Effect of constant versus adjusted dose of exogenous porcine growth hormone (pGH) on growth and reproductive characteristics of gilts.

Growth, carcass traits, and selected reproductive characteristics were evaluated in prepubertal gilts treated with either a constant mass of pGH or a mass of pGH adjusted periodically for changes in BW. Gilts (64 kg, n = 24) were given 24 daily injections of either vehicle (C; control) or one of two doses of pGH: 70 micrograms/kg of BW, with dose adjusted every 5th d for changes in BW (A; adjusted), or 70 micrograms/kg of initial BW (U; unadjusted). Gilts were slaughtered on d 25. Gilts treated with pGH had higher ADG (P less than .002) and improved feed efficiency (kg of feed/kg of gain; P = .0003) compared with controls. Weights of adrenal glands, liver, heart, and kidney were higher (all P less than .01) for Groups A and U than for Group C gilts. Average backfat thickness was less (P less than .004) for A and U gilts than for C gilts and less for Group A than for Group U (P less than .02). Furthermore, growth and carcass traits were similar (P greater than .05) for Groups A and U, except for measurements of first rib backfat, last rib backfat, and average backfat depth (P less than .05). Culture of granulosa cells (GC) was employed to assess ovarian function. Addition of FSH to the culture media enhanced secretion of progesterone (P4) by cultured GC from all in vivo treatments compared with unsupplemented cultures of GC (P less than .05). Addition of LH to the culture media enhanced secretion of P4 by cultured GC from pGH-treated gilts only (P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)