More Selected Comments on Nutrition by Chris Neaves

Submitted by Chris Neaves on Thu, 09/29/2016 - 11:49

Lets chew on the subject of Koi foods.

It is well documented that Koi – like all living creatures need certain nutrients in their diets in order to survive, grow, reproduce and be healthy. To this we must add that there should be enough of these elements for our Koi – not just minimum amounts - because we place a premium on body shape, skin lustre, colour (quality of colour and separation of colour) etc. These basic dietary requirements are energy, protein (amino acids), lipids, carbohydrates, vitamins and minerals.

The vitamins and minerals can be considered the spark plugs of the nutrition. They are needed in very small amounts and are involved in some way or the other with all function of the Koi’s body. Without them the protein and carbohydrates do not work. Deficiencies in vitamins and minerals are well documented and can have a devastating effect on our Koi. Elevated levels of vitamin C, E and A are extremely beneficial for koi.

It is extremely difficult for the average enthusiast to establish if the food they are feeding is of poor quality and deficient in vitamins and minerals. The symptoms of vitamin deficiencies only manifest themselves over time.

In the manufacturing process it is known that the heat destroys a portion of the vitamins and minerals. Adding a vitamin and mineral premix which will bring the levels of these elements back to where they should be after extrusion and increase them to the levels you want them to be, compensates for this.

Lipids are a great source of energy for our Koi. By increasing the lipid content you can reduce the protein content because the lipids provide the energy and then the protein (which can also be used by the body for energy) is spared for growth etc. Lipids are the part of the food that can go rancid over time. Commercial Koi foods have low lipid levels for extended shelf life. Therefore, it is not a bad idea to increase the protein level.

The carbohydrates used in Koi food are an essential part of the diet. Carbohydrates are a good source of energy and are utilised in some metabolic functions. References indicate that carp (Koi) food with out carbohydrate did not produce the same results as foods with carbohydrates. Carbohydrates have another important function – they are a digestible binder for the nutrients in Koi foods. In other words they are the medium in which the nutrients are delivered to the gut of the fish.

The single most important ingredient in the composition of a Koi pellet is protein. This is needed for growth, tissue replacement, lustre of the skin etc. The Koi’s body cannot absorb protein but it can absorb the molecules of which protein is built – amino acids. As a natural part of life protein is broken down into amino acids in the digestive system. The amino acids are then absorbed into the blood stream and carried to the cells where the amino acids are rebuilt into the cells as protein. The levels and balance of amino acids needed by Koi are well documented.

Protein digestion will take place at all temperatures. If there is no digestion then the pellet would pass through the gut and exit the vent. If digestion of a “low” protein diet takes place at all temperatures then the same apples to a “high” protein food source. This is subject to the body going into hibernation at very low temperatures. e.g. 35F – 45F. It’s the absorption rate and need for protein that varies with temperature.

The Koi’s body needs energy to metabolise the protein as well as energy to perform the bodily functions. Without the energy – no metabolism. There are two primary sources of energy – carbohydrates and lipids. If the Koi is moving and breathing it is using energy. If the Koi is eating it will need protein. The very act of ingesting a pellet will scour the gut of some cells which will need replacement.

Some of the questions that confront Koi keepers revolve around: the amount of protein a Koi food should contain and what to feed Koi as temperatures drop in winter. Perhaps another question that also arises is amount of carbohydrate in Koi foods. These questions are debated, argued about, fought about and may one day be the cause of another world war.

A Koi pellet is made up of different ingredients. (We don’t need a degree in the obvious at this stage). Some have very sophisticated sounding names that appeal to us. The reality is when the digestive enzymes get hold of any Koi food they break it down into molecules that can be absorbed by the gut. When formulating a Koi food nutritionists work with these nutritional elements and construct a formula based on what a Koi needs.

Provision is made to accommodate all aspects of the needs of the Koi and a balanced diet is the result.

As temperatures increase the metabolism increases and so does the hunger. More food can be fed more often. As temperatures drop the metabolism activity decreases and so to the hunger. Below certain temperatures the Koi’s body has very little need for food as the metabolism is very slow. The temperature of around 10C or 50F is given as a guide line.

The reality is that different Koi react differently. Some are more active at 50F than others. If the fish is swimming and breathing it is utilising energy and there is metabolism taking place in the body. Below 50F the metabolism slows dramatically and so does the appetite. In areas where the temperature gets really low the Koi stop feeding and they are best left to mumble obscenities at the occasional human face peering at then lying on the bottom. We can over-feed a pond and have a negative effect on the water but not over feed a Koi collection.

As temperatures drop the digestion slows down but does not change. So the same food can be fed year round. As temperature drop the food intake is regulated by decreasing the frequency and the quantity of the food. This happens naturally with the fish and artificially with us as koi keepers regulating the food given to the collection.

Some Koi keepers switch to a low protein diet for winter. I must question this. Koi pellets have different ingredients in them to make up what is called a balanced diet. If a Koi food has around 38 – 40% protein then it will have around 30 – 32% carbohydrate. However, as you decrease the protein levels in Koi food the carbohydrate levels increase. The protein and the carbohydrate levels directly affect one another. A good example is of a several Koi foods we analysed here that had 16 – 17% protein levels and around 66% carbohydrate.

Please have a look at the two graphs I have included to illustrate this point.

It makes no sense to increase the carbohydrate level in colder waters by decreasing the amount of protein. In colder water Koi need less carbohydrate and less protein. Koi do not need more carbohydrate in winter as their body temperature is that of the surrounding water. As temperatures decrease and you change the diet to a “low protein” diet what are you achieving? You are feeding amore of a nutrient that can be stored as fat (carbohydrate) deposits around the organs and this may shorten the Koi’s life and affect its body shape. It would be more beneficial to give them the same food (but with greatly reduce the quantities) than to give more carbohydrate. Protein that is not utilised will be excreted. That is protein at any level. The amount of protein can be regulated by limiting the amount of food as well as the frequency of food. You are feeding less of better quality food with higher nutritional values. We tend to over feed our Koi. Rather feed fewer high protein pellets than more low protein pellets.

The choice is yours.
Kind regards,

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