Unnatural selection

In 2000-2001, the four-million-odd cows making the NZ dairy herd were screened for their milk composition by ViaLactia. One cow, Marge, was thoughtfully purchased for $300 when it was found that her milk was particularly low in saturated fat. The total fat content of Marge's milk was about 1%, which fits rather nicely in the FSANZ's (Food Standards Australia New Zealand) definition for skim milk that stipulates a maximum of 1.5% fat. (Full cream milk is required to have a minimum of 3.2% fat.)

A side benefit of the low saturated fat content of Marge's milk is that butter made from her milk would be spreadable at domestic refrigerator temperatures (2-5°C), just like margarine.

The concept of a dairy herd producing skimmed milk and hence spreadable butter must be very exciting for Fonterra. The company has already found that some of Marge's daughters also produce low saturated fat milk and it is anticipated that a commercial herd may be in existence by 2011.

Media reports indicate that a single 'low-fat' gene is responsible for Marge's milk composition. The University of Sydney's Faculty of Veterinary Science and the Dairy CRC are world leaders in the genetic fingerprinting of dairy cows. Under the leadership of Professor Herman Raadsma, the group has developed genetic marker technology that will enable dairy farmers to accurately predict the on-farm performance of their animals. The CRC team has comprehensively linked 15,000 genetic markers with 37 key dairy production traits. Testing for the particular genetic markers associated with traits such as milk output and quality, resistance to disease, length of lactation or even overall profitability will enable dairy breeders to select the best animals for use in their herds. The markers are now being evaluated in the field.

The advance was achieved by screening a record number of known genetic markers against the DNA of 1500 performance-tested Australian dairy sires supplied by CRC partner Genetics Australia Cooperative to create a database of over 22 million records.

This new dataset was compared with performance data for each of these 1500 bulls, contained in the national database of the Australian Dairy Herd Improvement Scheme.

I would be interested to hear from Prof Raadsma about the rarity of Marge's low-fat gene. The entire story seems like a manipulated version of Charles Darwin's 'natural selection' and 'survival of the fittest' except that in this case it isn't survival of the fittest, rather survival of the closest fit to human health and marketing needs.