Explain the indirect method of measuring microbia growth by metabolic activities?

Can human eat dog food?

By dog food I take it what is meant is canned dog food. This is composed of meat and offal together with, in some products, a cereal or other non-meat filler. The product is cooked and sterilised/pasteurised during the canning process. It should therefore be microbiologically safe to eat for humans. Kibble, dried dog food, could also be taken into account, although it has significantly less moisture, and generally has a lower protein content.There are some issues that arise from consumption of dog food, however:Pet foods may be made from animals in which the presence of prions, which cause encephalopathies such as BSE in cattle and variant CJD in humans, may be likely. According to the Association of American Feed Control Officials (AAFCO), animal by-products in pet food may include parts obtained from any animals who have died from sickness or disease provided they are rendered in accordance to law. As well, cow brains and spinal cords, not allowed for human consumption due to the possibility of transmission of BSE, are allowed to be included in pet food intended for non-ruminant animals. As prions are not exactly living microorganisms, even cooking cannot prevent the transmission of Bovine spongiform encephalopathy (BSE).Nutrition in pet food is often substituted for a cheaper alternative. You may have noticed that pet foods are measured for "crude protein" or "crude fibre". Both have nothing to do with protein content and fibre content we have become so accustomed to in human foods. Crude protein is calculated by taking Total nitrogen multiplied by the nitrogen conversion factor = 6.25. Crude protein can therefore be artifically raised by adding non-protein nitrogen. Non-protein nitrogen (or NPN) refers collectively to components such as urea, biuret, and ammonia, which are not proteins but can be converted into proteins by microbia in the ruminant stomach. Due to their lower cost compared to plant and animal proteins their inclusion in a diet can result in economic gain, but at too high levels cause a depression in growth and possible ammonia toxicity (microbes convert NPN to ammonia first before using that to make protein.) Crude fibre is the term given to the indigestible part of foods, defined as the residue left after successive extraction under closely specified conditions, and has nothing to do with dietary fibre. Therefore long-term consumption of dog food may not be enough to meet a human's dietary needs and could possibly cause problems due to inability to use NPN to efficiently create proteins.