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Feeding of laboratory animals by Dr.SUNIL KUMAR BOYA
FEEDING OF LABORATORY
Diet is a potential source of pathogens for
laboratory animals(Williams et al, 1969).
Submitted by :-
PG scholar, Dept of LPM
Dept of LPM,
CVSc, Tirupati, SVVU.
• A laboratory animals nutritional status influences its ability to
reach its genetic potential for growth, reproduction and
• Feed palatability and feed intake, nutrient absorption and
utilization and excretion can be effected by physico chemical
characteristics of feeds such as physical form,
sensory properties, naturally occurring
refractory, anti nutritional compounds,
chemical contaminants and conditional
• Genetic differences among sps, breed, strains, stocks, sexes,
individuals, may effect nutrient requirements.
• Physical and mental processes are dependent on and influenced
both by what is ingested, and when and how food is eaten(Ritskes
–Hoitinga & chwalibog 2003).
• Food ingestion is essential for homeostasis a regulated state of
internal balance(Strubbe 2003;Ritskes-Hoitinga & strubbe 2004)
Aspects of feeding:
Rhythms of feeding in nature versus the laboratory situation:-
• Living organism continuously influenced by
external stimuli many of them having regular
or rhythmic patterns.
• These include lunar/tidal, solar/daily and seasonal/yearly patterns of light,
temperature, food availability so on.
• Species have evolved adaptive anticipatory strategies through the process
of natural selection resulted that many species have innate behaviour such
as hibernation, migration and seasonal reproduction.
• Animals are able to adjust their patterns of ingestive behaviour to adapt to
a wide spectrum of environment conditions, as long as these conditions are
predictable (Strubbe 1994b)
•These evolved characteristics and strategies are still present
in animals in laboratory today, although domestication has
led to changes (Strubbe,1999)
•Chickens housed in battery cages spend less time voluntarily
foraging for food than wild jungle fowl(Ritskes-Hoitinga &
•Rats are nocturnal and maintained under experimentally
controlled light-dark rhythms in laboratory.
•Under undisturbed adlibitum feeding 12 hr dark, 12 hr light
rat eats total daily food during dark hrs, with peaks at
beginning(dusk) and end(dawn) of the dark period (Kersten
•Even before the dawn peak the stomach is hard
packed(Armstrong et al 1978)
•Rats do not reduce feeding when liquid food is infused
into stomach(strubbeet al 1986)
• Nocturnal feeding in rats could, at least in part, be product
of light avoidance.
• Light is known to be aversive to some nocturnal species
and in particular to albino species.
• During the dark phase, rats eat in close proximity to food
hopper, whereas when they eat during light phase, they
make rapid excursions from the nest box to food hopper, take morsel of
food and quickly return to nest box to consume it.
• Consumption of food in nest box increases with light intensity and can
therefore be used as measure of light aversiveness (Brinkhof et al 1998;
strubbe & woods 2004)
• Rats forced to eat during light phase suffer gastrointestinal problems.
Memory for feeding time and feeding
•In the laboratory, feeding schedules can
be part of the experimental design .
•Rats are quick leaners and will readily
adapt to these feeding schedule, however,
in other rodent species , such as the
mouse and hamster, this can be much
more difficult, if not impossible.
•In research on pharmaceutical agents or
nutrients , it can be important to avoid any
negative influence of taste on food intake.
•It is required for radioactive isotopes or immunosuppressant's
for exact dosing and to avoid spilling into environment.
•However meal directly into stomach as compared to voluntary
eating of similar meal effects experimental results( vanchon et
Disadvantage is it avoid oropharyngeal processes
•Nutrient requirements change during stages of life
cycle especially response to growth , pregnancy,
•Housing types can also effect the amounts of nutrients
needed in diets for example laboratory rodents
maintained in either galvanized cages may have a lower
dietary requirements for zinc.
•Bcze zinc available in faeces and cage materials.
•These animals ingest bedding or other non food
materials this may provide an unintended source of
some nutrients or toxins.
• In rat and mouse most of microbial activity is in colon,
and many of the microbially produced nutrients are
not available to the host unless faeces are
• Prevention of coprophagy may require an increase in
the nutrient conc that must be supplied by the diet.
Formulation of diet types:
•Choice of ingredients will be influenced by the species to be
fed and the experimental or production objectives.
