To lay people, the word bioenergetics seems to be an overwhelming jargon. They may have the impression that the techy word has all the 'bio' prefix in them. But the concept behind could be put in much simpler terms. It is nothing but the energy budget of an animal or human beings. But what is an energy budget and what practical use can it have on our everyday life.
When one talks about budget, one deals with allocation (another big word). Simply put, how much will you earmark for every activity that you have. For example, if a college student is given a daily budget of 200 pesos, how much of it goes to transportation, to lunch, to snacks, and to any unpredicted expense. In the same token, for a given amount of energy from food that one eats/drink, how much of it is digested, assimilated, used in muscular activity such as swimming, running etc. In aquaculture, this is often applied to the allocation of energy consumed as feeds. It is the lookout of the aquaculturist to see to it that the feeds are highly digestible so that a high proportion is assimilated. The combination of ingredients tells a fish nutritionist what to expect on how it could support growth (if at all) on the basis of the ratio of protein and total energy content of the feed. Needless to say, there is the best combination/ratio of these two components for best growth (body protein deposition). The mixture of ingredients may also give an indication on whether more nitrogenous biological waste is expected. based on the quality of the protein. The higher the quality, the less ammonia wastes are going to be excreted by the aquatic animals.
But the application of bioenergetics is not confined to aquaculture alone but is of good use in most aspects involving living thing including human beings. In human beings, the application is mostly on diet and lifestyle. The whole science of bioenergetics rely on mesurement of each component of the energy budget. How does one measure digestibility, assimilation, nutrient deposition, waste output. If one talks about measurements, then it gets complicated especially if one aims to measure a component with as little errors as possible.
This then is the introduction for my master's students on my subject next semester on the subject Bioenergetics.
Monday, May 9, 2011
Wednesday, June 16, 2010
Are you sure it is an immunostimulant?
The search for immunostimulants in fish feeds have been one of the most popular thesis topics of both undergraduate and graduate students in aquaculture in the Philippines and abroad. Its popularity goes hand in hand with the search for the best anti-cancer, anti-aging, and anti-almost-anything for humans. As a result, the industry for neutraceuticals have emerged as a very lucrative business for the simple reason that it does not need any approval of a regulatory body such as the Bureau of Food and Drug Administration. One just has to add in the label of whatever form of neutraceutical he/she is selling that the there has been No Proven Pharmaceutical Value.
I guess for aquaculture, feed manufacturers are not so easily tempted to incorporate certain unknown ingredients unless they have been shown to promote immune enhancement. It is unlike the pharmaceuticals for humans which only need a little convincing from friends to say they are really effective simply because they work for them. But what is the acceptable proof of immunostimulants for fish or shrimp in aquaculture?
The interest in immunostimulants could have started when the shrimp industry in Asia and elsewhere suffered losses due to bacterial and viral attacks. But then again, I have not come across a reading about this and it should stay as a suspicion on my part. Shrimps are very good subject for such kind of tests because of the absence of what we call adaptive immune response or the ability to produce an antibody very specific to a certain kind of antigen. Thus, crustaceans lack the cell memory to recognize a certain pathogen and thus unable to combat it once it reappears in their system. The absence of the adaptive immune system makes it a lot easier for the researcher to measure quite conveniently only the indices for the other kind of defense, the first line of defense, the innate or non-adaptive immune system. The investigators are able to avoid complicated conclusions arising from both systems and thus are able to isolate the response of one system and are able to make more conclusive findings.
The innate defense system is a generalized kind of defense and does not act upon specific antigen and for this reason they are alternatively called the nonspecific immune system. Indices for the innate immune system includes the ability to produce the superoxide that oxidizes microbes to death, rate of phagocytosis (engulfing of microbe organisms by specialized body cells), the level of activity of enzymes responsible for producing the killer substance e.g. phenoloxidase or its dormant form prophenoloxidase, or whether the presence of the ingredient in question can inhibit the growth of the pathogenic bacteria on petridishes (i.e. in vitro), among other indices. So if all these indices increased their levels when the ingredient is administered to a group of shrimps, and the increase in level is considerably more than that of a control group of shrimps, the experimenter then concludes that the ingredient in question is an immunostimulant.
