WOOL PRODUCTION IN TRANSGENIC SHEEP - RESULTS FROM FIRST-GENERATION ADULTS AND 2ND-GENERATION LAMBS

In sheep transgenic for a sheep insulin-like growth factor 1 (IGF-1) c DNA driven by a mouse keratin promoter, we assessed wool production an d properties in 51 adults of the first generation (G1) and in 56 lambs of the second generation (G2). Transgenic G1 sheep had an increased r ate of wool production during spring and summer of year 2 compared wit h nontransgenic half-sibs, with a maximum increase of 17% in December, but during the winter nadir rates were similar. At second- and third- year shearing, however, fleece weights were not significantly differen t. There was a trend for transgenic animals to have coarser wool of lo wer staple strength. A controlled feeding trial revealed no significan t differences in feed intake. The transgene was expressed not only in skin but also in a wide range of other tissues. Circulating IGF-1 conc entrations were not significantly different between transgenic and non transgenic animals, suggesting that local mechanisms were more importa nt than systemic mechanisms for wool production, but were significantl y higher in males than in females. In the G2 sheep, transgenic fleece weight did not differ significantly from nontransgenic either as lambs or at the end of the lamb year. Although the transgene was inherited in Mendelian fashion and was widely expressed, the production advantag e seen in animals of the first generation did not persist in the secon d generation.