Carotenoids are widespread isoprenoid secondary metabolites. They and their metabolites are thought to provide diverse health benefits. In any case, their relevance from a nutritional standpoint is unarguable, as some of them can be converted into vitamin A in animals. Animals cannot synthesize carotenoids de novo and rely on the diet as a source. Species-specific differences in the absorption and metabolism of these compounds are known to exist among livestock species. The diet is another key factor affecting the carotenoid content in biological fluids (such as plasma and milk) and tissues. The study of carotenoids in animals is also important in the context of the increasing interest of consumers in the authentication of animal diets, as they can be used as markers of pasture-fed animals. In this paper, the authors review the current knowledge on the effect of the diet on the carotenoid levels of domesticated animals and the differences in the metabolism of these compounds into vitamin A among species.