Just take a look at the following table and you will realize that the digestive tract of our dogs and cats is VERY different from ours. This explains you why any abrupt change in the diet they are fed can potentially lead to the development of gastro-intestinal upset. From a clinical standpoint, vomiting and diarrhea especially will be observed.
Differences between human and dog / cat digestive systems
A progressive dietary transition
That’s why each time you need to switch a dog (or a cat) to a new diet, it is important to do what we call a dietary transition. This allows the digestive tract to “get used” to the new nutrients and improve its capacity to properly digest it. Key element here: this transition must be progressive! We usually recommend to do this over a 5 day period as described in the picture below. This is definitely an important thing to do in order to optimize the digestibility of the new diet in these animals.
But when we don’t have any history?
Sounds easy, right? In shelter environments however, it is not always that simple. For a simple reason: for many dogs and cats that enter the shelter unfortunately, we have no history at all… No idea where they come from, no idea what they went through, if they had been vaccinated or not… and obviously no idea what they were eating before. What to do in this kind of situation then, especially that now you know that “a dietary transition is required”?
DR. EMMANUEL FONTAINE 