Every other health decision on the place affects one animal at a time. A bull decision affects 25 to 40 cows at once, and you find out about it eight months later when the vet's arm comes out of a cow that isn't pregnant. A single-sire pasture with a bull that quit working in week two can hand you a 40% open rate, a 60-day-spread calving season, and a set of tail-end calves that weigh 120 pounds less at weaning. That's real money — often $8,000 to $20,000 on a 30-cow group — from one animal nobody looked at closely.

Bulls are also the easiest class of cattle to neglect. They spend 9 or 10 months of the year in a back lot where you don't handle them, don't weigh them, and don't want to sort them. Then they go out and do the most physically demanding job on the ranch. The management gap between those two states is where most breeding failures live.

Book the Breeding Soundness Exam 60 Days Out

A breeding soundness exam (BSE) is cheap insurance — typically $40 to $80 per bull — and about 1 in 5 bulls fails or defers on any given year. That number surprises people. It includes yearlings that aren't mature yet, older bulls with declining semen quality, and bulls carrying an injury or infection you can't see from the truck.

The exam covers four things:

  • Scrotal circumference — measured with a tape. Minimum thresholds run roughly 30 cm for a 12–14 month yearling, 31 cm at 15–18 months, 32 cm at 18–21 months, and 34 cm for mature bulls. Scrotal circumference correlates with daily sperm output, so a small-testicled bull is a low-capacity bull even if his semen looks fine.
  • Semen motility and morphology — the standard satisfactory threshold is at least 30% progressive motility and 70% normal morphology. Morphology matters more than most producers assume; a bull can have plenty of swimming sperm that are structurally defective.
  • Physical exam — feet, legs, eyes, teeth, body condition, and a palpation of the internal reproductive tract for seminal vesiculitis, which is common in young bulls.
  • Penis and prepuce exam — done during collection. Deviations, warts, hair rings, and healed injuries all show up here and all cause failure to breed in a bull that tests otherwise fine.

Timing matters as much as the test. Run BSEs 60 days before turnout, not two weeks. Spermatogenesis takes roughly 60 days, so a bull that failed because of a fever, a foot infection, or heat stress in the previous cycle can retest satisfactory after treatment and recovery. Two weeks out, your only options are "use him anyway" or "go buy a bull at auction in a seller's market."

The BSE is a snapshot, not a warranty. It tells you a bull was fertile the day you tested him. It says nothing about whether he'll still be sound in week five after breeding 20 cows on rough ground.

Bull Power: Ratios, Age, and Pasture Reality

The old rule of thumb — one cow per month of age, capped around 25 to 30 — still works as a starting point. A 15-month yearling gets 15 cows. A mature 3-year-old handles 25 to 30 in a 60-day season. But rules of thumb assume flat, small, water-close pastures with a synchronized, cycling cow herd, and most pastures aren't that.

Adjust down for:

  • Big or broken country — a bull in 600 acres of rough range walks a lot more than a bull in a 40-acre trap. Cut the ratio 20–30% on rough terrain.
  • Heat — breeding through temperatures above 90°F with high humidity suppresses both bull libido and semen quality. Bulls working in summer heat need lighter loads and shade.
  • Synchronized breeding — if you've synced cows so 60% cycle in five days, a 25:1 ratio collapses. Sync work wants 10–15 cows per bull or AI plus a cleanup bull.
  • Yearlings running with mature bulls — don't do it. The older bull will dominate and the yearling will spend the season on the fence line, and you'll pay for two bulls' worth of grass to get one bull's worth of work.

The other side of this: in single-sire pastures, you have no redundancy. If you're running one bull per group and a group is worth more than a spare bull, consider multi-sire groups of two or three mature bulls of similar age and size, or keep one proven bull back as a designated backup. The backup bull earns his hay the first year he saves a breeding season.

Condition Him Like an Athlete, Not a Show Steer

Target BCS 6 at turnout on the 1–9 scale. Bulls lose 100 to 200 pounds over a 60- to 90-day breeding season — some lose more — because they're walking, fighting, and breeding instead of eating. Starting at 6 leaves room to come out at 4.5 or 5 and still recover before next year. Starting at 4 means finishing at 2.5, which costs you fertility, libido, and often the following season.

The opposite problem is just as real. Bulls bought off a high-energy sale ration at BCS 8 are fat, soft, and heat-intolerant, and fat deposits in the scrotum interfere with thermoregulation. Those bulls need 60 to 90 days of let-down on a forage-based diet with modest supplement before turnout — not a crash diet, just 2 to 2.5 pounds of gain per week on roughage to convert bloom into condition. Take the shine off before he goes to work, not during.

Yearling bulls are a separate problem: they're still growing while they breed. Run them a shorter season (45 to 60 days), lighter cow load, and plan to put 1.5 to 2 pounds a day back on them afterward. A yearling that ends the season thin and never recovers becomes a 2-year-old that fails his second BSE.

Ready to put this into practice? Download on the App Store — it’s free and works offline.

