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RUMINANT DIGESTIVE TRACT
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Stomach Small intestine Large intestine Reticulum, rumen & omasum
Fermentation Absorption of fermentation endproducts Abomasum Secretion of hydrochloric acid and pepsinogen Small intestine Similar to non-ruminant No sucrase Large intestine More important in browsing species
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CARBOHYDRATE DIGESTION IN RUMINANTS
Starch Structural CHO Methane Undegraded Small intestine (Digestion similar to NR) Fermented Volatile fatty acids (VFA) Liver & peripheral tissues Energy and fat synthesis
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PROTEIN DIGESTION IN RUMINANTS
True protein NPN Undegraded Small intestine Metabolizable Degraded protein Recycled via saliva (20% of dietary N) NH Microbial protein NH3 Liver Urea Kidney Excreted
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LIPID DIGESTION IN RUMINANTS
Fat Undegraded Small intestine (Digestion similar to NR) Degraded Glycerol VFA Long chain FA Saturated FA Liver & peripheral tissues Energy and fat synthesis
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What is the primary volatile fatty acid produced in the rumen fed a high forage diet?
Acetic acid Butyric acid Lactic acid Conjugated linoleic acid Propionic acid
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CHEMICAL ANALYSIS OF FEEDSTUFFS Pages 87-93
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FEED ANALYSIS SYSTEMS Feed analysis systems
Needed to rationally group feed nutrients and requirements Makes analysis relatively easy and cost-effective Feed analysis systems Proximate analysis system (Weende system) Developed in 1864 at Weende Experiment Station in Germany Detergent analysis system (Van Soest system) Developed in 1964 at USDA Beltsville Research Center
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PROXIMATE ANALYSIS COMPONENTS
Dry matter (DM) Ash Crude protein (CP) Ether extract (EE) Crude fiber (CF) Nitrogen-free extract (NFE)
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FEED NUTRIENTS
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Dry matter (DM) DM,% = wt after drying/wt before drying x 100
% moisture = 100 – DM,% Example Ending weight = 550 grams Beginning weight = 750 grams What is the % Dry Matter? What is the % Moisture (water)? 73.3% Dry matter 26.7% Moisture (water)
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Problems with the DM method
Errors from losses of volatile components Major issue for fermented feeds Toluene distillation or freeze drying Drying at 100o C destroys some nutrients and sample for further analysis Freeze drying Dry at lower temp for longer time for sample needing further analysis (will still need to run DM on portion of sample)
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Significance of Dry Matter
Considerable variation in the DM, % of feedstuffs Corn grain, 88% DM Alfalfa hay, 90% DM Alfalfa silage, 45% DM Alfalfa pasture, 26% DM Whey, 7% Other nutrients are present within the dry matter Affects expression of concentrations of nutrients in feedstuffs Example Crude protein, % DM,% Wet basis DM basis Dried distillers grains Modified distillers grains Wet distillers grain
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Significance of Dry Matter
Affects storage properties of feedstuffs DM,% <30 30-60 60-75 68-75 >82 Putrefaction Ensiled forages Mold & heating High moisture grains Dry grains and baled forages
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FEED NUTRIENTS Ash
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Ash Material remaining after oxidation of a sample in a muffle furnace. % Ash = wt after ashing/sample wt x 100% % Organic matter = % ash Problems No indication of amounts of individual minerals Some minerals (Sulfur, Selenium, Zinc, Iodine are lost) Significance May indicate soil contamination or adulteration of feedstuff or diet.
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What is in organic matter?
