Biochemistry of Energy Metabolism Species Comparison Flashcards
Digestion of starches
Amylase breaks down starch into smaller chains of glucose molecules
Other enzymes break down the saccharides into glucose
Digestion of sugar
Simple sugars are also broken down to glucose
Glucose can be used for energy
Digestion of cellulose
No known mammalian enzyme can break down cellulose
Bacteria can break down cellulose with cellulases
Fermentation in digestion
Fermentation is the decomposition and utilization of food, particularly carbohydrates, by microbes
Fermentation occurs throughout the GI tract of all animals
In carnivores and omnivores, fermentation generates little energy
In herbivores fermentation provides majority of energy
Main carb metabolism in ruminants
Diet consists mostly of grasses and grains
Grains – starches and simple sugars
Grasses provide complex carbohydrates
Cellulose, hemicellulose, pectin
Structural components of the plant
No known mammalian enzyme can break down complex carbohydrates
Provide main nutrition for ruminants
Ruminants and the relationship with micro-organisms
Ruminants have developed a symbiotic relationship with microorganisms in digestive tract
Microorganisms use nutrients for their own growth and development
Produce end or waste products
Ruminant uses these products for their own growth and development
Microorganisms can be digested for protein
Ruminants metabolism in the reticulorumen
Bacterial enzymes break down carbohydrates by hydrolysis
Saccharides are further metabolized by bacteria to pyruvate
Pyruvate is converted into volatile fatty acids (VFAs)
Acetic acid, propionic acid, butyric acid
VFAs are important for
VFAs absorbed into blood
VFAs are main source of energy for ruminant
Same role as glucose in monogastric animals
Glucose production in ruminants
Although ruminants receive most energy from metabolizing VFAs, glucose is still needed
Glucose made through gluconeogenesis in liver
From propionate
From glucogenic amino acids
Glucose is conserved in ruminants
Not used to make fatty acids
Fatty acids made from acetate in adipose tissue
Metabolism in hindgut fermentors
Starches are digested to glucose and used for energy
Fermentation occurs in large intestine
Bacteria can use cellulose to produce VFAs that can be used for energy
Do not have ability to use protein from fermentative microbes
Ketosis in herbivores
Consumption of sufficient starch and cellulose is vital
In last trimester of pregnancy and during lactation nutritional demand increase
When pregnant ewes and cows receive inadequate nutrition, they compensate by breaking down fat reserves
Ketones bodies are formed and ketosis can occur
Ketosis and eclampisa
Ketosis may lead to eclampsia
Often fatal metabolic disorder
Primary sign is hypoglycemic encephalopathy
Guinea pigs, rabbits, and ferrets also predisposed to eclampsia
Can be prevented by providing adequate carbohydrates
Ketosis and lactation
Lactation requires large amounts of glucose to make lactose
When inadequate carbohydrates are consumed:
Glycogen stores are depleted
Fat stores are broken down for energy
Can lead to ketosis
Ketosis during lactation is self-limiting
Reduced food intake causes milk production to stop
Glucose drain stops
Carnivore metabolism
Prey animals are high in protein, moderate in fat, and low in carbohydrates
Cats use proteins as primary energy source
Cats can digest and absorb carbohydrates
Produce glucose by gluconeogenesis
Glucogenic amino acids
Cats require more of what nutrients than omnivores
Protein, arginine, taurine, methionine, cysteine, arachidonic acid, niacin, pyridoxine, vitamin A, vitamin D
