FEED RESOURCE ASSESSMENT

Prepared by- Sweety Singh
Department of Aquaculture
TamilNadu Dr. J. Jayalalitha
Fisheries University

 Feed resource Assessment is also called
evaluation of feed resources, which include
physical, chemical, biological and
microbiological evaluation of fish feed or
feed resources.
 Quality of aqua feed and feed ingredients are
tested by evaluation methods.

 Both the aqua feed and feed ingredients can
be tested by the following evaluations:
 1. physical evaluation
 2. Chemical evaluation
 3. biological evaluation
 4. microbiological evaluation
 Evaluations of a feeds and feed ingredients
are more important than formulations.
 Evaluation may be done by adopting various
procedures.

 To check on the accuracy of manufacturing
process in arriving at a finished feed of
desired concentration.
 To measure the nutrient loss during
manufacture and storage.
 To predict nutritional value of particular
formulation.

 ADVANTAGES OF PHYSICAL EVALUATION
1. No cost is required.
2. No skill is required.
3. Easy to perform when compared to other
evaluation methods.
4. Quicker method.
5. Minimize adulteration of final product.

 It indicates only qualitative aspects and not
quantitative one.
 The first step in assessing the quality of
ingredients and processed feeds are to
examine or inspect its physical
characteristics.
 The criteria included in the physical
characteristics are:

1. Purity of ingredients- with the aid of
microscope one can confirm purity of
ingredients( identifying foreign contaminants
or adulterants).
2. Particle size and distribution
3. Density
4. Water stability
5. Texture
6. Feed shape and pallet quality
7. Homogenity of ingredients
8. Colour and contrast
9. odour

 Among the nine factors listed, the factors
such as pellet stability, shape and density is
very important because the property greatly
influence the extent of feed utilization.
 The following are the few quicker methods,
which help to assess the quality of feed and
feed ingredients before purchase:

1. Feed should have uniform colour and
shape.
2. Avoid spots in the feed which indicate
improper mixing of ingredients.
3. Avoid dark colours in feeds( which indicate
poor quality ingredients or over cooking)
4. Feed should not have any impurities.
5. Feed should be free from fungi etc.
6. There should not be any caking of feed.

 Push your hand into the feed bag and draw it
out.
 Presence of powder sticking to your hand is
not good which indicates poor processing of
feed.
 While broadcasting in to fish ponds, the
powder would be blown away, reducing the
quantity of actual feed and resulting in
wastage and inefficiency.

 Fresh fish smell indicates good feed.
 Smell of heavy oil indicates poor oil quality
or poor soya oil used without deodourising.

 Good feed should be slightly salty and give a
sweet after tastes, indicating good fish meal.
 Bad and bitter taste indicates rancidity of oil
used.
 A clean bite also indicates that moisture
content is low.

 Test by putting feed into glass of water and
the shape should be maintained at least two
hours.
 Some colour should have diffused into water
within 30 min.
 It also indicates attractant used the feed has
dispersed.

 It is carried out by two simple methods:
 1. qualitative evaluation
 2. quantitative evaluation

Take 10 gm of pellets in 500 or 1000 ml beaker
Add 850 ml water
Gradually stir with a magnetic stirrer or hand stirring
for every 10 min for a fixed time
Look for visual observation( time taken for the feed to
disintegrate in water )

Reporting of the results as water stability in terms of
duration ( in hrs)

Take measured quantity of feed
suspended on a 2-3 mm mesh
screen repeatedly immersed or
submerged in and out of water
After particular time,
filter the feed through 20
mesh screen

Dry the residue at 100oC for
1 hour
Compare residual weight
to the original wt in
terms of percentage

1. Put a piece of feed into a glass beaker
2. Observe the sinking rate and express the
results in terms of length or diameter of
the feed / second and expressed for 1.5 m
depth of water.
Water stability of feeds is greatly influenced by
a number of factors.
 Composition of diets.
 Manufacturing processes.
 Binders used.

