South Island dairy goat farmers still have no large-scale market for goat milk some 18 months after a Chinese-backed processing plant began to be built -- with some fanfare – at Ashburton.
Milk is made up of protein, fat, carbohydrate, water, minerals and vitamins.
These components are packaged inside cells within the mammary gland and are released from the cells by two different pathways of secretion:
1) merocrine secretion -- proteins, lactose, minerals and water are released without disruption of the cell;
2) apocrine secretion -- milk fat is enveloped by the cell membrane before being pinched off from the cell. In this process some of the cell components are also released into milk.
Milk proteins consist of whey and casein proteins. There are four casein proteins: a1-, a2-, ß- and k-casein. Low levels of A1-casein cause the proteins, lactose, minerals and water in milk to be secreted by the apocrine pathway.
In New Zealand goat milk A1-casein makes up only 5-10% of the total protein. Similarly, around 5% of the total protein of human is A1-casein.
As a result much of the proteins, lactose and water in both goat and human milk are secreted by the apocrine pathway. In cow milk, however, about 25% of the total protein is A1-casein. Therefore, proteins, lactose and water in cow milk are only secreted by the merocrine pathway.
Studies show that goat milk reduces intestinal permeability and intestinal inflammation. Other studies show that oligosaccharides extracted from goat milk reduce symptoms of colitis and support the growth of Bifidobacteria isolated from breast fed infants.
To date, these outcomes have only been seen in laboratory studies and need to be investigated clinically. However, there is a closer similarity in fecal microbiota between goat formula and breast fed infants than breast milk and cow formula.
Lactose is the name of a specific carbohydrate or sugar of milk. Unlike proteins and fats, lactose in all milks is chemically and biologically identical. Goat milk contains lactose just like cow milk. There is no difference so it is unlikely that the lactose in goat milk will help directly with lactose intolerance.
However, other factors may play a role in this. For example goat milk contains oligosaccharides similar in structure to human milk oligosaccharides. Oligosaccharide concentrations in goat milk from NZ are about 10 times higher than cow milk. These oligosaccharides may influence how lactose is metabolised.
• Information for article sourced from NZ Dairy Goat Cooperative (DGC)