25/08/2021
Winter Feeding myths
This article was written by Ken Austin, one of the K.O.I. instructors, for the SKAPA Club Newsletter. Notes added by Karen Pattist.
Nighttime air temperatures have become cooler as we approach winter. The coolest weather will be in January. Your pond water temperatures will also get cooler. These cooler temperatures are signals that your Koi now need to be fed differently.
At low temperatures, Koi generally will not eat more than the body needs. As the metabolism slows down the intake of food is gradually reduced. Throwing in more food than the fish consume is poor water quality management. Uneaten food will heavily pollute the pond and bio- converter system even to the point of the fish being poisoned by the degeneration in water quality. At water temperatures below 40°, the Koi’s metabolism is so slow, but it is an old urban koi-keeping myth that food actually rots in their guts and becomes toxic before the Koi can digest it. Koi should actually eat a tiny amount all winter.
There are claims that in winter the type of food given to the Koi should change from an animal based protein to a plant based protein food. Other claims are that an easy to digest hi-carb diet should be fed in winter. The protein content of many of the extruded plant based Koi foods – e.g. wheat germ type feeds, are as high in protein as animal based protein Koi foods. However the raw plant products are low on protein, deficient in some of the essential amino acids and are more difficult to digest. Raw wheat Germ has 26 – 29% protein whereas the finished wheat germ Koi foods have a have around 32 – 34% protein.
Some plant protein products have a good nutritional value (high in digestible protein, good amino acid profile) and are economical at the same time, e.g. wheat germ meal. The use of certain plant products should be limited because plant protein is high in starch and fiber. Note that plant protein also has low palatability, which is often overcome by adding fish lures which attract the fish to eat anything
For water temperatures below 50◦, stop feeding your Koi anything. They can go all winter without eating. Continue to make periodic water changes all winter long and your water quality will improve and you Koi will have a good healthy start when they come out of dormancy next spring.
Note - In CT, the Koi are often not fed for as long as 6 months, because water temperatures are below 50° all that time! And yet, the Koi grow a bit, and look fabulous in the spring. Why? Because they nosh just a bit all winter on pond algae, which is high in carotenoids – one of the ingredients used in Koi food as a color enhancer. Nature provides her own color enhancers! The cold water also decreases the Koi’s slime coat which can make colors appear blurry (although provides the Koi’s first line of defense against disease). Between the increased algae consumption and the decreased slime coat – the Koi look fabulous!
Note 2 - Here is what Professor Richard Strange says about food rotting in the gut:
"As for the high protein feed rotting in the gut, I've heard that one before. IMO, it is unequivocally false. It ranks up there with bicarbonate reducing coloration, as a tale with no scientific basis that persists in a segment of the koi community. In all my years of working in physiology of fishes, I'd never heard it proposed for any other temperate fish. No other aquaculturists change the composition of the feed in response to water temperature. Let's examine the facts. Below 40 is extremely cold for any temperate fish (though they are well adapted for it). No growth occurs and there is minimal feeding. That doesn't mean gut transit stops anymore than heartbeat. Also, 40 is refrigerator temperature, not very conducive to rot! Further, the koi's gut has a microbiome, just as we do, that encourages certain bacteria and discourages others. A 100 years ago intestinal gas was thought to arise from beans due to "putrification of excess protein in the colon" now we know it is due to hard to digest sugars. In summary, while bacteria are active in all animal's guts, it is a symbiotic relationship best described as digestion, not rot."
Thanks Professor Strange!
