3 August 2001

Outside grazing proves challenging for heifers

By Richard Allison

HEIFER management is proving more difficult this summer due to changeable weather, surges in grass growth and falling grass quality.

Grass growth rates are fluctuating widely this year, according to Staffs producer Roly Tavernor.

"Record growth rates of 126kg DM/ha were achieved in late May and remained at more than 100kg DM/ha for three weeks. However, growth rapidly declined a week later and is currently at less than 25kg DM/ha.

During periods of low grass growth, heifers should have as much priority as dairy cows for grazing, says MDC Pasture to Profit consultant Carol Gibson.

Some producers believe managing heifers inside is the easiest option, but it creates extra health problems and increases costs. Heifers can be successfully reared on grazing and calve within 24 months. Rearing outside also allows heifers to get used to grazing before joining the main herd post-calving, she adds.

Following her advice, Mr Tavernor rears heifer calves in a free-range system. Several cull cows with high cell counts were put with the calves, acting as suckler cows. "Calves suckling cull cows are performing well and at least something is being gained from cows which cannot be disposed within the OTMS.

"Calves move freely under the electric fence to obtain the best grazing," he explains.

During summer, its easy to lose two months heifer growth, according to Agricultural Research Institute of Northern Ireland researcher Alistair Carson. "Periods of zero liveweight gain will result in heifers calving beyond the target 24 months."

To avoid declining growth, monitor heifer liveweights monthly and compare with target weights. Aim for about 0.75kg/day liveweight gain and re-adjust grazing or introduce supplementary feeding when necessary, he says.

Miss Gibson stresses there is no point weighing animals when the information is not used. "Remove under performing animals and feed supplements when necessary.

"Alternatively, grazing stragglers in smaller groups to reduce competition can sometimes be sufficient for heifers to recover. But once heifers fall a couple of months behind, it is difficult to recover."

The ideal mature cow body weight is about 500-550kg in grazing systems, says Miss Gibson. Cows larger than 550kg will significantly add to costs with little extra income within a grazing-based system.

When grass growth recovers following a dry spell, it is crucial to continue feeding supplements for 2-3 weeks, she stresses. "This will allow time for grass cover to build up. It also prevents weight loss due to dry, mature grass rotting off in damp conditions, which was probably maintaining heifers."

Late summer is a crucial period as both grass supply and quality declines, stresses Dr Carson. "Grass protein content has remained high this year at more than 20%, but is expected to fall as grass becomes more mature."

Spring born calves may require 1-2kg of concentrates from mid-august, he says. Concentrates fed should contain 17-20% protein to meet the high protein requirements of growing heifers.

At the institute, heifers are grazed in a leader/follower system to maximise grass use, says Dr Carson. "Young calves are grazed in front of in-calf heifers."

Mr Tavernor is also using in-calf heifers to clear mature grass from pastures to maintain pasture quality.

Normally this is achieved with minimal topping by alternating fields between grazing and silage, but there has been no second cut silage made as grass was needed for grazing instead.

Despite grass supply being lower than last year, heifer growth is on target for calving at 24 months of age without providing any supplementary feed. The secret is to monitor grass growth, plan ahead and manage grass to maintain grass quality during late summer, adds Mr Tavernor. &#42