Which to use, as fed, or dry matter?

[merlinmarshall]

Hi all,

I've been looking at the cat food lists, and looking at cans in the stores, and for those not on the list, doing the approximation calculation for carbs.

I understand that if you wish to compare carbs between cat foods, you should compare dry matter percentages.

But in terms of feeding, which do you use - the as fed percentages, or dry matter percentages?

An example, I am looking a canned cat food which says 2.5% carbohydrates. But this has 82% moisture. If I remove the water and recalculate for dry matter, the carb value increase a lot.

But I am not feeding dry matter, I'm feeding as it comes, with all the water in it.
And there are benefits from feeding something with a lot of water in it.

Merlin

 

[Anitafrnhamer]

At least for cats in Renal Failure we prefer to use DMA as the numbers are totally different (higher) than what is safe.

 

[billysmom (GA)]

What is usually used here is the % of calories from carbs or sometimes called metabolizable energy (ME) from carbs.

 

[Elizabeth and Bertie]

Hi Merlin,

The carb calculations for cat foods are most often done on an 'as fed' basis (ie. wet matter).
If kitty gets a can of food a day (or whatever), we want to know what percentage of calories in that particular food come from carbs. And for diabetics the recommendation is that the food has less than 10% calories from carbs.

You can do a dry matter carb calculation if you wish. Sometimes these actually come out very similar to the wet matter calculations, and sometimes they can be quite a bit different. The following chart drawn up by Dr Lisa Pierson shows both wet and dry matter calculations for the same foods:
http://www.catinfo.org/docs/FoodChartPublic9-22-12.pdf

There are instances though when it's particularly useful to be able see an element of the food with the water/moisture removed. For example, dry matter calculations are essential when calculating the amount of phosphorous in a food (very important for kitties with kidney disease). Even the slightest difference in the amount of water/moisture in a food can make a big difference to the phosphorous percentage.
And some people monitoring their cats' fat intake will do dry matter calculations for fat content so that they can compare fat values between different foods.

..And there are benefits from feeding something with a lot of water in it.

Water is very good for kitties, and especially so for older kitties. Water is essential for kidney function and urinary tract health. And for diabetics (especially those with high blood glucose levels) water is essential for ensuring the kitty doesn't become dehydrated.
Cats naturally have a low thirst drive (because they've evolved to get most of their water from their food - animal prey) so we need to ensure that they get all the water they need.
Some people here add a little water to their cat's canned food. And many of us have drinking fountains that encourage our cats to drink.

The moisture content of wet cat foods seems to range between about 75% to 85%, with many foods being in the middle of that range.
Something I have observed is that foods with higher moisture levels are often (but not always) lower in calories. And this may be a consideration for someone who is trying to get their kitty to either gain or to lose weight.

I hope this helps.

Eliz