•Target nutrient conc must take into account estimated
nutrient requirements possible nutrient losses during
manufacturing and storage(NRC 1975; Harris and
karmas,1975)bioavailability of nutrients in the ingredients
and potential nutrient interactions.
•Wastage is problem with some types of diets, which may be
disadvantage if quantitative intake is to measured.
Natural ingredient diets:
•Diet formulated with agri products and by-products
such as whole grains, mill by-products, high protein
meals mined or processed mineral sources and other
livestock feed ingredients.
•Relatively inexpensive to manufacture.
• Individual ingredients can produce changes in nutrient cocn of
these diets (knapka,1983).
• Soil and weather conditions use of fertilizers and agri chemicals,
harvesting storage procedures and manufacturing can all influence
the composition of individual ingredients with the results that
know to production feed are identical.
• Potential contamination from pesticide residues, heavy metal or
other agents that might effect experimental data( ICLA, 1997)
• Unsatisfactory for studies to determine micro nutrient
requirements for toxicological studies.
• Depending on composition there can be problems with palatability
and variation in intake.
• The formulation of natural ingredient diets is complicated by the fact
each ingredient contains many if not most nutrients so that an
adjustment in the amount of the any ingredients produces change in
the conc of most nutrients in final product.
•Fixed formulae diets( open formulae diets):-
An alternative approach as been the development of fixed formulae
diets in which the kinds and amounts of ingredients do not vary from
batch to batch.
•It is imp to recognize that bioavailability nutrients
may be lower in Natural ingredient diets than in
purified diets.( due to binding of chemical form of
nutrient such as lignin, phytate and tannins).
•Common practice is to use greater margins of
safety for particularly labile vitamins and for trace
•Methionine is example of a nutrient with narrow
• The recommended nutrient levels for good health and
those cause toxicity vary between species.
• Ex:- in sheep copper density of the diet is critical as
the difference between that good health and toxicity
is very narrow.
• Errors in feed mixing can easily lead to mortality.
• Dietary phosphorous levels are critical in mice, rats
• Diets that are formulated with a more refined restricted set of
ingredients are designed purified diets.
• Only relatively pure invariant ingredient should be used in
Example of such ingredients are
• Sugar and starch as a source of carbohydrates
• vegetable oil and lard as source of fat and essential fatty acids
• cellulose as a source of fibre
• Chemically pure inorganic salts and vitamins
• Purified diets are often used in specific nutritional deficiencies and
excesses and are more expensive to produce.
Chemically defined diets
•Diets have being made with most elemental ingredients
available such as individual amino acids such as sugars,
chemically defined triglycerides, essential fatty acids,
inorganic salts and vitamins.
• Highest degree of control over nutrient concentrations.
• These are not readily consumed by most species of lab
animals and usually to expensive.
These are developed for use in germ free and low antigen
studies(pleasants,1984; Pleasants et al., 1986)
PHYSICAL FORM OF DIETS
•Pelleted diets :-
The most common form is pelleted diets which is
typically formed by adding water to the mixture of
ground ingredients and forcing it through a die.
• Binders are some times used to increase the pellet
•Pellet diets are easy to handle, store, use and reduce
dust in animal facilities, prevent animals from
selecting choice ingredients and tend to minimise
•The hardness of blocks and pellets is measured as the amount
of pressure that is required for crushing a pellet.
If pellets are too hard, the growth of preweaned mice is
reduced significantly.(koopman etal. 1989)
Young mice have to work hard to eat pellets and partly because
the lactating females are not able to eat enough to satisfy the
need of both themselves and their young (koopman etal. 1989)
•The higher fat diets marketed for these animals are not as
hard, so mice do not need to work as much and can ingest
food more easily
•Disadvantage is risk of atherosclerosis.
•These are similar to pelleted diets expect the
meal is forced through a die under pressure and
high temperature after steam has been injected.
•So the product expands has its emerges from the dye.
•Extruded diets are less dense than pelleted diets
preferred by some animals Dogs, cats and non-human
Ex: These diets are not commonly used for laboratory
rodents because of increased wastage during feeding
and high production cost.
Meal form diets
•These are used because they permit incorporation of additives
and dust compounds after the diet is manufactured.
•The diet often insufficient large amount may be wasted,
hazardous if toxic compounds have added.
•Jelling agents and water are added to form jelled mass can be
cut into cubes for cutting but this require refrigeration to
maintain moisture and to retard microbial growth.
Prepared by crushing
pelleted and extruded diets.
