Re: [RML] Food for thought

Al anderson (killiman at indy.net)
Sun, 15 Jun 1997 04:55:38 -0700

At 05:20 PM 6/15/97 +1000, you wrote:
>My apologise for the long post but seeing the list is very quiet at the
>moment it might give you all something to read.
>
>Adrian.
>
>A history of intermittent deaths of Rainbowfishes displaying similar
>symptoms over a period of time prompted me to have a number of specimens
>undergo a series of pathology tests. Condensed results and general
>discussion follows.
>
>History:
>
>I have been having problems with a number of Rainbowfishes dying of unknown
>causes over a period of years. The main species that suffered from this
>problem was the Goyder River Rainbowfish. Although I have had some other
>species suffer from the same symptoms, the ratio of Goyder River to other
>species was staggering. I have had other specimens affected but they were
>also mainly Trifasciata species. Usually only one or two fish at any one
>time were affected. However, this past summer, I lost around a dozen adult
>specimens of the Goyder River Rainbowfish within a period of about 8-12
>weeks. I then decide to have the surviving three Goyder River specimens
>examined by a qualified veterinary practitioner to see if the cause could be
>established.
>
>The symptoms presented itself as signs of patchy darkening of the skin
>around the head, inappetance, isolation from the rest of the aquarium
>community, surface swimming and increased respiration. Death usually
>followed somewhere from 1 or 2 days to 2 or 3 weeks. In some cases this
>period may have been even longer as I had found from previous experience
>that all specimens suffering these symptoms eventually die, so I would
>short-circuit the prolonged death by disposed of them before they actually
>die. I was particularly concerned that they may be suffering from
>tuberculosis and thought it better to dispose of them rather than risk
>further contamination of the aquarium and other residents.
>
>I collected the three remaining specimens and gave them to Dr. Stephen B.
>Pyecroft (BVSc Hons.) for examination. The fish came from a 650 litre
>aquarium containing a mixture of Australian and New Guinea Rainbowfishes.
>
>Gross pathology results showed that all fish were in good to fat condition.
>All showed signs of generalised oedema, behavioural signs as above, and
>sectional darkening of the skin over random areas of the body. Body surface
>signs: Oedematous epidermis with scale loss. However, no pathogens were
>found on the skin scraping examined. Fins were normal and gills were pale in
>colour.
>
>Post-mortem results showed that the liver was grossly enlarged and contained
>fat globules (hepatic cells examined were full of these fat globules).
>Spleen was small and revealed a reduction in heamopoetic tissue. Kidneys
>were oedematous and enlarged. Purulent material was present in distinct
>cyst-like structures. Wet prep. revealed a loss of parenchymal tissue and
>many vesicles were filled with purulent material. These varying in shape and
>size. The peritoneal cavity was filled with a clear effusion. The heart was
>enlarged and had a granulated appearance over all myocardium. The
>pericardial sac enlarged due to the presence of a clear pericardial
>effusion. One fish had discrete areas of purulent material present within
>the cranium. Air dried smears were prepared from kidney tissue from the
>examined fish and stained with Ziel-Neilson stain (acid-fast stain). Only
>one of the tissue preparations was positive for acid-fast bacteria. The most
>likely bacteria type that would exhibit this staining characteristic would
>be Mycobacterium.
>
>Although Mycobacterium bacteria was found in one specimen, it was general
>concluded that this was most likely a secondary infection. However, all
>three specimens showed hepatic lipodosis possibly due to nutritional
imbalance.
>
>Discussion:
>
>Often investigations of this type produce more questions than answers. After
>looking at the diet of these fish, the picture is still not clear as to the
>cause of the lipodosis. I have bred and raised these fish and know exactly
>what food has composed their diet from birth to death. Upon hatching they
>were fed newly hatched brine shrimp nauplii, microworm and dry powered food
>(Sera micron & OSI microfood). When they were large enough to take other
>food they were primarily fed a home-made diet consisting of NZ Whitebait
>(fish) 20%, Prawns (Shrimp) 40%, Mussels 20%, Frozen Spinach 10% and Beef
>Liver 10%. All ingredients were finely ground and set with gelatine. In
>addition to this, their diet was supplemented with frozen bloodworms and a
>granulated pellet imported from Taiwan. The ingredients of the pellet food
>is stated to be fish protein, white fish meal, wheat germ, dried yeast,
>wheat flour, soybean meal, shrimp paste, mineral and vitamins. In what
>proportions is not stated. Analysis showed crude protein 46% min., crude fat
>4% min., crude ash 16% min., and moisture 9% max. Growing fry were fed
>twice a day and sub-adult and adults fed once per day.
>
>Their diet consisted of about 80% home-made food and 20% pellets and
>bloodworms. However, for the last 12 months of their lives this percentage
>changed, and the pellets basically replaced the home-made food. Mainly
>because I found that these pellets were readily accepted by the fish and the
>costs were reduced. The pellet diet was continued to be supplemented with
>the bloodworms and home-made food.
>
>Some authorities feel excess carbohydrates and fat in fish foods can be
>harmful to many species and fatty degeneration has been reported in a number
>of fish including Characins and labyrinth fish. However, such fatty
>degeneration considered as a pathological change and attributed to certain
>types of foods may not be caused by the food ingredients but by the volume
>of food fed. It was generally agreed that the above diet fed to the
>Rainbowfishes seemed adequate and reasonably well-balanced and it may just
>be a case of feeding too much. I must admit that I probably do feed a bit
>heavy - perhaps a carry-over from my Cichlid keeping days. However, perhaps
>there is another explanation. When we look at it there is very little known
>about the dietary habits of Rainbowfishes in the wild. It may well be that
>Rainbowfishes and other tropical fishes for that matter, feed heavy during
>the wet season when food is abundant and store any excess consumed to carry
>them through the dry season when food items are scarce. In other words,
>Rainbowfishes may have the ability to store excess proteins and fats in
>their body tissue rather than just passing it out. If we then maintain these
>fishes into the aquarium and feed them every day, then they will just store
>the excess causing lipodosis and eventually death.
>
>All this is of course only conjecture, but in the absence of other hard data
>it could be a possibility. Also, to add to this mystery, I have another 15
>Goyder River Trifasciatas in a 450 litre aquarium from the same brood and
>have not lost one specimen from that tank. These fish are the same age, size
>(if not bigger) and have been fed the very same diet as the other fish. They
>were separated about 8-12 months ago and share their aquarium with some
>Ambassis.
>
>I would be pleased to hear any suggestions, solutions or alternative
>theories. I for one will be drastically reducing the amount of food fed to
>my fishes.
> ........................................
> Adrian R. Tappin
> Home of the Rainbowfish
> http://www.ecn.net.au/~atappin/home.htm
> ........................................
>
>
BREED YOUR FISH
TODAY MAN'S OVER-
POPULATION IS
KILLING THE WILD
SUPPLY
Al Anderson
killiman at indy.net