Digestion in exotics Flashcards
Describe the beak
- Differs due to diet and habitat
- Crushing in seed eaters, tearing in carnivores
- Consists of bone, vascular dermis with modified keratinised germinal layer
- Covered with leathery keratin
- Epithelium has thick stratum corneum (hard)
- High density of mechanoreceptors, stimulated during feeding
- Upper jaw rigid trangular block (premaxillary, nasal bones, small maxilla)
- Flat mandible
- Elastic zone articulation between upper jaw and cranium
- In larger birds is synovial joint
- Egg tooth on rostral beak of newly hatched
- Many muscles to close jaw, one to open
Why is there such diversity in the class Aves?
- Diverse diets/habitats
Describe the oropharynx of birds
- No soft palate, oral cavity or pharynx - all in one
- Choana connects nasal cavity and oropharynx
- Infundibular cleft caudal to choana (common opening for eustachian tubes)
- Hyoid apparatus supports keratinised tongue
- No teeth
- Tubular salivary glands (mucin, some species amylase)
- More mucoid than mammalian
Describe the proximal oesophagus of birds
- Oesophagus dilates to accomodate unmasticated food
- Right of neck, vagal control
Describe the crop of birds
- Crop small pouch or large structure with basic sphincter (variation)
- Cranial to thoracic inlet
- Histologically siimilar to oesophagus, fewer mucus glands
- Food stored in crop
What is the function of the crop in birds?
- Food storage
- Degradation of starch (salivary amylase)
- Bacterial fermentation (gram positive bacteria and Candida)
Describe the proventriculus of birds
- Glandular
- Similar to mammalian stomach
- Left in craniodorsal body cavity, nno oesophageal sphincter
- Between proventriculus and gizzard is isthmus
- Produces HCl and pepsinogen from oxynticopeptic cells
- Other epithelial cells produce mucus
Describe the gizzard of birds
- Muscular
- Similar function to mammalian teeth
- Left of midline caudal to sternum
- Protein digestion, mechanical food breakdown, smooth muscle
- Kiolin tough lining of gizzard, protects mucosa, formed from mucosal cell secretions, composed of proein and carbs, stained yellow with bile reflux from duodenum
Describe the mechanics of eating in birds
- Papillae in oropharynx directed caudally
- Move food in conjunction with tongue and gravity
- Tip head upwards
- no soft palate or pharyngeal muscles, no peristalsis to facilitate swallowing
Describe the mechanics of drinking in birds
- Birds immerse beak in water when drinking
- Water moved caudally in oropharynx by movement of tongue
- Tipping head, water enters oesophagus
- Pssitacines use tongue to lap water
- Laryngeal mound not protected by epiglottis
Describe the location of the epiglottis in birds
Birds do not have an epiglottis
Describe the mechanics of the crop
- Peristaltic movements oesophagus to crop
- Emptying of proventriculus stimulates crop to move food caudally
- Crop motility regulated by vagal impulses
What is unusual about the crops in columbiformes?
- Pigeons
- Epithelial cells sensitive to prolactin
- Production of crop milk, regurgitated for young
- Also penguins and flamingos
What muscles of the gizzard contract for prograde movement?
- Thin muscles
- Ingesta to duodenum
What muscles in the gizzard contract for retrograde movement?
- Thick muscles
- Ingesta to proventriculus
Describe particle movement in the stomach of birds
- Stimulated by particle size discrimintationin gizzard
- Small particles to duodenum
- Large stay (herbivores) or regurgitated (carnivores)
Describe the process of egestion in birds
- Egestion of bones
- Occurs after nutritious component of prey has been digested
- During reflux gastric motility inhibited
- Pellet expelled through mouth by oesophageal antiperistalsis
Describe digestion in owls
- Egest after every meal
- Eat whole carcass
- No storage capacity in crops
Describe digestion in Falconiformes
- Tear prey apart
- Use crop for storage
- Digest bony material
- Egest once daily
Describe digestion in herbivorous birds
- Grit to aid mechanical digestion in gizzard
- If high in calcium grit needs repleneshing
- Dissolves in acidic conditions
Describe the liver of birds
- Right and left lobe
- Gall bladder contained within right lobe
- Left and right bile ducts enter distal duodenum
In what families of birds is the gall bladder absent?
- Psittaciformes
- Columbiformes
- Struthioniformes
Describe the bile of birds
- Bile aids emulsification of fats, also contains amylase and lipase
- Many birds lack bilirubin reductase
- Biliverdin main bile pigment
- Reabsorbed in duodenum, back to liver via enterohepatic circulation
How can hepatic malfunction be measured in birds?
