Advice for ensuring heifers are the correct weight after calving

Too many heifers are still less than 85% of mature weight after calving because farmers try to “guesstimate” weights, says farm consultant Andy Dodd.

Many farmers say they have had bad experiences calving heifers at 24 months, saying it affected lifespan and productivity, but they wrongly assume it was down to age, says Mr Dodd.

In fact, it is because heifers are not big enough to cope within the herd, explains Mr Dodd, from The Farm Consultancy Group, who ran AHDB’s Calf to Calving project.

He says the two-year initiative, which aimed to improve calf performance, found many farmers took their foot off the pedal once heifers were safely in-calf.

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“We regularly saw animals were 70-75% of mature weight post calving, so they were a long way off target. A lot of time it comes down to labour availability and facilities to weigh them. If heifers will go away [to another site], it’s not as easy to weigh them.”

To ensure heifers are the right size at calving, farmers need to measure at critical points during the first two years (see “Targets”).

Mr Dodd says regular weighing is a good indicator of management success and can help pinpoint where improvements need to be made.

“You are looking for consistent growth through to calving. And if you are not hitting targets you need to understand why that heifer isn’t growing.”

Management improvements and genetic gains mean mature cow size will constantly be evolving and therefore it needs to be reviewed annually.

Top tips to hit targets

  • Colostrum management is the most important factor.
  • Feed the same concentrate from day one right through. The Calf to Calving project found no benefit to feeding a weaning nut and transitioning onto a rearing pellet.
  • Avoid making too many changes to reduce stress and checks in weight gain.


  1. Understand your herd mature weight target: This can vary from farm to farm and year to year. Weigh between 5-10% of the herd. Target third- and fourth- lactation cows at 100-120 days in milk. If your genetics are changing or you are cross-breeding, you need to consider what effect this will have on cow size. You can get a big variation within a breed if you change your cow type or cross-breed.
  2. Once you have a mature weight target, start weighing calves at birth so you can monitor progress.
  3. Next, weigh calves at three weeks to give an indication of how well your colostrum management and first few weeks of transition milk/powder have worked.
  4. Then weigh again at weaning (calves should double their birthweight by 56 days as a minimum).
  5. Weigh 10-14 days after weaning to make sure calves maintain their growth curve and they transition well onto the next diet phase.
  6. Six-month target: 27% of mature weight.
  7. 12-month target: 50% of mature weight. Heifers reach puberty at 45% of mature weight. Weighing at 12 months allows for time for heifers to catch up before breeding.
  8. At breeding: 60% of mature weight.
  9. Post-calving: 85% of mature weight (traditionally the target was 90% pre-calving, but it’s not advisable to weigh heifers and stress them close to calving).

Case study: Keith Durston, Chesnut Farm, Highbridge, Somerset

Making the move from all-year-round calving to autumn block highlighted the importance of weighing and ensuring heifers were big enough at service for Somerset dairy farmer Keith Durston.

Previously, heifers from the 140-cow herd calved at three but age at calving has been reduced to 24 months in the last two seasons.

“We knew we had to sharpen up. With block calving there isn’t anywhere for heifers to hide if they don’t make the weight,” says Mr Durston.

Farm facts

  • Milks 140 cows
  • Yields 10,000 litres at 4.1% butterfat and 3.4% protein
  • Supplies Tesco
  • Autumn block calving
  • Calves October to January
  • Grazes cows from April
  • 100ha (250 acres) farmed, 90ha (220 acres) of which is owned

Getting involved in Tibbs and Simmons Vet’s calf to calving group helped highlight areas for attention.

The aim now is for heifers to double their birthweight by weaning at eight weeks and for them to weigh a minimum of 350kg at service by 20 October.

To achieve this, four main improvements have been made: colostrum management, housing, feeding and monitoring.

Colostrum is now measured and only fed to calves if it’s good quality (more than 22 on a Brix refractometer). They are fed three litres within the first six hours.

They are then fed skimmed milk powder (22% crude protein and 21% fat) up to weaning at eight weeks. Calves are housed in hutches in pairs for the first two to three weeks before being put into groups of five.

They are offered chopped straw and ad-lib concentrate, and transition on to a ration of maize, grass silage and 50% chopped straw at 12-14 weeks. Straw is then slowly reduced.

“In the past, heifers would have got poorer-quality silage, but now they get the best of everything and we try not to make any rubbish,” he explains.

Previously, nothing was weighed, but now they use a weigh band and monitor growth rates each time they do key jobs such as disbudding or vaccinating.

Heifers are weighed eight weeks before service and the smallest will be regrouped and fed more concentrate to get them up to target, if needed.

Last summer the farm put up a new loose housed shed for heifers and are changing their rearing policy after noticing how well housed heifers have grown indoors.

“We had 53 heifers last year and we came to the spring and had too many for the shed, so we turned the largest 10 out to grass,” Mr Durston explains.

“I weighed them recently and the heifers that grazed are 40-45kg behind the rest.”

As a result, Mr Durston will be housing heifers year-round up to calving. The plan is to expand to 150 by the end of the year and once at target they won’t need to keep as many heifers.