iCowApp – Page 27 – Portal for the icow Apps content

Fish Pond Construction

Credits: Biovision-Infonet

The importance of proper designs, construction and the need for involvement of experts during the process of setting up aquaculture production units is paramount. Ideally, production units should be designed in such a way to allow total control of:

What gets in or out
When it gets in or out
How it does this
How much gets in or out
Rate of getting in or out

The production site is of great importance. It does not only dictate the fish species to be produced but also important, the cost of construction is directly related to the nature and location of the site. A good site should therefore meet the following criteria:

Have water in quantity and quality needed for the proposed production. Not in a pollution prone area.
Suitable topography to allow cost effective setting up the proposed production facility and have adequate room for possible future expansion
Have soil suitable for pond construction (if ponds are planned).

A simple test of the suitability of a soil for pond construction:
- Dampen a handful of soil with water. Use only enough water to dampen the sample (do not saturate it).
- Squeeze the sample tightly in your hand.
- Open your hand:
  - If the sample keeps its shape, it is probably good enough for building a pond (sufficient clay present).
  - If the sample collapses and does not keep its shape, it is probably not good enough for building a pond (too much sand present)
The site be in a region or area that is suitable and allowed for aquaculture production
Well drained and away from flood-prone areas or at least having potential for flood control
Allow for acceptable effluent disposal as required by environmental management authorities
Have a climate suitable for production of the intended species
Have accessibility to a good and all-weather market
Have easy access to services and technical assistance

The final size of a fish farm is determined by: Amount of water available, the target production and the available capital. Intensive systems require less land compared to semi-intensive systems, to produce the same quantity of fish but require more capital to invest.

The number, size and the shape of ponds will be determined by:

Topography of the land and the shape and size of the land. Rectangular ponds are easier to manage
Intended use of the pond. Fingerling ponds should be smaller than fattening ponds.
The species to be produced
Frequency of harvest
Target quantity per harvest
Whether juvenile production is intended etc.

Pond design

Once the site has been identified, surveyed and the producer has made decision on the number and sizes of ponds that will be needed when the farm is fully operational, it is time to make a decision on the design of the ponds.

During the process of designing ponds, decisions on the following should be made:

Total area of the pond water surface (this is the actual pond size)
The length and the width of the pond water surface
The water depth and the total pond depth at the deep end
The slope of the dykes and the pond bottom
The size of the free board (height of dyke above water level)
The width of dykes

A cross section on an earthen fish pond showing the slopes and the dykes

Once this is done, all other pond dimensions can be calculated. The diagram below gives the relationships between various pond dimensions.

Calculations for the following design are based on the assumptions that:
– Dyke slope: 50% (0.5)
– Bottom slope: 1% (0.01)

Based on the above, the following apply:

Total pond length	d+4c
Total pond width	e+4c
Shallow end water depth	a-x
Shallow end total depth	b-x
Shallow end bottom width	e-4a-4x
Deep end bottom width	e-4a
Dyke top-Inner toe horizontal distance at deep end	2b
Dyke top-Inner toe horizontal distance at shallow end	2b-2x

Pond designed to take maximum advantage of the winds
(c) Mbugua Mwangi

Three-dimensional pond design
(c) Mbugua Mwangi

Steps in the construction

Step 1. Mark out the area that the pond will occupy using wooden pegs and strings and then remove all the vegetation.

Clearing vegetation from the pond site
(c) Mbugua Mwangi, Kenya

Step 2. Remove the top soil and keep it in a good location close to the site. It will be used to cover the pond bottom and the dyke tops to enhance fertility. Remember that if the soil is kept far away, this will increase the cost of pond construction since the soil will need to be brought back.

Step 3. Clear the area within the pond limit of all vegetation including the area within 10 m of dykes and pond structures and any access, water supply or drainage area.

Step 4. Establish a Temporary Bench Mark (TBM). A bench mark is a mark on the ground that establishes the elevation of a place and is used as a reference point for all other elevation. This will allow you to determine and check by use of leveling equipment (e.g. spirit level) the elevations of the dykes, canals and other structures. The Temporary Bench Mark should be set and permanently fixed in a protected location during the whole construction period.

Step 5. Using spirit level, measuring tape, pegs and strings, mark out:

The dykes
Dyke slopes
Inner and outer toes
The pond bottom

A site pegged ready for digging and filling
(c) Mbugua Mwangi, Kenya

Step 6. Using the determined pond depths and the actual elevations of the site, determine which areas need digging and which need filling. This is very important because it eliminates unnecessary movements of soil and thus keeps the construction cost at a minimum.

Step 7. Dig out the soil at the ‘dig’ areas and place it on the ‘fill’ areas. Most of the fill areas will be on the dyke position.