Raised bile acids
Describe the pancreas of birds
- Lies within duodenal loop
- In poultry dorsal and ventral lobes connected distally
- Exo and endocrine gland
Describe the small intestine of birds
- Short (facilitates high metabolic rate)
- Histologically little difference between duodenum, ileum and jejunum
- Merkel’s diverticulum present
- Thin walled, narrow, normal layers
- Epithelia does not contain lacteals
- D. higher pH than gizzard
- Amylase and esterase
What is the lymph drainage of the intestines in birds?
- No mesenteric lymph nodes
- Lymphoid nodules (Peyer’s patches) in lamina propria
Why is the pH higher in the duodenum then the gizzard?
- Secretions from pancreas and gall bladder
- Digestion and absorption process similar to mammals
Describe the caeca of birds
- Blind ending sacs
- Ileocaecocolic junction
- Gram positive bacteria and protozoa
- Lymphoid material at proximal end = caecal tonsils
- Aid digestion of cellulose
- Vary in size
- Cannot utilise proteins formed by bacteria in caeca
- Antiperistaltic movements cause transport of chyme into caeca
- Small particles retained, coarse fibre excreted
- Caeca emptied a few times a day
Describe the appearance of caecal droppings
- Caramel coloured
- More fluid
Describe the large intestine of birds
- Short
- Walls no thicker than small intestine
- Reabsorb water and electrolytes
- Can absorb glucose and AAs in colon by secondary active transport
Describe the cloaca of birds
- Termination of digestive and urogenital tracts
- 3 compartments: copradeum, urodeum, proctodeum
Describe the copradeum of birds
- Most cranial department of cloaca
- Where rectum empties
- Absorption of water and ions
- Can distend massively with faecal material
Describe the urodeum of birds
- Beyond coprourodeal fold
- Ureters and genital ducts empty into dorsal wall
Describe the protodeum of birds
- Empties contents into vent on relaxation of external anal sphincter
What are some commonly encountered digestive diseases seen in domesticated birds?
- Malnutrition and digestive disorders common
- Enteritis (lack of grit)
- Coccidiosis (caused by coprophagy)
List the features of the reptile mouth
- Mucous glands
- Salivary glands
- Venom glands
- Tongue
- Glottis
Describe the mouth mucous glands of reptiles
- Most prominent in squamates
- Multicellular
- Lubricate prey, help swallowing
Describe the salivary glands of reptiles
- Palatine, lingual, subligual, labial, dental
- Lubrication
Describe reptilian venom glands
- Sublingual (Helodermatid lizards)
- Temporal (Elapidae, Viperidae)
- Venom complex - various toxins and enzymes
What is the function of venom in reptiles?
- Immobilise prey
- May have some digestive function
Describe the tongue in snakes
- In sheath under epiglottis
- Highly mobile
- Forked
- Heavily keratinised, few taste buds
- For olfaction
Describe Jacobson’s organ
- Accessory paired olfactory organ
- Most developed in snakes
- Roof of oral cavity
- Vomeronasal organ
- Chemical scents
Describe the tongue of lizards
- Mobile, protrusible
- Fleshy or keratinised
Describe the tongue of chelonians
- Large
- Fleshy
- Immobile
- Many taste buds
Describe the glottis of snakes
- On floor of oral cavity
- Rostral
- Highly moveable
- Allows breathign during eating (snorkel effect)
Where is the glottis located in lizards and chelonians?
Base of tongue
Describe the oesophagus of reptiles
- Mechanical and enzymatic digestion
- Thin
- Fragile
Describe the oesophagus of snakes in particular
- Highly distensible
- Largely amuscular
- No well define gastroesophageal sphincter (easily regurgitate)
- May store food
Describe the stomach of reptiles
- Similar to mammals
- Pepsin, HCl from gastric mucosa
- Chelonians have gastrooesophageal and pyloric sphincters
- In squamates is highly distensible
- In snakes stomach not prominent, digestion begins when prey reaches stomach, faster if inject venom
What factors affect the function of the stomach in reptiles?
- Body temp
- Hydration
- Food type
- Meal size
- General health
Describe the small intestines of reptiles
- Surface area: herbivore>omnivore>carnivore
- Need large surface area for microbial fermentation
- In snake relatively straight
- In lizards and chelonians convulted
- Mucosal surface variable
What is significant about the large intestine or herbivorous reptiles?
