**Core Concept**
Purine metabolism is a complex biochemical pathway responsible for the synthesis and breakdown of purine nucleotides. The end product of purine metabolism varies between different species, reflecting their unique physiological and evolutionary adaptations.

**Why the Correct Answer is Right**
In non-primate mammals, the end product of purine metabolism is allantoin, which is formed through the action of the enzyme uricase. Uricase catalyzes the oxidation of uric acid to form allantoin, which is then excreted in the urine. This pathway is more common in non-primate mammals, such as rodents and rabbits, whereas primates, including humans, lack uricase and excrete uric acid as the end product of purine metabolism.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately represent the end product of purine metabolism in non-primate mammals.
* **Option B:** This option is incorrect because it is not a recognized end product of purine metabolism in any species.
* **Option D:** This option is incorrect because it is actually the end product of purine metabolism in humans, not non-primate mammals.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that the end product of purine metabolism varies between species, and this knowledge can be useful in understanding the pathophysiology of gout and other purine-related disorders.

**Correct Answer:** C.