Abstract Example for Transgenic Animal Conference V, August 12-16, 2007
Carcass composition resulting from cross of an IGF-1 transgenic boar with two lines
of hybrid swine
V.G. Pursel*1, A.D. Mitchell1, J.S. Eastridge1, K.D. Wells1, R.J. Wall1, M.B. Solomon1,
M.E. Coleman2 & R.J. Schwartz3
1
USDA, ARS, Beltsville Maryland
2
Valentis, Inc., The Woodlands, TX
3
Baylor College of Medicine, Houston, TX
Although growth hormone is considered the primary growth-promoting hormone in
mammals, many of its effects are thought to be mediated by insulin-like growth factor-I
(IGF-I). A dam-line genetic background was used to produce transgenic pigs with a
fusion gene composed of avian skeletal -action regulatory sequences and a cDNA
encoding IGF-I. This trangene directs IGF-I expression specifically to striated muscle.
The objective of the present research was to determine whether enhanced muscle
development observed earlier in IGF-I trangenic dam-line hybrid progeny would be
obtained when a dam-line transgenic boar was crossed with sire-line hybrid females.
Twelve non-transgenic gilts from two hybrid sirelines were mated to a founder IGF-I
transgenic boar (hybrid dam-line) to produce G1 transgenic and non-transgenic sibling
control progeny. Pigs were provided feed ad libitum until they reached 120 kg body
weight. Average daily gain was similar for transgenic and control pigs. At 120 kg body
weight 33 transgenic and 42 sibling control pigs were killed. The right half of each
carcass was scanned by dual-energy X-ray absorptiometry to estimate total carcass fat
and lean, and then physical measurements were taken. The left half was used for
determination of individual muscle weights. Transgenic gilts and barrows, respectively,
had 36 and 29% larger loin-eye area (P < 0.001), 9 and 12% more carcass lean tissue (P
< 0.001), 18 and 23% less total carcass fat (P < 0.001), and 14 and 18% less average
back-fat thickness (P < 0.05) than sibling control pigs. Muscles were significantly
heavier for transgenic than control pigs for rectus femoris (19%), psoas major (19%),
biceps femoris (13%), triceps brachii (10%), and semitendinosus (7%). While many of
the carcass characteristics differed significantly for progeny of the two sire lines, IGF-I
transgene expression had a beneficial effect on progeny of both lines. Based on these
results we conclude that enhancing IGF-I specifically in skeletal muscle had a positive
effect on carcass composition of terminal cross market swine.