biological resource, for human benefit." Marine conservation activist Paul Watson argues that the reduction in forage fish such as those commonly used in cat food (sardines, herring, anchovy etc.) negatively affects fish higher up the food chain like cod, tuna and swordfish, not to mention marine mammals and birds. Based on 2004 numbers, cats in the US consume the caloric equivalent of what 192,000 (0.0655%) Americans consume. While pet food is made predominantly using byproducts from human food production, the increase in popularity of human-grade and byproduct-free pet food means there is increasing pressure on the overall meat supply. AAFCO recommends 26% crude protein for feline diets on a dry matter basis. High animal protein in cat food has increased in popularity due to consumer demand for natural diets, in which protein content is usually much higher than the AAFCO minimum levels. This trend has led to a higher need for animal protein, which may have a detrimental effect on sustainability. In 2015, there were an estimated 77.8 million dogs and 85.6 million cats in the USA. The consumer desire to feed their pets premium foods which advertise healthy and human-grade ingredients, coupled with more pet ownership, requires more meat; this could require more land for raising livestock. In a study conducted by Okin in 2017, he suggests that if a quarter of all animal protein used in the food of American pets was human-grade, it would be equivalent to the energy needs of 5 million Americans. Okin uses an estimate of 33% of an animal's energy needs is derived from animal products; however, this is conservative in that many diets now have more than 33% of their diet in animal protein alone. Lowering protein levels in feline diets may help to improve the sustainability of both the human and pet food system by decreasing pressure on livestock agriculture and ultimately improving environmental effects. Other ways to improve sustainability include using animal byproducts (organs not eaten by humans), plant (mainly pea) proteins, and insect proteins. In addition, feeding less food to an animal helps reduce the carbon footprint and chances of obesity. Nutrient chart Notes The European Union does not use a unified nutrient requirement. A manufacturer committee called FEDIAF (European Pet Food Industry Federation) makes recommendations for cats and dogs that members follow. Both AAFCO and FEDIAF publish in two formats: one in the amount-per-kilogram form above, another in