What is the first step to take when performing a rectal temperature check on an animal?

The appropriate first step when performing a rectal temperature check on an animal is to shake down the thermometer. This action ensures that the mercury or electronic sensor is reset to the starting point for an accurate reading. By shaking the thermometer down, the mercury column is moved back to the lower part of the scale, allowing for a more precise measurement when inserted.

Starting with a properly calibrated thermometer is critical because any previous measurements may skew the results if the thermometer is not reset. This step lays the foundation for accurate temperature readings that are essential in assessing the animal's health.

Following this, lubricating the thermometer is also an important step; however, it should come after ensuring the thermometer is ready to use. Inserting the thermometer right away without preparation can lead to inaccurate readings or discomfort for the animal. Holding the thermometer for three minutes is part of the process but only after the thermometer has been inserted.