Measuring Dog Food - Is the measure distorted using big chunks vs the small chunk?

Factual Questions
1

Interesting Volume measure question for the Dopers. :wink:

We normally buy the small pebble size dog food. It’s easier for my Chihuahua to eat. The Boston Terrier finds it a little small but she does ok with it. We give the 4 lb Chihuahua a full rounded scoop (it’s roughly 2/3 cup). The 10 lb Boston gets 2 full rounded scoops plus a little more.

I goofed and bought the regular chunk bag last time. Didn’t take long to notice both dogs were looking less full. Their tummies and sides were still drawn in after eating. We got concerned they’d drop weight if we didn’t increase the amounts to 1 1/2 scoop Chihuahua and almost 3 scoops for the Boston.

Did we uncover a flaw in volume measure? Is less food being measure with regular chunk vs pebble size? What if we took a hammer and pounded the dog food into a course powder and measured by volume? Would that be significantly more food than they need? If so then what is causing the inaccuracy?

Would weight by scale be accurate regardless of the nugget size? We’re not anal retentive enough to measure by weight but just curious.

2

For a given particle shape, the packing factor (the percentage of space filled with matter instead of void) is independent of particle size, although this assumes that your measuring cup is large compared to the particle size. So if your particle (nugget) is fairly large compared to the cup, then the particles/nuggest may not be able to arrange themselves in as dense a configuration as a smaller particle size could. Once your particle size gets small relative to the container, then making the particle size smaller doesn’t significantly improve the packing factor.

To sort this out for sure, get a scale and weigh one cup of the large-nugget mix and one cup of the small-nugget mix; then you’ll know exactly where you stand.

3

That brings up another question. I’ve always heard dry measure by weight does not equal dry measure by volume? 8 oz of corn meal by weight does not equal 8 oz by cup?

This stuff gets confusing in a hurry. :wink:

But, I see what you’re referring too. one scoop of big chunk dog food holds about 8 or 9 chunks. Not a heck of a lot. If I measured that by weight. Then measured a scoop of the small chunk (there’s at least 20 in that scoop) I could see how much food I’m giving by weight.

4

What Machine Elf said is correct, with the proviso that all the particle sizes and shapes are similar. If you have mixed large and small particles you can improve the packing factor by using the smaller oners to fill the voids left by the larger. Think about using marbles to fill the voids left in a container of basketballs for example.

5

Glad we noticed the problem before both dogs lost weight. They are both are the slim side already.

I see what you mean. With such a small scoop those big chunks just can’t fit inside efficiently and pack in like they needed to.

6

Since it looks like the packing question has been address, another possibility: not all foods are the same density.

I’m noticing this with my gold fish food. The last pellets were very light, like a puffed Cheeto - a whole can weighed only 16 oz. The new pellets are dense - a similarly sized can of them is 30 oz. I keep overfeeding the fish using the new food because I keep thinking I want a tablespoon, but the actual weight of food has nearly doubled for the same volume. What I want is about two teaspoons instead.

7

Water weighs about one avoirdupois ounce per fluid ounce. eight fluid ounce of water then will weigh around a half-pound.

Corn meal is surely not as dense as water, so no, one 8-ounce cup of corn meal will weigh less than half a pound.

8

There’s volume (the least informative measure), there is weight, and then there’s total digestible nutrients. The TDN will be on the bag, and it is the one that counts.