Oestrus synchronization is routinely used in over a third of cows in larger US herds to improve pregnancy rates and reduce days open. Angela Rhodes examines the part it could play with cows in the UK. Over the last 10 years the number of herds in theUS routinely using oestrus synchronization programmes has increased from just 1% to almost 20%. During the same period the proportion of cows in these herds that are served to a synchronized oestrus has also risen from just 2% to 35%. These figures indicate how American producers, especially those in the 200+ cow category, are increasingly coming to rely on oestrus synchronization to get their cows back in calf. In a paper published earlier this year in the Journal of Dairy Science, Dr R H Miller from Animal Improvement Programs Laboratory in Maryland looked at 10 years' worth of Dairy Herd Improvement data to assess both the extent of usage and the impact on reproductive performance of synchronization programmes. In addition to the rise in usage, Dr Miller and his colleagues also reported a 17-day reduction in days to first service and a nine day reduction in days open in synchronized cows.
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