What equipment may be necessary to collect faeces without interference?

A metabolic cage is specifically designed for the collection of fecal samples in a controlled environment, which minimizes contamination and interference. This specialized equipment allows for the monitoring of an animal's intake and output, ensuring that the sample collected is solely the result of the subject's own biological processes. It provides a contained space where the animal can live normally, and the design often includes features that separate waste products from food or bedding materials.

The other choices, while they may play roles in sample collection or analysis, do not provide the same level of control. Standard specimen containers might be used to store samples after collection but do not prevent interference during the collection process. Invasive collection tools could introduce variables or stress that might affect the sample collected, while recording devices for output are primarily for data logging and do not aid in the physical collection of the samples themselves. Thus, the metabolic cage is the ideal equipment for this purpose.