PRODUCERS WHOSE heifers are more than 24-months at first calving are adding to rearing costs and losing out on valuable milk yield.

Most producers state their target is a two-year calving, but NMR data show the average age at first calving is 30 months. Figures for the first six months of 2004 reveal just 17% of heifers calved between 21 and 25 months. Some 37% calved aged 26-29 months and a further 20% at 30-32 months.

Calving later than planned adds to rearing costs, says Berks-based consultant William Waterfield of the Farm Consultancy Group. But he doubts whether many producers would recognise a few months’ delay because of the way they run their management systems.

Yet with replacement costs of up to 2.25p a litre in some herds, calving on time saves money. “Producers may think it’s cheaper to keep heifers when they are older, but rearing costs increase significantly for animals over 30 months,” he says.

“An in-calf heifer is worth something and there is her loss of production to consider because she isn’t calving on time.”

Mr Waterfield admits it’s hard to calculate rearing costs and believes only producers who contract out rearing would have a firm idea – often £500-£600 a head. “On-farm, I suspect this figure is much higher due to poorer economies of scale – nearer £800,” he adds.

“We tend to work on the basis of 100 weeks – months one to 23 – at £5.50 a week in routine rearing costs: Feed, vet and med, labour, machinery and vaccination. This doesn’t include getting her in-calf.”

To know whether targets are being achieved, he advises weighing heifers routinely. Judging by eye can be 25% out, he says. “It’s not the average that’s important, but the bottom 25% of animals which don’t hold to service and struggle through their first lactation.”

Kate Burnby of Sussex-based Stock1st Vets agrees that on many farms heifers are served according to look. The aim is for heifers to reach 65% of their mature bodyweight by the time they are ready for bulling – regardless of breed – and 85% by calving, she says.

“This is critical as it delivers good fertility and a tight calving pattern at 24 months. You can serve heifers at lighter weights, but they take longer to get in-calf.”

She recommends monthly weighing, initially. That way feed can be cut should heifers be performing well or increased for those under par.

Miss Burnby believes investing about £1000 in a digital load cell to fit under a crush is quickly repaid in better fertility, cheaper rearing costs and calving on time.

Weighing monthly over two years will build up a detailed picture of growth rates.

“This helps establish when key weighing times are and allows you to cut the number of weighings to combine it with other jobs such as worming, freeze branding or fly control.”