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Breeds of Geese

Credits: Biovision-Infonet

There are two main types of domestic geese, derived from the wild Greylag goose (Anser anser) in Europe, and from the wild Swan goose (Anser cygnoides) in Asia.

The FAO’s Animal Genetic Resource database (AnGR) identifies 204 different breeds or varieties of geese. Many of these are thought to to have little economic importance because of their relatively low production or performance levels, or a limited geographic distribution.

CZECHOSLOVAKIAN WHITE (Anser anser)

This goose is a white goose with orange shanks and an orange beak. It is also known as the Bohemian goose. It has a relatively small body size, with the males weighing 5.0 kg and the females 4.0 kg but its egg production, averaging 45 eggs with an egg weight of 140 g, is fairly good for Anser anser type geese.

This means it can be useful as a female line in the production of a crossbred commercial goose.

**EMBDEN (Anser anser)**

The Embden is a white goose with relatively tight feathering, an erect stand, orange shanks and an orange beak. Most strains of Embden can be sexed on the down colour of the goslings, as males are a lighter grey than females. This difference is evident until the goslings are two to three weeks of age.

The breed has been relatively popular for many years in both Europe and North America. It is one of the larger breeds with males weighing up to 10.0 kg and females up to 9.0 kg.

It has a moderate egg production producing 40 eggs per year with an egg size of 170 g. The Embden is suitable for heavy type meat production but is probably of more value when used as a male line in the production of a crossbred commercial goose.

A small flock of geese
(c) S. Fontana, BioVision

**KUBAN (Anser cygnoides)**

This breed was developed at the Kuban Agricultural Institute (southern Russia) by crossing Gorki and Chinese geese. The feather colour is brown which results in relatively dark pin-feathers and thus an unattractive carcass.

These birds have orange shanks while their beaks and knobs are black to dark green. The adult body weight for the male is 5.2 kg and 4.8 kg for the female.

The advantage of this breed is that they have a relatively high egg production of between 50-60 eggs with an average egg weight of 150 g.

This makes the Kuban suitable for use as a female line in a crossbreeding programme provided it is used in such a way that the resulting commercial crossbreeds are essentially white and that the poor body conformation associated with the Kuban can be overcome.

**LANDES (Anser anser)**

Both the males and females of this breed are grey and their shanks and beaks are orange to yellow. This breed originated in France but has been widely used in a number of other countries, notably Hungary, for the production of fatty livers (Foie Gras).

Today there are a number of lines of the Landes that have been selected for their ability to produce fatty livers. They originate from the grey Toulouse geese, but today their feather phenotype is similar to the wild Greylag goose although they are much larger in body size.

The adult body weight of the male is 6.0 kg while that of the female is 5.0 kg. The annual egg production is 40 eggs per female per year with an egg weight of 170 g.

**POMERANIAN (Anser anser)**

Pomeranian geese originated from the north-western part of Poland but they are also present in northeastern Germany and the south of Sweden.

They come in three colours: white, grey or white and grey. In all cases, they have orange shanks and beaks.

The Pomeranian as been described as a solidly built goose with the adult body weight of the male being 6.0 kg and that of the female being 5.0 kg. The average egg production is 40 eggs per female with an average weight of 170 g.

**WHITE ITALIAN (Anser anser)**

The White Italian is a very popular breed in Europe and one often finds reference to it in the formation of local stocks. It is also a breed that has been well researched.

The White Italians reported on in this publication are those kept at the Koluda Wielka Experimental Station in Poland where they have been under genetic selection since the 1960s and where separate male and female lines have been developed.

Goslings of both lines can be sexed during the first ten days of life on down colour, as males are lighter in colour than females. As the name indicates, the adult plumage is white while the shanks and beaks are orange. In the male line, the average body weight of males is 7.0 kg and of females is 6.5 kg, while in the female line the average is 6.5 kg for the males and 6.2 kg for the females.

Annual egg production for the male line is 55-65 eggs while for the female line it is 60-70 eggs and egg weight for both is 160-180 g. The White Italian, at least for these strains, has the highest egg production of any of the Anser anser type breeds.

Thus these lines can be used directly as male and female lines respectively to produce two-way commercial crosses or the female line can be used to produce a crossbred female parent line. The White Italian and, particularly, these lines are therefore one of the breeds of choice for anyone wanting to produce geese for meat production.

For more information on goose production see the publication by Buckland and Guy, which includes sections on reproduction, breeding, flock management, housing, meat production, killing and processing. This publication also includes papers on goose production in South America, Indonesia, and Poland and Eastern Europe. References and Further Reading Buckland, R. and Guy, G. (2002). Goose Production. FAO Animal Production and Health Paper 154. FAO, Rome. FAO’s DAD-IS: Information system for the Global Strategy

Introduction to Geese

Credits: Biovision-Infonet

Introduction

Geese are part of the duck family but are much bigger than ducks and, unlike ducks, they feed entirely on grass and other herbage and spend very little time in water. When they do swim, they do not dive.

