'Human grade' is another term that is now used all over the pet food industry. The first thing to note is that no food produced in a pet food factory, no matter how good it is, can be legally classed as human grade. For this reason most claims are restricted to the ingredients with phrases like 'made from human grade ingredients', 'with human grade meat' or 'ingredients fit for human consumption' becoming increasingly popular, but do they really mean anything?
In the UK, the regulations governing what animals can and can't be fed are relatively stringent meaning that the vast majority of pet food ingredients come from human grade sources. For example, unlike in the US where dead, dying, disabled and diseased animals can be used in pet food, here in the UK all animal materials in pet foods must come from animals passed as fit for human consumption. This is also the case for foreign foods being imported into the UK. This means that any food you find in the UK containing meat (which accounts for 99.9% of the foods out there) can put 'human grade meat' or 'human grade ingredients' on the label if they wish.
The problem is that many ingredients that start out as 'human grade' are no longer classed as suitable for human consumption once they have been processed. For example, although a piece of meat may come from a human-grade animal, once it has been rendered into meat meal it is no longer categorised as suitable for human consumption. Nevertheless, a food containing meat meal can still legally say that the meat comes from 'human grade sources' even though the meat ingredient itself is not human grade.
Basically, since virtually any pet food in the UK can say that it has 'human grade ingredients' and since none (that I know of) are human grade at the end of processing, any claim about a food's human-grade-ness should be disregarded.