Boldenone Undecylenate injection Consequences on Male Rabbit Behavioral Response, Fertility and Testicular Utrastructural Changes with Special Respect to the Withdrawal Effects

Boldenone esters (mainly the undecylenate form) are heavily used in the field of animal production in order to increase the productivity and reduce breeding expense. The current study was conducted to evaluate boldenone undecylenate (BOL) effect on behavioral and reproductive responses. Therefore, 18 mature male New Zealand rabbits and 10 females were used in this study. The Animals were assigned to two groups, the control group received 0.25 ml corn oil ? kg bwt and BOL-treated group received 4.5 mg? kg bwt BOL, 3 intramuscular injection with two weeks interval. Six rabbits from BOL-treated group were withdrawn from the treatment which served as a BOL withdrawal group (6 weeks post 3rd injection). Blood, semen and testis specimens were collected for serum hormonal assay, semen evaluation and ultrastructural investigation. Sexual behavior was tested using a receptive female and aggressive behavior was assessed via a male intruder. The BOL-treated animals showed a significant increase in serum testosterone, diminished LH and estradiol levels, elevated sperm count and motility percentage. In contrast, diminished testosterone and elevated estradiol levels were recorded in animals withdrawn from BOL. Besides, low sperm count and motility percentage and severe ultrastructural alterations. Males treated with BOL showed significant increases in both sexual and aggressive behaviors. While, BOL-withdrawal group showed significantly lower levels of sexual behavior compared with control and did not show any heightened aggression. Considering the results of this study, BOL injection affects animal future fertility even after cessation of its use.