A goose can live in excess of 20 years, so if looked after and managed properly, it is an easy domestic animal to keep and can be a cheap and productive asset.

They have a reputation for being very good askaris, and some farmers keep them penned with livestock at night as they make a lot of noise if they are disturbed and can be intimidating if they attack as a flock.

Origins

Geese were one of the first animals to be domesticated, probably in Egypt about 3000 years ago (Buckland and Guy, 2002). They are found in most parts of the world, and can adapt to both hot and cold climates- as long as adequate shelter, especially shade, is provided.

They are especially well suited to aquatic areas and marshlands and are completely at home in warm, shallow waterways. However, commercial production of geese is currently important in only a few countries in Europe and Asia.

Limiting factors for goose farming in developing countries are that geese are not fully mature until two years of age and, except for the Chinese geese, they are not prolific layers. Their overall reproduction rate, therefore, is comparatively low.

In addition, the processing of geese is more complicated than processing chickens, particularly if down and feathers are involved. Technical skills are needed to pluck the birds efficiently and some equipment may be necessary in order to handle the down and feathers properly.

Geese belong to the family Anatidae, and were one of the first domesticated animals. The name “Goose” itself has its origins as one of the oldest words of the Indo-European languages – the proto-Indo-European root, ghans, from which the Sanskrit, Latin, Greek, Germanic, Norse, English, Irish and Russian names for the goose are derived.

A majority of wild geese of Europe, Asia and North America are migratory. There are two main types of domestic geese, derived from the wild Greylag goose (Anser anser) in Europe, and from the wild Swan goose (Anser cygnoides) in Asia.

The FAO’s Animal Genetic Resources database (AnGR) identifies 204 different breeds or varieties of geese. Many of these are thought to to have little economic importance because of their relatively low production or performance levels, or a limited geographic distribution.

Domestic geese come in a wide range of colours, sizes and shapes. In general, domestic breeds are much larger than their wild ancestors although they have in many cases retained their ability to fly.

There are two main types of domestic geese. The first are thought to have their origins in Europe, descendants of the wild Greylag goose (Anser anser) and the second are thought to have their origins in Asia, descendants of the wild Swan goose (Anser cygnoides).

Crosses between the domestic breeds which have originated from these two species of wild geese are fertile and in fact have resulted in a number of recognized breeds.

Understand geese as animals

Geese are tremendously social animals and form flocks. They are highly communicative – which we perceive as ‘noisy’.

They can live for many years. They are monogamous and loyal to their partners, as well as in their flock. They establish a pecking order, and once having established that, they do not need constant fighting.

They can become territorial in their breeding season. Unlike most birds, most geese species have males and females with similar feather coats. Males often protect females, and they protect their goslings, and can be very aggressive to humans.

Even though they are prey animals, their size and strength and the fact that they can fly make them quite bold animals, which can and dare to protect themselves. They thrive on habits and tranquillity and do not like changes, including new people around. Especially in their breeding season, they are very sensitive to change.

They are water animals, and should have access to a pond or somewhere, where they can swim. They forage and should be allowed grazing. Geese have been shown to be imprinted by humans, to see humans as their fellow animals and parents, and follow humans, if they were influenced by them during a certain sensitive period after hatching. Even if not imprinted as such, they can become very bonded to humans and greet as well as ‘talk’ to their keepers.

They have a very good memory, as domesticated animals for example regarding how different humans treat them.

Keeping geese in East Africa

Scarcity of land, labour and capital obliges small holder farmers in Africa to reorient their livestock production towards species that are cheap and easy to maintain and that provide animal protein as well as cash income.

Geese are particularly well suited to such systems. Mature geese are independent, larger than other poultry species and thus less vulnerable to predators. When kept in small flocks and allowed to roam the farmyard or field, they are adept scavengers, requiring less attention than any other domestic bird.

Geese adapt easily to captivity, and if small quantities of supplementary feed are provided in the evening they will even return home by themselves.

Geese require extensive space to become profitable. They cannot be economically raised in confinement.

Where farms have swamps or large water pools, such lands can be made profitable by means of geese. The birds practically feed themselves on pasture. All the breeding flock needs is a dry place to sleep and moderate feeding.

Geese are among the fastest-growing avian species commonly raised for meat.

Goose meat is fatter than other poultry meats, but it is well accepted by many local populations, including some in West Africa. In Egypt, geese are found widely as scavengers around the village.

Geese also huge eggs and rich fat for cooking, as well as soft down and feathers for bedding and clothing, which makes them particularly appropriate for providing farmers with a supplementary income. Geese can also be used as weeders and are good guard animals.

Sub-clinical mastitis

Dr.iCow’s Diary

Date: 28.01.2020

Dear Dr.iCow,

Yule ng’ombe wangu ameanza kupunguza maziwa asubuhi na jioni na simugonjwa. Shida ni nini? Ni Sylvester from Bomet, Kenya.

