Metabolizable Energy - Riddle me this

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nanney1
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Metabolizable Energy - Riddle me this

Post by nanney1 » Fri Jul 05, 2019 9:53 am

This kind of thing always bugs me. I look at two similar foods from the same manufacturer. But, how do you determine which has the most energy?

1. 30/20 - ME: 3,982 kcal/kg (448 kcal/cup)

2. 26/18 - ME: 4,310 kcal/kg (435 kcal/cup)

So, product 1 has higher protein and fat percentages and a higher kcal per cup. Product 2 has a lower protein and fat percentage and lower kcal per cup, but, has a higher kcal per kg.

Which has the most energy?

birddogger2
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Re: Metabolizable Energy - Riddle me this

Post by birddogger2 » Fri Jul 05, 2019 6:46 pm

I believe you are trying to equate two different types of measurement that may not be exactly equal.

One measure is by volume (kcal/cup) and one is by weight(kcal/kg). If both feeds had the same density then you could compare...but obviously, they do not.

Think of it this way... How much does a cup of water weigh? A few ounces. Now... How much does a cup of lead shot weigh? A couple pounds, I think. That is because lead is much, much more dense than water.

Industry standards are most likely expressed as kcal/kg. But since most normal folks feed by volume, the company is giving you the kcal value in terms of cups also.

I did find it surprising that the feed with lower protein and fat had a higher ME(by weight).

Since I pay for dog food by the pound and not by the cup, that is the measure I would use to determine which one is more economical.

I hope this helps.

Interestingly(at least to me), the Greek term EUREKA(I have found it!) comes from the realization that gold is much more dense than lead and therefore displaces a much different volume of water for the exact same weight. Check it out.

RayG

nanney1
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Re: Metabolizable Energy - Riddle me this

Post by nanney1 » Sat Jul 06, 2019 9:48 am

Bird digger2: I agree with your assessment. However, I feed by the cup and would want the food that provides the most energy per cup. I would assume the 30/20 is a smaller, denser kibble, and therefore has more energy per each 8 oz cup.

In this case, though, the two are so close in terms of kcal per cup, that it’s almost a wash. And the 26/18 is a bit cheaper to purchase. So, between the two, the 26/18 is the better overall value. At least that’s how I’m seeing it.

birddogger2
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Re: Metabolizable Energy - Riddle me this

Post by birddogger2 » Sun Jul 07, 2019 8:40 am

nanney1 wrote:
Sat Jul 06, 2019 9:48 am
Bird digger2: I agree with your assessment. However, I feed by the cup and would want the food that provides the most energy per cup. I would assume the 30/20 is a smaller, denser kibble, and therefore has more energy per each 8 oz cup.

In this case, though, the two are so close in terms of kcal per cup, that it’s almost a wash. And the 26/18 is a bit cheaper to purchase. So, between the two, the 26/18 is the better overall value. At least that’s how I’m seeing it.
You got it.

RayG

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roaniecowpony
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Re: Metabolizable Energy - Riddle me this

Post by roaniecowpony » Sun Jul 14, 2019 9:58 am

Unless you have a specific reason to want the smallest number of cups, I'd say the one with the highest kcal/kg is the one that meets what I think you're looking for. I'm assuming you want to keep the bulk down to keep the stool bulk down and bloating down.

How much stacks into a cup is not a good measure of much, IMO. There is so much void between the kibble that the shape of the kibble affects the amount of food that is actually in there. You measure a lot of air by using a cup.

Weight would be my method of determining specific calorie content of one food vs the other (dry dog food).

But then again, those calories in the 26/18 food that are not in protein or fat are likely just carbs. If that's what you need, that works.

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