Stuff - More farmers DNA testing dairy herds as reality of 'peak cow' hits

Written by Esther Taunton

More farmers are turning to DNA testing as the dairy industry focuses on breeding better cows, not building bigger herds.

Livestock genetics company LIC has seen an increase in demand for its DNA parentage testing service as farmers place increasing emphasis on cow quality over cow quantity.

More than 250,000 calves from around the country will have their parentage confirmed by LIC's service this spring. 

So far this year, the co-operative has had an average of one new herd a day sign up to the service, which operates from its laboratory in Hamilton.

LIC's general manager of NZ markets, Malcolm Ellis, said the increased demand reflected the industry's new reality of "peak cow".

"Our industry is changing rapidly. Cow population in New Zealand has remained static in recent years, so farmers are increasingly aware that if they can't generate income by milking more cows, they need to be milking better cows."

Calving was a critical time for farmers to manage future herd productivity and DNA testing helped them identify the best calves to keep as herd replacements, Ellis said.

"With the cost of breeding a replacement sitting at around $1600 per animal, it's important that farmers bring in the new season's calves with confidence," he said.

"Confidence in parentage is a key component to taking a farm's herd improvement plan to the next level."

LIC's whole herd testing matches the current season's calves to dams and sires and costs $26.50 per sample.

Waikato farmer Liz Johnson said the investment in DNA testing had helped her improve the productivity of her farm.

"We now look for the genetically proven cow, rather than the maximum number. The main advantage is monitoring the parentage between each sire and dam and keeping the best heifers."

Monitoring and accurately recording calving details was one of the biggest challenges for farmers and as many as one in four calves could be mis-mothered over a season.

"DNA testing has made calving time much easier to manage. We can't be there 24 hours a day for every birth," Johnson said.

"This takes the pressure off the team because we know the technology has got us covered."

Ellis said confirming a calf's parentage was a simple task for farmers but a technical process behind the scenes.

"To begin the process, farmers take a tissue sample from a calf's ear, and then send the sample to LIC's diagnostics lab where the DNA is extracted and analysed."

The lab used enzymes extracted from bacteria living in thermal hot pools to digest the tissue away and free the DNA from the nucleus of the cells. Microscopic metal beads coated with binders captured the DNA and isolate it using magnets.

"At the end of the process, the samples from each animal are microscopic, they're smaller than the head of a pin but that's got every bit of information we need to determine the parentage," Ellis said.

Once the lab had generated a unique genetic marker profile or DNA fingerprint for a calf, it was compared against the profiles of the potential dams and sires to accurately identify its parentage. 

The parentage testing could also be combined with other tests, such as a gene test which identifies what cows produce A2/A2 milk and a test that detects the BVD virus in individual animals.

More than 2.4 million samples have been processed by LIC since it began G3 DNA profiling in 2009.