Bull Selection for Dairy Herds

Every sire you pick will show up in your herd for years through his daughters. A little planning before you open the catalog keeps you from buying traits you do not need.

Key points

Pick a few goals based on your own herd records.
Mix proven sires with some young bulls and spread your risk.
Do not sacrifice fertility, health and herd life for yield alone.
Use calving ease sires on heifers.
Watch relatedness and review your choices every year.

Start with what your herd needs

Before looking at a single bull, write down what is holding your herd back. Is it fertility, udder health, feet and legs, milk components, calving trouble or herd life? Pick a small number of goals that match your records and your milk check, not every trait on the page.

Talk to your herd veterinarian and nutritionist. They see patterns in your cows that a sire summary cannot show, such as repeated retained placentas or a poor record of cows lasting into later lactations.

Involve the people who work with the cows every day. A milker or herdsperson often knows which cows are hard to breed, which have trouble with feet and which families produce calves that struggle. That knowledge is worth as much as any printed number when you set goals.

Use proven information, not hype

Good sire proofs come from independent evaluations of many daughters, and young bulls have predictions built on pedigree and genomic information. Young bulls can be a good choice, but their numbers carry more uncertainty than those of bulls with many daughters in milk. A sensible plan mixes both.

Keep your eyes on the summary the breed association and the national evaluations publish. Ignore claims you cannot check against a published source.

Look at breed association and national evaluation summaries
Treat young sire numbers as predictions, not guarantees
Spread your risk across several sires
Ask how reliable a number is before leaning on it

Balance production with health and fitness

A sire who raises milk but lowers fertility or herd life may cost you more in the long run than he adds. Look at traits for daughter fertility, calving ease, livability, somatic cell score and udder and feet traits along with yield and components.

Match the traits to your system. A grazing herd, a robotic milking herd and a large freestall herd may weigh them differently. Your milk buyer may pay on components, so check what your contract rewards.

Remember that traits move together. Pushing hard on one often shifts another, so look at the overall package a sire brings. If you are unsure how much weight a trait should get, ask your adviser to show you how the choice would change your herd over several generations.

Calving ease and heifer sires

Heifers need sires with a good calving ease record. A hard birth hurts the calf, the heifer and her next lactation. Use the sire calving ease numbers that your supplier lists and ask your veterinarian which traits matter in your heifers.

Think about size too. Heifers that are bred too small or fed poorly have a harder time regardless of sire.

Keep a written record of every difficult calving, along with the sire, and share it with your veterinarian and supplier. Over a few years that record tells you more about which sires suit your heifers than any catalog description.

Use sires with strong calving ease records on heifers
Check heifer size and body condition before breeding
Keep records of calving difficulty by sire

Watch relatedness and genetic diversity

Many popular sires are related. If you use the same few lines again and again, your herd will drift toward higher inbreeding. Ask your supplier or breed association about a mating program that screens for relatedness between sire and cow.

A simple rule: do not let a single sire or family account for most of your matings.

Many herds find it useful to set a simple limit for themselves, such as a cap on how many cows any one sire may be used on in a year. Your adviser can help you pick a limit that fits your herd size and the number of sires you use.

Questions to ask your semen supplier

A good representative will explain where the numbers come from and help you use them. Ask for a list built around your goals, not just their top sellers.

Ask for printed or digital summaries you can compare against the published evaluation.

Also ask for references. A supplier who has worked with herds like yours, in your housing and milking system, will usually be able to tell you what worked and what did not. Take notes at every meeting so you can compare offers fairly later on.

How reliable are the numbers on this bull?
How does he rank for fertility and calving ease?
Is he related to the sires I used last year?
What are the semen handling and return policies?
Do you offer a mating program?

Common mistakes

Chasing a single trait, buying on price alone, using one favorite bull on too many cows and ignoring your own culling records are the usual errors. Another is changing course every year, which makes it hard to see results.

Review your sire choices every year with your veterinarian and advisor. Compare daughters to herdmates and adjust slowly.

When to get help: Ask your herd veterinarian and your breed association or AI representative to help you set breeding goals based on your records. Your extension dairy specialist can review a sire list with you if you want an outside view.

Sources and further reading

Organization homepages are linked so you can search them for current guidance on this topic.

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