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Sexual development in beef bulls following zeranol implants
Journal of Animal Science
|February 1, 1985
Summary
Zeranol implants in bull calves can hinder sexual development and growth, particularly when administered early. However, older bulls may overcome these effects, and implants can enhance carcass quality in some cases.
Area of Science:
- Animal Science
- Reproductive Biology
- Meat Science
Background:
- Zeranol implants are used in cattle production to improve growth.
- The effects of zeranol on sexual development and carcass characteristics require further investigation.
Purpose of the Study:
- To evaluate the impact of zeranol implants on the growth and sexual development of bull calves.
- To assess the effects of zeranol on carcass traits in bulls and steers.
Main Methods:
- Two trials were conducted involving bull calves and steers.
- Zeranol implants of varying doses and timings were administered.
- Measurements included scrotal circumference, testicle weight, hormone levels, growth rate, and carcass quality.
Main Results:
- Early zeranol implantation (at branding) decreased scrotal circumference, testicle weight, and ejaculate production in bulls.
- Repeated implants in bulls led to reduced testosterone and increased penis abnormalities, though effects diminished with age.
- Implanted steers had heavier carcasses, while implanted bulls had lighter carcasses but improved quality and marbling.
Conclusions:
- Early zeranol implants can restrict sexual development in bulls but do not cause sterility.
- Older bulls may exhibit compensatory growth and overcome some effects of zeranol.
- Zeranol implants influence carcass quality differently in bulls and steers, enhancing quality in bulls but reducing it in steers.