The recommendation is to pregnancy test cows around 30 days after being bred to identify cows that are open so that open cows can be rebred in a timely manner. Cows that are pregnant by 130 days in milk have a lower chance of becoming overconditioned in later lactation and have been shown to rebreed in a more timely manner in their subsequent lactation. 

Pregnancy losses in the early stages of gestation are quite high. A recent study looked at the records of almost 20,000 cows and estimated pregnancy losses by various stages of gestation. Hence, explaining why cows need to be rechecked post 60 days from breeding and confirm they are still pregnant. If not pregnant, these cows need to reenter protocols for getting them bred and pregnant in a timely manner.

Reference: JDS Communications April 2023