Từ điển khoa học động vật vần T | Transgenic Animals Improved Performance Vernon G. Pursel United States Department of Agriculture Agricultural Research Service Beltsville Maryland . INTRODUCTION With the world s population increasing by more than 70 million people each year modern agricultural methods that include animal biotechnology will need to be adopted if this ever-increasing population is going to avoid massive conflict over agricultural resources. The ability to isolate clone and transfer individual genes into farm animals provides the opportunity for scientists to produce transgenic animals with modified traits that are unattainable through genetic selection. This article reviews progress on transfer of genes for productivity traits into farm animals and some areas that offer promise for the future. GROWTH-RELATED TRANSGENES Early transgenic farm animal research was inspired by the dramatic growth of transgenic mice that expressed a growth hormone GH transgene. 1 A number of transgenic pigs and sheep were subsequently produced with human bovine rat porcine or ovine GH under the control of several gene Although pigs expressing GH transgenes grew faster utilized feed more efficiently and were much leaner than their nontrans-genic siblings they were not larger and exhibited several notable health problems which included lameness susceptibility to stress gastric ulcers and reproductive prob-lems. 2 The GH transgenic lambs did not grow faster or utilize feed more efficiently than control lambs but they were much leaner and had serious health More recently an insulin-like growth factor-I IGF-I transgene has been used to produce transgenic pigs with enhanced muscle development and reduced fat in the carcass but the transgene did not improve growth rate or feed efficiency. In contrast to the GH transgenic pigs definitive phenotypes for the IGF-I transgenic pigs were not detected and no gross abnormalities pathologies or health-related problems were .
