Quote:
Originally Posted by aquitori
Compared to other fresh water fish, koi digest a higher percentage of starch, but at the most no more than 35% of the protein consumed should be given. If a fish is given more starch than this over a long period of time, then it will develop a swollen abdomen.
If the fish are given feed containing protein that is only 35% of the starch, then the fish will take on unwanted proportions; not so much what is usually called a swollen abdomen, but a swollen breast or a double-pot belly and a narrow tail joint. However wild carp or koi that are very close to the original species or even good koi if they have a strong constitution, do not always develop drooping bellies.
When it comes to koi with good white ground, high-quality Hi and good quality Sumi, which are generally genetically weak, their bellies almost invariably droop.
These proportions in the feed must not bealtered, throughout the four seasons. When the water temperature is low, then protein with a low calorific value should be given and in summer when the temperature is high and the koi can easily exhaust their physical strenght, protein with a high calorific value should be give. If in addition to this the koi are given digestives and care is taken not to waste feed, then it is reasonable to aim for good growth right from the new-born stage.
Should the belly droop, then we need to deviate from our aim of growth; if a feed mix with less than 35% starch in proportion to the protein is given, a swollen breast breast will be cured in one summer, and a double-pot belly will be completely remedied in three years. Once the phyical proportions have returned to normal, then the fish will start growing again.
To make a koi into jumbo, it is necessary to rear it so that up to about 70cm, it has risen shoulders and a flesh-out tail joint.
We do not see so many of them nowadays, but there was a time when a koi was called jumbowhen it had a body just like a toad, very thick around the abdomen; but koi reared this way are short lived and do not frow in lenght.
This kind of body occurs when starchy feed has been given after the temperature has dropped in order to make the fish look chick; it is the result of suddenly fattening up (only around the abdomen) a slender koi.
In my opinion a koi can only be said to have grown 65cm koi kept in a concrete pond of about 30tons grows 5cm or more a year; a mere 2 or 3cm is not enough to say that it has grown.
A well-proportioned koi has well-raised shoulder; the back of a koi with a swollen breast (pigeon breasted) is less well risen and when a koi develops a double-pot belly the back is almost horizontal, with just the lower abdomen abnormally swollen and the fish looks very unsightly.
Old article from Nichirin 91' by:Takayuki Izeki