 Ingredients which are difficult to grind or to
have no binding properties should be kept to
a minimum (e.g. Rice bran, bone meal).
 Hydroscopic ingredients such as salt, sugar
and molasses absorb water, making the feed
moist and crumbly even before being
disposal.
 Generally, stacking products have good
binding properties and gelatinization of the
starch in the manufacturing process renders
the final product more stable.

 Grinding increases the surface area of a feed
and thereby permits more space for steam
condensation during conditioning processes
resulting in harder and more desirable
pellets.

 It increases the hardness and water
durability of pellets.
 Binding reduce the void space in the
mixtures and thus provide a more compact
and durable pellet.

 PROXIMATE ANALYSIS: COMPOSITIONS AND
DETERMINATIONS
 The compositions of categories in proximate
analysis normally considered are:
 WATER- WATER
 It is determinated by drying a sample in a
hot air oven until a constant weight is
reached.
 5 hours of drying in vaccum oven at 95- 100
oC or 2 hr drying at 135oC.

 Essential amino acids, non essential amino
acids, free amino acids, amines, nucleic
acids.
 It is determinated by kjeldahl procedure in
which N2 content is directly measured using
a conversion factor 6.25.
 Most protein have 16 per cent N in their
composition.

 Triglycerides, phospholipids, sterols, fat
soluble vitamins, miscellaneous lipids (waxes
etc).
 It refers to the fat or lipid content for
sample.
 Using soxhlet apparatus, dry sample is
extracted with hot ether.
 After extraction, the ether is evaporated and
weight of the material extracted is
determined.

 Insoluble polysaccharides (cellulose, chitin,
hemicelluloses).
 It measures the material remaining in a
sample after it has been boiled in weak acid
base minus the inorganic residue.

 Monosaccharides, oligosaccharides, soluble
saccharides, water soluble vitamins.
=100 –(% moisture + ash+ %fibre+ % of fat+ %
protein)
Or
=dry matter- (% ash + % fibre+ %fat + %protein)
All dry matter basis.

 Essential elements, non essential elements,
toxic elements.
 It measures inorganic materials that remain
after a sample is burned at 600o C.
 This temperature is sufficient to burn the
organic material is a sample.

 Two major concerns with lipids are hydrolytic
and oxidative rancidity.
 Both are undesirable in dietary lipids and in
finished feeds.

 It is caused by the hydrolytic or liberation of
fatty acids from triglycerides and is detected
by elevated levels of the fatty acids in a fat
or oil.

 It is caused by the reaction of 02 with double
bands of unsaturated fatty acids.
 the products are hydro peroxides- peroxides-
aldehydes- ketones.
 The methods used are:

 It measures the initial products of lipid
oxidation.
 Good quality oils usually have PV<1 mili
equivalent.

 It measures another intermediate product of
lipid oxidation.
 TBA numbers in oils increase with decrease in
oxidation.
 More TBA numbers, less oxidation takes
place.

 It measures the presence of aldehyde rather
than intermediate product in a sample.
 It is useful method for oil, not for feeds
because of colour interference caused by
chromogens in the diet.

 It is a rapid test which indicates oxidative
rancidity when a red colour appears in a
sample mixed with phloroglucinol.
 Red colour indicates presence of aldehydes.

 Fish meal is often tested for ash and NaCl
content to meet the specifications required
by many fish food industry.
 5-6 percent NaCl in fish meal is undesirable.

 Some of the ANFs can be destroyed by heat
treatment.
 Those that cannot be destroyed include
gossypol in cotton seed meal; phytic acid in
soyabean meal and cotton seed meal.

 The quality of protein in a protein source is
decided by the quantity of essential amino
acid content present.
 The EAA content of source is compared with
that of a standard protein.
 The usual standard protein used by the
nutritionist is hen’s egg white.

 Cs is calculated as follows:
 Limiting amino acid in test protein *100
Limiting amino acid in whole egg protein

 This method does not provide any
information on chemical composition, but it
provide more information about nutritional
value.
 BE of feed ingredients and finished feeds
involve feeding fish and analysing some
aspect of fish performance and or diet
digestibility.

