FEEDING OF LABORATORY ANIMALS

Diet is a potential source of pathogens for laboratory animals(Williams et al, 1969).

Submitted by :-B.SUNIL KUMARPG scholar, Dept of LPMTVM/2015-024

Guided by:Dr.Y.RAVINDRA REDDYProffesor, Dept of LPM,CVSc, Tirupati, SVVU.

• A laboratory animals nutritional status influences its ability to reach its genetic potential for growth, reproduction and longevity.

• 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 storage.

• 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 & strubbe 2004).•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 et al.1980).

• 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)

Light aversiveness:-• 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 schedules

• 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.

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Gavage feeding• 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 al 1988)

Disadvantage is it avoid oropharyngeal processes

•Nutrient requirements change during stages of life cycle especially response to growth , pregnancy, lactation.•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 consumed.(stevens 1988).•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.

Types of diets

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.

Advantages:•Relatively inexpensive to manufacture.•Palatable.

• 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.

Nutrient concentration• 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).

•Safety margins:-•Common practice is to use greater margins of safety for particularly labile vitamins and for trace minerals.•Methionine is example of a nutrient with narrow safety margin.

Toxic effects • 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

and rabbits.

Purified diets• 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

formulation. 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

quality.•Pellet diets are easy to handle, store, use and reduce

dust in animal facilities, prevent animals from selecting choice ingredients and tend to minimise wastage.

• 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.

Extruded diets• 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 primates.

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.

Crumbled diets;Prepared by crushing pelleted and extruded diets.It offers the convenience without problems of diets in meal form

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 fumigants.•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 conditions. •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 diets1. Pesticides2. Pests3. Bacteria, bacterial toxins and mycotoxins.4. Natural plant toxins.5. Break down products of nutirents.6. Nitrates, nitrides and nitrosoamines.7. Heavy metals.

Dietary restriction 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.Ex:- adlibitum feeding can result in kidney degeneration in rodents, whereas food restriction prevent kidney degeneration completely ( Hart et al. 1995).

Diets: 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 1994a, 1994b)

Group housing •Housing and husbandry conditions can influences both

amount of food animals ingest, and the animals feeding patterns

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 devicesDevices vary with type of food , type of cage and sps of animal present.Feeding devices• 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

cleaning.• Ensure that all animals are able to gain access to food.• Experimental designs require specific type of feeds and

feeding containers.

•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.

Watering devices•Clean and fresh water must be available to all animal at all

times.•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.Disadvantage:-• 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 requirments.

•Water required for lubrication of food and hydration, insufficient fluid is available they have difficulty eating.• 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 mice•Medicines are administered in water.

Feeding of micefeeding 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 b.wt/day).• Copraphagia is important component of mouse

nutrition.• 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 based mixes.•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 animal.

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.

• Daily feed consumption (g) 15-20• Daily water consumption (ml) 22-33• Recommended environmental temperature 21-240C• Recommended environmental RH 45-55% • Avg adult body weight (gr) male- 267-500gr female 225-325

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

G.pigs.• 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 requirement.

• Guinea pig having simple stomach unlike other animals, here stomach lined with glandular epithelium.• Coprophagic•New born animal can consume semisolid and solid food

immediately.•Weaning followed at 3 weeks of age.• Avg daily gain is 5 to 7 g per day ( adlibitum feeding practiced)• Growth slows after 2 months and maturity reached at about 5

months.• 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

chow. •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

defecation.

• Daily feed consumption (g) 10-15• Daily water consumption (ml) 9-12• Recommended environmental temperature 21-240C• Recommended environmental RH 40-60%

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%

fibre.• 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

obesity.

• 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

floor.• 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

Concluding remarks•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 knowledge.•Much more research is needed in to how different feeding methods can be used to as enrichment in order to improve laboratory animal welfare.

Thank u