Ruminant Nutrition (PDF)

Ruminant Nutrition What happens to what is eaten?? Objectives Be able to explain the healthy GIT and its function Describe how ruminants break down carbohydrates/fibre into useful products Explain and understand how energy is derived from the products of fibre digestion and are then utilised Describ...

Ruminant Nutrition What happens to what is eaten?? Objectives Be able to explain the healthy GIT and its function Describe how ruminants break down carbohydrates/fibre into useful products Explain and understand how energy is derived from the products of fibre digestion and are then utilised Describe how protein and lipids are utilised in the ruminant diet So nutrition affects… Milk yield Fat content Protein content BCS Diarrhoea Constipation ‘Immunity’ Abomasal displacements Ketosis Fatty Liver Fertility Acidosis Bloat Milk fever Hypomagnesaemia Growth Support pregnancy But ultimately! Foodstuffs FORAGE a whole plants) Grass (silage, hay, haylage) Brassicas - kale Roots – potatoes, beet, turnips, swedes Straw Maize 60 formulated based CONCENTRATES Cereals – barley ‘Cake’ (Not couch Soya Rape seed Molasses 40 on forge available Relative Volumes Ruminant Stomachs NEONATE ADULT Rumen – 25% Rumen – 62% Reticulum – 8% Reticulum – 11% Omasum – 8% Omasum – 5% Abomasum – 60% Abomasum – 22% So when food is eaten what happens? =R z Rumen Left hand side of cow First stomach entered Large holding capacity (100-200 litres) releases Rhythmic contractions endorphine Food regurgitated and ‘re-chewed’ Then digested (fermentation vat) and utilised Absorption of VFAs and NH4 to maintain pH - Relaxing. : when Xchew stressed. Normal conditions easily destable food 38 - IT-b 40°C : wh Anaerobic – all oxygen utilised – fermentation & bicarbonates -o pH butter pH 6.0 – 6.5 ephosphate Buffering capacity – salivation (150 l/day cows) Produces gas – CO2, CH4, 10⁹ - 10¹⁰ per ml of bacteria (flora) 10⁶ per ml of protozoa (fauna). Normal Rumen Storage facility allowing time for foodstuffs to be digested sufficiently As food enters same volume leaves Soluble components ie sugars soon fermented Insoluble components gradually broken down by microbes Large particles form a fibrous mat until broken down. Fibre mat important for: Rumen movements Saliva flow Via stimulation of the vagal nerve netrate (schutzon gabes Particles need to be about 3-4mm to leave rumen High roughage diets increase transit time due to salivation but this decreases digestion Aim to have quickly digestible small sized concentrates that provide maximum energy quickly without rumen acidosis RETICULUM No absorptive capacity Controlled by the N vagus (Cranial nerve, X) emanly Mechanical breakdown Rumen contractions start here Microbial fermentation Proportionally larger in small ruminants. in numen Omasum Biphasic contractions First contractions removes fluid Fluid with VFA and NaCHO3 This is then absorbed Second contractions then expel solids into abomasum Controlled by N vagus Abomasum Glandular Digests food chemically Releases HCl and pepsinogen (gastric area in the pylorus) Proteins broken down to be absorbed in SI Has intrinsic motility Weak contractions strengthen as reach the pylorus to aid expulsion of contents Proportionally larger in small ruminants Small Intestine Duodenum neutralises stomach acid * prome to infection. Pancreas and bile duct secrete in duodenum for fat, carbohydrate and protein breakdown Jejunum site for absorption aided by long microvilli Ileum absorbs remaining nutrients and vit B12 Ileum contains lymphoid tissue Ileo-caecal valve prevents backflow from unge T V diff G To small bacteria parasites, Large Intestine Shorter than SI Caecum blind ended sac in right sub-lumbar fossa Storage and allows further breakdown of foodstuffs Colon primary site for water and Na absorption Bacteria in colon produce necessary Vit K + thiamine -thenabsorbed large intestine Used as a channel for removal of waste in What are Microbes? Yyears) Include bacteria, protozoa and fungi - Feed on forages ingested by the cow Then via anaerobic fermentation they produce end products that can be utilised by the cow as well as by the microbes themselves Digest up to 70% dry matter but microbes have differing functions ie some digest cellulose, others digest sugars Essential diet contains sufficient energy and protein for the growth and multiplication of microbes so that rate of digestion is maximised End Products of Microbes VFAs cow’s main energy source Ammonia used to form microbial protein Microbial bacteria are digested and are the cows main source of protein Gases Waste products that are eructated out (CO2 and CH4) So what happens when a cow eats carbs? Consist of Cellulose Hemicelluloses Starch Water-soluble sugars § Fructans mainly Straw/hay – CELL WALL Young lush pasture - CELL CONTENTS LIGNIN – non-digestible by rumen microorganisms ie. No nutritional value Reisen Fibre analysis degestion in runen Crude Fibre (CF): Crude fibre is a traditional measure of fibre content in feeds. Neutral detergent fibre (NDF) and acid detergent fibre (ADF) are more useful measures of feeding value, and should be used to evaluate forages and formulate rations. Neutral Detergent Fibre (NDF): Structural components of the plant, specifically cell wall. These are slowly digested. An increased NDF → decreased intake Acid Detergent Fibre (ADF): The least