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Records from unsynchronized cows (n = 2073; 60-day breeding season) were compared with records from synchronized cows (n = 517; 45-day breeding season) collected between 2000 and 2006. A single injection of prostaglandin F2α was administered approximately 108 hours after bull turn-in to synchronize estrus in spring calving mature beef cows. Estrus synchronization increased the percentage of cows calving in the first 21 days without affecting pregnancy rates. However, weaning BW of calves was not significantly different. Estrus synchronization improves synchrony of calving in a shorter breeding season with similar overall pregnancy rates.