An evaluation of the use of synchrony technology in beef breeding herds

Abstract A model which was originally developed to derive the probability density of a calving distribution for beef cows under natural breeding has been modified to incorporate the effects of using oestrous synchronization at the beginning of the breeding period. The model has been used to investigate five oestrous synchronization strategies over four herds, each with differing calving patterns: no synchronization; every cow in the herd is synchronized; every anoestrous cow is synchronized; every cow calving more than 20 days after the date of the planned start of calving is synchronized; every cow calving 30 days after the date of the planned start of calving is synchronized. Two of the herds previously had long calving periods and two previously had short, compact calving periods. Model results showed that synchronization improved average herd calf live weight by 21 kg in the two herds with long prior calving periods but showed little effect in the two herds with compact prior calving periods. Synchronizing cows which calved more than 20 days after the start of calving in the herd showed similar results to synchronizing every cow in the herd and thus would be more cost effective. Synchronizing cows which calved more than 30 days after the start of calving in the herd showed a smaller advantage but only in the herds with long prior calving periods. The optimal strategy for oestrous synchronization in a herd will depend on the prior calving distribution and the average duration ofanoestrus in that herd as well as the relative costs of the treatment.