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DIGESTIBILITY OF FEEDSTUFFS PP 96 – 101

DIGESTIBILITY OF FEEDSTUFFS PP 96 – 101. PURPOSES FOR DETERMINING FEEDSTUFF DIGESTIBILITY. Evaluate and quantify available nutrients from individual feed ingredients Evaluate and quantify available nutrients from diets (complete food matrices )

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DIGESTIBILITY OF FEEDSTUFFS PP 96 – 101

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  1. DIGESTIBILITY OF FEEDSTUFFSPP 96 – 101

  2. PURPOSES FOR DETERMINING FEEDSTUFF DIGESTIBILITY • Evaluate and quantify available nutrients from individual feed ingredients • Evaluate and quantify available nutrients from diets (complete food matrices) • Quantify the available energy concentration of feedstuffs and or feeds • Partition digestion of nutrients in different compartments of the digestive tract

  3. DIGESTION TRIALSStandard Protocol • Place animal in metabolism stall

  4. Without Metabolism Stalls/Crates

  5. Adjustment Period • First 10 to 14 days (can be shorter or longer depending on species, experimental design, discipline, etc…) • Free digestive tract of prior undigested feed • Accustom animals to environment • Feed to a constant rate • Isocalorically (maintain body weight) • Feed animal to attain 10% waste to determine ad libitum feed intake (typical for production animal trials) • Do not collect feces or urine

  6. Collection Period • Next 4 to 7 days • Non ruminants: 3 – 5 days • Ruminants: 5 – 7 days • Carefully record feed intake • Feed at 90% adlib intake (if feeding ad lib) • Collect all orts • Must have accurate intake data • Collect a diet sample – subsample • Collect all feces excreted, weigh • Large animals - collect a 5 to 10% subsample • Small animals (dogs, cats) – 100% fecal sample • (Optional) Collect urine, measure volume, collect a 5 to 10% subsample, and add to a composite urine sample

  7. Important Measures • Accurate feed intake • Include weight of all orts • Accurate fecal output • (must know 100% weight even if you are subsampling) • Appropriate diet samples • Accurate urine volume (if included)

  8. Post Collection • Determine chemical composition and/or energy concentration of feed samples, feces, orts • (Optional) Determine chemical composition and/or energy concentration of urine • Calculate digestibility • Digestibility (%) = Consumed – Excreted x 100 • Consumed

  9. DIGESTIBILITY CALCULATIONS • Dry matter intake (DMI) • Average amount of feed x %DM • Fecal output (FO) • Average amount of feces excreted x %DM (feces) • DM digestibility (DMD) • (DMI – FO)/DMI x 100% • Individual nutrient digestibility • Example: Protein • (DMI x %CPdiet – FO x %CPfeces)/(DMI x %CPdiet )x 100%

  10. Application • Concentration of the target digestible nutrient in diet (Example: Protein) • Crude Protein (%DM) x Protein Digestibility % = Digestible protein, %DM • Can be done for each nutrient of interest

  11. LIMITATIONS OF STANDARD DIGESTIBILITY TRIALS • Apparent Digestibility (Apparent Digestion Coefficient) • Feces composed of undigested nutrients and endogenous materials • Endogenous materials • Sloughed mucosa cells • Bacteria • Enzymes and bile salts • How do you determineTrue Digestibility? • Endogenous materials must be accounted for and removed from FO • Accomplished by: Ileal cannula (swine, dogs) or ceca removal poultry • Used for amino acid digestibility in non-ruminants

  12. Limiting feed intake to 90% adlib will slow rate of passage of digesta in the digestive tract • Spillage and wastage of feed or feces • Errors in analyses • Sorting of feedstuffs

  13. Production or Group HousingWhen animals cannot be placed in metabolism stalls/crates

  14. Methods to determine digestibility in producing animals • Fecal pans, bags • Need to know individual feed intake • Digestibility markers and indicators • Characteristics • Physiologically inert • Contain no element under investigation • Will not diffuse • Totally indigestible • Pass at uniform rate • Readily determined chemically • Examples • Carmine • Titanium oxide • Acid Insoluble Ash (AIA) • Chromic oxide

  15. Apparent Digestibility (%) = 100 – % indicator in feed x % nutrient in feces x 100 % indicator in feces % nutrient in feed

  16. Factors that Affect Digestibility • Physiological stage of the animal • Particle size/processing • Disease state (parasites, antibiotic treatment, etc…) • Feed source and composition • Level of intake • Rate of passage • Too slow = high fermentation and putrefactive compounds • Too fast = incomplete digestion • Nutrient imbalance (excess or deficiency) • Matrices might be different than individual feedstuffs used

  17. Balance Trials • Account for losses associated with urine • More precise measure of nutrient retention • Commonly done for nitrogen to measure protein gain or loss • Measurement: Nitrogen balance = = (Nitrogen intake) – (fecal nitrogen + urine nitrogen)

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