Yes, Safe-Guard Dewormer Cattle Pellets are safe for your pregnant cows to consume.
Safe-Guard Dewormer Cattle Pellets are only labeled for use only on beef and dairy cattle.
For cattle, mix 1 lb of Safe-Guard Dewormer per 100 lb of body weight into the daily ration. Feed as the sole ration for one day to provide 227 mg of fenbendazole per 100 lb of body weight (5 mg/kg). So the 50 lb bag will treat up to 5000 lbs of cattle