Dig the soil from the dig areas and move it to the fill areas
(c) Mbugua Mwangi, Kenya

Remove boulders and tree stumps from the pond
area.
(c) Mbugua Mwangi, Kenya

Make sure to remove boulders and tree stumps from the pond area.

Step 8. Once the soil is placed on the fill area, make sure that this soil is properly compacted. To achieve good compaction, place soil in layers not exceeding 15 cm in height and compact back to at least 10 cm. When constructing dykes, soil layers are place 20 cm inside on top of each other to reduce amount of work during dyke cutting.

Compact the soil properly
(c) Mbugua Mwangi, Kenya

Good dykes should:

Be able to resist water pressure resulting from the pond water depth
Be impervious
Be high enough to keep the pond water from overflowin

Shape the dike slope and the pond bottom
(c) Mbugua Mwangi, Kenya

To determine the height of the dyke to be built, take into account:

The water depth you want in the pond
The freeboard (upper part of a dyke that is never under water). It varies from 0.25 m for very small ponds to 1 m for very large ponds
Dyke height that will be lost during soil settlement. This varies from 5 to 20 percent of the construction height of the dyke
Dyke width depending on the water depth and the role the dyke will play for example transportation in the farm
- It should be at least equal to the water depth, but not less than 0.60 m in clay soil or 1 m in somewhat sandy soil
- It should be wider as the amount of sand in the soil increases

Getting the desired slope and uniformity
(c) Mbugua Mwangi, Kenya

Dyke slopes should be determined bearing in mind that:

Steeper slopes erode easily
The more the soil becomes sandy, its strength decreases, and slopes should be more gentle
The bigger the pond size, the stronger is the erosive power of the water waves
As the slope ratio increases, the volume of earthwork increases, and the overall construction cost and the land area required for the ponds increases

Note that the more gentle the slope, the more solid the pond, but very gentle slopes make ponds more expensive and make rooted weeds control difficult. A slope of 50% is the minimum recommended.

Fill the trench with moist clay and compact thoroughly
(c) Courtesy of Ngugi C. N., Kenya

The ability of the dykes to hold water can be enhanced by:

Using good soil that contains enough clay (about 25% clay is best)
Building a core trench (clayey core) within the dyke where the soil is pervious
Building a cut-off trench when the foundation is permeable
Proper compacting of the soil
Ensuring that the thickness of the dyke is appropriate

Newly built dykes should be protected against erosion by planting a grass cover on the crest of the dykes, on outer slope and on the free board.
The pond bottom should be constructed such that water drains towards a harvesting sump at the deepest part of the pond, in front of the outlet, where all the fish can be concentrated during complete draining of the pond.

Water intakes

Water intake weir for a trout farm
(c) Mbugu Mwangi, Kenya

Main water intakes are used for the overall regulation and transportation of water to the fish farm. They ensure constant supply of water and allow regulation of the amount of water to the farm allowing for diversion of what is not needed.
When setting up main the intake, consider:

The levels of the water source (river, stream, etc.) in relation to the elevations of the water supply structure and the ponds themselves and where the water will eventually leave the farm.
The depth from which you want to take the water (surface, lower levels or the complete depth of the water supply source) at the intake

An open water supply canal lined with concrete slabs.
(c) Courtesy of Ngugi C. N., Kenya

There are several types of canals depending on their use:

Feeder canals to supply water from the main water intake to the fish ponds
Drainage canals to take away water from the fish ponds
Diversion canals to divert excess water away from ponds
Protection canals to divert water runoff/floods away from the fish farm

All canals should be well designed to have the required water carrying capacity at the required rate. If the water quantity is low and the rate of delivery is slow, pond will take too long to fill.

Pond inlets

Water inlet for a trout raceway
(c) Mbugua Mwangi, Kenya

There are two common types of inlet structures used in Kenya:

Pipe inlets
Open inlets

When designing and constructing an inlet:
a) Place the inlet at the shallow end of the pond
b) Make sure that the bottom level of the inlet is at the same level as the bottom of the water feeder canal and at least 10 cm above the maximum level of the water in the pond
c) Design the inlet structure to be horizontal, without a slope.
d) Make it wide enough to fill the pond completely in reasonable time
e) Make it such that water splashes and mixes as much as possible when entering the pond.
f) Provide a screen to keep unwanted fish and other organisms out
g) Control mechanism e.g. gate valves

Pond Outlets

Pond outlets are built to:

Keep the water in the pond at its optimum level, which should be the maximum water level designed for the pond
Allow for the complete draining of the pond and harvesting of the fish when necessary

A good outlet should ensure that:

The time needed to drain the pond completely is reasonable
The flow of the draining water is as uniform as possible to avoid disturbing the fish excessively
Fish are not lost even during the draining period
Water can be drained from any pond levels
Allow for overflow of excess water
Can be cleaned and serviced easily
Construction and maintenance costs are kept at a minimum

In most cases, outlets have three main elements:

Water control plugs, valves, control boards, screens or gates
A collecting sump inside the pond, from which the water drains and into which the fish is harvested
A conduit through the dyke through which the water flows out without damaging the dykes or the drainage canal

For small rural ponds, investing in elaborate outlets may not be necessary. Complete drainage of the pond can be done by cutting the dyke open at one of the deepest point of the pond. Repairing the dyke should not take more than two hours.
Materials that can be used to construct pond outlets and inlets include bamboo poles, PVC pipes, wood, bricks, cement blocks or concrete.

A cross section of a completed pond showing the position of various structures.
(c) Mbugua Mwangi

Pond construction costs

Through experience in Kenya, one pond of 100 m2 will take 15 people about 8 days to complete, working 8 hours a day.

This will cost 15 x 8 x KShs X
X = wages per day

Note that the construction cost will vary with soil types and the weather. Rocky soils are hard to work on and construction will be more expensive. Black cotton soils are very difficult to work on during rainy weather and this too will increase construction cost.

Inlet canal and outlet canal: Include the cost of cement, sand, pipes, valves etc. Consider other incidentals costs especially due to the nature of the site and the prevailing weather.
Available pond construction experts in Kenya charge about KShs 150 to 500 per square meter of pond depending on the soil type and weather (2009 rates).
This should give the total cost of constructing one pond but not setting up the fish farm.

Remember that many but small ponds are more expensive to construct as compared to a few but larger ponds. Small ponds also waste a lot of space in comparison. However, very large ponds take long to fill and drain and are also difficult to manage.

Hatchery and Fingerling Production

Credits: Biovision-Infonet

Although tilapia breed freely in ponds, it is important for farmers (producers) to consider using properly produced fingerlings. They need to invest in hatcheries for fry and fingerling production. Quality fingerlings in tilapia aquaculture are very important. For this reason it is advisable for farmers to generate their own fingerlings if they can not ascertain the quality of those from other sources. Poor fingerlings result in poor harvests.

Developing a hatchery will allow the farmer to have ready fingerlings whenever he needs them. As long as the demand for fingerlings exists, a well-managed hatchery can turn out to be a good business.

Three methods of tilapia fingerlings production are commonly practiced in Kenya:

open ponds (most commonly used)
tanks
hapas in ponds (net enclosures)

For these methods, fry are collected from the spawning units and stocked into fertilized ponds for rearing to the fingerling stage before they are stocked into grow out ponds.

Open Pond method

Poorly constructed earthen ponds
(c) Mbugua Mwangi, Kenya

This is the simplest and most common method of tilapia fingerling production in Kenya. A properly constructed and well fertilized pond serves both for breeding and rearing fry. Brooders are stocked into the ponds and allowed to spawn naturally. The brood fish are stocked at the rate of 100 to 200 kg/ha at a sex ratio of 1:3 or 1:4 (males to females). A female brood fish of 90-300 g produces as much as 500 eggs per spawning. They should produce 6 – 15 fry/m²/month. To increase seed production, use larger brooders. Brooders of 1 – 1.5 kg can produce 45 fry/ m²/month. For this case, you need to harvest every 17-19 days.

Harvesting fry from the ponds is done every 15 – 21 days or more frequently with water temperatures above 25degC). The brooders can be used for 3 – 5 years. Fry harvesting should be done by hand scoop nets along the edges of the pond to minimize pond disturbance and fry mortality.

The Tank method

Circular tanks for a trout hatchery
(c) Mbugua Mwangi, Kenya

Tank-based hatcheries are relatively expensive to set up. The tanks should be circular in shape and can be made of concrete, plastic, fiberglass or even metal. The tanks should be 1-6 m diameter with a water depth of 0.5-1 m. Diet should contain 30-40% crude protein and daily supply at 1-2% of body weight. Fry can be collected every 10 – 14 days. Yields of up to 400-3,000 fry/m2/month can be realized using this method. Tanks are easy to manage but are relatively expensive to set up compared to ponds and hapas.

The ‘hapa’ method

A hapa is a cage like net impoundment placed in a pond for holding fish for various purposes. They are made of fine mesh netting material. The mesh size is such that the fry or fish inside can not escape. The ideal hapas is 3 m long, 3 m wide, and 1.5 m deep.

