New Transgenic Pigs with Lean Pork PotentialBy
Pigs genetically engineered with a growth factor gene may give consumers
leaner pork in the future, Agricultural
Research Service scientists say.
The new transgenic pigs carry a gene for insulin-like growth factor-I
(IGF-I). The pigs were produced by ARS researchers in collaboration with
GeneMedicine, Inc., of The Woodlands, Texas.
The IGF-I transgenic pigs have some of the same positive carcass composition
characteristics as transgenic pigs previously injected with a growth hormone
(GH) transgene. However, none of these IGF-I transgenic pigs have developed the
health problems encountered earlier in the GH transgenic pigs.
IGF-I is a growth factor normally present in small amounts in most mammalian
cells. It stimulates development of bone, muscle, nerve and organ tissues.
IGF-I produced in muscle increases significantly without affecting the amount in
the other tissues, making the IGF-I transgenic pigs unique.
The scientists injected the IGF-I gene into pig embryos soon after
fertilization. They mated several IGF-I transgenic pigs to non-transgenic pigs
to produce a second generation in which half the offspring inherited the
transgene and half did not.
ARS scientists compared pigs with and without the transgene to see how IGF-I
affected their growth rate, feed efficiency, carcass composition and general
health. They compared those results with the results obtained earlier with the
GH transgenic and non-transgenic pigs.
The researchers found the IGF-I transgene helped reduce carcass fat and
boost lean body mass, making those hogs worth $6 more at market than control
pigs without the IGF-I transgene. The study also confirmed that the IGF-I pigs
didn't suffer from severe health problems associated with the GH transgene.
ARS scientists say this preliminary work is a first step to producing leaner
pigs, but it will have to be tested on market-grade animals. Their next step
will be to cross IGF-I transgenic pigs with market-line hogs to see if increased
levels of the hormone enhance muscle development in already lean, heavy-muscled
crossbred market hogs.
Scientific contact: Vernon G. Pursel,
Gene Evaluation and
Mapping Laboratory, Beltsville, Md., phone (301) 504-8342, fax (301)