___ feed specifies the presence and concentration of contaminants.

Certified feed specifies the presence and concentration of contaminants, serving an essential role in laboratory animal care and research. This type of feed is rigorously tested and must meet defined quality standards established by regulatory agencies or specific organizations. By detailing the levels of potential contaminants, certified feed ensures transparency and allows researchers to make informed decisions regarding the health and well-being of the animals involved in their studies.

In contrast, standard, contaminated, and specialized feeds do not inherently provide the same level of detailed information regarding contaminants. Standard feed may meet general nutritional guidelines but lacks specific testing for contaminants. Contaminated feed implies that there are undesired substances present but does not provide a reliable assessment of concentration. Specialized feed may be formulated for specific dietary needs of certain species or research purposes, yet it still does not guarantee the presence and concentration of contaminants will be specified.