Here’s the article: https://rrvet.com/homemade-vs-store-bought-pet-food-which-should-you-choose/
One part says:
When researchers from the University of California, Davis, School of Veterinary Medicine performed a nutritional evaluation of 200 homemade dog food recipes, they discovered that most were missing key nutrients. The team evaluated recipes from websites, pet care books, and veterinary textbooks.
They reported that 95 percent of the recipes lacked one essential nutrient. Multiple deficiencies were found in 83 percent of the recipes. A 2017 Portuguese study also found nutritional deficiencies in home-prepared diets. Diets often didn’t have enough vitamins E and B12, iron, riboflavin, choline, thiamine, or calcium.
Pets that don’t receive the appropriate mixture of proteins, fats, carbohydrates, vitamins, and minerals are more likely to be underweight, have dull coats, dandruff, allergies, or suffer from heart conditions in extreme cases.
And for cat food, it’s taurine. If you home prepare cat food, please ensure it has the correct proportion of taurine.