Lysozyme destroys harmful bacteria like Escherichia coli by tearing open the cell wall, causing its insides to leak out. The enzyme is found in the milk, saliva and tears of all animals, but human breast milk contains about 3,000 times more than goats milk. By injecting the human gene for lysozyme production into the gene in goats that controls mammary production, researchers at the University of California, Davis, created transgenic goats that produce milk with 68 percent as much lysozyme as human milk. The researchers then fed the lysozyme-rich milk to young goats and pigs to see if it affected the bacteria population in the animals guts. In goats, to the researchers surprise, the modified milk actually multiplied the amount of coliform gut bacteria. This did not have negative health impacts on the animals themselves and the researchers suspect that it may be a result of the digestive anatomy in multistomached ruminants such as goats. In pigs, which were studied in place of humans because of their similar digestive systems, the transgenic milk had the effect the researchers hoped for: they had much lower levels of coliform bacteria, including E. coli, than animals consuming regular goats milk.
This should have an impact particularly on E. coli based gastrointestinal diseases, says Jim Murray, an animal scientist at the University of California, Davis, and an author of the study. The team is now repeating the experiment with pigs that will be infected with harmful bacteria to see if the modified milk enhances their natural immune response. Murray hopes that eventually such milk from transgenic goats could confer a boost to the immune systems of children who no longer breast-feed or whose mothers cannot produce milk. This is a feasible way to provide a natural leg up against some of these infections, particularly in those areas of the world that largely use goats anyway, says Murray. The research appears in the current issue of Transgenic Research.