Effects of treating young boars with a GnRH depot formulation on endocrine functions, testis size, boar taint,...

A study was designed to determine the effects of triptorelin (Decapeptyl C.R.), a GnRH-agonist in a depot formulation, on androst-16-en-3-one (androstenone), LH, oestradiol and testosterone and on carcass composition and muscle structure in boars. Treatment with this highly potent GnRH analog ensured peptide release for 4 weeks when given to 18 animals at 135 days of age (group 1). Control animals (n = 20, group 2) received a saline injection. Blood samples (n = 10) were collected by venipuncture from each boar from 7 days before hormone treatment to 28 days after treatment. During the treatment period, three samples of back fat were taken by biopsy to determine the levels of androstenone and skatole. Testis size was determined at slaughter at 165 days of age. The treatment of boars with triptorelin increased concentrations of LH, oestradiol-17 beta, and testosterone for one day, followed by a decrease to base-line concentrations. The result of sensorial testing for boar taint detection at slaughter showed a slight reduction in this trait (0.76 vs. 0.99). The concentration of androstenone in the body fat of all treated animals was lower than the generally accepted limit of 0.5 microgram/g for the absence of boar taint, compared with the concentrations from 20 control animals among which 13 showed levels higher than this limit. The hormonal treatment significantly reduced the weight and size of the tests. There was no effect on skatole levels in backfat (0.141 vs. 0.150 microgram/g). The GnRH-agonist did not influence the carcass composition of treated boars. The muscle meat percentage was not significantly altered in the experimental group (51.39 vs. 50.50%). Overall, these results indicate that the use of this form of GnRH-agonist in a depot formulation offers a new possibility for reducing concentrations of androstenone which is mainly responsible for undesirable boar taint.