Switching kibble

It starts from the bag, not from the animal

This page answers one question only: how many grams from the new bag give the same calories as the ones you were feeding before. It does not work out the animal's ration and it does not change it: the ration stays the one you have now, the one your dog or your cat has been living on for months, and only the food that carries it changes. If your animal is doing well on the ration it has now, this is the place to start.

If instead the sums have to be redone from scratch, because it is a growing puppy, because it has just been neutered or because it has to lose weight, then you start from the animal and not from the bag, and the right tool is Daily kibble portion. The calories to put in there are worked out by Dog calorie needs.

And there is a reason why starting from what you already feed is not just handier, and it is written on the requirement page: between two dogs of the same weight, the same age and the same lifestyle the real requirement can differ by twenty per cent, because of the breed, the muscle mass, the coat, the temperature they live in. No formula knows that. A ration that has kept the animal in shape for months is better evidence than any estimate.

The mistake that divides or doubles the bowl

On the packs the energy shows up as «metabolisable energy», «ME» or «EM», and it is not always written the same way: a great many bags print it per kilo (3,800 kcal/kg), others per 100 grams (380 kcal), others again per cup. They are the same figure said three ways, but if 3,800 is read as if it were per 100 grams the ration comes out ten times smaller, and the other way round.

That is why the unit is picked for each bag separately, which is the real case: it happens all the time that the old one states the calories per kilo and the new one per 100 grams. The page always writes which reading it used, and it complains when the figure falls outside the plausible range: a dry food sits between 250 and 550 kcal per 100 grams, a wet one between 40 and 160. Outside that there is no strange food, there is the wrong unit.

If the pack does not carry the energy, and it happens, it is not guessed here. It is not estimated from the percentages of the analysis, because that sum needs digestibility coefficients that are not on the label: you ask the shop, or you look at the product page on the brand's website, where it is nearly always published.

The seven days are a percentage of calories, not of grams

The gradual switch is there because a dog's or a cat's gut needs a few days to get used to it, and a sudden change is the most common way of ending up with diarrhoea. The classic table goes up in steps: a quarter, half, three quarters, all of it, usually over seven days. Here it can be stretched to ten or fourteen, which is what you do when the animal has a delicate stomach or when the change is a big one.

The part nearly everybody gets wrong is that «25% new food» is a percentage of calories, not of grams. If the new bag is more concentrated, a quarter of the calories is not a quarter of the grams, and that is exactly why this table has to be worked out rather than drawn once and for all. The right-hand column carries the total in kcal, and it stays the same on every row: if it wobbled, the sum would be wrong and you would see it.

During the switch the two foods get mixed in the same bowl. And it is worth weighing them properly on a scale instead of using the cup: the same cup of different kibbles weighs as much as twenty per cent more or less, and over a week in which the amounts change every day the error piles up.

The pouch, and what this sum does not say

Adding wet food to the kibble is the second thing done by eye, and the result is nearly always a bigger ration than before. The pouch carries its own calories, and those have to be taken off the dry food, not added: the page says how many grams of kibble are replaced by one pouch of that size and those calories. The weight of the pack is asked for because it matters enormously: between an 85 gram sachet and a 400 gram tray the calories are four times apart.

One thing to expect: for the same calories wet food weighs about four times more than dry, because it is nearly all water. So as soon as a pouch goes in the little mountain of kibble collapses, and it looks like a mistake. It is not, and it is the reason the figure is better looked at here than guessed at in the bowl.

Finally the limit, which is better said than hidden: this sum matches the calories, not the diet. Between a maintenance food and a light one, or between an adult food and a puppy one, it is not only the energy density that changes: protein, calcium, phosphorus and all the rest change too, and matching the calories is not matching the nutrition. It holds as a conversion between two foods of the same kind for the same animal; in the other cases the figure is a starting point. This is not veterinary advice, and if the animal is on a prescription diet the switch is decided with whoever prescribed it. For a cat the starting calories are worked out with Cat calorie needs.