Effects of boldenone undecylenate on growth performance, maintenance behaviour, reproductive hormones and carcass traits of growing rabbits.

The present study was done to evaluate the effect of boldenone undecylenate (BOL) on growth performance, maintenance behaviour, reproductive hormones and carcass traits of male rabbits. Sixty apparently healthy New Zealand White male rabbits, 5 weeks of age, were allotted to 3 equal groups. Each group was subdivided into 5 replicates, where the first group is control. The second group (B1) comprised rabbits that received 2 intramuscular injections of BOL (5 mg/kg) with 3 week intervals (9 and 12 weeks of age), while the third group (B2) included rabbits that received 3 intramuscular injections of BOL (5 mg/kg) with 2 week intervals (8, 10 and 12 weeks of age). The end of the trial was after 4 weeks from the last injection (16 weeks of age). The results revealed that the treated groups had a significant increase in total body weight, daily gain and feed efficiency, with a significant decrease in feed conversion ratio (FCR). Ingestive, locomotion and grooming behaviors were significantly higher in treated groups. Lateral pasture and exploratory behaviors were significantly higher in the control group. Administration of BOL resulted in a significant increase in dressing % and a significant decrease in testes %. Groups treated with BOL had a significantly (P<0.05) decreased serum testosterone level, simultaneously with a significantly increased estradiol level. The results indicate that BOL improves performance and carcass traits. Furthermore, there are hormonal-behavioral correlations through enhancement of ingestive and locomotion behaviors of treated animals.