Is the finding conclusive that the compound in question is now considered immunostimulant? When this field of research was at its early stage, acceptance of publications in scientific journals of this type of research has relied on conclusions based on the above-mentioned immune responses. But now, I have the impression that more stringent journals consider only the findings to be conclusive if there is a parallel study. It is a challenge test in which the crustaceans, following administration, are deliberately challenged with the pathogenic organism in question under laboratory conditions. If in addition to increased levels of immune responses (not necessarily all of them), the crustaceans are able to demonstrate acceptable rate of survival, only then can the reviewers consider the compound immunostimulant.
Wednesday, June 9, 2010
My pet fish and pet dog are growing- scientific or nonsense?
How do we define growth? Layman definition of growth is an increase in size or perhaps in weight. But this definition seems to direct animal husbandry men to the wrong direction. This is even a more sensitive issue to the pet lovers. Would they want growth for their pets when they are past the linear area of the sigmoid curve for growth? Or put in another way, would they like to feed their pets which have stopped 'getting bigger' since attaining maturity to gain more or 'grow' more? They don't want this to happen since it will only result in the accumulation of unnecessary fat in the body which may lead to sluggish movement or perhaps cardiovascular diseases as dogs are prone to have. When pets are the topic, the idea of feeding at around maintenance level seems very logical but when you talk about food animals such as fish in aquaculture, it is hard to convince the fish farmers. But I agree that in the fish farm, it is hard to be so exacting about feeding the fish just the 'right amount' and so the rule of the thumb is that you feed them proportionately less in amount with time. The fact is that fish may not have reached the plateau yet during the culture period or even towards harvest time but more likely that the growth curve is gradually flattening out. So what's the fuss about growth all about?
Strict definition of growth is what is needed by scientists, the animal nutritionists, to be stringent on their statement of hypothesis and whether their data supports the hypothesis they have put forth. Thus, it is primarily needed by nutritionists to generate basic knowledge so that application of such knowledge (which is technology) is assured. Does this mean that fish farmers do not care and that they do not have anything to do with strict definition of growth? They should care because the technology everybody uses in their daily activities should be based on sound science, otherwise, the technology based on trial and error would soon crumble and we are back to square one.
And what is the strict definition of growth? It is the accumulation of body protein in the body and with an acceptable deposition of fat. This means to say that it is not enough to say that an animal gained so much weight per se but what is the composition of that gain. Is it mostly protein or mostly fat or bones/scales? Of course when it comes to farm animals, there are various objectives in raising the animals - is it for the hair (e.g. wool of sheep), is it for the amount and quality of milk, etc.? In aquaculture, it could be as food fish, broodstock fish which are judged according to the quality of eggs and their hatchability, it could be for aquarium display, etc. Assuming that we are concerned mainly on food fish such as tilapia, milkfish, grouper, salmon, grouper etc., then definitely we are interested in the body protein accumulation as against fat accumulation as the definition of growth.
If you happened to have read journal articles on feeding experiments in animals, you would notice that some experiments try to evaluate some feed ingredients mixed with other ingredients to make a balanced diet. All factors equal except the ingredients, say A, B or C. Diets which incorporated A, B or C are fed separately to each lot of fish and the experimenter will evaluate and rank the efficacy of each diet. Assuming that digestibility of the ingredients are equal, the indexes that will be measured will be growth in its usual sense of weight gain. But in addition to this, the composition of the diet and the composition of the whole body of fish (yes, they will have to be sacrificed at the end of the experiment) will be determined. So that not only growth in terms of weight gain, but what kind of growth in terms of protein accumulation, fat accumulation would be considered in the evaluation (i.e. ranking) of diets A, B or C. The findings will benefit the feed manufacturer directly and the fish farmer indirectly if these feed ingredients are cheaper replacements of some feeds that they are currently using.
