Physical quality affects nutritional value of the fish feeds

Posted on by TheFishVet - Richmond's School of Fish

Aquaculture Nutrition Volume 17, Number 6 (December 2011)

Nutritional responses in rainbow trout (Oncorhynchus mykiss) fed diets with different physical qualities at stable or variable environmental conditions

Authors: T.S. AAS1,2, B.F. TERJESEN 1, T. SIGHOLT 3, M. HILLESTAD 3, J. HOLM 4, S. REFSTIE1,5, G. BAEVERFJORD 1, K.-A. RØRVIK6,7, M. SØRENSEN6,8, M. OEHME1,6,7, T. ÅSGÅRD1,6 Author Affiliations:

1: Nofima, Sunndalsøra, Norway
2: Centre for Research Based Innovation in Aquaculture Technology (CREATE), SFI, SINTEF Sealab, Trondheim, Norway
3: BioMar AS, Trondheim, Norway
4: BioMar A/S, Brande, Denmark
5: Aquaculture Protein Centre, CoE, Department of Basic Sciences and Aquatic Medicine, Norwegian School of Veterinary Science, Oslo, Norway
6: Nofima, Ås, Norway
7: Norwegian University of Life Sciences (UMB), Department of Animal and Aquacultural Sciences, Ås, Norway
8: Aquaculture Protein Centre, CoE, Department of Animal and Aquacultural Sciences, Norwegian University of Life Sciences, Norway

Source: Aquaculture Nutrition, Volume 17, Number 6 (December 2011) Page Numbers: 657 – 670 Available Full Text:

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Abstract: Rainbow trout with initial body weight 1144 g were fed two diets with high (feed A) or low (feed B) water stability for 6 weeks. During the last 2 weeks either stable or fluctuating oxygen saturation, salinity and temperature was introduced. High water stability of the feed was associated with harder pellets, less dust formation and less broken pellets compared to feed with low water stability. During the first 4 weeks, feed intake was 23% higher in trout fed diet B than in those fed diet A. Fluctuating environment resulted in a severe drop in feed intake for both dietary groups. At termination of the trial, stomachs of trout fed feed B contained mashed pellets and free water and oil. Stomachs of trout fed feed A contained more intact pellets and little fluid. The apparent digestibility of protein, starch, dry matter and energy was highest in feed A. The apparent digestibility of P and Zn was highest at stable environment, and the absorption of P was highest from feed A. In conclusion, physical quality affected the nutritional value of the feeds, and differences in nutritional value at stable or fluctuating environment appeared to be related to feed intake.

Citation: T.S. AAS, B.F. TERJESEN, T. SIGHOLT, M. HILLESTAD, J. HOLM, S. REFSTIE, G. BAEVERFJORD, K.-A. RØRVIK, M. SØRENSEN, M. OEHME, T. ÅSGÅRD . Nutritional responses in rainbow trout (Oncorhynchus mykiss) fed diets with different physical qualities at stable or variable environmental conditions. Aquaculture Nutrition, Volume 17, Number 6 (December 2011), pp. 657-670,

URL: http://ejournals.ebsco.com/direct.asp?ArticleID=495C9BEF6CD1522EF1DA

What is the best net to use?

Posted on by TheFishVet - Richmond's School of Fish

What is the best net to use for fishes?

Pictured are several nets you can use and their physical properties are summarised.

The black net: small holes, soft flexible material, knotless.
The white net: medium-sized holes, soft flexible material, knotless.
The green net: fine holes, semi-flexible material, knotless.
The blue net: large holes, flexible material, knotted.

My preferred choice is a net would have a soft material to support the fish’s body, be knotless so that it will not scratch the fish and small holes to prevent fins and lips from getting caught. But those fish with spiny fins, the rubbery net or the fine sieve-like net may be preferable to prevent the fin spines from becoming tangled in the net.