(My cow has started producing less milk in the morning and evening and the cow doesn’t look sick. What could be the issue?)

From Sylvester from Bomet, Kenya.

Discussion:

The cow belonging to Sylvester calved a few months ago but her milk yields have been going down by about 1 kg both in morning and afternoon milking. Feeding is good as before and the cow is not showing any signs of illness.

Dear Sylvester,

The reduction of milk production from your cow could be caused by subclinical mastitis which is a very common cause of sudden drop in milk yield in dairy cows. You may fail to notice the infection because it does not show clinical signs.

A cow with subclinical mastitis will appear unaffected by the illness, experience a reduction in milk yield potential and is a possible source of infection for other cows, who can become infected and show clinical mastitis or suffer from subclinical mastitis depending on a cow’s immune status. To be sure that she is free from subclinical mastitis it is important for a vet doctor to take milk samples from the cow for analysis, culture and sensitivity tests in a veterinary investigation laboratory –VIL. Please call a vet.

Other causes of reduction in milk production are; during heat or oestrus, ingestion of mycotoxins or toxic weeds in the forages or pastures, inadequate drinking water and dry forages, minerals imbalances, debilitating conditions or diseases and internal parasites.

Please consider the cow to have suspected subclinical mastitis until laboratory results are out. To avoid infecting other cows it is advisable to separate her from healthy ones and she should be milked last awaiting laboratory results ad treatment.

In dairy cattle mastitis assumes a major economic importance. Mastitis causative agents can be contagious, spread from cow to cow, or environmental from dirty or wet conditions in the cow’s area of stay like zero-grazing unit.

In clinical mastitis infection signs like udder redness and swelling can be seen. Subclinical mastitis is not readily detectable by manual palpation or visual examination using a strip cup and its diagnoses depend largely on indirect tests and hence the need to take milk samples for analysis in a laboratory.

Subclinical mastitis reduces milk production, decreases milk quality and suppresses reproductive performance. The cost of subclinical mastitis is higher than that of clinical mastitis.

Thank you.

From your Friend and Advisor,

Dr.iCow

Anthrax Disease

Dr.iCow’s Diary

Date: 28.01.2020

Dear Dr.iCow,

Anthrax signs in livestock. How can a farmer notice?

From: Mr. Lang’at, County: Bomet, Kenya.

Discussion:

A neighbour’s sheep had died suddenly and it was suspected it died of anthrax though farmers were not sure whether sheep can be infected by the disease.

Dear Mr. Langat,

Anthrax is a highly infectious contagious and is often a fatal disease of animals and is commonly seen in cattle, sheep, goats, wild animals, and can be transmitted to humans by contact with infected animals or their products. In case of sudden death in livestock, anthrax disease is the first suspected cause. Such a case should be reported immediately to the area veterinarian or area administration for immediate action. Farmers should be vigilant for anthrax and prompt reporting of suspected cases help in a great way to reduce contamination of affected farm.

Clinical signs for anthrax infection in an animal are; sudden death 2 to 3 hours of being apparently normal, animals may show trembling, high body temperature, difficult breathing, collapse and convulsions before death, blood may not clot after death resulting in some bloody discharge from mouth, nose anus and other body openings. Please do not open a carcass of a dead animal due to sudden death.

Anthrax infection is through ingestion of contaminated pastures, soils or fodder. Other animals in the pastures where sudden death has occurred should be removed immediately. Please call a vet immediately and follow the vet’s instructions regarding correct disposal of carcass, correct disinfection, decontamination and disposal of contaminated materials. The recommended method of disposal is by incineration.

A carcass of livestock animal from sudden death should not be moved. It should be tested for anthrax by the veterinarian or the county veterinary officers. Movement of animals and animals’ products from a suspected farm is suspended as anthrax testing is carried out.

Where anthrax is confirmed after veterinary examination and laboratory testing of the samples, the affected property and area is quarantined, exposed livestock are vaccinated, carcasses are disposed preferably by burning and contaminated site are disinfected.

Thank you.