When using hapas to generate fingerlings, stock brooders should be weighing about 100 to 200 g at a ratio of about 1:5 to 1:7 males to females. Stock the brooders at a density of 4 – 5 brooders / m2. Hapas should be inspected for fry every day. Remove the fry using a scoop net after two week and stock them into tanks, other hapas, or in a rearing pond. Fry-production in hapas range from 150 to over 880/ m2/month. Fry should be fed 4 times/day until the fry reach the desired size (5 g). Use a diet in powder form at the rate of 5-10% of the total body weight per day

Production in hapas range from 150 fry/m2/month to over 880 fry/ m2/month.

Breeding hapas in a fish pond
(c) Mbugua Mwangi, Kenya

Inspecting tilapia breeding hapas
(c) Mbugua Mwangi, Kenya

Feeding

Advantages of using this method are easy handling of fry ad brooders, a high production per unit, uniform fry of the same age, minimal losses and hapas can be set up in a pond with other fish.

Disadvantages of the hapa method tha it is more demanding than open ponds and tanks, mortalities may occur due to agressiveness during spawning, the fish has to be fed, poor water quality is likely due uneaten feed and fish waste and mesh will get clogged limiting water circulation and need periodic scrubbing. In stormy weather hapas can be destroyed and the material will degrade in sunlight and need replacing. Fish may easily escape from damaged hapas.

Disadvantages of the hapa method

Management is more demanding compared to the other methods
Mortalities may occur due to agressiveness during spawning
Feeding is a must
Hapas can be destroyed during stormy weather
Hapa material will degrade in sunlight and need replacing
Fish may easily escape if the hapa is damaged
Localised poor water quality is likely due uneaten feed and fish waste
Hapa mesh will get clogged limiting water circulation and need periodic scrubbing

Harvesting Fish

Credits: Biovision-Infonet

Harvesting

Fish produced for consumption should be harvested when they reach market size. In Kenya, tilapia are ready for harvesting within six to nine months depending on the size at stocking, target harvest size, water temperature and level of management employed. The time of harvesting is determined through regular sampling which should be done monthly. A day or two before harvesting, feeding and fertilizer application should be stopped. During harvesting:

Fish should be checked for off flavours
Fish should be harvested during cool weather
Harvesting and transportation equipment should be set up well in advance to ensure reduced stress and minimal fish mortality.

Tilapias are best harvested by seining for partial harvesting and complete drainage for complete harvesting. Once harvested, fish should be handled with care and transported to the market while still fresh.

De-Worming

Credit: Dr. iCow

Worms can be grouped as round worms, tape worms and flukes. They can be controlled by good feeding and watering practices and regular use of effective broad-spectrum anthelmintic or dewormers.

In organic herds, it is not permitted to use medicine for prevention of diseases but parasite infections should be prevented through good management practices, such as clean grazing areas and making sure that the young calves are also fed other feed and can have access to milk as long as possible, so that they do not rely heavily on grazing, and by not mixing calves of different age groups in the same flock. Treatment should depend on worm counts, as recommended by the local veterinarian, and the general state of health of the animal.

Deworming dairy cows at early lactation consistently increases milk yields more than any other time of treatment.

If your livestock have worms, it is important to make the right choice of the dewormers as some are not recommended for treating pregnant animals.

When de-worming livestock it is important to ensure the right worms are being treated with the right medication in the right dosage. Always consult a veterinarian for advice in determining which dewormer is best to use in your livestock.

It is advisable to deworm pregnant livestock after the first trimester. For cows avoid deworming the first 3 months of pregnancy.

In sheep and goats the critical period to avoid deworming is in the first 2 months in order to avoid abortions and birth defects in lambs and kids. Some dewormers cannot be used just before, during and just after breeding.

Animals of different weights require different dosages of medications, thus knowing and recording an animals weight is not only good for general management practices but also to enable you administer medications safely and cost effectively.

Deworm your animals 1 month or 30 days before artificial insemination –A.I. or natural service. Dewormers have conditions of use due to their toxic effects on the developing fetus. Some dewormers are restricted during the first trimester e.g. albendazole based products.

It is advisable to deworm during morning hours after milking and deworm all your livestock on the farm at the same time.

Observe the manufacturer’s recommend withdraw periods for milk and meat after deworming.

Weighing cows for de-worming

To get the correct weight of your cows, measure them with a weigh tape, readily available from most agro dealers. This is a tape measure that is calibrated to give you a chest reading that is associated with an animals weight. There are different weight tapes for different breeds of cattle.

To get the correct weight, do the following:

a) Measure the cow with it’s head up. When the head is down the chest expands and you will get the wrong measurement.

(b) Measure the heart girth region just behind the shoulders, not the abdomen

Positioning weight tape. Measurement is taken across the heart girth region just behind the shoulders, NOT the abdomen

c) Make sure the tape touches the animal and is not too loose nor too tight as this will give a wrong reading.

