EFFECT OF DIFFERENT PATTERNS OF ADMINISTRATION OF RECOMBINANT PORCINE SOMATOTROPIN ON GROWTH-PERFORMANCE AND ECONOMIC RETURNS OF PIGS IN THE STARTER GROWER VS FINISHER PHASES OF PRODUCTION

The effect of administration of porcine somatotropin (pST) on the production efficiency and economic returns of market hog production was determined based on temperate climate production and carcass merit marketing systems. No differences were detected in average daily gain (ADG), feed efficiency (FE) or carcass index for pigs receiving the same total dose (50-mu-g kg-1 d-1) of pST from 5 to 15 wk of age (9-50 kg) in any of three administration patterns (pST once per day, n = 12; pST once per day for 7 d and no injection for the next 7 d repeated, n = 11; pST once every 3 d, n = 11). However, when pST was administered from 15 wk of age through market weight (50-96 kg, n = 18), ADG increased 15.4% (P < 0.01), FE increased 30.0% (P < 0.01), backfat was reduced by 28.2% (P < 0.01) and grading index increased by 2.9 points (P < 0.01) compared to control animals (n = 24). Economic analysis indicated that breakeven costs for administration of pST for responses obtained varied from $13.68-$21.96 CDN, depending on the value of the carcass ($1.20-$2.10 CDN kg-1) and feed costs ($160.00-$240.00 CDN t-1). These results indicate that application of pST to pigs in the finisher phase of growth would result in improved production efficiency and significant economic return under present hog marketing conditions in Canada where carcass merit settlement is used without an increase in carcass weight.