| Honmei
Join Date: Oct 2004 Location: Lakewood, So Calif Posts: 2,855
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Originally Posted by MikeM I often come across comments that a food is "more digestible" as proved by the fact that there is "less waste". I do not understand the supposed connection.
A fish is largely composed of water. If you have ever had a fish jump out and dry out completely, you know that the dry weight of the fish was a very small percentage of the natural weight. Very little of any dry food is going to be absorbed by a fish through the digestive process. Virtually everything that is consumed will be expelled. So, how can there be a noticeable difference in waste volume?
Seems to me that there are two possibilities: (1) the food is so nutritious that less dry weight of it is fed [note: not less volume, but less dry weight...some foods are full of air], but I've not noticed people commenting that they feed less of particular foods on a weight basis; or, (2) the waste is just as voluminous, but not as easily observed.
Wheat germ is often identified as a highly digestible food. In mammals, wheat germ has a mild laxative effect. I expect the same is true of fish. During cool weather this can be very desirable, because we do not want food rotting in clogged-up intestines. However, the reason wheatgerm has a laxative effect is because it contains indigestible fiber, high oil content, and low starch levels (as well as high protein content). It results in less visible waste because the starches which bind waste into visible stools are very low. This does not necessarily mean the fish are getting more nutrient out of the food.
So, I see the photo on the Saki-Hikari label showing filter mats with less visible waste trapped and I wonder: If the waste is no longer getting captured in the matting, where is it? [If there is 50% less visible waste, are the koi gaining dry weight every meal equal to 50% of the weight of the food fed? ... Of course not. ] Wherever it is, is it better for the fish that the waste is not visibly trapped in the matting? Do I want waste that does not settle out in the vortex chamber? Or, do I want solid stools that I can see and that do settle out in the vortex without breaking apart?
I really do not know the answers. I have purposefully phrased my thoughts to create doubt about the usual "less visible waste means better digestibility" concept. That concept may be wrong, but the foods involved could still be the best for a different rationale.
Anyone aware of published scientific studies on digestibility in fish and absorption of nutrient from different food sources? |  | |  | Digestibility & Waste I had a friend do a little research for me, on this post. I often come across comments that a food is "more digestible" as proved by the fact that there is "less waste". I do not understand the supposed connection.
A fish is largely composed of water. If you have ever had a fish jump out and dry out completely, you know that the dry weight of the fish was a very small percentage of the natural weight. Very little of any dry food is going to be absorbed by a fish through the digestive process. Virtually everything that is consumed will be expelled. So, how can there be a noticeable difference in waste volume? NOTE: Actually your comment “very little of any dry food is going to be absorbed by a fish through the digestive process” is not and if you think about it logically cannot be correct. Just for your reference, the lab guys tell me 67% to 80% of the body weight of a fish is water, but that’s another subject. The most important factor in any koi diet is the balance of the formulation. This means there has to be a balance between the proteins, carbohydrates and fats that will allow the koi to properly utilize the nutrition. Of course, there also has to be certain vitamins and minerals that round out the diet. The objective of the diet producer is to develop a diet that will allow the fish to use the nutrition from the food for kinetic energy (metabolizing action) which allows the koi to remain active and maintaining their health. This conversion of the nutrition to usable energy has to take place or the fish would steadily lose body mass until they eventually died. Furthermore, through this action some of the nutrition (assuming the diet is a proper one of course) is absorbed to provide growth. The main by-products of this activity are carbohydrates and ammonia. So >from a clinical perspective you have the following action taking place: Fish Food Weight = increased body weight + released CO2 + released slime coat + other released chemicals including NH3 + the dry weight of the feces In this instances a high amount of the nutrition will result in CO2 and chemicals like NH3, but without a proper nutritional balance or source the first sign would be increased feces which might relate more to your point above. This is not a normal occurrence for a well-balanced and complete diet! Always remember, as the digestive properties of the food are reduced, (to save money or increase production output which saves money) less and less of the nutrition can be absorbed and thereby utilized by the fish. When this occurs it has to exit the fish as waste. As another example, if you have diet A that is 80% efficient and diet B that is 40% efficient, you would have to feed twice as much of diet B to give the koi the same amount of nutritional input as diet A. This means that instead of 20% of the amount of diet A being excreted as unusable solids there would be almost 6 times the amount put out in the water. A significant and noticeable increase no doubt! Of course, this is an extreme example, but it gives you a very clear picture.
