Starch in fish food

[mattrox]

I have found the digestibility figures I am after, but I knew they would be out there somewhere. Now I'd like to find info about blood glucose levels as a result of stach in the diet. I doubt this is a major concern for aquaculture of table fish as they don't last long enough to feel the chronic effects.

[Noddy65]

Ive got a reference somewhere about blood glucose levels in fish with carbs in the diet...Ill have to find it

Mike

[Noddy65]

Not the ones i was thinking of but its a start:

Nutritional regulation of hepatic glucose metabolism in fish.

Fish Physiol Biochem. August 2009;35(3):519-39. 101 Refs

P Enes

1

; S Panserat; S Kaushik; A Oliva-Teles

1

Departamento de Zoologia e Antropologia, Faculdade de Ciências, Universidade do Porto, 4169-007, Porto, Portugal. enes@portugalmail.com

Article Abstract

Glucose plays a key role as energy source in the majority of mammals, but its importance in fish appears limited. Until now, the physiological basis for such apparent glucose intolerance in fish has not been fully understood. A distinct regulation of hepatic glucose utilization (glycolysis) and production (gluconeogenesis) may be advanced to explain the relative inability of fish to efficiently utilize dietary glucose. We summarize here information regarding the nutritional regulation of key enzymes involved in glycolysis (hexokinases, 6-phosphofructo-1-kinase and pyruvate kinase) and gluconeogenesis (phosphoenolpyruvate carboxykinase, fructose-1,6-bisphosphatase and glucose-6-phosphatase) pathways as well as that of the bifunctional enzyme 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase. The effect of dietary carbohydrate level and source on the activities and gene expression of the mentioned key enzymes is also discussed. Overall, data strongly suggest that the liver of most fish species is apparently capable of regulating glucose storage. The persistent high level of endogenous glucose production independent of carbohydrate intake level may lead to a putative competition between exogenous (dietary) glucose and endogenous glucose as the source of energy, which may explain the poor dietary carbohydrate utilization in fish.

Selected nondigestible carbohydrates and prebiotics support the growth of probiotic fish bacteria mono-cultures in vitro.

J Appl Microbiol. March 2009;106(3):932-40.

E Rurangwa

1

; J L Laranja; R van Houdt; Y Delaedt; Z Geraylou; T Van de Wiele; J Van Loo; V Van Craeyveld; C M Courtin; J A Delcour; F Ollevier

1

Laboratory of Aquatic Ecology and Evolutionary Biology, Katholieke Universiteit Leuven, Leuven, Belgium. eugene.rurangwa@bio.kuleuven.be

Article Abstract

AIMS: To search for nondigestible but fermentable (NDF) carbohydrates and prebiotics with a potency to promote the growth of selected bacteria in vitro. METHODS AND RESULTS: The growth of three reference bacteria strains Bacillus subtilis LMG 7135(T), Carnobacterium piscicola LMG 9839, Lactobacillus plantarum LMG 9211 and one candidate probiotic bacteria Lactobacillus delbrueckii subsp. lactis was investigated over a minimum period of 48 h in the presence of beta-glucan, xylo-oligosaccharide, arabinoxylo-oligosaccharide, inulin, oligofructose and glucose. Besides the capability to grow on inulin and oligofructose containing media, a distinct high growth in beta-glucan based substrates and a low growth in (arabino)xylooligosaccharide containing media were evident for most bacteria tested. With the exception of B. subtilis and L. plantarum, other bacteria grew equally well or even better on different substrates than on glucose. The fermentation of studied carbohydrates by these micro-organisms was dominated by the production of acetic acid as the main short chain fatty acid. CONCLUSIONS: Selected bacteria are able to ferment and grow on NDF and prebiotic carbohydrates but in a substrate dependent manner. SIGNIFICANCE AND IMPACT OF THE STUDY: This study delivers a first screening of which NDF or prebiotic carbohydrates are the most promising for aquaculture feed supplementations.

Some insights into energy metabolism for osmoregulation in fish.

Comp Biochem Physiol C Toxicol Pharmacol. November 2008;148(4):419-29. 149 Refs

Yung-Che Tseng

1

; Pung-Pung Hwang

1

Institute of Cellular and Organismic Biology, Academia Sinica, Nankang, Taipei, 11529, Taiwan, ROC.

