This is a natural habit among all males: free males or slaves. What is important upon delivery of a slave are that all measurements are taken. Height, weight, inside leg, small or large penis, small or large testicles. waist and chest and hips. Length of penis from base to tip, both flaccid and erect. These are useful barometers of the slaves health from delivery over time.
My slave will be so measured and repeated on a quarterly basis. As with livestock an interest and check of ones slave is essential to maintain its health and value.