DL-methionine and methionine hydroxy analogue are different molecules and are absorbed differently by the animal. In the end, however, both molecules are efficiently and completely converted to L-methionine for use by the animal.
Many petfood companies stress the importance of meat-first formulations. The implication to consumers is that these diets are better for their pets. However, meat-first diets may result in overages for a number of nutrients, especially protein, fat, calcium and phosphorus.
In light of the advancing age of the pet population, optimal nutrition should aim to decrease the risks for these diseases and other age-related problems such as obesity, bone loss and lean muscle mass loss. Recent research in geriatric cats has demonstrated that by formulating to an optimal lysine:calorie ratio as well as to an ideal protein content, dietary protein could be lowered without causing lean muscle mass loss.