Article Abstract

A sufficient and timely energy supply is a prerequisite for the operation of iono- and osmoregulatory mechanisms in fish. Measurements of whole-fish or isolated-gill (or other organs) oxygen consumption have demonstrated regulation of the energy supply during acclimation to different osmotic environments, and such regulation is dependent on species, the situation of acclimation or acclimatization, and life habits. Carbohydrate metabolism appears to play a major role in the energy supply for iono- and osmoregulation, and the liver is the major source supplying carbohydrate metabolites to osmoregulatory organs. Compared with carbohydrates, the roles of lipids and proteins remain largely unclear. Energy metabolite translocation was recently found to occur between fish gill ionocytes and neighboring glycogen-rich (GR) cells, indicating the physiological significance of a local energy supply for gill ion regulatory mechanisms. Spatial and temporal relationships between the liver and other osmoregulatory and non-osmoregulatory organs in partitioning the energy supply for ion regulatory mechanisms during salinity challenges were also proposed. A novel glucose transporter was found to specifically be expressed and function in gill ionocytes, providing the first cue for investigating energy translocation among gill cells. Advanced molecular physiological approaches can be used to examine energy metabolism relevant to a particular cell type (e.g., gill ionocytes), and functional genomics may also provide another powerful approach to explore new metabolic pathways related to fish ion regulation.

Effect of copper on liver key enzymes of anaerobic glucose metabolism from freshwater tropical fish Prochilodus lineatus.

Comp Biochem Physiol A Mol Integr Physiol. November 2008;151(3):437-42.

Cleoni Dos Santos Carvalho

1

; Marisa Narciso Fernandes

1

Department of Physiological Sciences, Federal University of São Carlos, PO Box 676, 13565-905 São Carlos, São Paulo, Brazil.

Article Abstract

We investigated the effect of copper on liver key enzymes of the anaerobic glucose metabolism (hexokinase, HK; phosphofructokinase, PFK; pyruvate kinase, PK; lactate dehydrogenase, LDH) as well as of the pentose pathway (glycose-6-phosphate dehydrogenase, G6PDH) from the fish Prochilodus lineatus. The fish were acclimated at either 20 degrees C or 30 degrees C at pH 7.0, transferred to water at pH 4.5 or 8.0, and exposed to 96 h-CL(50) copper concentrations. Copper accumulation in liver was higher in fish acclimated at 20 degrees C and maintained in water pH 8.0. Three-way analysis of variance revealed a significant effect of temperature on all enzymes, a significant effect of pH on all enzymes except for PK, and a significant effect of copper on only PFK, and LDH in pH 4.5 at 20 degrees C and, at 30 degrees C, on PFK and PK at pH 4.5 and 8.0, HK at pH 4.5 and G6PDH at pH 8.0. There were significant interactions between treatments for many enzymes. These changes suggest that the activity of enzymes in question is modified by a change in ambient water. At least at 30 degrees C, the overall reduction in the glycolytic enzyme activities of copper-exposed fish seems to reduce energy availability via glucose metabolism, thereby contributing to enhance copper toxic effects.

Responses of digestive enzymes of tambaqui (Colossoma macropomum) to dietary cornstarch changes and metabolic inferences

Comp Biochem Physiol A Mol Integr Physiol. August 2007;147(4):857-62.

Cristina Ferro Corrêa

1

; Lúcia Helena de Aguiar; Lícia Maria Lundstedt; Gilberto Moraes

1

Department of Genetics and Evolution, Federal University of Sao Carlos, Rod. Washington Luís Km 235, CP 676, Sao Carlos, SP, CEP 13565-905 Brazil.

Article Abstract

Digestive enzyme responses plus metabolic implications were studied in tambaqui (Colossoma macropomum) fed isoproteic diets containing 28% crude protein, 3300 kcal of gross energy/kg and different amounts of cornstarch (30, 40 and 50%). Amylase, maltase, acid protease, trypsin and chymotrypsin from the alimentary tract were assayed. Plasma, liver and white muscle metabolites were gauged to profile metabolism of the fish. The alimentary tract of tambaqui is compartmentalized morphologically and enzymatically. Amylase was present through the gut; acid protease was detected in stomach; maltase, trypsin and chymotrypsin were found in pyloric caeca and proximal and distal intestine sections. Increase of cornstarch levels from 40 to 50% in the diet resulted in an increase in amylase and maltase. Trypsin and chymotrypsin were unresponsive to starch levels. Acid protease follows the protein/carbohydrate ratio decrease. The increase of dietary cornstarch resulted in liver glycogenesis and the increase in plasma triglycerides is suggestive of lipogenesis. Digestive biochemical responses of tambaqui correlated with changes of feeding plus the analyses of metabolic profile are assumed as a tool for optimizing diet formulation and are a clue to other feeding optimizations for freshwater tropical

[mattrox]

Ok so I found some answers:

Yes this in context of a wider discussion, but I am only looking at the parts about starch.

