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Nutrition and Bull Fertility

A bull has to be right from the inside out to breed well. Feed affects growth, body condition, libido and the quality of sperm, and some of those effects take weeks to show up.

Fertility starts long before the season

Sperm production takes time. A problem with nutrition or health can show up in semen weeks later, long after the cause has passed. That is why bull feeding plans should be built months ahead of breeding.

Ask your veterinarian when to schedule a breeding soundness exam so you have time to correct problems before cows are exposed. This lag is the reason a bull that looked fine at turnout can still turn out to be a poor breeder. Testing early and correcting problems gives you a second chance before the season begins. Talk with your nutritionist at the same time so feed and mineral plans are in place for the weeks leading up to the exam, not after.

Young bulls and development

Young bulls are growing while their reproductive system is developing. Poor growth or too much fat can both cause problems. Ask your nutritionist or extension specialist about development rations suited to your breed and goals.

Many bull development programs aim for steady growth without excessive fat. Overfeeding on high concentrate diets can harm feet, legs and later fertility. Rapid gain on rich diets can look impressive on a scale, but it can hide problems that show up later in feet, joints and breeding performance. Ask your breed association or extension office what they recommend for development.

• Steady growth is the goal
• Avoid over-conditioning young bulls
• Check feet and legs regularly
• Keep records of weights and condition

Body condition and energy

Both thin and fat bulls can have trouble. Thin bulls may lack the energy to work and may produce poorer semen. Fat bulls may be less active and more prone to leg problems. Use the 1 to 9 body condition scale and discuss targets with your vet.

Make feed changes gradually to avoid digestive upset. Condition also changes over the year. A bull may be in good shape in fall and thin by spring if winter feeding is not matched to his needs, so score him more than once.

Protein, minerals and vitamins

Protein, minerals and vitamins all play a role in reproduction. Some trace minerals and vitamins are known to matter for fertility, but needs depend on the forage and region, and too much can be harmful.

Do not add supplements by guesswork or follow rates from the internet. Ask a nutritionist to review your feed analysis and your mineral program. Follow label directions. Well-balanced minerals support many body systems, not only reproduction. Check that the bull has access to the same mineral program as the cows, or to one your nutritionist designs for him, and follow label directions exactly. Remember that purchased bulls often arrive in high condition from a development program, and they may need a gentle transition to your forage and routine.

Heat, stress and illness

Heat stress, fever and illness can affect sperm production for weeks. Provide shade, water and a calm environment during hot weather. Call your veterinarian for any sick bull.

Injuries and lameness can also reduce breeding ability. Keep feet in good shape, and watch for problems. Ask your veterinarian about other causes of poor fertility too, such as infections or injuries, because feed is only one of several possible explanations.

Testing and records

A breeding soundness exam is the best tool for judging fertility. It evaluates physical soundness, scrotal measurements and semen. Ask your veterinarian when and how often to test your bulls.

Keep records of each bull's exam results, condition scores, feed and calf crop results. These help you spot trends. If a bull fails an exam, ask your vet whether the problem could be temporary and when to retest. Some bulls recover with time and good care, while others will not.

Common mistakes and what to ask

Common mistakes include skipping the exam, feeding bulls for fat, ignoring minerals and failing to allow lead time. Another is assuming a bull that bred last year is fertile this year.

Ask your vet: When should I test? Ask your nutritionist: What ration and minerals fit? Safety note: bulls are dangerous, so use sturdy facilities and follow safety guidance from manufacturers, OSHA and extension. Keep a simple file for each bull with exam dates, results, weights, condition scores and any health events. A history makes it much easier to decide which bulls to keep and which to replace.

• Test before every breeding season
• Allow time to correct problems
• Do not assume last year's result holds

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