 BE methods can be divided into 3 general
categories:
 Retention studies or carcass deposition
 Loss studies
 Performance studies

 In which the deposition of nutrient in the
carcass over a short time in measured.
 The retention of specific nutrients or energy
in the carcass of fish over a specific time
period can be a useful way of evaluating
availability and balance of amino acid and
essential elements. Carcass deposition may
also be expressed as apparent retention
(AR).

 AR =
 (Carcass nutrient content at end of expt)
_ (Carcass nutrient content at start of expt)
Nutrient intake during experiment

 in which the various losses of ingested
feeds via the faces, urine andg ills are
measured.
in which some measure of growth are
used to evaluate and compare feeds.

 In other words, Biological Evaluation
methods are organized into 3 groups.
 General methods used for various
nutrients.
 Methods used for proteins
 Methods used for energy.

 GROWTH
 Over a specific time period, growth of groups of
fish fed various experimental diets are
calculated and compared.
 DAILY INSTANTANEOUS GROWTH RATE (GW).
 SGR or GW = inW, - lnWo/T.
 W1= Wt. at the end of study
 Wt0 =at start of study
 T = Time interval in days. To convert 'GW' to per
cent increase in Wt/day (%W/day),
 use per cent W/day (eGw -1) x 100

 FCR (Feed Conversion Ratio) Apparent FCR =
Food given (Supplementary feed + Natural feed)
Weight gain/(g)
 FCE
 Feed conversion efficiency - It is the reciprocal
of FCR and converted in to per cent
Wt gain
x100
Food consumed

K=Weight (g) x 100
Length (cm)3
 The relationship between weight (w) and length (1)
can be used to determine condition factors for fish.
 In farmed fish, condition induces may be used to
confirm visual inspections as to whether the fish have
a typical conformation or are too big or too thin.
 The results obtain may predict a change of feeding
level or a switch to a feed type with a different
nutrient density. (Rain bow trout - 1.3 - 1.6; Atlantic
salmon-1.0 -1.2; Channnel catfish-1.0 - 2; Common
carp-1- 2.5).

 PER - Protein. Efficiency_Ratio-
 It is measure of wt gain/unit protein fed and is a
useful method to compare protein in a single
experiment.
 PER is calculated as PCR = Wt gain (g)/Protein fed on
dry Wt. basin (g)
 PCE-final carcass protein - initial carcass
protein/protein fed x 100
 PCR =Protein gained/protein compound
 Net Protein Utilization (NPU) or BV x Digestibility
 It is measure of the protein gain during an
experimental period/ unit protein absorbed by the
fish
 (NPU - Final body protein - Initial body protein/Total
protein fed x 100).

 Apparent NPU is calculated as follows:
 (Protein content of fish (Protein content of
fish
at end of expt.) at start of expt.)
 Dry protein fed (g) x Protein digestibility.

 BV measurements are used to determine the
percentage of absorbed N2 retained by a fish by
measuring nitrogen excreted during a test period. BV
is thus similar to carcass deposition or apparent
retention.
 1. APPARENT BV =
 100 XFeed N - (Faecal N2 Urinary N2 + Branchial N2)
Food nitrogen
 TRUE BV
 Food N - (Faecal N - (Metabolic faecal N) -
(Urinary N - (Branchial N)
Nitrogen fed

 Protein conversion Ratio (PCR) =
Protein gained (g)
Protein consumed
 Assimilability of protein =
Protein consumed - Faecal protein
x100
Protein consumed

 Manufactures should be aware that bacterial
contamination is an ever-present threat in fish feed
manufacture.
 In fish feeds, a number of bacterial species are commonly
found.
 A programme of periodic monitoring of ingredients and
finished feeds for total bacterial counts, coupled with an
aggressive programme of in-plant sanitation and use of
commercial antimicrobials in the feed would be prudent
practices for all fish feed manufactures.
 Test include:
 Total aerobic bacterial count (cfu)
 Salmonella
 E. coli
 Staphylococcus

FEED RESOURCE ASSESSMENT

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