"Terrestrial plant matter, such as soybean meal, corn gluten meal, corn flakes, wheat middlings, etc. These types of ingredients aren't generally used in fish feed because of their fantastic amino acid profile or due to how grealty they can add to the bioavailability of the feed, they are added to save costs over more expensive raw ingredients. If I wanted to feed that grade of food I would buy generic farm feed.

I understand that a certain level of carbs/starch derived from cereal grains can have their place in a quality feed (especially as binding agents), but I have my own personal limits as to how much, and the source."

"Let me give you an example. When I look at one brand label I can't help but wonder how is it possible for them to be using processing plant waste, which I know has a very high mineral content from scales & bones (ash), yet their total ash content is listed as only a max of 8%? In my mind, and according to how they have things listed, there is only a couple of ways to push those protein numbers down (below 50% crude protein), which also pushes the overall ash content down, and that is by using a hefty amount of carbs, such as the ingredients that tend to follow all of their fish mixes - wheat flour, and in some formulas kelp. (kelp is also very high in carbs) Yet this same company condemns not only the use of fish meal, but also the use of "a whole lot of starch (like everyone else)". Or they are listing their 'fresh fish waste" on an as-is wet basis, which would also throw their entire ingredient listings off, if one is comparing it against the vast majority of other foods that list everything on a dry weight basis."

So far I have learned

1) Some fish food companies do add starch in large amount, which reduces ash.

2) Large amounts of starch are undesireable

3)You can run a quick ruler over a label to get a ballpark figure for carbs

4) All starch in fish food is cooked.

5) It is not completely invalid to look at data from studies using cold water species and apply the knowledge to the aquarium context. See below examples suggested by NLS.

http://nlsfishfood.com/index.php?option=com_content&task=view&id=29&Itemid=63&limit=1&limitstart=10

Lorentzen, Maage, Julshamn (1998)

Supplementing copper to a fish meal based diet fed to Atlantic salmon parr affects liver copper and selenium concentrations Aquaculture Nutrition 4 (1), 67-72.

Takeshi Yamamoto, Koji Konishi, Takao Shima, Hirofumi Furuita, Nobuhiro Suzuki, Mitsuo Tabata (2001) Influence of dietary fat and carbohydrate levels on growth and body composition of rainbow trout Oncorhynchus mykiss under self-feeding conditions

Fisheries Science 67 (2), 221-227.

I found data for digestibility of cooked corn starch for tilapia. In a 25% corn starch diet it is 78% and in a 50% starch diet it is 66%. Now from these I can crunch some rough numbers, but a fish food has carbs from wheat flour and other sources which will change the effective digestibility of the carbohydrates. (Number crunching will have to wait until after Christmas as will the blood glucose levels research)

http://affris.org/tilapia/nutri.php

And this provides some data that indicates tilapia typically utilize 35-40% of the digestible carbohydrates.

However, digestibility and utilization seem to be slightly different things. Do tilapia extract glucose from about 70% of the starch, but can only utilize 40% of the starch? Does that mean that the extra glucose -> glycogen in liver -> fat and maintain a high blood sugar level if fed improperly ie over fed or fed foods with too much starch?

[mattrox]

And thanks Mike, I'll will have a whole lot of reading to do in the post Chrismas "haze".

[RD.]

mattrox ........... don't you find it ironic that the answers that you have "found", came from none other than me? lol

FYI - I never said that it was completely invalid to look at any/all data from studies using cold water species and apply the knowledge to the aquarium context. In some cases that data can be used to disprove a hypothesis, just as easily as it can be to prove a hypothesis. In this instance, as in comparing the digestibility &/or utilization of carbohydrates of a coldwater rainbow trout, vs that of a warmwater mbuna, that carb data would in fact be totally invalid. As an example, from that data here's what you stated in one of your initial comments in this discussion.