Please read the product’s label, understand and follow the manufacturer’s instructions. Do not under dose or over dose when administering a dewormer.

Recording date, weight and dosage of worming medicine

Administering correct dosage of worming medication

Restrain the animal properly to avoid unnecessary struggles and injuries. Hold cows neck up straight and slowly feed the worming medicine into the side of its mouth. Rub often to allow the cow to swallow. Do not administer the medicine quickly or you may choke the cow. If the medicine gets into the lungs of the cow it may get pneumonia. Be careful.

Ensuring the right dosage is used is both economical and efficient. The wrong dosage may result in ineffective treatment. Overdosage is a waste of your money.

Fish Integrated Systems

Credits: Biovision-Infonet

Integrated systems

Tilapia and Catfish farming integrated with poultry
(c) Mbugua Mwangi, Kenya

Manure application can be made easy by placing animal production units adjacent to or over the fish ponds so that fresh manure can easily be delivered to the pond on a continuous basis. This also allows the feed wasted by the animals to fall into the fish pond and utilised by the fish. Effective and safe manure loading rates are maintained by having the correct number of animals per pond surface area.

Chicken/fish farming

Maximum tilapia yields are obtained from the manure output of 5,000 to 5,500 chickens/ha, which deliver 100 to 113 kg (dry weight) of manure/ha/day. Several crops of chickens can be produced in one fish production cycle.

Duck/fish farming

Pig house with fish pond
(c) Stephen Gikonyo, Kenya

Ducks are grown on ponds at a density of 750 to 1500/ha. The ducks are raised in confinement, fed intensively, and allowed a small portion of the pond where they forage for natural foods and deposit their manure. Ducks reach marketable size in 10 to 11 weeks and therefore staggering production cycles is needed to stabilize manure output.

Pig/fish farming

Pond harvesting using a sein net
(c) Mbugua Mwangi, Kenya

Approximately 60 to 70 pigs/ha are required to produce a suitable quantity of manure (100 to 115 kg of dry matter/ha/day) for tilapia production. The pigs are usually grown from 20 to 100 kg over a 6-month period. In certain cultures and religion, where pigs are considered unclean, used of pig manure might reduce the marketability of the fish.

Fish Feeding

Credits: Biovision-Infonet

Compared to terrestrial animals, fish have lower energy requirement (they are more efficient), they require less lipids in feed (except for cold water species such as trout), they have higher protein requirements and fish can absorb certain mineral element directly from the water.

There are three types of food used in aquaculture:

In organic fish farming the natural feeds and supplemented feeds not treated with chemicals can be fed:

1. Natural food occurs naturally in fish ponds. This includes detritus, bacteria, plankton, worms, insects, snails, aquatic plants and fish. Their occurrence and abundance depends on the water quality and in particular fertilization.

2. Supplementary feeds usually consist of cheap feed materials available locally such as terrestrial plants or agricultural by-products. Many kinds of feed materials may be used as supplementary feeds for your fish such as:

Terrestrial plants: grasses, legumes, leaves and seeds of leguminous shrubs and trees vegetables
Aquatic plants: water hyacinth, water lettuce, duckweed
Small terrestrial animals: earthworms, termites, snails
Aquatic animals: trash fish
Rice: broken, polishing, bran, hulls
Wheat: middling, maize bran: gluten feed, gluten meal
(Oil/cakes after extraction of oil from seeds of mustard, coconut, groundnut, cotton, sunflower, soybean. This group of feeds contains chemicals and is not used in organic fish farming.)
Cottonseeds
Brewers wastes and yeast
Slaughterhouse wastes: offal, blood, rumen contents
Manure: chicken droppings, pig manure

Supplementary feeds are available in two forms:

Dry feedstuffs such as cereals and cakes with about 10% moisture. These are easier to transport, store, and to distribute to the fish.
Wet feedstuffs such as blood, rumen contents, molasses and brewery wastes with 30 to 50% moisture. Moist feeds do not keep well, and only small quantities should be prepared at a time. These feeds require special treatment, for example mixing with dry feedstuffs to absorb part of the moisture or drying to improve storage life before feeding.

3. On large scale intensive fish farms complete feeds are made from a mixture of carefully selected ingredients to provide all the nutrients necessary for the fish to grow. They are made in a form which the fish find easy to eat and digest. These feeds are difficult to make on the farm and are usually expensive to buy. Under intensive systems, feed provided to the fish must meet all their dietary requirements. The fish rely wholly on exogenous feeds. The feeds must be complete in terms of nutrients supply. Fish dietary nutrient requirements

Protein

Important tissue building component
Also important in repairing worn out tissues
Important to juveniles for growth.

In semi-intensive production, protein comes from the algae (resulting from proper pond water fertilization) and exogenous feeding with supplemental feed. However in intensive production of tilapia, the diets should have 28-32% protein.