From your friend and advisor,

Dr.iCow

Fish Information Source Links

Credits: Biovision-Infonet

Carole, R.E. and Ivano, N. (2005). Tilapia Farm Business Management and Economics. A Training Manual. Arkansas: Aquaculture/Fisheries Centre.
Carole, R.E.,Kwamena, Q. (2006) Aquaculture Marketing. United Kingdom: Blackwell Publishing. ISBN 0-8138-1604-1
Curtis, M.J. and Howard A. C. (1993). Economics of aquaculture. New York: Food Product Press, ISBN 1-56022-020
Department of Fisheries (DoF) (2006). Fisheries Statistical bulletin. Nairobi: Department of Fisheries.
FAO (2006). FAO Training Series: Simple methods for aquaculture CD-Rom. ISBN: 9789250056128
Agromisa publications on fish farming 21: www.agromisa.org
Karen L.V. (2001). Aquaculture Handout For Farmers. Sagana: Sagana aquaculture Centre.
Charo-Karisa H, Gichuri M (2010). Overview of the Fish Farming Enterprise Productivity Program. In: End of Year Report Fish Farming Enterprise Productivity Program Phase I, Aquaculture Development Working Group Ministry of Fisheries Development, Kenya
Mbugua H.M. (2008) A Comparative Economic Evaluation Of Farming of Three Important Aquaculture Species In Kenya
Ngugi, C. C., Bowman, J.R.and Omolo, B. O. (2007). A new guide to fish farming in Kenya. ISBN 978-0-9798658-0-0
Pillay, T.V. and Kutty, M.N. (2005). Aquaculture Principals and Practices United Kingdom: Blackwell Publishing. ISBN: 1-4051-0532-1
SRAC fact sheets srac.tamu.edu/ – SRAC 280 Pond Culture of Tilapia – SRAC 350 Small-Scale Marketing of Aquaculture Products – SRAC 381 Developing Business Proposals for Aquaculture Loans

Fish Predators

Credits: Biovision-Infonet

Some common fish predators and their control measures

Predator	Type of fish eaten	Control measure
Insects and insect larvae	Juvenile fish and eggs and fish just hatched.	i) Oil emulsion to prevent aerial breathing. ii) Use of fish that feed on insect larvae especially those that have gills and can remain in the bottom.
Frogs and toads	Juveniles of tilapia and catfish	i) Fence with frog proof wire mesh. ii) Clear bush around pond. Screen both in and outlets. iii) Use traps. Adult catfish and bass eat frogs.
Fish	all types of fish	i) Use screen in the inlets and outlets. ii) Do pond draining periodically
Snakes	Destroy larval and juvenil fish	Clear bush around the pond and fence properly, using cacti (crown of thorns).
Crocodiles, alligators and large lizards.	All types of fish	Proper fencing and keeping dense bushes cut down.
Turtles	Prey on catfish	Fencing around pond with wire mesh, trapping.
Birds: Wading birds e.g., Herons and egrets Diving birds. Kingfisher, fish eagle cormorants, pelicans	All types of fish and at all stages especially in shallow waters. Cormorants feed on fish just after the fish are fed- when they are most concentrated.	i) Proper fencing all round and then above with netting material or manila ropes/strings on poles with bright colored cloth or metal crossed over the pond. ii) cover ponds with nets or wire mesh, use flash guns, windmills that revolves and flash brilliantly and bells to scare the birds a way. iii) The birds can also be actively discouraged by destroying their nest.
Otters	Prey on large fish at night killing more than they can eat. They burrow and live under the roots of trees near the water. Otters are very clever They can even open latches on gates.	i) Proper fencing around the ponds. ii) The otters can also be trapped using special otter traps set in their passages. iii) Guard by use of trained dogs. iv) Fence the pond half way across and thus provide hiding places for fish. v) In general, measures to combat monkeys are also effective on otters’ meaning both are very difficult to control.
Man (theft)	All types of fish. This is also considered among the major predators through which fish are lost.	Extremely difficult to control and is most common in cage culture and other intensive fish farming. Can however be controlled by: i) Employing security personnel ii) Use of trained dogs iii) Hidden obstruction to prevent pond seining. iv) Fence farm and lock securely. v) Burglar alarms or electrified fence

If the situation is bad, then trapping or shooting can be used as the last resort in cases of birds and otters but in consultation with the authorities
Be careful when poisoning: predators, humans and non target animals can be affected.

Coccidiosis in Calves

Dr.iCows’ Diary

Date: 28.01.2020

Dear Dr. iCow,

My calf (male) is 7 days old. I have examined his faeces today and there is some blood in the last drop. Please advise.

From: Rose Muteshi, County: Kakamega, Kenya

Discussion:

Dear Rose,

The young calf with blood in the faeces could be having an infection due to exposure to dirty environment.Coccidiosis is caused by a protozoan parasites and can occur in young calves as young as four weeks and between 3 to 8 months of age. It affects all animals. The coccidia parasites are present in most normal animals.

Coccidiosis in young calves is caused by protozoan parasites which infect the lining of the alimentary tract causing loss of absorptive capacity of the gut with consequent diarrhoea with rapid dehydration. It may develop following stressful events like weather changes and unsanitary conditions like dirty environment. Treatment requires proper drugs in consultation with a vet doctor. Sulfa drugs like S-Dime tablets which you have already administered, and amprolium e.g. Coccid are available, and or Baycox oral solution if available. Also indicated is giving of oral fluid therapy to treat dehydration in cases of diarrhoea. Observe strict hygiene and move the calf to a clean environment free of contamination.

