Gene Technology in Animal Farming
Farmers have long tried to improve farm animals and crops through
traditional breeding and selection programs. In the past, the cow
that produced the most milk on a farm may have been mated to
male offspring of high producers in hopes that the cow’s offspring
would also produce a lot of milk. But these traditional processes
were slow and inefficient.
Now, many farmers use genetic-engineering techniques to
improve or modify farm animals. Some farmers add growth hor-
mone to the diet of cows to increase milk production. Previously,
the growth hormone was extracted from the brains of dead cows.
But now the cow growth hormone gene is introduced into bacteria.
The bacteria produce the hormone so cheaply that it is practical to
add it as a supplement to the cows’ diet.
By alternating the gene responsible for GH production, scientists
have stimulated natural GH in pigs, increasing their weight.
Though these procedures are still new, they may lead to the cre-
ation of new breeds of very large and fast-growing cattle and hogs.
Making Medically Useful Proteins
Another way in which gene technology is used in animal farming is
in the addition of human genes to the genes of farm animals in order
to get the farm animals to produce human proteins in their milk.
This is used especially for complex human proteins that cannot be
made by bacteria through gene technology. The human proteins are
240 CHAPTER 11Gene Technology
http://www.scilinks.org
Topic: Cloning
Keyword: HX4047
Mammary cells were
extracted and grown in
nutrient-deficient solution
that stops the cell cycle.
A mammary cell
was placed next
to the “empty”
egg cell.
An electric shock opened up the cell
membranes so that the cells fused. Cell
division was triggered.
Egg cells were extracted
and the nucleus from
each removed and
discarded.
Nucleus containing
source DNA
In 1997 scientists announced the first successful cloning using
differentiated cells—a lamb named Dolly.
Figure 12 Cloning a sheep from mammary cells