Carbohydrates

Provides energy needed by the fish to carry out its physiological activities like respiration. Any excess is converted and stored as fat.

Fats

They are utilized to supply energy like the carbohydrates. They also provide structural support and act as precursors to physiological chemical processes. Excess of fats reduce the marketability of fish. Diets for adult fish should not have high amounts of fats because it accumulates and reduces flesh quality. However, trout is able to utilize fats much more effectively and can ingest considerable amounts with their diet.
Deficiency in essential fatty acids result in reduced growth, de-pigmentation, erosion of fins, fatty liver and even shock.

Vitamins

Vitamins are required in very small quantities but play a major role in the chemical processes within the fish body. Deficiency results in poor health and deformities. When fed with a variety of green plants, vitamin supply will be sufficient. In artificially produced feeds, a balanced mix of vitamins and minerals (premixes) can be obtained from specialized feed manufacturers. They should be used in proportions that meet the nutritional needs of the fish under culture.

Minerals

These inorganic elements are needed in smaller or larger amounts for various metabolic functions. Fish can obtain some of them through the gill surfaces into their bodies. Some important minerals include calcium, potassium, sodium and magnesium. When fed with a variety of plant material, mineral supply will be sufficient.

Other feed additives

In intensive, non organic fish farms feed additives could be used in fish feeds includes attractants, binders, dyes and medicinal agents like vaccines. In ponds and other outdoor fish farms one should be very careful not to pollute and spoil the surrounding water and animal life in it.

FISH FEEDING

i). Small fish need more food than larger ones.
ii). Where there is plenty of natural food, less supplementary feed should be used
iii). Where low stocking densities are used, less supplementary feeds are used
iv). The better the quality of the feed (low FCR), the less the quantity needed to feed the fish
v). More food is required in warm water than in cooler water.
vi). It is therefore recommended for producers to constantly adjust the feeding throughout the production cycle for better results.
vii). FCR will be affected by overfeeding, poor feeds, poor pond fertilization for semi-intensive production and poor fish health.

Some practical guidelines in feeding fish to adjust the feeding throughout the production cycle.

Small fish need relatively more food than larger ones. The small ones are less efficient in using their feed.
* When plenty of natural feed is available, less or no supplementary feed should be used. I general supplementary feed is more expensive.
* Where stocking densities is low in a pond, less supplementary feeds are used. Fish can grow on the available material
* More food is required in warm water than in cooler water, depending on the temperature zone of the species.
In ponds it is not easy to estimate the amount of feed to provide. However, underfeeding should be avoided because it will lead to loss in fish production. Overfeeding should be avoided because it is uneconomical (it raises the production costs) and it may also result in poor water quality

A producer must at all times know approximately how many fish there are in each pond to be able to estimate the amount of feed to apply. It therefore recommended that a producer conducts fish sampling in the ponds at least on monthly basis and keeps record of it.

How to feed:

For most fish, feeding twice a day is sufficient – at about 10 am and 4 pm. Earlier than 10 am in the morning, the water is a bit cold and oxygen levels are low so this is not a good time to feed the fish. If you feed at close to the same time and at the same place in the pond every day, the fish will learn to come for the feed

Recommended feeding rates for tilapia or tilapia/clarias polyculture in g per fish per day

Age in month	1-2	2-3	3-5	5-8	8 and more
Weight of fish (g)	5-20	21-50	51-100	101-200	Over 200
Wheatbran (g/day)	1	1-3	3	4	5
Pelleted diet (g/day)	1	1-2	2	3	3-4

FEED CONVERSION RATIO (FCR)

Feed Conversion (FCR) is the ratio of the quantity of food given to the fish (in kg) to the weight gain of fish (in kg), over a given period. It can be used to estimate the quantity of feed needed in a production season for a given crop of fish. For example, if the estimated FCR for a certain feed is 3:1, it means that a farmer needs 3kg of that feed to produce 1kg of fish. The better the quality of the feed (low FCR), the less the quantity needed to feed the fish. It is a measure for intensive, industrialized farming were all feed is weighed (and processed). When fish is fed with alga, other plant material and droppings from animals etc. it is impossible and not sensible to account a feed conversion ratio. FCR will be affected by overfeeding, poor feeds, poor pond fertilization for semi-intensive production and poor fish health.

