project - which involved many of the same New Zealand research groups in a bid to reduce methane emissions from livestock - "did not give the kind of results needed for a large genetic study because there was no large herd designed to answer the questions about metabolic efficiency", she said.

Dr Bertrand said the New Zealand researchers would not be targeting Australian work on genes linked to molecules in the milk of marsupials and monotremes such as kangaroos and echidna.

Australian researchers want to identify development signals given to the young of these species in milk so that the milk of dairy cows might be manipulated in terms of production of fats, proteins and bioactives.

- NZPA