Clinical coccidiosis occur when a calf is exposed to heavy infections, stress like overcrowding, sudden change of feeds, poor nutrition and dirty environment and when a calf eats infected pasture, feed and water. Signs in calves suffering from coccidiosis include; loss of weight, profuse foetid diarrhoea with flecks of fresh blood and mucous, straining the perineum and tail, poor appetite, chronic wasting and unthriftyness. It is a treatable condition. Toltrazuril e.g. Baycox Æ oral suspension and diclazuril e.g. VecoxinÆ can be used for treatment and prevention of coccidiosis in calves. Other medications are sulfa and amprolium drugs.

Thank you.

From your Friend and advisor,

Dr.iCow

Fish Diseases

Credits: Biovision-Infonet

Occurrence of disease and parasites in farmed fish is mainly as a result of poor husbandry. Disease causing organisms are always in the environment fish live in and they cause few problems.

The pathogens naturally exist in an unstable “equilibrium” with their hosts until this balance is disturbed through environmental changes and human activities. Fish are stressed through inadequate dietary or environmental conditions.

The water quality parameters such as pH, temperature, dissolved oxygen may lead to outbreak of disease pathogens and parasites.

Prevention

It is better to try to prevent diseases than to wait to cure them once they start to cause problems. Avoid all kinds of stress (from feeding, handling, overcrowding, water quality) that affect resistance of fish

When you only cure fish without taking the cause of the disease away, the fish gets diseased again and again. To cure a fish disease is much more difficult and may require the services of a specialist. By the time proper treatment can be sought, the disease may have caused a lot of damage. Most disease problems in aquaculture result from events that can be avoided.

Some fish stressors that lead to diseases that need to be avoided are:

Poor handling of fish is a major cause of both bacterial and parasitic infections.
Translocation of fingerlings/fry from one place to another without proper care can spread diseases and parasites.
Increased nutrient levels due to intensive cage culture promote proliferation of parasites.
Pollution due to high levels of ammonia predisposes fish to succumb to large numbers of parasites. Human faeces may be a source of gut parasites especially to common carp.
Damages of fish by predators lead to secondary bacterial or fungi infections. The predators especially birds and mammals play an important role in life cycles of certain parasites.

Disease, parasites or pathogens may enter fish through gills, penetration of egg membrane, ingestion and rupture of skin, wounds or through the digestive tract.

Fish diseases may cause severe losses in fish farms because of reduced fish growth and production caused by lack of appetite, increased feeding cost because of inefficient digestion of feed and waste of uneaten feed, increased vulnerability to predation, increased susceptibility to low water quality and by death of fish

Main causes of disease in farmed fish

Disease, parasites or pathogens may enter fish through gills, penetration of egg membrane, ingestion and rupture of skin, wounds or through the digestive tract. Fish diseases may cause severe losses in fish farms through:

Poor feeds and feeding; When fish are not provided with the right food in the right way, nutritional diseases occur.
Exposure to extreme conditions or toxic environments
- Unsuitable water quality
- Extremes in pH towards acidic or basic conditions
- Presence of toxic gases such as ammonia
- Lack of dissolved oxygen
- Overcrowding and/or behavioural stresses, for example in storage or transport
- Improper and/or excessive handling
- Toxins in food such as fungal toxins in stored feeds ,pesticide residues etc
- Water pollution by agricultural or industrial effluents, sewage effluents, heavy silt loads.
Actual attack by disease causing organisms; Fish can be attacked by disease organisms, either externally (on the skin, gills or fins), or internally (in the blood, digestive tract, nervous system).

Preventing diseases through proper management

Prevention is better than cure, so it is very important to:

1. Ensure good water quality: sufficient supply, with adequate dissolved oxygen and free of pollution
2. Maintain clean pond environment by controlling silting, plants and proper phytoplankton and zooplankton balance. Regular pond disinfection is recommended, for instance by letting it dry in the sun for a week when empty.
3. Keep the fish in stress free conditions by controlling stocking density, keeping different sizes separate to reduce fighting, providing proper food, handling the fish properly etc.
4. Prevent the entry of wild fish by using screens so they can’t enter your farm. Ensure that all fish got from outside to the farm are clean without parasites or diseases.
5. Use good quality feed
6. Regular monitoring of the water entering the farm to ensure of its quality

Prevent the spread of disease within the farm by:

Controlling predators, particularly birds and mammals
Disinfect ponds regularly to kill both the disease organisms and their intermediate hosts
Avoiding water sharing among ponds
In case of disease outbreak, remove sick and bury diseased fish with quicklime away from the ponds; carefully treat infected ponds and disinfect all dead fish from the ponds immediately
Always disinfect pond and fish handling equipment

Common disease symptoms in fish

Behavioural signs:

Decreased feeding
Weak, lazy or erratic swimming
Floating on water belly up
Roughing against hard surfaces
Crowding/gathering at the inlet

Physical signs

Gaping mouth
Open sores, lesions, loss of scales, bloated belly
Pale, eroded, swollen, bloody or brownish gills
Abnormally folded or eroded fins
Cloudy or distended eyes
Presence of disease organisms on skin, gills, fins

Fish diseases can either be:

(i) Bacterial – which causes diseases like fin rot and tail rot

(ii) Fungal infections – wooly or cottony patches on the surface of fish, and gill rot causing asphyxia.

