However, bulls are an expensive asset to a beef cow enterprise, so proper attention should be given to the bull power, not only during the breeding season but also in the off-season.
Because bulls account for half the genetics of a calf crop, an individual bull’s fertility success is arguably more important than an individual cow’s fertility success. Post-weaning is a great time to evaluate whether your herd bull is meeting the expectations outlined for him in your operation. A bull’s job is to increase value of the calf crop. If a bull is not making his contribution to this economic impact of the herd enterprise, now may be a good time to part ways and upgrade genetics prior to the next breeding season.
The nutritional status of bulls also needs to be monitored throughout the winter months. Just like the cow herd, thin bulls or overconditioned bulls will have an impact on fertility. Contrary to popular belief, bulls carrying excess condition results in fat deposited around the scrotum, which impacts temperature regulation, especially in the cold months, resulting in long-term fertility implications.
Nutritional requirements of young bulls and mature bulls vary greatly, so bulls should be separated by age and requirements. Likewise, bulls should have access to a quality mineral and vitamin supplementation year-round, as many minerals and vitamins play a key role in reproduction. Regardless of age, adequate feeder space (suggested a minimum of 2 foot per bull) is necessary to ensure all bulls can access feed at once when managed in a group.
Cold weather often increases animal intake and nutritional requirements necessary to maintain body temperature. Scrotal frostbite is a big concern for bulls during the winter months. Providing adequate bedding and windbreaks are beneficial to avoid permanent damage and reductions in semen quality. A breeding soundness exam (BSE) should be completed on all bulls within 45 days of the start of the breeding season.
Last, don’t forget to work with your veterinarian to ensure you’re providing bulls with an adequate health program, including regular vaccinations, internal and external parasite control, and testing for reproductive diseases. 
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Erika Lundy
- Extension Beef Program Specialist
- Iowa Beef Center - Iowa State University
- Email Erika Lundy