It offers the convenience
without problems of diets in
Manufacture and storage procedure
and other considerations.
•Laboratory animal diets should not be manufactured
or stored in facilities used for farm feeds or any
products containing additives such as rodenticides,
insecticides, hormones, antibiotics, growth factors or
•The storage room should be kept clean and enclosed
to prevent entry of rodents, birds and insects.
• Routine pest control is essential.
Environmental conditions of storage area
•Nutrient stability of feeds generally increases as
temperature and humidity decreases.
•The shelf life of any particular feed depends on these
•Feeds stored where temperature and humidity are high
can detoriate several weeks.
•Natural ingredient diets stored in air conditioned areas
and should be used with in 180 days of manufacture.
•Diets containing vitamin c use within 90 days of
manufacture(National Institutes of health, 1985).
•Diets formulated without antioxidants or with large
amounts of perishable ingredients such as fats
require special care.
• unsaturated lipids in the diet is susceptible to
oxidation which reduces the available essential fatty
acids(Rancid characteristics of oxidised lipids may
reduce diet acceptability).
(The international council for laboratory animal
science,1987) noted 7 unwanted substances in
laboratory animal diets
3. Bacteria, bacterial toxins and mycotoxins.
4. Natural plant toxins.
5. Break down products of nutirents.
6. Nitrates, nitrides and nitrosoamines.
7. Heavy metals.
Number of studies indicated that restricting the
calorie intake of laboratory animals may have beneficial effects
on lifespan, incidence and severity of degenerative diseases
and onset neoplasia(WEINDRUCH & WALFORD, 1988).
• It is important to achieve calorie restriction of test animals
without producing unintended nutrient deficiencies.
adlibitum feeding can result in kidney degeneration in rodents,
whereas food restriction prevent kidney degeneration
completely ( Hart et al. 1995).
When rats were given the choice
between various diets providing energy from
different sources, the rats chose carbohydrate
rich diets in the evening hours, and fat rich diets
just before the start of rasting period(Stubbe
•Housing and husbandry conditions can influences both
amount of food animals ingest, and the animals feeding
Individually housed mice of both sexes were found to have
higher food intake than mice housed in groups of two, four
or eight per cage (chvedoff etal 1980;Benyen & coates 2001).
•Mice housed individually or at two per cage had higher
body weight and body weight variability than other groups.
Reduced heat loss per animal in the group is the result and
due to this ‘behavioural thermoregulation, food intake is
reduced.(De Vries et al1993 woods and strubbe 1994).
Feeding and watering devices
Devices vary with type of food , type of cage and sps of animal present.
• These must be placed so that food is readily available but not
allowed to become contaminated with faeces or urine.
• Devices – stainless steel or plastic for durability and ease of
• Ensure that all animals are able to gain access to food.
• Experimental designs require specific type of feeds and
•V shaped & J shaped( rabbits & g.pigs) feeders
are used for pelleted feeds. Water bottles are
placed within same area.
•Powdered rodent diets are provided in bowls,
these are placed on cage floor and require
frequent cleaning due to faecal contamination.
•Clean and fresh water must be available to all animal at all
•Bottles that are suspended with in the cage should be glass
maded, outside- plastic maded.
•Sipper tubes must be examined daily.
•If ball bearing or tube damaged, water empties freely from
bottle, resulting in wet cage, no water to animal.
Automatic watering systems-
Advt:- eliminate need of constant refiling and washing of bottles.
And expensive require routine care and maintenance.
• System flushed regularly to remove build up bacteria in water lines.
• Inability to determine water consumption of an individual animal.
• Valves must be regularly checked for evidence of
leaks or clogging.
• Some animal unfamiliar to system require training.
Feeding of mice:-
• Mice are usually fed ad lib with a complete pelleted diet, from
hoppers suspended above the floor to prevent faecal contamination.
• Generally, mice will consume 3-5 g of pelleted diet daily, but there are
strain difference and disease states and pregnancy affect food
• Water required for lubrication of food and hydration,
insufficient fluid is available they have difficulty
• It is supplied in automated systems or bottles.
• The usual requirements is 6-7ml water daily. water
may need acidified or chlorinated to reduce
contamination especially for immunocompromised
• Medicines are administered in water.
Feeding of mice
feeding vary with different sps of mice
• Consumption – 15 ml per 100 g body weight per day.(Swiss
mice – consumes normally 12 to 18 g of feed per 100 g
• Copraphagia is important component of mouse
• Protein content of feed should be 14%.
