When do I put the bull in for spring 2027 calving?

For first calves on 1 March 2027, put the bull in on 22 May 2026 (beef herds, 283-day gestation) or 25 May 2026 (dairy herds, 280-day gestation). For February calving, move that to 24 April 2026 (beef) or 27 April 2026 (dairy). Use the AgriOps calving date calculator for exact dates based on your specific service window.

How long should I leave the bull in?

An 8-week service window achieves approximately 90% conception in a well-managed herd. 10 weeks reaches approximately 95%. 12 weeks is common in commercial beef systems and is the practical upper limit for a tight block calving system — beyond 12 weeks the calving spread becomes difficult to manage and calf batching is affected. Remove the bull promptly when the window ends.

What gestation length do I use for beef cows?

The average beef cow gestation is 283 days, with a normal range of 279–287 days. Continental breeds (Charolais, Limousin, Simmental) often sit at the higher end — 284–286 days. Native breeds (Hereford, Aberdeen Angus) are often closer to 280–281 days. Heifers carrying their first calf typically gestate 3–5 days longer than the breed average. Use your herd's own data if you have it.

What gestation length do I use for dairy cows?

The average dairy cow gestation is 280 days, with a range of 276–284 days. Holstein-Friesian cows average 279–280 days. Jersey cows average slightly less at 278–279 days. Heifers should have 3–5 days added to the breed average. For crosses (e.g. Hereford × Holstein), use the beef sire breed's gestation as the best estimate.

Can I use a bull on heifers at the same time as cows?

Many farmers run heifers separately with the bull introduced 3–4 weeks ahead of the cow group, so heifers calve down before the main cow block begins. This means more labour availability for heifer calvings (which are more likely to need assistance) and the cows can be watched more closely during the peak period. If running together, ensure the bull can physically serve both groups and that heifers are not pushed off by older cows.

How do I calculate a calving date from a service date?

Add the gestation length in days to the service or bull-in date. For beef: add 283 days. For dairy: add 280 days. The AgriOps Cattle Calving Date Calculator does this instantly for both single AI service dates and block bull-in / bull-out periods, and generates a free PDF report you can keep with your herd records.

What body condition score should cows be at for bull turnout?

Beef cows should be at BCS 2.5–3.0 (5-point scale) at bull turnout. Cows below BCS 2.0 will have reduced conception rates due to anoestrus — especially first-calf heifers. Dairy cows should be at BCS 2.75–3.0 at mating. Cows still in a negative energy balance at mating time (common in early-lactation dairy cows) have significantly reduced submission and conception rates.

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When to put the bull in — planning your calving date for 2027

The bull-in date determines everything downstream — when calves arrive, when grass needs to be ready, when labour peaks, when you can expect the cows back in calf. Get it right by working backwards from your target calving window. All 2027 bull-in dates are worked out below for both beef and dairy herds.

Free Cattle Calving Date Calculator

Enter your service or bull-in date — get exact calving dates and a PDF report

The maths — gestation by type

Subtract from your target first calving date to find your bull-in date. Heifers add 3–5 days.

Beef cows

283

279–287 days

Dairy cows

280

276–284 days

Heifers

+3–5

add to breed avg

Bull service window

10–12

weeks for 95%

The rule: take your target first calving date, subtract 283 days for beef or 280 days for dairy. That is your bull-in date. For a 10-week service window, the bull comes out 70 days later. All 2027 dates are pre-calculated in the tables below.

Spring 2027 calving — bull-in dates

Spring calving is the most common UK system. Target dates assume first calves arriving on the 1st of the month — adjust up or down by a day per day difference in your actual target.

Target first calves

1 February 2027

Bull in (beef)

24 April 2026

Bull in (dairy)

27 April 2026

Bull out (10wk)

3 July 2026

Bull out (12wk)

17 July 2026

Suits housed systems and early grass. Tight management required.

Target first calves

1 March 2027

Most common

Bull in (beef)

22 May 2026

Bull in (dairy)

25 May 2026

Bull out (10wk)

31 July 2026

Bull out (12wk)

14 August 2026

The most common UK spring calving target — calves match grass growth well.

Target first calves

1 April 2027

Bull in (beef)

22 June 2026

Bull in (dairy)

25 June 2026

Bull out (10wk)

31 August 2026

Bull out (12wk)

14 September 2026

Late spring — suits drier systems but later grass utilisation.

Dates calculated using 283-day beef gestation and 280-day dairy gestation. Individual cow variation is ±4–5 days. Use the calculator for any specific service or AI date.

Autumn & winter 2027 calving — bull-in dates

Autumn calving suits suckler herds and some dairy systems. The bull goes in during late autumn or early winter — check the Christmas note below before committing to an October calving target.

