A CALVING RATE close to 90% in a 46-day breeding period has proved achievable in six consecutive years in spring-calving suckler cows using triple synchronisation.

Colin Penny said SAC”s Easter Howgate Farm synchronisation and AI system allows cows up to three service opportunities over a 46-day breeding period. The results show 90% can achieve a pregnancy in this time (see table).

Such good results are unlikely to be achieved on many farms using natural service. “A proportion of cows would be anoestrous during the short breeding period and at least one sub-fertile bull was likely,” he explained to the British Cattle Conference.

Assuming all cows are cyclical when bulls are introduced, it would require an all service pregnancy rate of at least 70% for bulls to match this calving rate in 46 days.

He believes triple synchronisation is a good option for those wanting to realise the benefits of a tight calving pattern. However, it”s not proved practical for use on the farm”s heifers.

To ensure heifers calve in the first month of the calving block, giving them the best chance of conceiving quickly as first calvers, they have only been served twice in the last three years, said Mr Penny.

But during the past two years, heifers have had poor pregnancy rates, giving Mr Penny cause for concern. “These heifers have achieved target mating weights. But it is possible that by selecting purebred beef heifers based on late maturing Continental breeds, we are also selecting for later onset puberty or poorer fertility compared with the herd”s traditional dairy cross heifers.

” Timing of AI may also be a factor, as heifers will ovulate earlier than cows following oestrous synchronisation. In this instance, Mr Penny advised inseminating heifers first to ensure the timing of the first AI is no more than 48 hours after removing the CIDR uterine devices.

Although the breeding figures prove the system can work, particularly with cows, he warned that good handling facilities and amenable cattle, as well as considerable planning, were essential.