Calving at two rather than three years old reduces rearing costs by about £600 a heifer and increases its lifetime productivity.
In addition, it ensures genetics with the best potential are introduced into the herd sooner, says Sarah Pick, AHDB knowledge exchange manager.
“A failure to get beef heifers in-calf at the target time [to be bred at 14-15 months] will result in an increase in the number of unproductive stock carried on-farm, increasing the farm’s carbon footprint.
“In the best case, where spring and autumn blocks are run, a heifer that fails to get in-calf will be carried for an additional six months, but if a single block is operated that animal will accumulate increased costs for a year,” she adds.
Miss Pick says a tight breeding period will make heifers easier to manage through to calving. It should be possible to get heifers pregnant in two cycles if they are properly grown, she adds.
- A heifer should be 45% of her mature bodyweight at weaning at about 200 days old and 65% of mature bodyweight at first service
- For example, if mature cow weight is 650kg, the heifer needs to grow at 0.85kg/day from birth and weigh 423kg at first service
Working out targets and monitoring weights
If cows are not regularly weighed, you can get a good indication of mature weight in your herd by looking at abattoir returns for cows culled in good condition, advises Miss Pick.
“Assuming calves on the dam are growing at 1kg/day then you need to ensure growth rates of at least 0.7kg/day from weaning through to service.
“Get into the habit of regularly weighing heifers between weaning and breeding as you want to ensure they grow at a steady rate.”
On units where weighing cattle is not practical or possible, she advises using weigh bands or even wither height markings on a wall to give an indication of growth rates.
This will ensure heifers develop a good frame and do not get overfat.
Should you split up replacements for feeding?
Providing replacement calves from the same year were born in a close block, it should not be necessary to group them by calving date or bodyweight, she adds.
“Splitting will just increase workload and may put unnecessary strain on the facilities.
“However, if any animals do show poor weight gain, it is advisable to separate these, check the health status with a vet, and adjust the ration accordingly to get them back on track.
“If they are still underweight at the start of the service period, then it might be advisable to hold them back and introduce them to the bull later, as a last resort.”
Feeding replacement heifers
Mark Hall, ruminant technical manager with Trouw Nutrition GB, gives advice
1. Make the most of home-grown forage
Home-grown forage can be expected to form most of the diet for heifers, but it is essential to monitor grass growth and quality.
An average heifer will require 32MJ/kg of liveweight gain and roughly 10% of bodyweight, expressed in MJ/day, for maintenance.
For a 350kg heifer to gain at 0.8kg/day, roughly 61 MJ/day is needed. As she will have a dry matter (DM) intake equivalent to 2.5% of bodyweight, or 8.75kg/day, she should perform well on good-quality grazing (11MJ/kg DM+).
Measuring grass growth with a plate meter and analysing energy content monthly will allow available grazing to be monitored and supplementation to be added as required to keep heifers on track.
2. Make the most of early growth
The efficiency of feed conversion to growth drops as the animal gets older. Declines can be from about 2:1 to 8:1, depending on diet and breeds, so it is important to make the most of early growth.
3. At housing, analyse silage
When cattle are housed, the big consideration in diets is energy, so ensure that silage has been analysed.
Feeding too much energy will lead to animals being overfat, especially if high levels of starch are included in supplements.
This can lead to problems at calving, particularly for early-maturing breeds which run to fat quickly.
For a 300kg heifer on a poor-quality forage grass silage, below 25% DM and less than 10MJ/metabolisable energy (ME), a diet of up to 3.7kg a head a day of a beef-grower type compound may be needed to meet the target of 0.8kg/day liveweight gain.
However, if silage is of better quality (more than 30% DM and 11MJ/ME) then feed rates for concentrates will need to be lower, at about 1.9kg a head a day.
4. Starch levels
Starch levels should be no more than 5-10% of the total diet because animals will become too fat, as previously explained.
However, around service, this can be increased slightly by 2-3% to raise circulating insulin levels, encouraging ovulation. Protein levels of 14-16% in the total diet are more than sufficient to support growth.
5. Trace elements
Diets should be supplemented to provide sufficient trace minerals such as copper, zinc, selenium, and cobalt, which play a key role in ensuring a robust immune system and good reproductive performance.
Heifers should have access to free-access minerals or licks to ensure they are receiving sufficient trace elements and minerals over the grazing period.
Magnesium will also be required when heifers are on spring grass to prevent staggers.
When heifers are housed, the amount of supplementary minerals will depend on the amount of compound fed and the premix it contains.
This should be confirmed with your feed supplier and an appropriate mineral formulated to be fed alongside the silage and compound feed or blend.
It is also important to pay attention to any potential antagonism in silage. High levels of antagonists can lock up essential trace elements, making them unavailable to the animal.
In cases such as these, it is vitally important to use a highly bioavailable source of trace elements to prevent any issues with animals getting in-calf.
This content has been produced as part of Farmers Weekly and AHDB’s new Maternal Matters series.
Maternal Matters is an AHDB initiative putting a spotlight on the importance of maternal performance in driving profitability in the suckler herd.
As part of the series, we will be bringing you regular articles on how to improve the efficiency of your suckler herd, including:
- How improved maternal performance reduces costs
- Using maternal genetics to breed profitable females
- Calving heifers at two years to reduce cost of production
- Reducing calf losses
- Heifer management for rebreeding success
Find out more at ahdb.org.uk/maternal-matters