Larger in herbivores
Describe the gall bladder of reptiles
- In chelonians and most lizards, GB close to liver
- In snakes and some lizards, GB far from liver
Describe the pancreas of reptiles
- In chelonians and lizards close to stomach and duodenum
- In snakes form triad of spleen , pancreas and gall bladder
- Enzymes depend on feeding strategy (e.g. chitinase, amylase, trypsin etc)
Compare the rate of digestion in reptiles to mammals
- Slower in reptiles, especially herbivorous
- Rate of passage varies can be between 2-4 days in small carnivorous squamates and 3-5 weeks in large snakes, herbivorous chelonians and lizards
Describe fat storage in reptiles
- Little fat storage
- Fat bodies, often caudal coelom
- Base of tail in many lizards
What are the types of dentition in reptiles?
- Pleurodont
- Acrodont
What is pleurodont dentition?
- Labial wall present
- Shed and replaced
What is acrodont dentition?
- Sit on crest of bone
- Not replaced if lost
Describe snake dentition
- All pleurodont
- 2 rows of maxillary teeth
- No regional differentiation
- Thin, point caudally so prey cannot escape
- Different types of fangs
- Posterior, anterior fixed, anterior hinged
Describe chelonian dentition
- No teeth
- Sharp, keratinised beak instead
- Egg tooth to break out of shell
Describe the skull anatomy of squamates and why this is important
- Cranial kinesis - can move upper and lower jaw
- Quadrate bone loose articulation with lower jaw
- Important for feeding, can eat large things
- Jaw very mobile
- Jaws close in parallel so prey is not “squeezed out”
Describe the snake skull anatomy
- No mandibular symphysis
- Quadrate bone present
- Can walk along prey with jaw while ingesting due to symphysis
What sensory systems are present in reptiles?
- Vision
- Chemosensory (gustation, olfaction, vomerolfaction)
- Thermal in some snakes
Describe which and how some snakes can use thermal sensory systems in feeding
- Boidae, Pythonidae, Viperidae
- Heat pits detect temp of prey
- Bilaterally symmetrical
- Nostril, heat pit opening and ye closely related
- Heat sensitive membrane inside pit organ
- Locate prey via triangulation
Compare herbivorous and carnivorous reptiles
- Greater surface area of SI in H. (microbial fermentation)
- Colon larger in H.
- H. chelonians heavily convoluted colon, partitions (slow movement of food)
- More intestinal microflora in H, longer GI tract
- Young H. need innoculum of adult faeces
Describe the GI microflora of reptiles
- Aeroic, anaerobic, Gram neg, Gram pos, yeast, protozoa
- Most commensals are opportunistic pathogens
Describe the GI system of amphibians
- Short simple tract
- Prey swallowed whole
- Sphincter between oral cavity and oesophagus
- Pyloric sphincter
- Liver, GB, pancreas present
- SI - enzymatic digestion (folding, villi for absorption)
- LI - water, salt absorption
- Cloaca
- Little distinction between LI and Si, some species may have a sphincter
Describe the digestive glands of amphibians
- In buccal caavity have mucus and salivary glands (lubrication) and intermaxillary gland (sticky compound)
- In oesophagus and stomach pepsinogen released
- Liver bile
- Pancreas diffuse, digestive enzymes and insulin
List the organs of the GI system of fish
- Oesophagus
- Stomach (not present in all)
- Intestine ( varies greatly)
- Some fish have intestinal bulb instead
- Pancreas, liver and GB present
Describe the oesophagus of fish
- Taste buds
- Short, thick walled
- Highly distensible
Describe the stomach of fish
- Not present in all
- Striaght, U- or J-shaped (majority J)
- U-shaped have diverticulum
- Pyloric sphincter present
- Some can inflate stomach by gasping
Describe the intestine of fish
- Length varies greatly
- Longer in H than C
- Some specieshave pyloric caeca (blind sacs at proximal intestine, absorptive)
- Functional differentiation of segments
- Proximal for lipids
- Middle for proteins
- Distal for ionic regulation
- Thickened mucosa, spiral valve
- H. have coiling
Describe the pancreas, liver and GB of fish
- Pancreas diffuse in most species, digestive enzymes and insulin
- Liver no discrete lobes
- GB empties into pyloric end of stomach
Describe the diet of amphibians
- “Larval” form herbivorous
- Adults all carnivorous
- Generalist predator, prey choice limited by size of animal
- Often invertebrates, some larger eat invertebrates
Describe amphibian dentition
- Crowns curve towards pharynx
- Shed and replace teeth throughout life (pleurodonts)
- Varied locations of teeth
Where are teeth located in salamanders and caecilians?
