Flashcards
Ruminant Digestion and Salivary Secretion
Cards in this deck (54)
- 1What are the stomachs like in young ruminants?well-developed abomasum and immature forestomachs
- 2What is the purpose of the reticular groove reflex?enables milk to bypass the rumen and enter the abomasum directly
- 3Why is there an interest in preserving the reticular groove reflex in adult ruminants?Commercial interest to allow food supplements or medicine to bypass the rumen
- 4What is the problem with only feeding young ruminants once or twice a day?may gorge when fed, and the excess ingested milk can 'leak' into the rumen
- 5What is the problem with milk entering the rumen of young ruminants?the lactose is broken down into lactic acid, which lowers the pH of the rumen and affects the growth of a developing microflora population
- 6In the adult ruminant, what becomes the dominant input for stimulating the reticular groove reflex?Pavlovian conditioning with associations with events preceding the presentation of milk
- 7What part of the brain is responsible for controlling the reticular groove reflex?Medulla
- 8What can send signals to the Medulla to bring about the reticular groove reflex?Milk in pharynx/chemo receptors (via afferent fibres) and the vago-vagal reflex (via efferent fibres)
- 9What stimulates the growth of forestomachs?abrasive/churning action of forage particles and the chemical effects of fermentation products e.g. butyric acid
- 10What percentage of gross energy in the ruminant comes from carbohydrates?85%
- 11Ruminants can break down all carbohydrates except for those bound to or masked by which molecule?Lignin
- 12What bond is hydrolysed in ruminants that can't be hydrolysed in other mammals?Beta-bonded cellulose, hemicellulose and pectin
- 13How are beta-bonds hydrolysed in the ruminant?hydrolysed by anaerobic microbes by fermentation
- 14In ruminants, what are the products of carbohydrate digestion?Volatile Fatty Acids: acetate, propionate, butyrate
- 15What effect does a high-starch diet have on VFA in ruminants?VFA are produced much faster with a higher proportion of propionate to other acids
- 16What are the only two paths by which glucose can be produced in ruminants?from propionate: formed from OAA via succinate or formed via lactic acid when too much feed has been ingested
- 17What three key factors influence fermentation?Substrates (carbohydrates, lipids, proteins), Microbes (substrate preferences and tolerance to conditions), Conditions (pH and substrate conditions)
- 18Why does pyruvate produce VFA in ruminants but not in other mammals?there is no TCA in ruminants (entirely anaerobic)
- 19What is the importance of producing Methane during carbohydrate fermentation?regenerates NAD+ from NADH
- 20What does the diet determine in terms of rumen ecology?number of microorganisms and the balance between different types of them
- 21How does a change in diet affect fermentation?alters the substrates which leads to a change in balance of microbes, also alters the conditions including end products and pH
- 22How are some end products recycled within fermentation?they can act as substrates for other microbes (inter-dependency)
- 23How is the production of VFA different as a result of protein digestion as opposed to carbohydrates?VFA are still produced but some differ by having branched carbon chains
- 24What percentage of available energy from fermentation is used by the microbes themselves?7%
- 25In a high cereal diet, fermentation is mainly driven by which type of factors?post-absorptive factors, VFA in blood and sensory output from the liver (picked up in bloodstream as products of digestion)
- 26In a normal/high roughage diet, what is fermentation mainly driven by?pre-absorptive factors, rumen volume
- 27Why is it important in young ruminants that fermentation is driven mainly by pre-absorptive factors?they have a small, underdeveloped rumen which has a limited capacity for digestion. post-absorptive factors would be too slow to stop eating
- 28Why is retention time important?digesting fibre-containing feed is time-consuming and so a long retention time is needed to fully break it down and absorb nutrients
- 29What effect does increasing the amount of food fed have on the amount of energy extracted from it?available energy decreases as the food moves through the gut more quickly and so there is less time for energy to be absorbed
- 30What are the functions of salivary secretion?oral hygiene and food lubricaiton
- 31In the ruminant, why does saliva contain anti-frothing proteins?many plants have foaming agents and so specific enzymes are needed to break these down
- 32In ruminants, why does saliva contain wetting agents?grass is protected by a layer of air that makes it hard to break down, so these proteins allow contact with grass to reduce the grass/air cohesion (gets grass wet)
- 33In ruminants, why is saliva needed as a fluid?acts as a replacement of fluid, as it's the only source of fluid that isn't dietary based
- 34What does the consistency of saliva depend on?depends on which salivary gland had the largest stimulation
- 35What, in the ruminant, is dependent upon CNS control?salivary secretion and stomach motility
- 36How does primary salivary secretion compare to ECF?always isomotic with ECF due to effective osmosis
- 37What is saliva derived from and what effect does this have on blood flow?derived from plasma and so blood flow to acini is highly regulated
- 38In monogastrics, what alters salt composition?duct cells to create saliva that is hypotonic and with low Sodium concentrations
- 39In ruminants, what is different about the action of the Na+/K+ coupled transporter in ducts?only operative with Aldosterone - have to excrete excess dietary K+ into alimentary canal and retrieve Na+ from saliva
- 40Approximately what percentage of body water is recycled throughout the GI tract every day?50%
- 41In ruminants, what is the main stimulus for salivary secretion?food in mouth and anticipation
- 42What nerves control salivary secretion in ruminants?parotid and sublingual nerves (never zero as there's quite a high basal secretion)
- 43How is saliva important as pH buffer in ruminants?neutralises 1/3 of acid in forestomach, bicarbonate and phosphate at high concentrations
- 44What is the pH of ruminant saliva?around pH 8
- 45What is the importance of phosphate ions in ruminant saliva?needed for the buffering effect and microbial growth
- 46What is the importance of saliva as a source of Nitrogen in ruminants?Urea 'recycling' : urea diffuses from blood into saliva to be used for protein synthesis in reticulorumen when dietary protein is too low
- 47How does eating rate vary with food water content?dry = slow
wet = fast - 48What effect does parasympathetic innervation have on saliva secretion?increases salivary secretion with a watery content
- 49What effect does sympathetic innervation have on saliva secretion?increases the secretion of viscous saliva
- 50In what way does sympathetic control of saliva secretion work?noradrenaline-induced contraction of smooth muscles around acini and small ducts & increased protein synthesis in acini epithelial cells
- 51What effect does parasympathetic innervation have on blood flow?increases blood flow to a larger extent than when exercising
- 52What two types of long reflexes can increase the rate of saliva secretion?Inborn reflexes and conditioned reflexes
- 53What are inborn reflexes?taste/smell sensory cells, mechanosensitive sensory cells in mouth, oesophagus and reticulorumen and chemosensitive cells in ruminant forestomachs
- 54How are conditioned reflexes created?created when certain sensory stimuli are repetitively combined with feeding
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- Animal Disease 1 Veterinary Medicine Flashcards on Ruminant Digestion and Salivary Secretion, created by Louise Mason on 06/03/2017.
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