(iii) Parasititic

Ectoparasites – causing Black spot, white spot, fish louse and nematode.
Endoparasites – like the Contraceacum, and the Ligula intestinalis.

(iv) Dietary – High carbohydrate levels in trout feeds, lack of proteins and lipids will result to liver tumour.

Some common fish diseases and their prevention

PATHOGEN	SYMPTOM	PREVENTION
Fungus	Cottony grey-white or brown patches on the skin	Proper fish handlingAvoid handling fish in cold water.Low organic matter in water
Trematodes	Black spotsYellowish cysts on gills	Control snails and control predators like birdsRemove infected fish.
Bacteria	Loss of appetite.Fin and tail rot.Pale gillsFluid in abdomen	Improved water quality
Nematode (Contracaecum)	Round worm in spiral shape near gills	Not really a problem for fish health but leads to consumer dissatisfaction
Parasitic protozoan	Fish try to scrap their bodies on hard surfaces (flashing)	Salt, potassium permanganate or formalin bath.Keep water temperature near optimum range for that species of fish.

Nutritional Diseases

CAUSE	SYMPTOM	PREVENTION
1. Lack of proteins	Poor growth.Caudal fin erosion.Loss of appetite.	Feed protein rich food e.g. soya beans, slaughterhouse by-products, fish meal.
2. Lack of lipids	Poor growth	Feed with energy-rich foods

The following points should be followed in treatment of infected ponds.

Ponds with infections should be drained and badly infected fish culled.

Dry the pond under the sun for about seven days
Dampen the pond bottom
Spread Lime (Calcium carbonate) evenly over entire surface of pond bottom at the rate of 1500 kg/Ha
Wait for 15 days then restock the pond with healthy stocks.

Some common chemicals for use in fish farming

– Limes and agro-industrial by-products e.g. rice bran and molasses: Pests control in drained ponds.
– Organic poisons such as rotenone can control pests in filled ponds.
– Household bleach is a good disinfectant of non-metallic equipment and working areas.
– Chlorine bleach liquid and powder can be used as strong disinfectants for fish handling equipment.
– Common salt is cheap and easily available. Kills several disease organisms and have positive effects on the fish by stimulating appetite and increasing mucus secretion, improving resistance to handling.

–Formalin is toxic to fish particularly in soft water because it lowers dissolved oxygen levels, make sure treatment water is well oxygenated.

Fish Water Quality

Credits: Biovision-Infonet

Fish live and are totally dependent on the water they live in for all their needs. This means that we must understand the water quality requirements of the fish under culture very well.

Different fish species have different and specific range of water quality aspects (temperature, pH, oxygen concentration, salinity, hardness, etc.) within which they can survive, grow and reproduce.

Each species has its own optimum range, that is, the range within which it performs best. It is therefore very important for fish producers to ensure that the physical and chemical conditions of the water remain within the optimum range (the tolerance limits) of the fish under culture all the time. Outside these optimum ranges, fish will exhibit poor growth, erratic behaviour, and disease symptoms or parasite infestations.

Under extreme cases, or where the poor conditions remain for prolonged periods of time, fish mortality may occur. Pond water contains two major groups of substances:

Suspended particles made of non-living particles and very small plants and animals, the plankton.
Dissolved substances made of gases, minerals and organic compounds.

The composition of pond water changes continuously, depending on climatic and seasonal changes, and on how a pond is used.

It is the aim of good management to control the composition to yield the best conditions for the fish. For producers to be able to maintain ideal pond water quality conditions, they must understand the physical and chemical components contributing to good or bad water quality.

Mass trout mortality due to poor water quality
(c) Mbugua Mwangi, Kenya

Physical Aspects of Water Quality

Temperature

Fish are “cold-blooded” and therefore assume the temperature of the water they live in. Water temperature is therefore the most important physical factor for fish survival and growth. Body temperature, and thus the water temperature, has an effect on level of activity, behaviour, feeding, growth, and reproduction of the fish. Each species has its tolerance limits and optimum range. When water temperatures are outside the optimum range, fish body temperature will either be too high or too low, animal welfare is at risk and fish growth will be affected or the fish will even die.

Tolerance limits and optimum temperature ranges for commonly cultured fish species of Kenya (Nile tilapia, African catfish, common carp and rainbow trout):

Fish species	Lethal water temperature (degC)	.	Optimum temperature range for adults (degC)	Temperature range for spawning (degC)
	Lower	Upper
Oreochromis nilotica (Nile tilapia)	12	38	27-30	22-32
Clarias gariepinus (African catfish)	–	–	25-27	20-30
Micropterus salmoides (Largemouth bass)	2	35	23-30	17-20
Cyprinus carpio (Common carp)	2	36	23-26 (25)	Above 18
Oncorhynchus mykiss (Rainbow trout)	Close to 0	22	15-17 (16)	4-18

Turbidity

Fine solid particles suspended lead to a turbidity. Turbid Water can be said to be “cloudy”. Turbidity can result from suspended solids (clay) or plankton.

