Pigs fed goats' milk that was genetically modified to carry an
important antibacterial enzyme found in human breast milk showed signs of
better resisting attack by common E. coli bacteria than did pigs fed
unmodified goats' milk without the human enzyme, report researchers at the
University of California, Davis.
The findings, published in the May issue of the Journal of Nutrition,
provide evidence that milk carrying high levels of the human lysozyme
enzyme -- produced by genetically modified, or transgenic, goats -- may
improve the gastrointestinal health of pigs and other animals that consume
the milk. Pigs were used in this study because they have digestive systems
that are similar to those of humans.

"These results demonstrate that biotechnology can be used to improve
the healthfulness of the milk of dairy animals by introducing beneficial
properties of human milk," said James Murray, who led the study with animal
scientist Elizabeth Maga.

"We are hopeful that milk with similar benefits one day will be
available to protect infants and children against diarrheal illnesses, which
every year kill millions of children around the world," Maga said.

The enzyme lysozyme is found in the tears, saliva and milk of all
mammals. While lysozyme is found at high levels in human breast milk, goats'
milk contains only 0.06 percent as much lysozyme as does human milk. In this
study, the transgenic goats produced milk with 67 percent as much lysozyme
as human milk.

Lysozyme inhibits the growth of bacteria by destroying the bacterial
cell wall, causing the cell contents to leak out. Because lysozyme limits
the growth of bacteria that cause intestinal infections and diarrhea, and
encourages the growth of beneficial intestinal bacteria, it is considered
one of the main human-milk components that contribute to the health of
breast-fed infants.

In this study, the researchers gave the young pigs solid feed and
pasteurized, lysozyme-rich milk produced by transgenic dairy goats. A
control group of young pigs received solid feed and pasteurized regular,
non-transgenic goats' milk that did not have human lysozyme.

Half of the pigs were also given a dose of enteropathogenic
Escherichia coli (E. coli), a common bacterial strain known to cause
gastrointestinal illness. During the study, the researchers found that the
pigs fed the lysozyme-rich milk from transgenic goats had significantly
lower levels of coliform bacteria, including E. coli, in their small
intestines, than did the control group of pigs fed regular goats' milk.

Furthermore, the pigs receiving the lysozyme-rich milk and the pigs in
the control group demonstrated normal weight gain, growth and blood
composition.

These results substantiated findings from a similar 2006 study by the
researchers, which investigated the impact of transgenic goats' milk with
human lysozyme on young goats and pigs.

The researchers note that further studies are needed to more
completely characterize and understand the full impact of transgenic
lysozyme-rich goats' milk on young pigs' intestinal bacteria, including
potential positive effects on beneficial bacteria.

The research was funded by a grant from the UC Davis Academic
Federation Committee on Research.


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