• Pelleted commercial rodent chow is adequate and can be fed
from v-shaped trough of wire cage lid or placed in food
hopper that hangs inside the cage.
• Water Ambient temp is between 180 to 290 c with relative
humidity 40 to 60%.
•Feeds available for pet mice include pellets and seed
•Spiny mice may be maintained with seed based diets .
•Feeding of seed based diets or seed in other species
results in an obese and nutritionally deficient
Feeding of Rat :-
• Rats usually consume there food in
several small meals through out the day.
• Pregnant or lactating females require up to 4 times the
requirements normal females.
• The feed should contain 20-25% protein and 4% fat.
• Pet rats may be given small amounts of fruits,
vegetables or seeds.
• Like most rodents rats are coprophagiac.
Feeding of guinea pigs
• G.pig tend to develop meticulous dietary habits and do not respond
well to changes in their diet or feeding methods.
• Should fed a commercial high quality feed designed specifically for
• Rabbit feed is not acceptable substitute because it contains too
much fiber and not enough protein.
• Major consideration of feed is dietary source of vit-c( cabbage &
kale). These are only non primate mammal to have such
• Guinea pig having simple stomach unlike other animals, here
stomach lined with glandular epithelium.
• New born animal can consume semisolid and solid food
• Weaning followed at 3 weeks of age.
• Avg daily gain is 5 to 7 g per day ( adlibitum feeding
• Growth slows after 2 months and maturity reached at about
• Adult body weight for female is 700 to 850 gms and males
950 to 1200 g.
• Guinea pig are highly susceptible to heat stress do not
tolerate temp greater than 90oF.
• Optimum environment temp range is 18o to 26o C with
relative humidity of 40 to 60%.
• These are notorious for pushing partially chewed food
up into the sipper tube of water bottle causes clogging,
algal and bacterial growth.
• Copraphagia is an important component of g.pig
nutrition, it loss wt, if copraphagia is prevented.
Feeding of hamsters:-
•Hamsters can fed commercial rat
•Because of their broad muzzle, they are unable to eat
through wire hopper feeders.
•So hamster feed placed directly on floor of cages.
•Hamsters carry food in their food in their cheek pounches to
their preferred location.
•They tend to set aside an area of the cage for urination and
Feeding of Rabbits
• Rabbits are herbivorous and coprophagiac.
• Wild and feral rabbits consume a diverse
diet of grosses, leaves, buds, tree bark and roots.
• They notorious for consuming lettuce, cabbage, root vegetables
and grains from gardens and farm fields.
• Commercial rabbit feed contains approx. 15% protein and 10%
• Higher fibre diets are given as needed to prevent hairballs
formation and minimize tendency towards obesity.
• Addition of proteolytic enzymes such as papaya juice
used prevent hairball formation.
• Supplementary foods like raw carrots and other
vegetables can be fed.
• Daily feed consumption 50gr/kg b.wt
• Daily water consumption (ml) 50-150/kg
• Recommended environmental temperature 16-210C
• Recommended environmental RH 30-70%
Feeding of Gerbils
•Gerbils tend to eliminate very small amount of wastes,
so cage usually clean weekly
•Feeding with commercial a rodent chow is adequate.
•The diet may be supplemented with small amount of
sun flower seeds and clean fresh vegetables.
•Adlibitum feeding should be avoided to prevent
• Daily feed consumption (g) 5-7
• Daily water consumption (ml) 4
• Recommended environmental temperature 18-220C
• Recommended environmental RH 45-50%
• Adult body weight male 46-131gr female 50-55gr
Feeding of Ferrets
•Commercial ferret chow is available, or cat chow may be
fed if it contains protein content of at least 30%.
•Feed is often given in large, heavy bowls placed on cage
•The bows must be made of indestructible material heavy
enough to not be easily tipped over.
•Water can also be provided in heavy bowls.
• Daily feed consumption (g) 140-190
• Daily water consumption (ml) 75-100
• Recommended environmental temperature 39-640C
• Recommended environmental RH 40-65%
• Avg adult body weight(kg) male 1-2 female 0.6-0.9kg
•When carrying research using animals, it is
challenge to feed them in such a way that their
health and welfare is maintained and results are
reliable and reproducible.
•To do this it require nutritional and behavioural
•Much more research is needed in to how different
feeding methods can be used to as enrichment in
order to improve laboratory animal welfare.