Testosterone-induced precocious sexual behavior in chickens differing in adult mating frequency

Area of Science:

• Animal Behavior
• Endocrinology
• Genetics

Background:

• Sexual behavior in chickens is influenced by genetic selection.
• Testosterone plays a crucial role in the development and expression of avian sexual behaviors.

Purpose of the Study:

• To investigate the effects of early testosterone cypionate (TC) exposure on precocious sexual behavior in chickens selected for high and low adult mating frequency.
• To determine if early hormonal treatment influences later sexual behavior development and performance.

Main Methods:

• Two lines of chickens, selected for high and low adult mating frequency, were used.
• Three-day-old chicks received injections of either testosterone cypionate (TC) or a vehicle.
• Sexual responses were assessed using a hand thrust test (HTT) at various ages (10-18 days).
• Mating behaviors were evaluated at 7 weeks of age.

Main Results:

• TC administration induced copulatory behavior in 3-day-old chicks, while vehicle-injected birds did not copulate.
• Differences in precocious sexual behavior were observed between the high and low mating lines at a young age.
• At 7 weeks, high mating line birds exhibited significantly higher scores for all measured sexual behaviors (courts, mounts, treads, matings) compared to the low mating line.
• Early TC treatment did not directly affect sexual behaviors observed at 7 weeks of age.

Conclusions:

• Early testosterone exposure can induce precocious sexual behavior in chickens, with potential line-specific differences in response.
• Genetic factors underlying mating frequency selection appear to influence sexual behavior maturation independently of early hormonal priming.
• Further research is needed to understand the neurobiological mechanisms and long-term effects of early hormonal exposure on sexual behavior.