That goes the story of the strict definition of growth, impractical in the actual raising of fish but very essential in establishing scientific basis of some fish nutritional findings that indirectly benefits the fish farmers.
Strict definition of growth is what is needed by scientists, the animal nutritionists, to be stringent on their statement of hypothesis and whether their data supports the hypothesis they have put forth. Thus, it is primarily needed by nutritionists to generate basic knowledge so that application of such knowledge (which is technology) is assured. Does this mean that fish farmers do not care and that they do not have anything to do with strict definition of growth? They should care because the technology everybody uses in their daily activities should be based on sound science, otherwise, the technology based on trial and error would soon crumble and we are back to square one.
And what is the strict definition of growth? It is the accumulation of body protein in the body and with an acceptable deposition of fat. This means to say that it is not enough to say that an animal gained so much weight per se but what is the composition of that gain. Is it mostly protein or mostly fat or bones/scales? Of course when it comes to farm animals, there are various objectives in raising the animals - is it for the hair (e.g. wool of sheep), is it for the amount and quality of milk, etc.? In aquaculture, it could be as food fish, broodstock fish which are judged according to the quality of eggs and their hatchability, it could be for aquarium display, etc. Assuming that we are concerned mainly on food fish such as tilapia, milkfish, grouper, salmon, grouper etc., then definitely we are interested in the body protein accumulation as against fat accumulation as the definition of growth.
If you happened to have read journal articles on feeding experiments in animals, you would notice that some experiments try to evaluate some feed ingredients mixed with other ingredients to make a balanced diet. All factors equal except the ingredients, say A, B or C. Diets which incorporated A, B or C are fed separately to each lot of fish and the experimenter will evaluate and rank the efficacy of each diet. Assuming that digestibility of the ingredients are equal, the indexes that will be measured will be growth in its usual sense of weight gain. But in addition to this, the composition of the diet and the composition of the whole body of fish (yes, they will have to be sacrificed at the end of the experiment) will be determined. So that not only growth in terms of weight gain, but what kind of growth in terms of protein accumulation, fat accumulation would be considered in the evaluation (i.e. ranking) of diets A, B or C. The findings will benefit the feed manufacturer directly and the fish farmer indirectly if these feed ingredients are cheaper replacements of some feeds that they are currently using.
That goes the story of the strict definition of growth, impractical in the actual raising of fish but very essential in establishing scientific basis of some fish nutritional findings that indirectly benefits the fish farmers.
Tilapia suffering from high blood pressure...
From the first article, we know that the energy content of the food we eat per gram (called energy density of the food) influences our appetite (the amount of meal consumed until satiety). In general, the higher the energy density of the meal, the lesser is the appetite and vice versa, the lower the energy density of the meal, the higher is the appetite. This is true for all animals with the possible exceptions of human being since appetite seems to be influenced also by how delectable the presentation of the dessert is after a meal. Remember that this generalization was made after numerous observations in the laboratory. Needless to say, the meal and conditions were under control to make this kind of conclusion.
Animals in general eat to satisfy its energy requirement in tune with their growth rate. Thus, younger animals consume more energy relative to their body weight because they have faster growth rate than do the adult animals. In human context, when you get to be 20 years old or older, you have to eat at maintenance level because your growth has slowed down or has stopped altogether. Growth, again is loosely defined as additional weight at the level of the animal, or increased tissue weight at the tissue level. In human context, before you attain your maximum height in your early 20s, your increase in weight corresponds to your increase in height. This correspondence is almost linear until you approach the end of teenage years where the correspondence become less steep. In effect, biological graphs of growth of animals, including human beings, are depicted as sigmoid. In fish, the plateau of this sigmoid curve could be reached in a matter of weeks or months.