Target first calves

1 September 2027

Bull in (beef)

22 November 2026

Bull in (dairy)

25 November 2026

Bull out (10wk)

31 January 2027

Bull out (12wk)

14 February 2027

Early autumn calving — cows need to be flushing well in November.

Target first calves

1 October 2027

Plan Christmas cover

Bull in (beef)

21 December 2026

Bull in (dairy)

24 December 2026

Bull out (10wk)

1 March 2027

Bull out (12wk)

15 March 2027

Bull-in falls on or near Christmas. Plan labour and checks over the holiday period.

Target first calves

1 November 2027

Common autumn target

Bull in (beef)

23 January 2027

Bull in (dairy)

26 January 2027

Bull out (10wk)

3 April 2027

Bull out (12wk)

17 April 2027

November calving suits autumn grass systems and suckler herds housing early.

Heifers — what to do differently

Heifers present two specific complications: they gestate slightly longer than cows, and they are more likely to need calving assistance. Both affect your planning.

Gestation is 3–5 days longer

A heifer served on the same date as a cow will calve approximately 3–5 days later. For a block calving system, this means heifers served alongside cows will trail behind in the calving spread — not usually a problem, but worth knowing when scanning results come in.

Put heifers to the bull 3–4 weeks early

Many beef producers run heifers with the bull 3–4 weeks ahead of the main cow group. This brings heifer calving forward of the cow peak, so labour is available for the harder calvings before the main flush of cows starts. It also helps heifers recover from calving and return to cycle before the next service period.

Bull selection matters more for heifers

Use an easy-calving bull EBV on heifers regardless of what you run on cows. A high muscle-score bull that works well on mature cows can cause serious calving difficulty on a heifer. AHDB easy-calving EBV data is available for most registered bulls.

Target weight and BCS at mating

Heifers should be at 60–65% of mature cow weight at first mating. Below this, conception rates fall significantly and first-calf difficulties increase. Flush condition in the 6–8 weeks before bull turnout if needed.

How long should the bull be in?

The service window length controls your calving spread. A tight window means a tight calving — concentrated labour demand but uniform calf batches and a predictable calving date. A long window means the opposite.

8 weeks

~88–90%

conception

Tight block. Some empties at pregnancy scan.

10 weeks

~93–95%

conception

The practical sweet spot for most beef herds.

12 weeks

~95–97%

conception

Maximum for a manageable calving block.

Beyond 12 weeks, the later calves — born when the earliest calves are already 12 weeks old — are at a significant disadvantage for weaning weight. In a grass-based system, the very late calves miss the peak flush completely. Remove the bull at 10–12 weeks regardless of what the scanning shows.

A bull that has been with cows for 14+ weeks does not improve conception rates beyond what 10–12 weeks achieves — it just produces a wider calving spread, more empties at the end, and a batch of undersized late calves. Empty rate on scan is a management issue, not a service window length issue.

Planning milestones — counting from bull-in

–8 to –12 weeks

Pre-bull checks

Bull fertility test (if not done recently), body condition scoring, BVD status check, lice / fluke treatment if needed.

–4 weeks

Flush cows / transition heifers

Improving body condition before breeding lifts conception rates. Heifers should be at target weight and BCS for breed.

–2 weeks

Introduce bull to paddock / group

Allows the bull to settle and establish hierarchy before mating begins. Reduces fighting stress.

Bull in

Start of service window

Record the date — this is day 1 of your calving window calculation. First calves arrive ~283 days later (beef) or ~280 days (dairy).

+8 weeks

Pregnancy scanning

Scanning at 8 weeks identifies empties early, allowing management decisions before housing. Most accurate window.

+10 to +12 weeks

Bull out

Remove bull to end the service window. Extended bull-in periods stretch calving spread and complicate batching.

+16 weeks

Dry cow / heifer nutrition planning

With conception confirmed, plan ration changes for late pregnancy. Colostrum management and calving equipment checks.

Calving equipment on Amazon

Check your kit before calving starts — not at 2am when you need it. Replace anything worn or damaged well in advance.

Calving Jack / Calf Puller

Essential for a difficult presentation — quality matters when you need it to work first time.

Calving Rope Set (Obstetric)

Soft obstetric ropes for assisted delivery — always keep a clean set in the calving area.

Calf Resuscitator / Reviver

Clears the airway on a slow-to-breathe calf. Worth every penny when you need it.

Colostrum Feeder / Stomach Tube

For a weak calf that won't suck — getting colostrum in within 2 hours is critical.

Head Torch — Hands-Free Calving

Night calvings are inevitable. A good head torch keeps both hands free.

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Frequently asked questions

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