Nitrogenous compounds Protein Fat soluble vitamins Starch All of the above None of the above
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FEED NUTRIENTS Organic Matter
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FEED NUTRIENTS Crude Protein
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Crude protein (CP) Measures the nitrogen in a sample
Kjeldahl N – acid base titration N analyzer – combustion, measures nitrogen % Crude protein = %N x 6.25 What is % N? Most proteins contain 16% N; therefore every 100 mg of protein contains 16 mg nitrogen. 100 mg protein / 16 mg nitrogen = 6.25 CP,% = measured mg N/100 mg sample x 100 mg protein/16 mg N = measured mg N/100 mg/sample x 6.25
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Question Why have some foreign feed companies added the compound to some feed ingredients? Increase the energy concentration Increase the crude protein concentration Supply an essential amino acid Supply a required vitamin
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Problems with crude protein procedure – will not indicate protein quality, source of nitrogen, digestibility Sources of N: True protein Chains of amino acids bound by peptide linkages Can meet the protein requirements of either non-ruminant or ruminant animals Non-protein nitrogen Forms Free amino acids Nucleic acids Ammonia Urea Biuret
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What form(s) of crude protein can be used to meet the crude protein requirement of a 120 lb growing gilt? Chains of amino acids Ammonia Biuret Urea All of the above
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What form(s) of crude protein can be used to meet the crude protein requirement of a 800 lb growing steer? Chains of amino acids Ammonia Biuret Urea All of the above
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Crude protein says nothing about the digestibility of a protein
Example: % Crude protein % Protein Digestibility Soybean meal Feather meal
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Heat Damage of Proteins
When overheated (heat damaged) protein will bind to cell wall carbohydrates particularly across lysine Reasons for this: Molding of forages Over-heating during processing Over-drying of grains or soybeans Referred to as the Maillard or Browning Reaction Results % Crude protein % Protein Digestibility Well-preserved alfalfa hay Heat-damaged alfalfa hay
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FEED NUTRIENTS Ether Extract
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Ether extract (EE) Reflux ether through sample (solvent pulls lipid out) % EE = (Sample wt-residue after reflux)/Sample wt) x 100% Also called crude fat Problem with procedure Ether extract consists of: True lipids Fats and oils Non-nutritional ether soluble components Fat-soluble vitamins Chlorophyll Pigments Volatile oils Waxes
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FEED NUTRIENTS Crude Fiber
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Crude fiber (CF) Extract with dilute acid, then dilute base, the residue weighed then ashed. % CF = (residue wt - Ash wt)/sample wt x 100% Theoretically represents: the structural carbohydrates (Cellulose and hemicellulose) Limited digestibility in ruminants Poor digestibility in non ruminants Lignin Indigestible by ruminants and non ruminants Problems with procedure Poor recovery of components % recovered Cellulose 90 Hemicellulose 50-60 Lignin (very large error rate)
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FEED NUTRIENTS NFE
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Nitrogen-free extract (NFE)
No actual analysis Calculation by difference %NFE = %DM – (%ash+%CP+%EE+%CF) Theoretically represents: Starch Sugars Problems: Contains all of the errors from other analyses Largest error is unrecovered lignin will be placed in NFE
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WHY IS PROXIMATE ANALYSIS SYSTEM STILL USED?
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DETERGENT ANALYSIS SYSTEM
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Uses of the Van Soest system
Predict intake (NDF) Predict digestibility of forage (ADF) Determine heat damage (ADF) Determine Net Energy (NE) and Total Digestible Nutrients (TDN) Determine degradability of protein in rumen
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Neutral detergent fiber (NDF)
Consists of hemicellulose, cellulose, lignin, cell wall bound protein and insoluble ash Significance: Highly related to feed intake (index of “gut fill”) Acid detergent fiber (ADF) Consists of cellulose, lignin, poorly digested protein, and insoluble ash Highly related to forage digestibility and energy concentration Combination of DDM (determined from ADF) and DMI (determined from NDF) is used to determine Relative Feed Value (RFV) Useful for hay marketing
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Heat Damaged Forages Typically occurs during ensiling when air gets into the mass. Result is aerobic rather than anaerobic fermentation Increase in temperature Protein and carbohydrate combine = unavailable protein (Maillard reaction) Determined by ADIN (Acid Detergent Insoluble Nitrogen) Analysis = ADF; Total N; N in the ADF fraction
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General Guidelines on Heat Damage
0 – 10% Unavailable protein = little heat damage 11 – 25% Unavailable protein = moderate to severe damage > 26% Unavailable protein = Severe heat damage Example: Alfalfa silage Total N = 3.05% ADIN = 0.25% 3.05 – 0.25 = 2.80% N available 2.80 / 3.05 x 100 = 91.8% nitrogen available or 8.2% unavailable
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N bound to NDF and ADF is used to determine rumen degradable, rumen undegradable, and indigestible fractions Rumen degradable protein = Total CP – (NDFCP, % of CP x Total CP) Rumen undegradable protein = (NDFCP, % of CP xTotal CP) – (ADFCP, % of CP x Total CP) Indigestible protein = (ADFCP, % of CP x Total CP)
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