29 October 1999

Condition score to beat prolonged calving interval

By Marianne Curtis

PROLONGED calving intervals in suckler herds could be tackled by condition scoring, adequate nutrition and restricted suckling, whatever your production system, according to a recently completed SAC study.

"Many beef cows do not begin cycling until 60-70 days after calving. Conception rates in early cycles are always low, so they may not become pregnant until more than 100 days after calving, increasing calving intervals," says SAC Aberdeen researcher Kevin Sinclair.

Addressing the problem was the remit of an EU-funded study conducted on suckler herds in Scotland, Ireland, Spain and Italy. The effect of condition score at calving, feeding post-calving and restricted suckling on fertility were measured. Results were similar for all breeds and environments.

Cows with a low condition score of two at calving were compared with cows having a moderate score of 2.8. "The biggest effect on how soon cows started cycling was condition score at calving: Fitter cows, began cycling sooner after calving.

"Increasing feed intakes post-calving shortens the interval to when cows start cycling. But this interval was identical for cows calving in poor condition and well-fed post-calving as for cows calving in good condition and fed less post-calving," he says (see table).

Restricting access of calves to dams from 28 days after calving for two to three weeks also hastened the onset of cycling. "Where calves were only allowed to suckle once or twice a day and kept out of sight and smell of cows, 90% were cycling within 35 days of calving." This temporary separation breaks the maternal bond between mother and calf – accelerating ovulation – and may provide a valuable alternative to fertility enhancing drugs, especially for organic beef producers, believes Dr Sinclair.

But for those wishing to stick with more conventional methods, condition scoring is the key. "It is difficult to put condition on cows in late pregnancy, so aim for condition score three when housing spring calvers. When grass quality and quantity diminish in late autumn, consider supplementing with straw, hay or silage to avoid condition loss.

"Where grass quality is particularly poor, a maximum of 2kg of a barley-based concentrate can be fed to spring calvers to achieve a condition score of three by the end of October."

Spring calvers can lose some condition over winter, but should not score less than two at calving. When cows are losing too much condition, calves should be weaned a month or two early. Intakes of more than 150MJ a day of metabolisable energy when they are turned out on to spring grass assist fertility, he says.

But autumn calvers should score three at calving to ensure an early return to cycling, as the aim is to feed as little as possible through the housing period. Grouping thin cows and heifers separately through winter can also enable more precise targeting of feed, he adds. &#42

SUCKLER FERTILITY

&#8226 Calve spring calvers at CS two.

&#8226 Calve autumn calvers at CS three.

&#8226 Restrict suckling?

Effect of condition score and feeding on fertility

Condition score at calving Low: 2 Moderate: 2.8

Feed post-calving Low High Low High

MJ ME a day 65 105 71 118

Days to first ovulation 68 64 63 54