Seems to me that there are two possibilities: (1) the food is so nutritious that less dry weight of it is fed [note: not less volume, but less dry weight...some foods are full of air], but I've not noticed people commenting that they feed less of particular foods on a weight basis; or, (2) the waste is just as voluminous, but not as easily observed. NOTE: Of course it stands to reason that the better the digestibility of the diet the less food you have to feed to accomplish the same growth as the alternative diet. Waste is waste and in most ponds it’s quite visible. If not, any filter maintenance would certainly provide a visible answer to this question. The fact of the matter is if you used the two diets above A & B and fed the same amount of both (dry weight) you would experience faster growth and less waste with diet A and more noticeable waste and less growth with diet B. The real question is do you want to put some of your fish through this drill to prove the point?
Wheat germ is often identified as a highly digestible food. In mammals, wheat germ has a mild laxative effect. I expect the same is true of fish. During cool weather this can be very desirable, because we do not want food rotting in clogged-up intestines. However, the reason wheatgerm has a laxative effect is because it contains indigestible fiber, high oil content, and low starch levels (as well as high protein content). It results in less visible waste because the starches which bind waste into visible stools are very low. This does not necessarily mean the fish are getting more nutrients out of the food. NOTE: Technically your statement here is correct, wheat-germ is naturally high in dietary fiber, so if you were to feed only wheat-germ (outside of a well-balanced prepared diet) you could expect poor results at best. The key to our diet is utilizing the wheat-germ for its benefits along with a complete balance of other ingredients that help accelerate digestion while providing the koi with the nutrition they need to remain healthy in cooler water. It’s important to remember, one ingredient does not make a koi food!
So, I see the photo on the Saki-Hikari label showing filter mats with less visible waste trapped and I wonder: If the waste is no longer getting captured in the matting, where is it? NOTE: With this diet we are experiencing three primary activities with the food that help to bring about this result. (1) Extremely digestive ingredients are utilized to help the koi convert the nutrition to kinetic energy and usable nutrition for growth. (2) The enzymatic action in the digestive tract is increased by the beneficial bacteria further allowing the koi to utilize the nutrients in the food. A by-product of this action is a heightened level of available vitamins which help improve metabolism (3) the action of the beneficial bacteria continues once the waste is excreted from the body of the fish and works to decompose the waste that remains. This is a short term process yet is quite successful at reducing overall waste volume. [If there is 50% less visible waste, are the koi gaining dry weight every meal equal to 50% of the weight of the food fed? ... Of course not. ] NOTE: Your comment above oversimplifies the whole process taking place once the food is fed. The waste reduction is a result of multiple activities taking place simultaneously, not just one. In the absence of the beneficial bacteria, less visible waste would have to mean more absorption of the nutrition which would result in increased levels of kinetic energy for the fish to utilize or a noticeable improvement in the growth. Wherever it is, is it better for the fish that the waste is not visibly trapped in the matting? Do I want waste that does not settle out in the vortex chamber? Or, do I want solid stools that I can see and that do settle out in the vortex without breaking apart? NOTE: I would think that what would be desirable for any pond keeper is waste that can more readily be handled by the bacterial action of your filter. More efficiency in this area will result in less maintenance, better water quality and potentially less health issues for the koi. It’s not a matter of now you see it now you don’t in this instance. If the beneficial bacteria work to decompose the waste, it is simply not there. If this action results in a finer waste that the bacterial process can break down, good things can result!
I really do not know the answers. I have purposefully phrased my thoughts to create doubt about the usual "less visible waste means better digestibility" concept. That concept may be wrong, but the foods involved could still be the best for a different rationale. NOTE: I think it’s important to note here that Hikari is the only koi diet producer in the world that breeds koi. The results of any diet we bring to market have already passed the test of time in real-live conditions before our very eyes. We already know the diet’s impact on the fish in the short term and longer term before any consumer tries it on their pets. Furthermore, this first-hand insight coupled with an extremely modern research lab full of folks that know fish and can readily research the impact of nutritional ingredients, means we have a huge advantage over the competition. Add in our own production facilities that can guarantee the quality from start to finish and you have a clear picture why more koi breeders ask us to produce diets for them than all the other koi food makers combined. In the end, it’s not what we say any of our diets can do, it’s what the consumer sees them doing in their own situation and how the koi respond that matters most to us.
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06-29-2005
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