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Yours sincerely,

Dr Richmond Loh
BSc BVMS MPhil (Vet Path) MANZCVSc (Aquatics & Pathobiology) DipPM CMAVAVeterinarian / Adjunct Lecturer Murdoch University / Secretary Aquatic Animal Health Chapter ANZCVS
The Fish Vet, Perth, Western Australia. Mobile Veterinary Service for fish and other aquatic creatures.
http://www.thefishvet.com.au
Ph: +61 (0)421 822 383

Vitamin K in fish nutrition

Posted on by TheFishVet - Richmond's School of Fish

Aquaculture Nutrition Volume 17, Number 6 (December 2011)

Vitamin K in fish nutrition

Authors: C. KROSSØY 1, R. WAAGBØ 2, R. ØRNSRUD 2 Author Affiliations:

1: Department of Biology, University of Bergen, Bergen, Norway
2: National Institute of Nutrition and Seafood Research (NIFES), Bergen, Norway

Source: Aquaculture Nutrition, Volume 17, Number 6 (December 2011) Page Numbers: 585 – 594 Available Full Text:

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Abstract: Vitamin K belongs to the lipid soluble vitamins, and occurs naturally as phylloquinone (vitamin K1) and menaquinone (vitamin K2). In addition, there is a synthetic provitamin, menadione (vitamin K3), primarily used as a vitamin K source in animal feed. Menadione is unstable during feed processing and storage and the dietary content may reach critically low levels. Recent publications also question the availability of menadione in feed for salmonids. Vitamin K plays vital roles in blood coagulation and bone mineralization in fish, but the suggested minimum requirement varies considerably depending on the vitamin K source used. Vitamin K deficiency is characterized by mortality, anaemia, increased blood clotting time and histopathological changes in liver and gills. However, one should assess both inherent and supplemented forms of vitamin K in feeds for exact determinations, as relevant novel feed ingredients of plant origin may be sufficient to meet the requirement for vitamin K. The current review gives an overview of the biochemical role of vitamin K, and discusses vitamin K requirement in fish in light of updated literature, with special emphasis on salmonids.

Citation: C. KROSSØY, R. WAAGBØ, R. ØRNSRUD . Vitamin K in fish nutrition. Aquaculture Nutrition, Volume 17, Number 6 (December 2011), pp. 585-594,

URL: http://ejournals.ebsco.com/direct.asp?ArticleID=4879AEBD3D321DCF386C

What is ‘dropsy’?

Posted on by TheFishVet - Richmond's School of Fish

"Dropsy" is often used by hobbyists to mean bacterial septicaemia with consequent "bloating", protruding scales, etc. in freshwater fishes. This is true in some cases, but is not always true.

For me, as a veterinarian, "dropsy" is a non-specific sign of fluid build up within the fish due to failure of fluid balance. Not all fishes with bacterial infections end up with "dropsy" and not all conditions presenting as "dropsy" are due to bacterial infections.

This fluid build up may be due several reasons including the failure to keep water out, the failure to excrete fluid or the over-production of fluid. To simply things a little, the fish maintains its fluid in balance by properly functioning skin/mucus barrier, gills, kidneys and cardiovascular system. If there is damage to any of these systems (e.g. skin ulcers from fungal infections in barramundi, bacterial gill disease in guppy, kidney cysts in goldfish, ovarian cancers in koi), then fluid may build up in the fish.

Thus it is essential to get a proper diagnosis of the condition so that you know what to treat for.

Shark saves human

Posted on by TheFishVet - Richmond's School of Fish
———- Forwarded message ———-
From: Dr. David Scarfe <DScarfe@avma.org>
Date: Thu, Sep 29, 2011 at 6:16 PM
Subject: AquaVetMed: Squalamine’s Antiviral Properties
To:

September 29, 2011

Sharks’ Virus Killer Could Cure Humans, Study Suggests

 

“Remarkable property” already effective against six types of viruses. Sharks aren’t just tough on the outside—a substance in their bodies can stop viruses in their tracks, a new study says.

 

A cholesterol-like compound found in dogfish sharks’ tissue has been shown to combat several viruses that cause hard-to-treat human diseases, such as dengue fever and hepatitis, a new study says. Called squalamine, the compound is already in human clinical trials for cancer and eye disorders, and several hundred people have been exposed without major side effects.

