Which of the following is NOT a method of urine collection?

Choosing "biopsy" as the method that is NOT a urine collection technique is correct because biopsy refers to the procedure of taking a small sample of tissue from the body for diagnostic purposes. Unlike urine collection methods, which involve obtaining urine directly from the animal, a biopsy involves surgical intervention to obtain tissue samples for histological examination.

In contrast, free catch, catheterization, and cystocentesis are all established methods for collecting urine. Free catch involves collecting urine during urination, catheterization involves placing a catheter into the bladder to collect urine, and cystocentesis involves using a needle to directly aspirate urine from the bladder. Each of these methods is specifically designed to gather urine for analysis, contrasting with the tissue sampling purpose of a biopsy.