So as the animal and human being approach this plateau of growth, their energy consumption should be at maintenance level. You may now argue that even if additional food energy is consumed when one has reached this plateau, still weight will increase and since we define growth as increase in weight, then there is growth. You are correct. But there is something wrong with our definition of growth.
If Anna is now 23 years old and continue to eat considerably more food energy on a daily basis, on her 24th birthday, she has grown. Yes, that is correct, except that she has grown horizontally rather than vertically and if she continued this in the long run, obesity would result and she would be prone to some cardiovascular diseases and even diabetes.
What about fish? Three month old tilapia are fed continuously with energy-rich formulated diet and in no time will reach marketable size. Isnt this a good idea? Yes, the tilapia will gain weight very fast but it is not a sound animal husbandry practice. For one, you could have saved the extra expense of supplying extra food energy and could have channeled it to your profit. Another is that the tilapia may have accumulated fat in the body. You may argue that fatty tilapia are even tastier for the consumer since if he tried broiling them, oil would come oozing out of the fish's body and it really would be so sumptuous. Fine, your argument is acceptable. Except when you are a big time tilapia farmer and you handle tons of tilapia harvest in a tropical country such as the Philippines. Fatty fish are prone to rancidity when not stored properly after harvest. If you do not have these freezers, you will end up with harvest of very poor quality and thus low profitability. But if you have all these storage facilities, it would be nice to supply the consumers with the much needed highly unsaturated fatty acids instead of taking pills of these daily, which is very expensive.
Lastly, if obesity kept in the long run leads to cardiovascular diseases in human beings, it is also true for tilapia. But then again, before the period of what we call 'long run' is approached, we have already harvested and eaten them.
Then, are we wrong in our definition of growth. This will be tackled in the next post.
Animals in general eat to satisfy its energy requirement in tune with their growth rate. Thus, younger animals consume more energy relative to their body weight because they have faster growth rate than do the adult animals. In human context, when you get to be 20 years old or older, you have to eat at maintenance level because your growth has slowed down or has stopped altogether. Growth, again is loosely defined as additional weight at the level of the animal, or increased tissue weight at the tissue level. In human context, before you attain your maximum height in your early 20s, your increase in weight corresponds to your increase in height. This correspondence is almost linear until you approach the end of teenage years where the correspondence become less steep. In effect, biological graphs of growth of animals, including human beings, are depicted as sigmoid. In fish, the plateau of this sigmoid curve could be reached in a matter of weeks or months.
So as the animal and human being approach this plateau of growth, their energy consumption should be at maintenance level. You may now argue that even if additional food energy is consumed when one has reached this plateau, still weight will increase and since we define growth as increase in weight, then there is growth. You are correct. But there is something wrong with our definition of growth.
If Anna is now 23 years old and continue to eat considerably more food energy on a daily basis, on her 24th birthday, she has grown. Yes, that is correct, except that she has grown horizontally rather than vertically and if she continued this in the long run, obesity would result and she would be prone to some cardiovascular diseases and even diabetes.
What about fish? Three month old tilapia are fed continuously with energy-rich formulated diet and in no time will reach marketable size. Isnt this a good idea? Yes, the tilapia will gain weight very fast but it is not a sound animal husbandry practice. For one, you could have saved the extra expense of supplying extra food energy and could have channeled it to your profit. Another is that the tilapia may have accumulated fat in the body. You may argue that fatty tilapia are even tastier for the consumer since if he tried broiling them, oil would come oozing out of the fish's body and it really would be so sumptuous. Fine, your argument is acceptable. Except when you are a big time tilapia farmer and you handle tons of tilapia harvest in a tropical country such as the Philippines. Fatty fish are prone to rancidity when not stored properly after harvest. If you do not have these freezers, you will end up with harvest of very poor quality and thus low profitability. But if you have all these storage facilities, it would be nice to supply the consumers with the much needed highly unsaturated fatty acids instead of taking pills of these daily, which is very expensive.