On maxilla and mandible
- Maxillary and vomerine teeth
Where are teeth located in most frogs?
Maxilla only, used to hold prey, not chew
Describe the dentition of fish
- varies based on diet
- Tooth like structure on bones derived from gill supports
- No salivary glands
- Some have pharyngeal teeth
Describe the structure of the tongue in frogs and its role in feeding
- Genioglossus protracts, hyoglossus retracts
- Tailed fros (aquatic) - short tongue, caudal attachment
- Most frogs longer tongue, cranial attachments, more elaborate hyoid skeleton and associated musculature, glandular pad attached to muscular base
Describe the structure of the tongue in salamanders and newts and its role in feeding
- Aquatic: suction, 1 way water flow
- Terrestrial (newts) have thick sticky tongue, grabs presy, degree of tongue projection varies, posterior attachment tongue to hyoid
What is the role of the swim bladder in fish?
- Hydrostatic equilibrium, respiration, sound production
- Some have no swim bladder, use lipids instead
Describe the structure of the swim bladder
- Outgrowth of foregut
- Dorsal most object in cavity
- Can be connected to oesophagus by pneumatic duct or rete mirabile
What are the two classifications of fish based on swim bladder type?
Physostomes
Physoclistus
Describe physostome fish
- Swim bladder connected to oesophagus by pneumatic duct
- Gulp air to fill bladder
- Food can enter accidentally - rots and fish dies
Describe physoclistus fish
- Swim bladder connected to oesophagus by rete mirabile
- Capillary network as a source of gases
- Do not have to come up and gulp for air = safer
- Slower
Describe the housing requirements of boas
- Need full spectrum fluorescent bulb
- Custom cages to cater for large size
- Wire cage around bulb to prevent burns
- Optimal temperature 25-30degreesC
- Primary and secondary heat sources to create focal hot spots
- Humidity 60-70%
- Water bowl appropriate for size
- Hide boxes
Why are focal hot spots important in boa housing?
So the snake can find areas most comfortable to it and achieve their preferred optimal temperature zone
Describe primary heat sources in boa housing
- Keep enclosure within proper temperature range
- Incandescent lights over cage
- As size of snake increases, space heater may have to be used to heat a large enclosure
Describe secondary heat sources in boa housing
- To create heat in specific areas and offer choice
- Heat mats or “banking lights”
- Should not use rocks as heat sources as can cause severe burns
Describe the dietary requirements of boas
- At 9 months fed full grown mice/rates
- Ensure are not wider than snake’s girth
- Should be fed 5-7 days, extend to 10-14 days as grows
- At 2-3 years (adult) feed every 2-4 weeks
List calcium rich foods that can be fed to iguanas
- Escarole
- Kale
- Collards
- Bok choy
- Swiss chard
- Parsley
- Clover
- Alfalfa pellets
- Dandelion greens
- Turnip greens
- Mustard greens
- Beet greens and spinach occasionally
- Never iceberg
Why should iceberg lettuce not be included in an iguana’s diet?
Little to no nutritional value
Describe the diet of an iguana
- 60-70% calcium rich foods
- Other vegetables
- Small amounts of fruit
- Very small amounts of grains/fibre
- Strict herbivores
- Should be fed mostly in the morning
Why should iguanas be fed in the morning?
- Are cold blooded
- Need the higher day temperatures for proper digestion
Describe the optimal iguana environment
- Supplemental heat for digestion
- External heat sources
- Primary and secondary heat source
- Primary keeps whole enclosure in appropriate range
- Secondary provides hot spots
- UVB provided by reptile black light
What are the water requirements of iguanas?
- Needs to be large enough for the iguana to be immersed in
- Shoud be in bowl that cannot be tipped
- Changed regularly
- Especially in winter, iguanas should be misted with water several times a week
Describe the cage substrate for iguanas
- Absorbent and digestible
- Flat newspaper, sheets of brown wrapping paper, astroturf, indoor/outdoor carpet, alfalfa pellets
- Should not use cedar shavings, gravel, crushed corn cob, cat litter, wood shavings, potting soil that contains vermiculite, pesticides, fertiliser or wetting agents
Describe the cage enrichment that should be provided to iguanas
- Branches (secure, not spiky, no sap, as thick as iguana)
- Hisign places
- Plants (non-poisonous and not treated with pesticides)
- Smooth, flat bottomed rocks
Describe the optimal environment for tortoises
- Heat source (can drop temperature at some points to replicate night)
- Humidity (mist sprays, not too damp, mosses hold moisture well, sand for drier)
- Need source of UV light (only 14 hours a day)
Why is it important to provide UV light for reptiles?