From my reference digestible carbs should be less than 20% of the diet.

Please cite any peer reviewed paper or study that states that the diet of mbuna should be less than 20% carbs, including carbs based on aquatic plant matter such as algae.

And as previously posted, even the 20% range being the upper limit of carbs for rainbow trout has recently been challenged. Also note that they state "Depending on the source and quality of dietary carbohydrate"

This is why I have been constantly pointing out your flaw in only viewing the "total" starch found in a commercial food. It's not that simplistic.

At the same time, we also raise new questions about the upper limit of feed levels of carbohydrate in this species. Depending on the source and quality of dietary carbohydrate, the aquaculture industry standard of 20% carbohydrate represents a "conservative" value. We documented outstanding growth performance of trout receiving 24% (mostly wheat flour) or even 30% (mostly purified starch) fed aquaculture rations or to satiety, respectively.

The more you dig, the more you will find that the more omnivorous/herbivorous a warmwater species of fish is, the more efficient those species generally are at handling higher carb levels in their diet. This is partially due to warmwater species in general having much higher intestinal enzyme (specifically amylase) activity than coldwater fish, such as rainbow trout. As an example, as mentioned in the paper below, it has been reported in another study that carp can have as much as 10-30 times the amylase activity in their digestive tract, compared to a rainbow trout.

The following paper should be fairly easy for any layperson to understand.

http://www.cib.espol...apers/36558.pdf

Make sure to read the "conclusion" drawn at the end of the paper with regards to coldwater & marine species, vs warmwater freshwater species. That fact has been cited numerous times, in numerous papers, for numerous years.

That paper also includes "glucose tolerance tests" so that should be of interest to you as well. You will also come to realize why corn starch is used in some feeds, such as the one food you posted in this discussion. It has nothing to do with lowering ash content, even though that would be another end result.

One also has to keep in mind that in papers that involve commercial aquaculture, such as all of those posted thus far, when listing stats, percentages, etc, the researchers are NOT referring to carbs associated with aquatic plant matter, as those types of carbs are typically never utilized in commercial aquaculture due to their cost. Almost every last study that involves commercial aquaculture, and fish feed, is designed & typically funded by those who have a financial incentive to find less costly ways to feed fish. On a global basis, commercial aquaculture is a 100 billion dollar business, with one of the main costs of that industry being feed costs.

Only recently has the commercial aquaculture industry began taking a close look at various algaes as a replacement for fish meal/fish oil.

http://www.algaeindu...r-rick-barrows/

But even that research is limited in scope as Rick is mainly viewing that ingredient (spirulina) as a source of protein, as it's crude protein level is similar to fish meal. There are a number of other algae products avaiable to aquaculture, several that have been used for years, but not for their overall protein content. And while all of these algae contain carbohydrate, these are not the form of carbs typically studied within commercial aquaculture.

To put all of this in a very simplistic way, you are comparing eating a thin slice of whole grain wheat bread with a meal, to eating an entire loaf of that same bread with each meal. Obviously the latter will not be ideal, will cause blood sugar levels to spike off the chart, and over time will lead to obesity, and most likely organ issues.

The bottom line is you will never find a 100% conclusive answer to any of this with regards to species such as mbuna, as no such in depth studies exist. Clearly the tropical fish industry is not spending millions of dollars each year studying any of this on a species by species basis as there is no financial incentive to do so. Which is precisely why I previously stated that a lot of what we do in our own tanks, with our own fish, simply boils down to common sense & with time experience.

If I can raise a group of mbuna in captivity for a decade or more on a particular diet, with all fish appearing to be very healthy, showing no outward signs of obesity, suffering from no disease, breeding on a regular basis, and overall thriving for all of those years .............no amount of scientists wearing white lab coats, or any of their "commercially" based data is going to change my opinion of that diet.

One last thing, when running a quick ruler over a label to ascertain total carb levels, keep in mind that certain portions of the guaranteed analysis involve minimum values, which in some products could very easily throw your "ballpark" figures, way out in left field.

Cheers!

[mattrox]

Being efficient at processing carbs is a different concept than the resulting blood sugar levels.

Now as to wheather mbuna have been investigated as to how starch levels affect them I don't know. The lack of a peer reviewed paper may indicate a lack of research in this area rather than starch levels being irrelevant to mbuna.

