INFLUENCE OF A HORMONAL PREPARATION CONTAINING GLUCOCORTICOIDS (DEXAMETHASONE ESTERS), PROGESTAGEN (CHLORMADINONE ACETATE) AND ESTROGEN (ETHINYL ESTRADIOL) ON TESTOSTERONE, INSULIN-LIKE GROWTH-FACTOR-I (IGF-1), IGF-BINDING PROTEINS AND SPERMATOGENIC CELLS IN FINISHING BULLS

Growth-promoters are banned by the European Community, but different h ormonal cocktails are still illegally used. This experiment was theref ore conducted to evaluate the effects of one of the most currently use d cocktails on some hormonal parameters and spermatogenesis in finishi ng bulls in an attempt to provide a suitable screening technique for t heir illegal use. Sixteen double-muscled Belgain White Blue finishing bulls (mean weight: 535 (s.d. 37) kg) were blocked into control (C; no . = 7) and treated (Dex; no. = 9) groups. Animals were treated i.m. wi th the hormonal preparation (dexamethasone isonicotinate and phosphate , chlormadinone acetate and ethinyl oestradiol) on day 0, day 15 and d ay 30. Animals were slaughtered on day 45. Three h before each treatme nt and just prior to slaughter, jugular blood samples were collected t o monitor the testosterone (T) response to an i.v. injection of gonado tropin releasing hormone (GnRH) (0.5 mug GnRH per kg body weight). Tes ticular tissue was also collected at slaughter. Plasma T and insulin-l ike growth factor-1 (IGF-1) concentrations were measured by radioimmun oassay. IGF-binding proteins (IGFBPs) were evaluated using Western lig and blotting. Daily weight gains were lower in the control group (1.29 (s.d. 0.13) kg for C v. 1.60 (s.d. 0.39) kg for Dex) but the differen ce was not significant. After treatment, spermatogonia, spermatocytes, spermatids and spermatozoa disappeared from the testis and seminifero us tubules consisted only of Sertoli cells; these observations suggest that treated animals were sterile. Moreover, plasma T concentrations in response to GnRH stimulation were suppressed (P < 0.001) in the Dex group between day 15 and day 45 (mean maximal responses: 5.4 to 7.9 m ug/l in C group v. < 0.2 mug/l in Dex group at day 15, 30 and 45). Tre atment did not show any prominent effect on plasma IGF-1 levels but in creased IGFBP-3 band intensity. In conclusion, treatment with a cockta il containing dexamethasone esters, chlormadinone acetate and ethinyl oestradiol for a short period induced a number of changes in finishing bulls which might be possible to develop as a screening method for th e identification of illegally treated animals.