There is no definitive answer when it comes to the most profitable animal in FS19. Different animals can be more or less profitable depending on a variety of factors, such as the price of animal feed, the selling price of the animal products, and the cost of housing and caring for the animals. With that said, some animals tend to be more profitable than others. For example, cows are generally considered to be one of the most profitable animals in FS19, as they produce milk, cheese, and other valuable products. Chickens are also generally considered to be quite profitable, as they produce eggs which can be sold for a high price.