Influence of a gonadotropin-releasing hormone agonist on circulating concentrations of luteininzing hormone and testosterone and tissue concentrations of compounds associated with boar taint

Twenty-four Yorkshire boars and six barrows approximately 8 mo of age were used to evaluate the effects of a GnRH agonist (GnRH-A) on circulating concentrations of LH and testosterone (T), concentrations of skatole in fat, and concentrations of 16-androstene steroids in fat and salivary glands. Pigs were assigned to five groups of six pigs each: L200, boars injected with 200 micrograms of GnRH-A/kg BW; L50, boars injected with 50 micrograms of GnRH-A/kg BW; Boar, boars treated with vehicle; Castrate, males castrated on the same day that Groups 1 to 3 received injections; and Barrow, males castrated as neonates. Pigs in L200, L50, and Boar were only given one injection. Blood samples were taken twice daily from d -2 to 28 for determinations of T and LH concentrations and at 15-min intervals for 6 h on d -1, 1, 7, 14, 21, and 28 for characterization of pulsatile LH release. Pigs were slaughtered on d 30, and samples of backfat and salivary glands were collected for quantification of skatole and 16-androstene steroid concentrations. The LH concentrations increased immediately following GnRH-A injection in L200 and L50 (P < 0.001) and then declined to pretreatment values by approximately 29 h after treatment. Serum T concentrations in L200 and L50 increased after GnRH-A treatment (P < 0.0001) and then decreased to less than pretreatment concentrations by d 5 in L200 (P < 0.001) and by d 8 in L50 (P < 0.01). Concentrations of 16-androstene steroids in fat were less (P < 0.05) in L200 and Barrow than in Boar. Concentrations of 16-androstene steroids in salivary glands were less (P < 0.01) in L200, L50, Castrate, and Barrow than in Boar. Concentrations of skatole were less than 0.12 micrograms/g of fat in all groups, and no differences were detected in skatole concentrations across the five groups (P >.15). Testicular weights decreased (P < 0.05) by 48.6% in L200 and 31.9% in L50 by the end of experiment relative to those of Boar. Our results indicate that injecting young mature.