Effects of zeranol upon bovine testicular function

Area of Science:

• Veterinary Endocrinology
• Reproductive Biology
• Animal Science

Background:

• Zeranol is a non-steroidal estrogenic compound used in livestock growth promotion.
• Understanding zeranol's impact on reproductive health is crucial for animal welfare and agricultural practices.

Purpose of the Study:

• To investigate the effects of zeranol on testicular function in bulls of different ages.
• To determine if zeranol's impact on testicular function is reversible.

Main Methods:

• Young bulls were implanted with zeranol, and testicular development, testosterone levels, and sperm concentration were assessed.
• Older bulls were also treated with zeranol to compare age-related effects.
• Recovery periods and orchidectomy were used to evaluate reversibility and baseline function.

Main Results:

• Zeranol inhibited testicular development and reduced testosterone (T) concentrations in young bulls.
• Spermatozoa were absent in zeranol-treated young bulls during the treatment period.
• Testicular function and sperm concentration recovered to control levels after a 168-day recovery period.
• Zeranol had no significant effect on spermatogenesis or T production in older bulls.

Conclusions:

• Zeranol's inhibitory effects on bovine testicular function are age-dependent.
• Prepuberal bulls exhibit increased sensitivity of the hypothalamic-pituitary-testicular axis to zeranol.
• The effects of zeranol on testicular function in young bulls are reversible upon cessation of treatment.