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Description
Flashcards by Louise Mason, updated more than 1 year ago
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Created by Louise Mason
over 7 years ago
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| Question | Answer |
| What are the stomachs like in young ruminants? | well-developed abomasum and immature forestomachs |
| What is the purpose of the reticular groove reflex? | enables milk to bypass the rumen and enter the abomasum directly |
| Why 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 |
| What 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 |
| What 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 |
| In 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 |
| What part of the brain is responsible for controlling the reticular groove reflex? | Medulla |
| What 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) |
| What stimulates the growth of forestomachs? | abrasive/churning action of forage particles and the chemical effects of fermentation products e.g. butyric acid |
| What percentage of gross energy in the ruminant comes from carbohydrates? | 85% |
| Ruminants can break down all carbohydrates except for those bound to or masked by which molecule? | Lignin |
| What bond is hydrolysed in ruminants that can't be hydrolysed in other mammals? | Beta-bonded cellulose, hemicellulose and pectin |
| How are beta-bonds hydrolysed in the ruminant? | hydrolysed by anaerobic microbes by fermentation |
| In ruminants, what are the products of carbohydrate digestion? | Volatile Fatty Acids: acetate, propionate, butyrate |
| What 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 |
| What 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 |
| What three key factors influence fermentation? | Substrates (carbohydrates, lipids, proteins), Microbes (substrate preferences and tolerance to conditions), Conditions (pH and substrate conditions) |
| Why does pyruvate produce VFA in ruminants but not in other mammals? | there is no TCA in ruminants (entirely anaerobic) |
| What is the importance of producing Methane during carbohydrate fermentation? | regenerates NAD+ from NADH |
| What does the diet determine in terms of rumen ecology? | number of microorganisms and the balance between different types of them |
| How 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 |
| How are some end products recycled within fermentation? | they can act as substrates for other microbes (inter-dependency) |
| How 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 |
| What percentage of available energy from fermentation is used by the microbes themselves? | 7% |
| In 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) |
| In a normal/high roughage diet, what is fermentation mainly driven by? | pre-absorptive factors, rumen volume |
| Why 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 |
| Why 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 |
| What 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 |
| What are the functions of salivary secretion? | oral hygiene and food lubricaiton |
| In the ruminant, why does saliva contain anti-frothing proteins? | many plants have foaming agents and so specific enzymes are needed to break these down |
| In 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) |
| In 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 |
| What does the consistency of saliva depend on? | depends on which salivary gland had the largest stimulation |
| What, in the ruminant, is dependent upon CNS control? | salivary secretion and stomach motility |
| How does primary salivary secretion compare to ECF? | always isomotic with ECF due to effective osmosis |
| What 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 |
| In monogastrics, what alters salt composition? | duct cells to create saliva that is hypotonic and with low Sodium concentrations |
| In 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 |
| Approximately what percentage of body water is recycled throughout the GI tract every day? | 50% |
| In ruminants, what is the main stimulus for salivary secretion? | food in mouth and anticipation |
| What nerves control salivary secretion in ruminants? | parotid and sublingual nerves (never zero as there's quite a high basal secretion) |
| How is saliva important as pH buffer in ruminants? | neutralises 1/3 of acid in forestomach, bicarbonate and phosphate at high concentrations |
| What is the pH of ruminant saliva? | around pH 8 |
| What is the importance of phosphate ions in ruminant saliva? | needed for the buffering effect and microbial growth |
| What 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 |
| How does eating rate vary with food water content? | dry = slow wet = fast |
| What effect does parasympathetic innervation have on saliva secretion? | increases salivary secretion with a watery content |
| What effect does sympathetic innervation have on saliva secretion? | increases the secretion of viscous saliva |
| In 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 |
| What effect does parasympathetic innervation have on blood flow? | increases blood flow to a larger extent than when exercising |
| What two types of long reflexes can increase the rate of saliva secretion? | Inborn reflexes and conditioned reflexes |
| What are inborn reflexes? | taste/smell sensory cells, mechanosensitive sensory cells in mouth, oesophagus and reticulorumen and chemosensitive cells in ruminant forestomachs |
| How are conditioned reflexes created? | created when certain sensory stimuli are repetitively combined with feeding |
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