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Dystocia (Egg impactation)

Dystocia is a term that comes from the Greek word, meaning bad birth or difficult birth. Anyone who keeps koi will at some time come across a case of dystocia or egg binding, or sometimes called egg impaction, in a mature female. The condition will be evident in mid-summer, although in some instances things can go wrong in early spring.

 


This condition may occur in early spring through to midsummer, although the run-up to the problem may have started as early as mid winter. The question can then be asked why Dystocia occurs in the specific time window, or why at all?


Egg development in carp is not synchronised but is continually produced throughout the year, so a slow continuous stream of eggs are coming into the ovaries and under ideal conditions a female can spawn more than once per year. If spawning does not take place, the eggs can be reabsorbed but if the conditions are not ideal, such a process may take up to two years.


Seasonal changes, the length of daylight hours and temperature play a huge part in egg maturity in carp. A mature female will normally be ready to spawn as the days get longer and the temperature raises enough to stimulate the fish to ovulate around 20 to 22 degrees. In some parts in South Africa, this temperature may deviate a little, depending on the average temperature of the pond during winter. Remember there should be sufficient rise in temperature to trigger the process.

Although some spawning may also take place in late summer, we need to look at the reasons for the occurrence of dystocia during both these time windows where spawning usually takes place.

Development of the ovaries and the eggs inside them is temperature dependant prior to ovulation and spawning. There needs to be a certain amount of days at high enough temperature for the ovaries to mature. If it happens to be a very unstable spring-time and the process of ovulation is interrupted, complications may follow. There is more to that. The eggs do not lie free in the coelomic cavity, but they are encased in the ovaries. Considerable effort is needed to force the eggs out of the ovaries during spawning. The female are therefore not able to expel the eggs on her own. The process of spawning is a fairly rough affair where the eggs are forced out of the female by powerful contractions of the muscles in the body wall and literally bumped out of the female by the males.

In a koi pond, very few things are natural because it is a closed re-circulating system and very few of the conditions experienced by carp in the natural environment are present. There are few ponds that offer female koi different layers of temperature where she can move to, shallow warm areas for spawning, submerged plants, sufficient and suitably sized males and streams bringing fresh water into the water body. These are just a few variables that wild carp experience to trigger ovulation. In nature there is also the trigger-effect of other females spawning that will rush the process and prepare the rest of the females to enter “spawning mood”.

If this does not happen for whatever reason mentioned above, eggs will accumulate in the ovaries and will not mature. This process is continual, so even though the eggs are not mature enough to be spawned, more will be added as the season continues. This results in egg binding.


egg_bound
Photo: Johan Jacobs 


Added to the above, the inbreeding and possible genetic or injury related defects that may exist in the koi population and dystocia can become increasingly possible. The tendency of koi keepers to stock only females for show purposes, may also contribute to the problem.

Dystocia has several implications. As the eggs build up in the ovaries, the koi has to carry this burden and in some cases infection of the ovaries can set in. A female that is egg impacted will be quite bloated. Swimming will become laborious and “tadpole” like. The bloating will be soft to the touch, becoming harder as the condition progresses.

If the situation is not rectified, the chances are that the female may not survive.


 egg_bound_show_eggs

Photo: Johan Jacobs


Unfortunately, it is evident that dystocia is one of the few problems resulting from a well run koi pond.

 

Prevention of dystocia

There are no hard and fast rules to prevent egg binding but a number of factors accumulatively may assist in preventing dystocia from developing.

If you have a heating system in the pond, lower the temperature in mid-winter to ensure that the females experience a window of low temperature. Fasting during this period will reduce egg production and it also may assist in preparing them to ovulate with the rise in temperature and extended photoperiod during early summer.

If there are no heating systems, make sure that the females go through a fasting period of two to three months during mid-winter. This measure will assist in re-absorption of the eggs while it also reduces the production of new eggs.

In order to overcome the limitations that exist in well run koi ponds, some hobbyists provide spawning nets/ropes in the koi pond with the hope of providing females with the environment to induce spawning if necessary.

It is always advisable to keep a few mature males in the koi collection to induce spawning when required. This is of course not advisable if the intention is to breed koi, but then the whole approach will be different.

In order to prevent dystocia one can also create the ideal conditions in a separate, temporary pond for a female that is heavily loaded with eggs to induce spawning. In valuable koi this will reduce the chance of injury because there are no sharp objects or protrusions. The process is fairly simple if the female is not already in serious trouble.

It should be mentioned that if you are successful in spawning one female in the collection, the chances of spawning the rest of the females that may be heavy in roe under controlled circumstances in the temporary pond are greatly increased. I have found that by retaining some of the temporary pond’s water where the previous spawn took place in aerated buckets while the previous spawning is cleared out can be very valuable. As soon as the temporary pond is cleaned and filled with fresh pond water, pour the contents of the buckets into the temporary pond and place the “difficult” female in it for a few hours to settle down. Then add the required amount of rested males with her and most of the time spawning will commence early next morning. The various chemicals excreted during the previous spawning process will be the trigger for the female and males.

When a female is already in trouble and it is obvious she is under stain, the situation is more complicated. The reason is that there may be a physical deformity present in the fish that prevented spawning in the first place. Another reason for the more complicated situation is that pressure may have resulted in a blockage that makes the release of the eggs impossible.

For a hobbyist it will be almost impossible to determine if such a situation exists and the advice is to accept that it is a treatable situation and continue with controlled spawning or treatment.

Treatment

If the prevention of dystocia was not successful and the controlled spawning did not produce results, the hobbyist will have to interfere to prevent his stressful situation to escalate into either septicemia or a case where the internal pressure will interfere with the normal working of vital organs. Either way antibiotic injections will be required.

 encased_organs1
Photo: Johan Jacobs. 


Note how the ovaries have encased the eggs to smother the vital organs.

There are three treatments that can be effected. It may be risky and the assistance of a veterinarian will be required, either to supervise the process or to prescribe the medication. It must be stressed that following the prescribed injections, the help of someone with intimate knowledge will be required because I would not recommend this procedure for the inexperienced. Injecting the required hormones, sedating, drying and milking /stripping a large female koi ripe with eggs, is nowhere near as easy as books and magazines would have you believe.

The following injections may induce a state where the eggs can be stripped from the female:

Carp pituitary extract (CPE)

CPE is supplied as a powder that needs reconstituting with sterile water. Injection dosages are 0.3 mg per kg of body weight. This injection is repeated 18 hours later. 10 hours after the second injection manual spawning can be attempted. By this time the eggs will normally flow freely when the koi is lifted from the bowl of anaesthecs.

Luteinizing hormone/ Release hormone (LH-RH)


This hormone is injected at a dosage of 5 mg per kg bodyweight. A second injection may be required after 12 to 14 hours.

Human Chorionic Gonadotropin (HCG)

This hormone originates from humans and has been successfully used to induce fish to spawn. I have not used this substance before. Please enlist the aid of your veterinarian.

According to Duncan Griffiths, the recommended dose is 800 micrograms per kg bodyweight. 1000 000 micrograms = 1 gram.

 

Last Updated on Sunday, 31 October 2010 22:26