Clay turbidity in pond water (muddy water) can be harmful to fish and limit pond productivity. Clay turbidity in pond can be controlled by:

Treating affected ponds with animal manure at rates of 2.4 T/ha every three weeks or agricultural limestone, using recommended rates to improve soil pH and water alkalinity
Avoiding stocking species that stir up pond bottom mud e.g. the common carp
Designing water supply system such that muddy water can be diverted away from ponds

Plankton are small often microscopic aquatic plants (phytoplankton) and animals (zooplankton) found suspended in the water column. Phytoplankton form the base of the food chain while zooplankton form the second link in the chain in aquatic systems such as ponds.

Plankton are small often microscopic aquatic plants (phytoplankton) and animals (zooplankton) found suspended in the water. Phytoplankton form the base of the food chain while zooplankton form the second link in the chain in aquatic systems such as ponds. [In addition to their role as food for fish in ponds, phytoplankton produce large amounts of oxygen for the pond during the day by photosynthesis providing dissolved oxygen (DO) in ponds. Low phytoplankton density in ponds means less food and DO for the fish. On the other hand, too much (algal bloom) lead to minimized sunlight penetration causing algal deaths. Less phytoplankton and decomposing plankton also lead to less food and DO for the fish. Good water quality, in relation to plankton therefore means water with just right bloom. Visibility in a pond with the right plankton density should be about 30 cm. [/p/]

How to measure turbidity:

A simple method of measuring turbidity it to stretch one arm, and immerse it vertically into the water until the hand disappears from sight. Note the water level along your arm:

If it is well below your elbow, plankton turbidity is very high
If it reaches to about your elbow, plankton turbidity is high
If it reaches well above your elbow, plankton turbidity is low.

Suspended fish wastes are generally not a problem in semi-intensive aquaculture but in intensive systems, especially recirculation systems, they may be a major cause of poor water quality. Keep in mind that the production of 1 kg of fish produces 1 kg of waste. Up to 70% of the nitrogen in the system originates from fish waste, it builds up ammonia and nitrite levels and it reduces dissolved oxygen levels Chemical Aspects of Water Quality

pH and acidity
Alkalinity
Hardness
Dissolved gases: oxygen, carbon dioxide, nitrogen, ammonia
Salinity
Essential nutrients: N, P, K

pH and Acidity

Pond water may be acidic, alkaline or neutral. Depending on this, water will react in different ways with substances dissolved in it. It will also affect in different ways the plants and animals living in the water. The measure of the alkalinity or acidity of water is expressed by its pH value.

The pH value ranges from 0 to 14, with pH 7 indicating that the water is neutral. Values smaller than 7 indicate acidity and greater than 7, alkalinity.Fish production can be greatly affected by excessively low or high pH. Extreme pH values can even kill your fish.

The growth of natural food organisms may also be greatly reduced. The critical pH values vary according to the fish species, the size of individual fish and other environmental conditions. For example, fish are more susceptible to extreme pH during their reproductive seasons, and eggs and juveniles are more sensitive than adults.

Waters ranging in pH from 6.5 to 8.5 (at sunrise) are generally the most suitable for pond fish production. Most cultured fish will die in waters with pH below 4.5 and 10 or above. Fish reproduction and general performance can be greatly affected at pH below 6.5 and above 8.5.

How to correct the pH of your pond water

Pond water with unfavourable pH can be corrected by:

If the pH is below 6.5 (at sunrise), use lime and alkaline fertilizers
If the pH is above 8.5 at sunrise, you can use acid fertilizers

Ensuring that soil pH and acidity are within acceptable limits is a necessary part of managing the alkalinity, hardness, and pH of the water, which were discussed above. The key is to keep soil pH at 6.5 or above, which will usually maintain water pH, hardness, and alkalinity at desirable levels.

How to keep soil pH at the right level

Drying the pond for at least two weeks after each harvest before refilling and restocking.
Applying lime (preferably agricultural limestone) to the pond after each harvest. Normally lime should be applied to the pond bottom before it is refilled, but if necessary, it can be applied to the water surface after filling the pond. Only recommended liming materials and application rates should be used.

Pond water pH varies over the course of a 24-hour day. This variation is related to the light intensity which is important in photosynthetic activity of phytoplankton.

pH is lowest at sunrise and as photosynthesis increases as the light intensity increases, more and more carbon dioxide is removed from the water by the plants causing the pH to increase
A peak pH value is reached in late afternoon.
As the light intensity starts decreasing, which reduces photosynthesis less and less carbon dioxide is removed from the water; as respiration adds more carbon dioxide to the water, pH starts to decrease.
At sunset, photosynthesis stops, but respiration continues for the rest of the night. More and more carbon dioxide is produced, and pH keeps decreasing until sunrise, when it reaches its minimum.