 

The new study revealed that squalamine can also disrupt a virus’s life cycle and prevent it from replicating in both tissue cultures and live animals. Though there are plenty of drugs to treat bacterial infections, there are few pharmaceuticals that are effective against viruses. Current antiviral drugs are highly specific—each targeting just one strain of a virus—but strains can easily mutate and become resistant to the medication.

 

“It’s a whole new approach to treatment of viral disease,” said study leader Michael Zasloff, of the Georgetown University Medical Center. “It’s very possible we could cure several diseases we [now] treat as chronic infections.”

 

“Eureka Moment” for Shark-based Antiviral Drug

Zasloff discovered squalamine in 1993 while searching for antibacterial agents in sharks, which are immune to some diseases, including all viruses. He found that squalamine—which “looked like nothing else that had ever been described or discovered”—inhibits the growth of blood vessels,  suggesting the molecule could potentially stop cancer cells from multiplying. Human research eventually led to Zasloff’s “eureka moment,” when he realized squalamine can also disable viruses, he said. “I could see [how it works against viruses] almost as if it were a moving picture,” he recalled.

 

Squalamine is a positively charged molecule, so when it enters a cell, the molecule immediately sticks “like Velcro” to the cell’s inner membranes, which have negative charges, Zasloff said. By doing so, squalamine “pops off” any positively charged proteins that were attached to the cell membrane—an action that does no harm to the cell, Zasloff noted. When a virus invades a cell, it expects those proteins to be present on the cell membrane. Without them, the virus can’t reproduce. “There is no other compound known to science that does this—this is a remarkable property,” Zasloff said. It’s also one that has apparently served sharks well for hundreds of millions of years—and possibly explains the creatures’ evolutionary success. The shark’s “antiviral defenses have been extraordinary,” Zasloff said. “It has adapted a very remarkable immune system and stayed with it.”

 

Squalamine Effective Against Human Viruses

In the study, squalamine thwarted infection of the dengue fever virus in human blood vessel cells and of hepatitis B and D in human liver cells—and with little harm to sharks. Shark tissue is no longer required to produce squalamine, which has been synthesized in the laboratory since 1995.

Zasloff and colleagues also discovered that squalamine inhibited yellow fever, eastern equine encephalitis virus, and murine cytomegalovirus in lab animals—in some cases curing the subjects, according to the study, published this week in the journal Proceedings of the National Academy of Sciences.

 

Current squalamine compounds can access only cells that have …

 

See the source (http://tinyurl.com/3ft4rgt) for the full story.

 

[The PNAS study is accessible from http://tinyurl.com/3swqcpt. ADS-Mod.]

 

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AquaVetMed e-News provides information to veterinary and veterinary-allied subscribers concerning aquatic animal medicine, health, welfare, public health and seafood safety, obtained from a variety of sources (largely AquaVetMed subscribers). While provided by the American Veterinary Medical Association’s, Aquatic Veterinary Medicine Committee and are for public distribution, they do not necessarily reflect the opinion of the AVMA or the veterinary profession. See the AVMA Terms of Use (http://tinyurl.com/29h2rf) for further information.

 

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Now on: Twitter – Blog – Facebook – Linkedin – Flickr 

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Yours sincerely,

Dr Richmond Loh
BSc BVMS MPhil (Vet Path) MANZCVSc (Aquatics & Pathobiology) DipPM CMAVA

Veterinarian / Adjunct Lecturer Murdoch University / Secretary Aquatic Animal Health Chapter ANZCVS
The Fish Vet, Perth, Western Australia. Mobile Veterinary Service for fish and other aquatic creatures.
http://www.thefishvet.com.au
Ph: +61 (0)421 822 383

 

 

A closer look at fish feeding – Part 7 – References used for posts on fish nutrition – by Jessie Poon

Posted on by TheFishVet - Richmond's School of Fish

References

Cho, D. P. (1999). An Introduction to Nutrition and Feeding of Fish. Fish Nutrition Research Laboratory .

