Suckler Herd Fertility Focus – Managing replacement heifers to achieve earlier age at first calving

Date published: 8 April 2026

“Replacement heifers represent the future breeding cows within the herd. Ensuring these animals reach breeding weight at the correct age will influence their lifetime performance within the suckler system,” commented Jack.

Within year two of the DAERA Suckler Cow Scheme (Part of Beef Sustainability Package), farms are encouraged to achieve an average age at first calving of 32 months or less. However, from a production and herd productivity perspective, calving heifers at closer to 24 months of age represents the most efficient system where management and growth targets allow. Earlier calving reduces the period during which heifers remain as non-productive and allows heifers to enter the breeding herd sooner, increasing the number of calves they can produce over their lifetime. 

Achieving this target requires careful management of heifer growth from an early age. As a guideline, heifers should reach 60% to 65% of their mature body weight at first service. If heifers fail to reach this level their fertility performance may be reduced and the age at first calving can quickly slip beyond target. Monitoring liveweight gain throughout the grazing season can help ensure animals remain on track. Regular weighing, or at least regular handling and assessment, allows farmers to identify heifers that are not performing and act early.

Grass should form the basis of the heifer diet during the grazing season. Maintaining leafy, high-quality grazing helps maximise intake and support strong liveweight gains. “Rotational grazing systems can improve pasture utilisation and maintain grass quality. Ensuring heifers have consistent access to high-quality grazing throughout the season helps avoid check periods in growth. Achieving these growth rates ensures heifers reach breeding weight at the appropriate age,” added Jack.

During the second grazing season heifers should continue to grow steadily so they approach breeding weight in good time. In many systems heifers should weigh around 380 kg to 420 kg at breeding, depending on breed type, mature cow size and the age at which they are to be served. The important point is that breeding targets should be linked to mature cow size rather than applied as a single fixed figure across all herds.

Nutrition during the period before breeding is particularly important. Heifers should be on a rising plane of nutrition before service to maximise conception rates. Where grass supply becomes limited, supplementary feeding may be required to maintain growth and ensure heifers continue to move towards breeding targets. Heifers that experience a check in performance before service are more likely to cycle late, show weaker heats or conceive later in the breeding period.

Pelvic development also plays an important role in heifer performance and in the risk of calving difficulty. Heifers that are underdeveloped or too small at breeding may experience a greater risk of dystocia at first calving. Adequate skeletal growth before breeding is therefore essential. Heifers that fail to reach recommended breeding weight may not have sufficient pelvic size or maturity to calve unassisted. Ensuring heifers reach adequate weight and frame development before service can therefore help reduce calving difficulty, improve calf survival and increase the chance that heifers remain in the herd long term.

Bull choice is particularly important when breeding heifers. Using bulls with favourable calving ease Estimated Breeding Values (EBVs) can help reduce calf birth weight and the likelihood of difficult calvings. This is especially important where heifers are being bred to calve at a younger age. Difficult calvings not only increase labour and calf loss risk but can also negatively affect the heifer’s fertility in the following season.

Breeding management also plays an important role in achieving good reproductive performance from replacement heifers. In many suckler systems heifers are bred slightly ahead of the main cow herd. This management practice allows heifers extra time to recover after calving before they are required to conceive again during their second breeding season. 

“Breeding heifers earlier in the season allows them additional time to recover,” Jack says. Heifers that calve earlier in the calving period generally have more time to resume cycling before the next breeding season begins.

Where heifers calve late in the season they may struggle to recover sufficiently before breeding begins again, increasing the risk of extended calving intervals and eventual culling from the herd.

Reducing age at first calving can have a significant impact on the lifetime productivity of suckler cows. Heifers that calve earlier enter the breeding herd sooner and therefore have the potential to produce more calves over their productive lifetime. Earlier calving also reduces the number of non-productive days before the animal contributes to herd output, improving the overall efficiency of the suckler system.

Good heifer management therefore influences far more than just the first calving date. It affects calving difficulty, fertility as first-calvers, herd replacement cost and the number of calves produced per cow over time. 

Jack concludes that careful heifer management is essential. “Ensuring heifers achieve adequate growth rates, reach breeding weight, receive the right nutrition before service and are bred to easy-calving bulls will help farms achieve 24-month age at first calving, improving long-term herd productivity while also ensuring the scheme target for year two of 32-month target is comfortably achieved.”

For further advice on this topic please contact your local CAFRE Beef and Sheep Adviser at your local DAERA Direct Office.