Lastly, if obesity kept in the long run leads to cardiovascular diseases in human beings, it is also true for tilapia. But then again, before the period of what we call 'long run' is approached, we have already harvested and eaten them.
Then, are we wrong in our definition of growth. This will be tackled in the next post.
Why is the enrolment in the College of Fisheries and Ocean Sciences dwindling?
Going back to the issue of factors, it is my opinion ever since, that this field of study seems to belong to those classified by Filipinos as nonglamorous. But of course this is is too simplistic a reason since so many factors come into play. If it is nonglamorous but high-paying, it would still pick up takers I assume. But as it is, and when you read all the discussions in Facebook of the group site UP College of Fisheries, there are some insiders who say that this glamour thing is not even a consideration. On the other hand, one even asked, why are sons and daughters of Professors of the college do not encourage them to take fisheries. The implication of this question is that even those who profess in the field of fisheries are not at all passionate in this field. It is really complicated. But glamour may not be the right term which may have resulted in a discussant in the same group site to throw tantrums at me just for asking about it. Could the word be popular, high in status? Whatever it is, one thing for sure that the diminishing interest in the fisheries study is a worldwide phenomenon. In Japan, for example, my very own alma mater, Tokyo University of Fisheries has now merged with another university and is now called Tokyo University of Marine Science and Technology. One of the factors among many is the decreasing enrolment and perhaps the dwindling resources that the government provides.
Is the obsession of some parents towards the nursing profession a factor in the decreasing enrolment in fisheries? Discussion in the higher administration of UPV tends to agree. Nursing is a more glamorous profession if glamorous is loosely defined as a white collar job and high-paying. White collar yes but only high-paying if one works abroad. Otherwise, you better shift careers when you are to stay in the Philippines if you want to support your family well.
All in all, I would say that the factors contributing to the decreased enrolment are many and to me, foremost is the image of the profession which of course could be worked on gradually. What do you think?
Food energy and appetite
I'm new in this blog business so that I wanted to post some interesting things from the field of physiology. It is interesting to note that there are more common physiological phenomenon to most animals than one can ever suspect. I thought of some things very common to animals which is the role of food energy on appetite. From experience, this is hard to explain in simpler terms, and this is a challenge now to me to explain to you this physiological phenomenon.
Food contains energy, as we know it. It is our fuel especially when we do physical things. Although food is composed of protein, carbohydrates, fat and some minor things such as vitamins and minerals, these three major nutrients contribute food energy at different proportions. And if we add all these contributions, we have now the total energy contained in the food. Thus, energy from various sources are additive. Now, how does this total food energy influence our appetite? If appetite is loosely defined as the amount of food eaten to ones satisfaction, then this amount depends on the energy content of your meal relative per unit weight. So if the food contains 100 kilocal per gram and your appetite is up to 3000 kcal (this example is hypothetical), then it will take 3000/100 grams or 30 grams to satisfy your appetite. Thus, the higher the energy content of the food per gram, the lower is the amount of food that you will have to eat to reach satiety. An application of this phenomenon can be seen when you eat in an eat-all-you-can restaurant. If you eat mostly energy-dense diet such as roasted pork, beef with so much fat in it (because fat has the highest energy density than either carbs or protein), then you will reach satiety very shortly or after a few servings. On the other hand, if you choose less energy-dense meal such as vegetable salad or any meal which incorporated plant materials, you will eat a more substantial amount for you to reach satiety. But there is a physical limit to eating mostly salad and this is the distension of the stomach. Regardless of this, you will have eaten more if you eat less energy-dense diet.
The application in animal husbandry is much more appreciated especially if the feed is pelletized such as those fed to fish, pigs, poultry etc. Feed formulation should consider the optimum energy density of the formulation such that when satiety is reached, the animal should have consumed a balanced of all essential nutrients in the diet. This makes rasing these animals profitable by optimizing the amount of food given to produce a certain amount of growth (in terms of weight perhaps). Thus, we could say that energy content of food influences appetite.
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