Human breast milk has a lot more fat than bison milk, but much less fat than milk from polar bears or seals.
Credit Suisse circulated a research note on dietary fat consumption and its health and market implications. As part of their analysis of how much fat should be in a human diet, the authors of the report included a table comparing the nutritional breakdowns of breast milk from 23 different mammals, including humans.
Human milk is about 56% fat, according to the report, with the other 44% being a mix of protein and sugars. This is pretty similar to the fat content of the three cow breeds Credit Suisse included in the table.
Business Insider/Andy Kiersz, data from Credit Suisse