Research points the whey forward for milk

Milk is the first food that any mammal tastes, a fluid perfectly formulated by nature for the nutritional and developmental needs of newborn mammals.

Milk-fermenting bacteria like Lactobacillus probably gave nomadic herdspeople their first biotechnology-derived foods: yoghurt and cheese.

Modern biotechnologists have recently discovered that milk, in additional being a superb food, is laced with a cocktail of nutraceuticals -- biologically active peptides that promote growth and development, speed the repair of injured tissues, and even prevent and repair tooth decay.

All these developments have involved milk au naturel, straight from source. Can biotechnology now improve on nature's original recipe?

Dr Paul Donnelly, director of the new Cooperative Research Centre for Dairy Research, says the CRC's researchers are working to identify all of the genes involved in the process of lactation, including those that genes that contribute to milk's formula.

That formula varies markedly to accommodate the nutritional and developmental requirements of the young of mammal species that have adapted to very different environmental niches.

The CRC is hoping to tap into this diversity. It is extending its lactation-gene hunt beyond dairy cows to two native Australian mammals: another eutherian, the Australian fur seal, and a marsupial, the tammar wallaby.

Why the interest in these species? "The tammar wallaby is very unusual in its ability to produce milk of different composition, and at different rates, concurrently from adjacent mammary glands," Donnelly said.

"It allows the wallabies to feed two young at different stages of development. We're interested in the physiology of growth in the newborn wallabies -- the species has a 26-day gestation period, and is born very undeveloped.

"The neonate's growth and development are dependent on the composition of the milk, and we want to understand the similarities and differences to the dairy cow's system. In particular, we want to understand how the genes are regulated in each species.

"We could use these discoveries to make cow's milk more nutritionally beneficial to humans, or to custom-design milk for nutraceutical applications.

Donnelly said that as people aged their immune responses declined, so there could be a market for pharma-milks enriched with biological compounds to boost the immune system.

Other people are allergic to proteins in cow's milk, so it might be possible to modify the offending proteins to produce special allergy-free milk.

Udder-specific promoters -- the DNA 'switches' that confine the activity of certain genes to the mammary gland -- could also be linked to genes for therapeutic proteins, that would be secreted into milk.

The CRC's interest in the Australian fur seal lies in the fact that the female seals temporarily switch off lactation when they head to sea to feed. The dairy industry could benefit from the development of transgenic cows in which lactation could be switched on or off by an injection, or via a dietary supplement.