Comparative digestive physiology (Different GITs (Monogastric - Chicken…
Comparative digestive physiology
Grazers, Mixed and Browsers
Thick cell wall and greater proportion of cellulose/hemicellulose, Plant defence compounds = Silica. new growth added at base with uniform dispersion
Thin cell wall with greater proportion of lignin. Plant defence in the form of tannins, terpenes, alkaloids and other toxins, new growth added at tips, low to high growth form with a complex, diffuse branching architecture. plants are dispersed and discrete
Monogastric - Chicken and Pig
Pseudo Ruminants - Llama
Ruminant - Sheep and Cattle
Hind gut Fermenters - Pony
- In monogastrics area glandular regions is much greater than in ruminants who have a greater proportion of nonglandular mucosa - due to differences in digestion, monogastrics use enzyme/acid digestion to a much greater extent than ruminants
Digestion in stomach/abomasum- Pepsinogen from chief cells -> pepsin enzyme -> gastric lipase (fats) -> amylase (saliva) digests starch -> mechanical and chemical breakdown into Chyme -> chyme passes into small intestine
Small and large intestine
- Less variable among species than stomach and hind gut but is generally shorter in carnivores than in herbivores.
- Importance of hind gut fermentation dictates variation in structure and size however some hind gut fermentation occurs in most species
Digestion in the small intestine - Pancreatic juice, pH 6 in duodenum and 7 in ileum, Proteases present- trypsin and Chymotrypsin. Amylase and Lipases. Bile emulsifies triglycerides and helps lipases
Large intestine - Absorption of water, fermentation of undigested material, storage of faeces
GIT Classifications - Pig - Monogastric omnivore with limited post-gastric fermentation. Pigs have a simple stomach, not capable of effective utilization of forage based diets. Autozyme digestion, unable to digest of of the substances in grains, fruits and vegetables. Similar to a human
GIT Classifications - Chicken- Monogastric omnivore with limited post-gastric fermentation. Crop for storage, gizzard for grinding and mixing food. Autozyme digestion, Limited fermentation in the ceca. Unable to digest some of the substances in grains, fruits and vegetables.
GIT Classifications - Horse- Monogastric herbivore with extensive post gastric fermentation. Simple stomach incapable of utilisation of forage based diet. Extensive fermentation after primary sites of digestion and absorption. More efficient use of feed protein than ruminants.
GIT Classifications - Sheep- Ruminant herbivore with extensive pre-gastric fermentation. Highly developed stomach capable of extensive and effective use of forage based diets. Extensive fermentation before primary sites of digestion and absorption. Similar to cattle and goats
GIT Classifications - Llama- Pseudo-ruminant herbivore with extensive pre-gastric fermentation. highly developed sacculated stomach capable of extensive use of forage based diets. Similar for camels and other camelids.
Carnivores - Stomach (70%) bigger than intestines, small +large intestine equal in volume. GIT/Body surface: 0.6:1
Omnivores - Stomach - SI- LI all equal in volume, intermediate GIT/Body surface ratio
Herbivores (Ruminant)- Stomach (70%) - Small intestine greater in volume than large intestine. GIT surface/body surface 3:1
Herbivores (Non-ruminants) - Stomach (10%), SI (30%) LI (60%). GIT surface/ Body surface 2:1
Saliva is needed for moistening, lubrication, Enzymes, pH buffering, N recycling, rumination.
Enteric fermentation = Anaerobic process for the production of energy-yielding substrates, harness symbiotic microbial populations to digest feedstuffs that cannot be degraded by the host animal. Step one is glycolysis - glucose > pyruvate >ethanol > VFA
The Rumen- Large and complex population of microorganism, essential for energy and protein requirements. Microbial population carefully balanced- major pollutants (methane production)
The caecum - site of hind gut fermentation
Zoospores quickly attach to feed material, not obligate anaerobes
150 species across 29 genera- it is these microbes that produce methane
Protozoa - Numerically important (50% of rumen biomass). Role in the ecology is unclear but it is know to support methanogenesis, animals with protozoa removed are unaffected
Up to 50% of microbial protein is recycled, decreased protozoa levels actually increase protein levels. protozoa are known to breakdown 80% of bacterial protein