GI evolutionary adaptations of the digestive system Flashcards
How to carnivores eat, what is the food like that they eat, what is stomach like?
- Dog / Cat
- Predators (Catch prey) or scavengers
- High energy content
- Easily digestible
- Simple digestive tract
- Long interval between short meals – “wolf it down”
- Spacious stomach for storage to equate to long interval
How to omnivores eat, what is the food like that they eat, what is stomach like?
- Pigs (& bears)
- Pigs - can have lots of fermentation in colon.
- Bears - little hind-gut fermentation, tend to go for shoots / berries high in hydrolysable CHO.
- Best of both worlds – can switch
- Diet consists of both plant & animal origin
- Large species variation in digestive tract
- Bears range from herbivore to carnivores
- Degree of fermentation occurs in large intestine
How to omnivores eat, what is the food like that they eat, what is stomach like?
HERBIVORES
• Ruminants (cows, sheep, goats) / Horses
• Browsers (pick certain aspects of grass..) or grazers (pick up everything)
• Low energy content
• Microbial digestion
• Digestive tract adapted for fermentation
• Continuous eating
• 2 digestive strategies:
• Foregut fermenters – ruminants (antelope, wildebeest etc) , hippo
• Hindgut fermenters – horses, zebra, elephant, rhino
FERMENTATION Why does it occur? What does it require? What kind of process? How is the digestive tract adapted?
- Hydrolysable cho - can be broken down by enzymes.
- Non-hydrolysable carbohydrate requires fermentation
- Requires microbial degradation in absence of oxygen/anaerobic = fermentation
- Long, slow process
- Digestive tract adapted:
a) To allow microbial population to thrive
b) To ensure slow transit of food to allow fermentation
Fore gut fermenters:
who?
- Cattle / Sheep = Ruminants
- Stomach modified into fermentation chamber
- Very efficient fermentation - Lots of absorption occurs in stomach.
- Fermentation products absorbed in stomach
- Microbial protein can pass into abomasum & small intestine for digestion / absorption
Hindgut fermenters
- Horses (& rabbits)
- Large intestine modified into fermentation chamber
- Moderately efficient fermentation
- Fermentation products absorbed in colon - 70% as efficient as ruminants.
- Lots of absorption occurs in large intestine.
- Microbial protein lost in faeces
a) Rabbits practice coprophagy – RECYCLE FAECAL MATTER - digest microbial proteins
Which type of fermentation is more efficient? WHY?
- Hind gut fermentation is 70% as efficient as foregut ferm?
- • Microbes less efficient
• Lower degree of amylolytic fermentation – Amylolytic bacteria break down hCHO. Less in horse but fore-gut can digest hCHO.
• Hind-gut fermenters lose microbial protein in faeces
What is coprophagy?
- rabbits / rodents eat certain component of their faeces high in microbial protein
- What is a good adaption to fermentation? adn which type of fermentation?
- Why si this a good adaptation?
- Changing gut transit time as a result of changing rate of fermentation
- gut-transit time in fore-gut fermenters dependent on rate of fermentation and can’t be reduced whatever the nutrient quality of the fibre
- Horses on abundant poor quality forage can decrease gut transit time and therefore consume more
sooooo:
a) Ruminants more efficient on good quality forage
b) Horses more efficient on abundant poor quality forage
c) If forage is in short supply (as in most natural competitive situations) ruminants predominate
Within the ruminant foregut fermentation strategy what other adaptations?
- They have a further 3 nutritional strategies
- Carbs = simple sugars or complex
- 3 nutritional strategies =
Browsers = concentrate selectors
Grazers = grass/ roughage eaters
Intermediates = adaptable feeders
what are the 2 types of carbohydrates?
- SS = fruit, seeds, young shoots and leaves, high in hydrolysable carbohydrate
- Complex = stems, blades, older leaves high in fibre
What kind of food do the ruminant Grazers = grass/ roughage eaters type eat?
- Stems, blades, older leaves, high in fibre (complex carbohydrates)
- Cattle, sheep, hippos, most antelops
Examples of intermediate feeders? (adaptable)
goats, elk, moose, reindeer, camels, some antelope
What are the ruminant adaptations if browsers?
- Browsers = concentrate selectors = smallest ruminants, giraffes, most deer
- Narrow muzzels
- More mobile lips/ tongue
- smaller fore stomach
- Retain functional oesophageal ventricular groove
- Small intestinal glucose absorption remains high
What are ruminant adaptations if grazers?
- wide muzzels
- Less mobile lips/ tongue
- Large forestomach
- Ruminant grazers lose functional oesophageal/ ventricular groove
- Small intestinal glucose absorption declines
What ruminant retains the functional oesophageal/ ventricular groove and why?
- used when young so milk bypasses fermentation chamber.
- Most species lose but browsers keep this functional as if loads of sugar enter fore stomach = glucose used by bacteria. Therefore reflex closure straight into abomasum
Oesophageal/ ventricular groove
- Present in all young ruminants
- Enables milk to bypass fermentation chamber
- Grazer ruminants lose groove function by weaning
- Browser ruminants retain groove function to allow diet high in hydrolysable carbohydrate (hCHO) to escape fermentation
a) Normal digestion / absorption of hCHO yields more energy than fermentation
Comparative digestion carnivores vs omnivores:
Carnivores
1. No salivary amylase
2. High levels of enzymes from stomach / pancreas for proteins & fat
Omnivores
1. High levels of salivary amylase
2. High levels of enzymes from stomach / pancreas for proteins, fat & carbohydrate
Comparative digestion simple stomached herbivore VS ruminant herbivore
Simple-stomached herbivores
1. Moderate levels of enzymes for carbohydrate prior to fermentation in large intestine
2. Exploited in feeding concentrate diets high in hCHO
Ruminant herbivores
1. Low levels of enzymes for carbohydrate after fermentation in fore-stomach
2. Moderate levels of enzymes for protein digestion of microbial protein in abomasum / small intestine
Comparative absorption Carnivore/ omni, SS herbi and ruminant herbi
Carnivores / Omnivores 1. Monosaccharides / peptides / monoglycerides & fatty acids absorbed in small intestine Simple-stomached herbivores 1. Monosaccharides / peptides absorbed in small intestine 2. VFA absorbed in large intestine Ruminant herbivores 1. VFA absorbed in fore-stomach* 2. Peptides absorbed in small intestine
