Subcutaneous Stibestrol Implantation in Growing-Fattening Swine

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Abstract
Four trials have been completed using 136 growing-fattening barrows and gilts to study the effects of subcutaneous stilbestrol implants in the ear. Within 2 days following treatment gilts showed typical symptoms of edematous, hyperemic vulvae. Both barrows and gilts had enlarged teats and increased sexual activity. At slaughter the barrows had hypertrophied seminal vesicles, and gilts had either atrophied or enlarged, cystic ovaries. Implantation of 30 mg. stilbestrol in lightweight feeder pigs (58–73 lb.) resulted in reduced gains during the feeding-fattening period. On the other hand, the same treatment in heavyweight feeders (108–131 lb.) had no effect on gains. Coincident with reduced gain in the early treated pigs was a reduced feed intake and a trend towards greater feed utilization. The various trials gave evidence of leaner carcasses in the early-treated pigs, and analysis of variance (multiple classification) of combined data by the method of fitting constants on barrows implanted with 30 mg. or more of stilbestrol indicated that the early implants had shorter carcasses, less backfat, a greater percentage of lean cuts, and greater densities of untrimmed hams and bellies than controls. Leanness of the late-treated pigs was intermediate between the controls and early implanted ones. Largest weight differences between early implants and controls occurred at about 43–53 days following treatment, and pigs slaughtered at this time (approximately 135 lb.) showed maximal differences in backfat thickness, loin area at the 10th rib and densities of entire carcass, untrimmed belly, and the various untrimmed lean cuts. A possible protein anabolic effect of stilbestrol in pigs during the rapid protein storage phase of growth similar to that of methyl testosterone is suggested. Copyright © . .