digestible plant components, including cellulose and lignin. This often has a poor energy content and is excreted in the faeces Fermentation of Carbohydrates… Slowly! Such as straw, fibrous hay Produce a large proportion of acetate The bacteria that do this are sensitive to fats and high acidity. Therefore cows with high fats diet or which have acidosis are unable to break down celluloses Cellulose (rumen) VFAs (rumen) Glucose formation/ enter Krebs (liver) Fermentation of Carbohydrates such a lush pasture Hemi-cellulose (rumen) VFAs (rumen) Glucose formation/ enter Krebs (liver) Fermentation of Carbohydrates such as potatoes/beet which are rapidly digested thus increasing the levels of propionate rapidly These bacteria are not affected by acidity but supress the acetate forming cellulose digesting bacteria Starch (via amylase) (rumen) VFAs (rumen) Glucose formation/ enter Krebs (liver) Fermentation of Carbohydrates…. Rapid! Such as molasses, glucose, dissolved sugars Similar bacteria as to those that break down potatoes and beet. The difference is that they don’t have such a profound effect on reducing the rumen pH Sugars (rumen) Glucose formation/ enter Krebs (liver) short chain. Volatile Fatty Acids (SCFAs) - VFAs are the end products of anaerobic microbial fermentation of carbohydrates in ruminants VFAs are the major end products of the fermentation simply because C-skeletons cannot be completely oxidized to CO2 in the absence of oxygen They are readily absorbed into the blood stream and transported to the liver where they are converted to other sources of energy There they are used for hepatic gluconeogenesis, lipogenesis in peripheral tissues and milk synthesis. Volatile Fatty Acids (VFAs) Rapidly absorbed to minimise acidosis This is why try to dissuade farmers from feeding in parlour Determine milk fat and protein content Provide 70% cows energy Help promote growth of rumen papillae Absorbed through rumen wall and go to liver Used as an energy source by the liver Remember this!! (for future years) Event X Fromplease Acetate Butyrate. propionate Ref; J.E. Huston and W.E. Pinchal Acetate 55-65% of VFAs produced is acetic acid It predominates on a high roughage diet Synthesis of fatty acids in adipose Is a precursor for mammalian milk fat Found in peripheral circulation Some is also used for muscle metabolism and body fat Net gain of 10 (moles) ATP per mole acetate via acetyl CoA entering Krebs (TCA) cycle Butyrate 10-15% of VFAs produced is butyric acid Provides energy to the rumen wall It doesn't vary in proportion to other volatile fatty acids Found in poorly fermented silage Liver turns into betahydroxy-butyrate (BHBs), used by muscle, milk gland Net gain of 25 ATP per mole butyrate (via acetyl CoA entering Krebs) Propionate 18-21% of VFAs produced is propionic acid Predominates in a high concentrate diet Precursor of glucose Provides energy via the conversion of blood glucose in the liver Used in lactose (milk sugar) synthesis Net gain of 18 ATP per mole propionic acid via Krebs cycle Digestion of Protein Undegraded Dietary Proteins (UDPs) Dietary protein not broken down by microbes in the rumen and so pass to the abomasum Rumen Degradable Protein Broken down by rumen microbes (bacteria) The nitrogen and amino acids are used by the rumen microbes to grow As microbes can use any source of nitrogen little is needed (in fact can be a waste of money) Must be sufficient as if insufficient then not enough microbes and carbohydrate breakdown slows down # Leach Nitrogen fo in environmen ↓ miragen-cone Microbial Crude Protein OR BCP - bacterial crude protein Flow of protein contained in rumen bacteria which is produced in the rumen and is passed to the intestine for digestion 80% true protein and 80% digestible ie. The protein that reaches the abomasum and SI is either MCP or UDPs. Non-Protein Nitrogen If excessive RDP then the excessive ammonia is absorbed into the blood and carried to the liver Liver turns NH4 into urea, then excreted in urine If insufficient protein in diet then more ammonia returned to rumen This ammonia is then turned into MCP In this way, more protein may reach the SI then is actually consumed. Protein diagram Non-Protein Nitrogen Compounds This is why urea added to the diet Rumen acts as a leveller so constant stream of protein passing to SI Must ensure enough energy in the diet for protein synthesis If ammonia too high can overload liver capacity and cause toxic levels of NH4 in the blood. Lipids Minimal digestion in rumen (ideally 100g/kg inhibits microbe action LCFAs not absorbed by rumen Most fats consumed are triacylglycerides (TAGs) which are hydrolysed by lipases Fats are then saturated in the rumen Pass to SI for digestion If treated, dietary fats can remain unsaturated when get to SI and these alter milk fat content SUMMARY Glossary ADF = acid detergent fibre CP = crude protein DCP = digestible crude protein DE = digestible energy DMI = dry matter intake DUP = digestible undegraded protein ERDP = effective rumen degradable protein FME = fermentable metabolisable energy GE = gross energy LCFA = long chain fatty acids MCP = microbial crude protein ME = metabolisable energy MP = metabolisable protein NDF = neutral detergent fibre NE = net energy NP = net protein RDP = rumen degradable protein TMP = total mixed ration UDP = undegraded dietary protein VFA = volatile fatty acids