Dissolved oxygen in fish ponds

Dissolved oxygen (DO) is essential for respiration and decomposition. Dissolved oxygen in water comes from atmospheric oxygen and photosynthesis.

The atmospheric oxygen diffuses and dissolves into the water. But the diffusion and its subsequent dissolves into water is a slow process. The major source of dissolved oxygen in ponds is photosynthesis.

However this process depends on the amount of light available to the aquatic plants in water (Phytoplanktons). Oxygen production decreases during cloudy days and stops at night. It decreases with increasing water depth while the rate of the decrease depending on the water turbidity.

How to measure Dissolved Oxygen (DO)

DO can be measured by chemical or by electrical methods. Chemical methods rely on the use of kits which can be bought from shops dealing with laboratory equipment. They contain chemicals and equipment necessary to determine the DO content with sufficient accuracy for pond management purposes.Electrical methods use an oxygen meter, this too can be bought from laboratory equipment shops but it is expensive. Using this equipment, DO can be measured directly from the pond at any depth. DO and water temperature should be measured at the same time so as to be able to relate the DO to the temperature. DO is expressed as mg of oxygen/litre of water (mg/l).

Dissolved oxygen (DO) requirements commonly farmed fishes in Kenya (in mg/l or percent saturation values)

Fish species	Ova and juveniles	Adults
		Minimum DO level	Preferred DO level at least equal to
Trout	Close to 100%	5 mg/l (50%)	8 mg/l or 70%
Common carp	At least 70%	3 mg/l (30%)	5 mg/l or 50%
Tilapia	At least 70%	2 mg/l	4 mg/l or 50%
African catfish	At least 90%	1 mg/l or less (aerial respiration)	3 mg/l or 35%

Fluctuating oxygen levels

From sunrise to sunset

Photosynthesis increases the DO level
DO production is higher on clear sky days than on cloudy days
The higher the phytoplankton population, the higher the DO production.

At night,

Photosynthesis does not take place
Respiration and decomposition which are the main activities taking place, reduces the DO content until sunrise
The higher the plankton population and dead matter, the faster the DO will fall

There may be very little oxygen left by morning and fish may suffocate if corrective measures are not taken. In over fertilised ponds, where there is very high plankton density and high turbidity, the DO content of the bottom water may become anoxic (without oxygen) even during the day. The fish will concentrate at the surface of the pond to survive. This will be much worse at night.

Where DO test equipments are not available, signs indicating reduced DO in pond water include:

Fish not feeding well or even stopping feeding
Fish coming to the water surface to breathe from the better oxygenated surface water (this is called piping).

The DO content of pond water can be increased in several ways:

Through design and management
Through structures that cause water to splash e.g. by use of cascades along the inlet canal and raised inlet pipes before the water gets into the ponds
By use of mechanical aerators for the emergency aeration of pond water

A simple way to ensure a good supply of atmospheric oxygen to fish ponds is in the design of the pond. The ponds should be designed such that they take maximum advantage of the winds. The ponds should be designed so that the lengths are parallel to the direction of the prevailing winds.
Proper pond management can also improve the DO content of the water. The following measures can be taken before any emergency happens:

Flashing the pond by removing the less oxygenated bottom water and replacing it with better oxygenated water
Use of water aerators e.g. mushroom blowers and paddle wheels

Alkalinity and Hardness

It is desirable to maintain both alkalinity and hardness at 40 – 70 mg Calcium carbonate per litre. This can be done by:

Where water is ‘soft’ or acidic and soils are acid, apply lime (agricultural limestone) to the pond soil at recommended rates before to filling the pond
Lime may also be added after filling by spreading it uniformly over the water surface.
In areas where soils are alkaline and hardness and alkalinity are high, application of lime is not required.
Note that proper management of hardness and alkalinity will usually eliminate the need to worry about pH.

Ammonia

Un-ionized ammonia (NH3) concentrations in pond water should be kept below 0.5 mg/l Concentrations of this form of ammonia, which is toxic to fish, are influenced by DO, pH, and alkalinity, therefore it is important to manage this by:

Maintain water alkalinity at 40 mg Calcium carbonate per litre or above
Keeping pH near neutral, and at least below 9.0
Keeping DO concentrations high

Toxic Materials

Substances toxic to fish and other organisms (herbicides, insecticides, and other chemicals) should be kept out of the ponds. Ponds should be protected by:

Not using insecticides, herbicides, or other chemicals (except for recommended inorganic fertilizers) in or near your pond. Be sure that the inlet water doesn’t contain herbicides and don’t rinse spraying equipment in the water used for fish. On organic farms those chemicals can not be applied.
Keeping agricultural runoff from the ponds
Avoiding spraying agricultural crops near ponds on windy days.