Which leads me to the next point. The yellow labelled brand has a food specifically rift lake carnivores. The only difference is a slightly higher protein level and slightly lower carb content when using the rough calculations. But still quite high. Notwithstanding the prey they eat are gut loaded with (partially digested) vegetable matter, thier ability to digest carbs would be lower than a herbivore. In this case there is likely to be more waste (undigested) starch as a result. And there is still the blood glucose levels.

[mattrox]

I'm also pretty sure I'm talking about a meal that in some cases includes a triple serve of mash potatoes rather than a meal consisting of a loaf of bread.

I do find it ironic, because those answers could have started on page 1 of the thread.

[RD.]

I do find it ironic, because those answers could have started on page 1 of the thread.

I'm not sure what your point is? I've never suggested that all commercial foods are created equally. Just like everything else in life there are variables in quality of commercial feed, be it fish, dog, cat, bird, whatever. Does this come as some kind of surprise to you?

I can buy a 20 kg bag of generic trout chow for less than $50 at my local hardware store, that doesn't even have an ingredient list on the label. It actually states on the bag to contact the manufacturer for the ingredient list. lol But hey, it's cheap food.

The second quote of mine that posted has to do with a specific situation, regarding a specific brand of food, so why would I post that info here? In case you haven't noticed, I have bent over backwards in this discussion to NOT mention any brand names.

You seem to be fixated on blood sugar levels, yet have offered up zero evidence that this is an issue with the vast majority of commercial feeds on the market, when fed to warm-water tropical species of fish.

Perhaps I'm mistaken, but it seems to me that you are only wanting a one sided discussion, where your "hypothesis" is somehow going to be proven valid, and where you have somehow discovered the missing link in fish food, and proven that all commercial fish food manufacturers are evil & not to be trusted.

You seek answers, yet when any are supplied you reject them, and revert back to being the proverbial chicken little, "the blood sugars are rising, the blood sugars are rising".

I think that it's great to ask questions, and as I stated previously I am the original sceptic, but I'm not going to keep going 'round & 'round with someone who seems to be more interested in being right, than seeking actual facts as they pertain to our hobby.

[mattrox]

The original question was at what levels of starch in foods do blood sugar levels rise to a point where the fish's health is adversely affected? Pretty straight forward and not alarmist at all. And not one that is really discussed. Pretty fair question, I thought.

[Noddy65]

Oh dear..and its appears that its not just the nutrients in the food thats important...the time of day that the food is fed also has an influence

Glucose tolerance in fish: Is the daily feeding time important?

Physiol Behav. March 2009;96(4-5):631-6.

J F López-Olmeda

1

; M Egea-Alvarez; F J Sánchez-Vázquez

1

Department of Physiology, University of Murcia, Murcia 30100, Spain. jflopez@um.es

Article Abstract

Daily rhythms in glucose tolerance have been reported for several species of mammals, which seem to be linked to factors such as daily rhythms of insulin resistance and feeding habits. In this paper, we studied entrainment to a daily scheduled meal of blood glucose after carbohydrate intake (dextrin or glucose). After a meal containing dextrin, blood glucose showed different maximum concentrations (Cmax) and time to peak (Tmax) depending on mealtime, the greatest differences in Cmax being found 2 h after feeding. The highest Cmax (8.22 mmol/l) was obtained when mealtime was set in the middle of the light phase (ML), and the lowest Cmax (3.46 mmol/l) when goldfish were fed in the middle of the dark phase (MD). Cosinor analysis revealed a significant daily rhythm in dextrin tolerance with its acrophase around ML, amplitude of 1.99 mmol/l, and a mesor of 5.49 mmol/l. However, when the carbohydrate source in the meal was glucose, an inverse pattern was observed: higher blood glucose in goldfish fed at MD compared with ML (6.98 vs 4.32 mmol/l, respectively). Similar results were obtained when glucose was administered intraperitoneally, with higher values at MD than at ML (13.82 vs 9.54 mmol/l, respectively). Finally, no differences in amylase activity were observed in the gut after dextrin load at ML and MD (522 vs 446 U/mg protein), discarding the effect of digestive factors in the daily rhythm of tolerance. In conclusion, our results described for the first time a daily rhythm in tolerance to carbohydrate in a teleost fish, highlighting the impact of the time of day in glucose metabolism.