I2 - your dad and bro are checking the PUS cell count in the milk and maybe taking a sample for bio testing and to see if the farmer has put in water for a little more profit.
Quality dairy processing plants flush the milk if the pus count is too high, some sell it as a lower quality milk which has a shorter shelf life.
Add the fact that the majority of American dairy farmers use artificial growth harmones in production, milk in America can be a gamble.