- Needed to metabolise vitamins and minerals
- Used to produce vitamin D which is used to absorb calcium
Describe some signs of metabolic bone disease in tortoises
- Develop soft shells
- Carapace curves upwards along edges
- Skull develops abnormally
- Overgrown maxilla (parrot beak appearance)
Describe the nutrition of tortoises
- No iceberg lettuce
- Mixture of green leaves better
- Coarse mixed grasses, hays, clover and dandelions
- Kale in small quantities
- Fruit in moderation
- Some are herbivorous, others eat meat
Describe the housing for macaws
- Big enough to stretch fully horizontally and vertically
- No sandpaper on perches
- Perches of varying diameters
- Cage strong enough to withstand parrot bite
- Easily cleaned, non-toxic material
- Enrichment in cage (not reducing room for bird)
- Place food and water abover perches to acoid soiling and change daily
Describe appropriate enrichment for macaws
- Enjoy destroying toys so dog chews and wood to strip are more beneficial than mirrors and bells
- Should be let out of the cage and treated as part of the family
Describe the diet of macaws
- Seeds most
- Fruit 5%
- Vegetables 15-30%
- Should feed sources high in vitamin C
Describe how macaws should be fed
- Pelleted diet better than seeds, available at all times
- Feed fresh vegetables morning and afternoon (half hour after sunrise, 5-6pm)
- remove uneaten at next feeding
- Offer only what bird can eat in a day
- Foraging toys in cage for snacking and entertainment
What are some of the benefits of feeding a pelleted diet to macaws
- Balanced nutrition (precise levels of essential nutrients)
- Realistic diet (wider variety of ingredients, more similar to wild diet)
- Species specific nutrition
- Fun variety
- Less mess
- Reduced need for supplements
- Readily available
What are the signs of gut stasis?
- Small and/or malformed faecal pellets
- No faecal pellets in living environment
- Loss of appetite
- Lethargy/hunched posture
Describe the appropriate rabbit diet
- Fresh hay should be bulk of diet, avaialble at all times
- Some fresh vegetables (3 different vegetables each day, e.g. broccoli leaves, carrot tops, celery, dandelion leaves, lettuce, water cress)
- Feed rabbit pellets (reduce number as gets older, high in fibre, low in protein)
- Avoid treats high in carbs but can give in small amounts (strawberries, raspberries, bananaas, pineapple, apples - remove seeds)
Describe water provision for rabbits
- In bottles and bowls
- If not drinking much, can leave veg wet
Describe rabbit exercise requirements
- Needs pelnty of room
- Separate area that is bunny proof or supervised
Describe ferret diets
- No lactose (do not have lactase)
- High protein diet
- Very little carbohydrates
- No fruit (grapes and raisins toxic)
- Fresh water daily
- Premium quality kitten food better than dry dog food (high protein and fat)
- Specific ferret food best
Describe some appropriate treats for ferrets
- Commercially packaged meat-based cat or ferret treats
- Cooked eggs
- Cooked meat
- Freeze-dried muscle or organ meats
- Linoleic acid coat conditioners
Describe guinea pig diet requirements
- Vitamin C
- Pelleted may be sueful as forage food to keep teeth ground down
- Fresh fruit and veg (red pepper, kale, turnip greens, mustard greens, dark leafy greens, sugar snap, snow peas)
- Water by bottle and bowl
Describe appropriate guinea pig environments
- 2 square feet per pig, larger is better, like to have company
- Well ventilated but away from drafts
- Bedding pelleted or using shredded paper
- Provide darker area for hiding
- Rest of cage light
- Run outside on grass for exercise and to eat grass
- Provide shade and shelter, do not put in run if cold or windy
How should food and water be provided to guinea pigs?
- Water in bottle and bowl
- Clean bowl several times a day (play and toilet in it)
- Food in tip proof bowl
Describe enrichment for guinea pigs
- Unpainted, untreated wood chew sticks
- Toys to climb over
- Not exercise wheels
- May enjoy being handled