FEED FORMULATION

The purpose of feed formulation is to ensure that the aquaculture diets meet the nutritional needs of the fish under culture during it various stages of growth. Therefore, for one to be able to formulate a specific feed for a particular fish, they need to know the following nutritional needs as regards the fish:

Crude protein
Crude fibre
Energy
Specific amino acids and
Ash

The square method – How to formulate fish feeds: The square method
The most common and simplest method of formulation diets in Kenya is the square method. For example, if the desired feed should contain 25% protein, and there are two ingredients to use (fish meal with 50% protein and rice bran with 8%)

The square method of formulating fish feed
(c) A Wachira, Kari, Kenya

i). The desired protein level is inserted at the centre
ii).The two ingredients with their protein levels are placed at each corner on the left hand side of the square
iii). The differences between the centre and each feed ingredient are placed at each corner on the right side diagonally opposite the ingredient (ignoring the plus or minus signs)
iv). The upper right hand corner in this example indicates the proportion of fish meal needed and the lower one that of rice bran
v). This can be expressed as

Ratio i.e. fish meal:rice bran 17:25
Percentage 17/42 = 40.5% for fish meal and, 25/42 = 59.5% for rice bran.

Fertilization and manuring

Where the natural pond productivity is enhanced through water fertilization, reasonable production can be achieved without exogenous feeding. Although yields will be lower than those obtained with exogenous feeding, fertilization will reduce the quantity and expense of feeding. Application of an inorganic fertilizer high in phosphorus should be done prior to stocking fish to create an algal bloom. Tilapia productivity is stimulated mainly by an increase in phosphorus and to a lesser extent by an increase in nitrogen. The inorganic fertilizers used in Kenya are DAP (Diammonium phosphate) and CAN (Calcium ammonium nitrate) and are not allowed in organic fish farming, while animal manure is allowed.

Animal manure is widely used in Kenya in fish production in earthen ponds. The quality of manure as a fertilizer varies depending on the source animal and the quality of feed fed to the animal. Pig, chicken and duck manures increase fish production more than cow and sheep manure. Animals fed high quality feeds (grains) produce manure that is better as a fertilizer than those fed diets high in crude fibre. Fine manures provide more surface area for the growth of microorganisms and produce better results than large clumps of manure.

The manure should be composted before being used in the fish pond. It spreads easier and does not take oxygen from the water for the process of composting while minerals are kept in the material during composting

Manure should be distributed evenly over the pond surface area. Accumulations of manure on the pond bottom produce low oxygen conditions (during decomposition) in the sediment resulting to reduced microbial activity and sometimes result in the sudden release of toxic chemicals into the water.

Methods of applying manure

Crib method: A compost crib constructed using wooden sticks at one or more sides of the pond. It helps fertilize the water gradually. The manure in the crib requires frequent turning to facilitate the release of nutrients.
Bag method: A bag is filled with manure and tied to the corner of the pond. The bag is shaken weekly or daily to release nutrients.

Manure application rates for ponds

Manure application rates depend on the size of the pond, which is expressed as surface area of the water in the pond. The recommended rate is 50 g of dry matter per m2 per week i.e. 5 kg/100 m²/week.

The maximum rate depends on the quality of the manure, the oxygen supply in the pond and water temperature. If early morning DO is less than 2 ppm, manuring should be reduced or stopped until DO increases. When water temperatures are less than 18deg C, manure application should be discontinued. At low temperatures the rate of decomposition decreases and manure may accumulate on the pond bottom. A subsequent increase in temperature could then result in oxygen depletion.

Agricultural Lime

Used to improve soil quality, which helps the organic and chemical fertilizers to work better. It also helps to clear up muddy water.
In red soils; about 20 kg per 100 m² can be applied. Black cotton soils may require a little more.

Some characteristics of organic and chemical fertilizers

Allowed in organic fish farming: Organic (farm manure)	Not allowed in organic fish farming: Chemical: DAP, Urea, MAP, TSP

Contains trace minerals and vitamins.	Contains only what the label says
Uses oxygen to decompose.	Does not use oxygen when dissolving
Is highly variable in composition depending on feeds given to the animals and bedding used	Varies little in composition from what is indicated on the label.
Can help reduce turbidity due to clay silt in the ponds	Does not reduce turbidity
Can help reduce seepage in ponds	Does not act on seepage
Some of the ingredients can be consumed directly by the fish	Not directly consumed by the fish

Lumpy Skin Disease

Dr.iCows’ Dairy

Date: 30.01.2019

Case №: 06/12020

Signs of lumpy skin disease.

From: Daniel, County: Bomet, Kenya.

Discussion:

Daniel called with a concern of cattle having skin problems in his area, Bomet County.

Dear Daniel,

Lumpy skin disease (LSD) is a viral disease that affects cattle and is a very devastating disease. It is a notifiable disease. Please report such a case to the nearest veterinary or agriculture office near you.

The disease presents with a high fever, swollen nodules of about 2 to 5 cm in diameter which are found all over the animal’s body, on the skin and other parts of the body including mucous membranes of the respiratory and gastrointestinal tract and the disease can be fatal.