Feet and Legs Fail Before Anything Else

Ask any vet what takes bulls out of service and structure comes up before fertility. A bull that can't walk can't cover cows, no matter what his semen test said. Look at four things every time you have him in a chute:

  • Claw balance — uneven claws, scissor claws, or corkscrew claw. Corkscrew is heritable and gets worse with age; don't keep sons out of a corkscrew bull.
  • Pastern angle — weak, sloping pasterns break down fast under 2,000 pounds of working bull.
  • Rear leg set — post-legged (too straight) bulls develop hock problems and lose mobility early. Excessive sickle-hock is the other extreme.
  • Foot rot and abscesses — catch these in the first 48 hours. A treated foot rot case is a week off work; an untreated one is a season and sometimes a joint infection that ends the bull.

Trimming helps a bull with an overgrown foot, but it doesn't fix bad structure — it just buys time. Schedule trimming 90 days before turnout, not 30, so he's fully recovered and walking normally when you need him.

Buy feet and legs first, then numbers. An EPD sheet is worthless attached to a bull who's lying in the shade in week three.

Off-Season Management: Where Bulls Get Hurt

Most bull injuries happen in the bull lot, not the breeding pasture. Bulls pulled off cows and thrown into a group re-sort their hierarchy, and 2,000-pound animals settling arguments on frozen ground or through a woven wire fence produce broken penises, injured backs, and prolapses.

Reduce it with a few habits:

  • Pull all bulls at the same time and put the whole group together at once, rather than adding one bull at a time to an established group.
  • Give them room — a bull lot that's too small forces confrontation. An acre or more per bull with good footing lets the loser leave.
  • Build the bull lot fence heavier than your cow fence — 5 or 6 strands of barbed wire, or high-tensile with two hot wires, with posts on 10- to 12-foot spacing. Bulls test fences for a reason.
  • Keep bulls out of sight of cycling cows when possible. A bull lot across the fence from the heifer pasture is a bull lot that will not hold.
  • Feed to maintain, not to grow — a maintenance ration of decent hay plus mineral is enough for mature bulls from mid-season to 90 days pre-turnout.

Keeping records on individual bulls through the off-season is what separates a hunch from a decision. Note injuries, treatments, lameness dates, and condition scores as you see them. This is exactly the kind of thing that lives in a notebook that gets rained on — logging it on your phone while you're standing in the lot means it's still there in March. Barnsbook works offline, so a bull lot with no signal isn't an excuse. If you're also running a market garden or a few hives alongside the cattle, the same logging habit applies — CropsBook handles planting and harvest records for crop and vegetable ground, and HiveBook does the same for apiary inspections. Different species, identical discipline.

Mid-Season Monitoring: Catch a Breakdown in Week Two, Not Month Three

This is the highest-return habit in bull management and almost nobody does it consistently. Observe your breeding pastures at least twice a week for the first 21 days and answer three questions:

  1. Is the bull with the cows? A bull off by himself, standing in water, or lying down while a cow is standing in heat is a bull with a problem.
  2. Is he moving normally? Watch him walk 50 yards. Any head bob, short stride, or reluctance to rise gets a closer look today.
  3. Is he actually breeding? Watch a mount and a service if you can. A bull that mounts but can't achieve intromission has a penile deviation or injury — he'll look busy and settle nothing.

Use chalk or paint on the tailhead of a few cows as a cheap activity check, or run heat-detection patches on a sample. Better yet, record the breeding dates you observe. If you see the same cows standing in heat 21 days apart, you have a bull problem, not a cow problem, and you have 40 days left to fix it.

Preg-check at 60 days post-turnout instead of waiting until fall. It costs a little more in labor and tells you whether your bull worked in time to do something about it.

Culling Decisions and the Records Behind Them

Most bulls have a useful working life of 4 to 6 seasons. Cull on:

  • Failed or deferred BSE after a retest — one bad test can be a fever; two is a fertility problem.
  • Structural breakdown — chronic lameness, corkscrew claw progression, or an injury that hasn't resolved in 60 days.
  • Disposition — a bull that charges you, breaks facilities, or can't be handled without three people is a liability worth more as beef. No pedigree offsets an injured handler.
  • Relatedness — if you're keeping replacement heifers, a bull's daughters enter the herd in two years. Rotate before he's breeding his own daughters.
  • Performance data — calving ease on his heifer calves, weaning weights of his calf crop, conception rate in his pastures.

That last one requires actually attributing calves to bulls, which means recording which bull was in which pasture with which cows and on what dates. In single-sire groups it's straightforward bookkeeping; in multi-sire groups you'll need DNA parentage testing if you want real numbers. Either way, the pasture-and-date log is the foundation, and it's the piece people skip. Barnsbook lets you tag animals to breeding groups and log turnout and pull dates in the field, so at preg-check you know exactly which bull to hold responsible.

Bulls reward a small amount of deliberate attention more than any other class of livestock on the place. Test 60 days out. Turn out at BCS 6. Match bull power to real terrain and real cow numbers, not a rule of thumb. Watch the breeding pastures hard for the first three weeks. Write down what you see. Do those five things and you'll spend far fewer Octobers explaining a 15% open rate to yourself.