Sealing log ends before milling is not typically necessary or recommended. Sawmilling involves cutting the logs into lumber, and the freshly cut surfaces will be exposed during the process. Sealing the log ends before milling may interfere with the sawing process and can potentially contaminate the blade or affect the quality of the lumber.
Instead, it is more common to seal the ends of the lumber after it has been sawn to prevent excessive moisture loss and minimize end grain checking. Applying a sealant to the freshly cut ends of the lumber helps to slow down moisture evaporation and reduces the risk of splitting or checking.
If you are concerned about end grain checking during the drying process, it is best to focus on proper stacking and drying techniques, such as using stickers or spacers between the boards to allow for air circulation, maintaining proper airflow, and monitoring moisture levels. Additionally, monitoring the drying process and making necessary adjustments to temperature and humidity can help minimize end checking.