Like all other viral diseases there is no specific treatment for LSD. The only available treatment is supportive care for the cow which include wound care spray like Alamycin spray or CKL-Healing Oil for treatment of skin lesions. Please call a vet to give supportive therapy for the sick animals.

The disease is best prevented and controlled through vaccination which is given by the county veterinary department once in a year.

Lumpy skin disease – LSD is a viral disease of cattle and is very devastating with skin lesions which can be severe and permanent, lesions in the mouth, pharynx and respiratory tract resulting in rapid deterioration in condition, emaciation, chronic debility in infected cattle, and this can persist for months. Sick animals should be removed from healthy ones and given supportive treatment.

Thank you

From your friend and advisor,

Dr.iCow

Making Feed Concentrates

Dr.iCows’ Diary

Date: 31.01.2019

Case №: 05/2020

Dear Dr.iCow,

Give me the formula of preparing local dairy meal.

From Frida, County: Meru, Kenya

Discussion:

Frida is having a bumper harvest of maize and wheat and wanted a simple formula on how to make dairy meal for her cows using some of the harvest with other additions. Dairy cows require balanced diets with energy, proteins, vitamins, mineral supplements and free access to clean soft fresh drinking water. The dairy cows should be fed adequate and high quality forages as it is the base of high milk production.

Dear Frida,

It is important to observe the following when making homemade dairy feeds:

i. Source the ingredients from reliable suppliers.

ii. Mix the ingredients thoroughly.

iii. The feeds should be stored in a cool dry place.

The nutrients to be included in the dairy feeds are energy and the main source is maize, wheat, rice, sorghum and barley, proteins and sources are cottonseed, sunflower, soya beans cakes and fodder legumes, minerals and vitamins and these are included in premixes. With readily available ingredients like maize, wheat or rice bran, maize germ, cotton seed cakes, sunflower cakes, feed grade lime or di-calcium phosphate, minerals supplements and premixes if available, a simple formula like; maize germ – 35%, wheat or maize bran – 35 %, sunflower or cottonseed cakes -30%, minerals supplements -1%, is advisable.

Remember: forages have high crude fibre. Good quality forage is the base of high milk production and should be fed at the right stage of growth and this is usually around flowering. Consider growing forages to reduce costs and increase milk production. Conservation of forages like silage and hay do assist greatly with fluctuations of quality and adequate fodder.

Concentrates for high yielding dairy cows involves a combination of many ingredients which are blended and mixed in the right amounts and proportions.

Total Mixed Ratio -TMR, should be encouraged where cows are fed based on milk production and growth rate of young stock. It has the advantages of mixing all feeds forages and concentrates, minimizes cost per litre of milk and eliminates fear of grain overload.

Thank you

From your friend and advisor,

Dr.iCow

Foot and Mouth Treatment

Dr. iCow’s Diary

Inside of cows mouth suffering from foot and mouth disease. Photo Credit ZooLink/ILRI

Date: 31.01.2019

Case №: 04/2020

Dear Dr.iCow,

Please may I know how to treat FMD?

From: Charles, County: Kitui, Kenya

Discussion:

Charles has observed blisters in his cow’s mouth and some wounds near the hooves. The cow is having poor appetite and he suspects it could be suffering from Foot and Mouth Disease which has been reported around his area.

Dear Charles,

Foot and Mouth Disease is a notifiable disease. Please report such a suspected case to the nearest veterinary officer or practicing veterinarian in your area for immediate action.

FMD is a viral disease and is highly communicable disease affecting all cloven footed animals. The disease spreads by direct contact, indirectly through infected water, hay and other feedstuffs, pastures, manure, farm attendants, vermin and birds.

It presents with fever, profuse salivation, vesicles and blisters in the mouth, teats, the udder, scrotal skin, interdigital space and above hooves, lameness and reduction in milk production. Precautions is taken by isolating and segregating sick animals from healthy ones, and inform a veterinary doctor immediately. Like all viral diseases there is no specific treatment for FMD.

External treatment of the wounds or ulcers with an antiseptic solution and applying a healing and soothing wound product like CKL-Healing Oil would help in the ulcers healing and prevent flies attacks. Strict control on movement of animals, feeds, fodder, vehicles and people from infected areas or farms is very important in controlling an outbreak.

FMD is prevented through vaccination and the vaccination is carried out 2 times in a year at an interval of 6 months under the annual vaccination program by veterinary department.

Foot and Mouth Disease – FMD is a viral disease of cloven hoofed animals; cattle, pigs, sheep and goats. Other cattle in the herd will show clinical sings in 1 to 2 days and the spread is dramatic.

Thank you

From your friend and advisor,

Dr.iCow