Craig, H. (2009). Understanding Fish Nutrition, Feeds, and Feeding. Virginia Tech .

Kesena, E. J., & Arimiche, N. A. (2010). Improving the quality of fish feed through Omega-3-Fatty acid inclusion in diet. Agriculture and Biology Journal of North America , 654-657.

Loh, R., & Landos, M. (2011). Fish Vetting Essentials. Richmond Loh Press, Perth, 73-77.

Lovell, T. (1998). Nutrition and feeding of fish. Aquaculture Series , 55-65.

Soyaqua. (2008). Retrieved 7 22, 2011, from Storage and Handling of Feeds for Fish and Shrimp: http://www.soyaqua.org/pdf2/asafeedhandstorepub.pdf

Soyaqua. (2008). Fish Nutrition, Feeds and Feeding. Retrieved 7 29, 2011, from Soy in Agriculture: http://www.soyaqua.org/asaimusbtech/lvhdcagemanual/fishnutrition.pdf

A closer look at fish feeding – Part 6a – The Price of Good Food – by Jessie Poon

Posted on by TheFishVet - Richmond's School of Fish

Remember, the price of the food is directly related to the quality. Good quality foods should have a strong fishy fragrance, similar to the smell of the fish sauce that you get at the Vietnamese restaurants.

A closer look at fish feeding – Part 6 – Health and nutritional deficiencies – by Jessie Poon

Posted on by TheFishVet - Richmond's School of Fish

Health and nutritional deficiencies

The biological definition of optimum health in fish is the absence of disease, physical stress, and the ability to maintain growth, reproduction and stable metabolism.
Reduced growth is the most common clinical sign of any deficiency, however, for each vitamin and mineral type, deficiencies may present in more specific ways. These are tabulated below (Craig, 2009).

Table 1: Vitamins deficiencies and their symptoms

Vitamin

 Symptoms/ signs

Vitamin A

Eye/ vision problems (haemorrhagic eyes, eye lens deformation, eye lesions), oedema, haemorrhagic kidneys and skin.

Vitamin C

Anorexia, low disease resistance, slow wound healing, cartilage deformities, poor growth, scoliosis, haemorrhagic skin, liver, kidney, intestine and muscles.

Vitamin D

Scoliosis, tetany (white muscle), low bone ash, calcium, phosphorus.

Vitamin E

Nutritional myopathy, oedema, light skin colour, reduced reproductive activity, ceroid deposition, kidney and pancreas degeneration.

Vitamin K

Slow blood clotting, skin haemorrhages, anaemia

Vitamin B1 (thiamin)

Low haemoglobin, lethargy, poor appetite, skin haemorrhages.

Vitamin B2 (riboflavin)

Cataracts, cloudy eye lens, eye lesions, dark skin colouration, anaemia, fin erosion, anorexia.

Vitamin B3 (niacin)

Anorexia, oedema, lethargy, reduced co-ordination, skin lesions, loss of appetite, tetany.

Vitamin B5 (pantothenic acid)

Clubbed gills, eroded gill membranes, erratic swimming, liver necrosis.

Vitamin B6

Convulsions, rapid breathing/ gasping, erratic swimming, nerve disorders.

Vitamin B7 (biotin)

Muscle atrophy, gill degeneration, fatty liver, colon lesions, increased skin mucous.

Vitamin B12

Anaemia, poor appetite, low haemoglobin.

(Cho, 1999) (Soyaqua, 2008)

Table 2: Mineral deficiencies and their symptoms

Mineral

 Symptoms/ Signs

Magnesium

Renal calcinosis, poor growth, lethargy.

Iodine

Hyperplasia of thyroid gland, goiter.

Zinc

Cataracts, slow growth, skin and fin erosion.

Copper

Deformed collagen and bone development

Iron

Anaemia, low haemoglobin.

(Cho, 1999) (Soyaqua, 2008)

Luckily for us, good quality fish foods suited to a variety of fish species are easily available at your local fish shop. The staff at Boronia Aquarium can help you choose the right kind of food to satisfy each and everyone of your fishes.