Effects of exogenous porcine somatotropin on the development of fat cells and fatty acid composition in backfat of live finishing pigs

The effects of long-term application of recombinant porcine somatotropin (pST) to Landrace pigs on the development of backfat thickness, fat cells and fatty acid composition were investigated from about the 116th to the 186th day of life. Biopsy samples from the backfat of 56 castrates were taken at the beginning of treatment and after 5 and 10 weeks. The daily injection of 2 or 4 mg of pST induced a considerable decrease in backfat growth compared to untreated controls. This was attributed to a decreased size (about 18–20%) and number (about 13–25%) of fat cells. The higher dose of 4 mg pST/day induced a greater restriction of fat growth. This was obviously based on differences in fat cell number. Furthermore, pST treatment delayed the normal decrease of unsaturated fatty acids (C 18:2; C 18:3) during the period of growth examined. Therefore, the percentages of unsaturated fatty acids increased, indicating changes in fat cell metabolism of pST treated pigs.