EFFECTS OF TREATING YOUNG BOARS WITH A GNRH DEPOT FORMULATION ON ENDOCRINE FUNCTIONS, TESTIS SIZE, BOAR TAINT, CARCASS COMPOSITION AND MUSCULAR STRUCTURE

A study was designed to determine the effects of triptorelin (Decapept yl C.R.(R)), a GnRH-agonist in a depot formulation, on androst-16-en-3 -one (androstenone), LH, oestradiol and testosterone and on carcass co mposition and muscle structure in boars. Treatment with this highly po tent 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 b y 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 a ge. The treatment of boars with triptorelin increased concentrations o f 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 thi s trait (0.76 vs. 0.99). The concentration of androstenone in the body fat of all treated animals was lower than the generally accepted limi t of 0.5 mu g/g for the absence of boar taint, compared with the conce ntrations from 20 control animals among which 13 showed levels higher than this limit. The hormonal treatment significantly reduced the weig ht and size of the testes. There was no effect on skatole levels in ba ckfat (0.141 vs. 0.150 mu g/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-ag onist in a depot formulation offers a new possibility for reducing con centrations of androstenone which is mainly responsible for undesirabl e boar taint. (C) 1998 Elsevier Science B.V.