Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: June 17, 1999
Publication Date: N/A
Interpretive Summary: The regulatory elements from avian skeletal à-actin gene and 5' flanking sequences can provide a high level of IGF-I expression in skeletal muscle of transgenic pigs. Elevated IGF-I expression in skeletal muscle did not significantly increase serum IGF-I concentrations, alter the growth rate, or adversely impact the general health of transgenic pigs in comparison to their littermate controls. Transgenic founder males and females appeared to have normal reproductive capacity, and nine of ten transgenic founders transmitted their transgene to progeny. Based on these results we conclude that enhancing IGF-I specifically in skeletal muscle may have a positive effect on carcass composition of swine.
The aim of this research was to determine whether directing expression of IGF-I specifically to striated muscle would enhance lean muscle growth in swine. Transgenic pigs were produced by microinjection of zygotes with a fusion gene consisting of the regulatory sequences of an avian skeletal alpha-actin gene and a cDNA encoding human IGF-I. All but one of 13 transgenic pigs expressed the IGF-I transgene. Muscle IGF-I concentrations varied from 20 to 1702 ng/g muscle in transgenic pigs compared to less than 10 ng/g muscle in control pigs. Serum IGF-I concentrations in transgenic pigs did not differ from that of littermate control pigs. Daily weight gain from 20 to 60 kg body weight was similar for transgenic and littermate control pigs. Body composition of 16 pigs was estimated by X-ray absorptiometry (DXA) scanning at 60 kg body weight. The DXA results indicated transgenic pigs had significantly less fat and more lean tissue than littermate controls. Subsequently nine of 10 founders transmitted their transgene to G1 progeny, which will be used for evaluation of growth rate, feed efficiency and carcass composition. Transgenic and control pigs did not differ in general appearance, and no gross abnormalities, pathologies, or health- related problems were encountered. Based on these results we conclude that enhancing IGF-I specifically in skeletal muscle may have a positive effect on carcass composition of swine.