I have seen my neighbor walking around with a cathether hooked up and a urine collection bag hanging down in view. He needed to keep all the urine in the bag for some type of a urine volume test. The first day urine collection was light yellow, then it darkened as the days moved along.

He carried that bag attached to his leg like Matt Dillon carried his Colt 45. His wife was upset with him doing that without covering it up. It didn't bother me.

After a several days of looking at that, you could see the color change and sediment collecting in the bag bottom. I would rather see coyote or fox urine being collected personally. Just saying.

Okay, I admit, that's funny in a weird sort of way.

As Bob Jameson pointed out in the above post, you can see sediment and color changes in clean sterile urine,
which if doing the experiment I mentioned,
you may have a better understanding of how fast urine changes.

Much of the urine sold today through 'trapping supply houses', comes from a game or fur farm.
Not many true 'fur' farms these days.
Here in Ohio, much of it comes from the same source.