Apilarnil reduces fear and advances sexual development in male broilers but has no effect on growth.

1. An experiment was conducted to determine the possibility of stimulating sexual development at an early age in male and female broiler chickens by administration of apilarnil, a natural bee product, in the pre-pubertal period. 2. From 28 to 55 d of age, birds were given apilarnil orally. The effects of low (2.5 g/bird) and high (7.5 g/bird) doses of apilarnil on growth performance, testicular weight, secondary sexual characteristics, blood lipids, testosterone and fearful behaviour were evaluated. 3. Apilarnil administration did not cause a positive effect on growth performance of male and female broilers suggesting that apilarnil did not have an anabolic effect. 4. Apilarnil administration suppressed blood glucose and cholesterol. 5. Birds receiving apilarnil remained immobile for a shorter period in a tonic imobiliy test and showed less home-cage avoidance responses suggesting a lower level of fearfulness. 6. Increases in testicular weight, testosterone concentration and comb growth in males receiving apilarnil implied that it stimulates the sexual maturation at an early age. However, a similar stimulation of secondary sexual characteristics was not observed in females.