24 May 1996

Big No to serving too-small heifers

DAIRY producers concerned about future supplies of replacement heifers if selective slaughter of certain categories of animals goes ahead are advised against serving heifers too young.

"Put your energy into ensuring replacements are capable of producing 20% more milk to compensate for reduced animals, rather than trying to bring more into the system too quickly," says Robert Bull of ADAS Bridgets Research Centre, Martyr Worthy, Hants.

Heifers calving at two years should be at least 350kg at service.

He aims for the high-genetic merit heifers at Bridgets to reach service weights of 370kg at 13-15 months. This helps ensure heifers calve at over 600kg so that they are big enough to survive first lactation and milk to full potential.

"Calving undersized heifers causes calving difficulties and can reduce yields in the first lactation by 1000kg and damage subsequent lactations.

Instead of serving heifers when they are too small, he would rather see them bigger (over 300kg) at 12 months and served to calve slightly younger at one year and nine months. But success would depend on growing heifers at 0.9kg a day until they are four months and then at 0.85-0.9kg a day from 11 months. Between these ages restrict growth to 0.65kg a day.

Heifer growth rates

Age (months)Growth (kg/day)

5 to 110.65

11 to 150.90