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LIVESTOCK’S ROLE INTHE NITROGEN CYCLE IN AGRICULTURAL SYSTEMS

LIVESTOCK’S ROLE INTHE NITROGEN CYCLE IN AGRICULTURAL SYSTEMS. ROLE OF PROTEIN NUTRITION IN N MANAGEMENT OF LIVESTOCK. Proteins are the basic unit of life Average composition of protein % Carbon 53

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LIVESTOCK’S ROLE INTHE NITROGEN CYCLE IN AGRICULTURAL SYSTEMS

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  1. LIVESTOCK’S ROLE INTHE NITROGEN CYCLE IN AGRICULTURAL SYSTEMS

  2. ROLE OF PROTEIN NUTRITION IN N MANAGEMENT OF LIVESTOCK • Proteins are the basic unit of life • Average composition of protein • % • Carbon 53 • Hydrogen 7 • Oxygen 23 • Nitrogen 16 • Possibly sulfur and phosphorus 1

  3. PROTEIN STRUCTURE • Primary structure • Chains of amino acids linked by a peptide linkage • Amino acids are organic acids having an amino group on the alpha-carbon • O • C OH • H2N C H • R • The side chain ( R) is different for each amino acid and determines the properties of the amino acid and protein • There are 22 amino acids commonly found in proteins in varying amounts • Order of amino acids in any protein is specific and associated with the function of that protein.

  4. AMINO ACIDS FOUND IN PROTEINS • Sulfur-containing amino acids (Contain S) • Methionine • Cysteine • Cystine • Aromatic amino acids (Contain a benzene group) • Phenylalanine • Tysosine • Tryptophan • Imino acids (Heterocyclic amino acids) • Proline • Hydroxyproline • Neutral amino acids (No special group) • Glycine • Alanine • Serine • Valine • Leucine • Isoleucine • Threonine • Acidic amino acids (Have an extra COOH group) • Aspartic acid • Asparagine • Glutamic acid • Basic amino acid (Have an extra NH2) • Lysine • Arginine • Histidine • Glutamine

  5. PROTEIN ANALYSIS • In applied nutrition, protein content of feeds is normally determined as crude protein • Crude protein • Calculation • CP% = N% x 6.25 • Limitations of CP determination • Nitrogen in feeds may come from true protein or nonprotein nitrogen sources • True protein • Only source of protein that can be used by nonruminant (monogastric) animals • Nonprotein nitrogen (NPN) • NPN may be utilized to meet the protein needs of ruminant animals • Nonruminants can not utilize NPN • Crude protein says nothing about the amino acid composition of a feed • Assume that amino acid composition for any particular feed is constant • Crude protein says nothing about the digestibility of the protein

  6. PROTEIN DIGESTION IN NONRUMINANTS • Digestion Stomach and intestinal enzymes Protein Amino acids • Digestion is normally high, but variable • Protein digestion, % • (swine) • Corn 85 • Soybean meal 84-87 • Wheat 89 • Wheat bran 75 • Meat and bone meal 84 • Poultry byproduct meal 77 • Digestibility may be reduced by excessive heating.

  7. PROTEIN DIGESTION IN RUMINANTS • Rumen • True protein • NPN • Undegraded Small intestine • Metabolizable • Degraded protein • Recycled via • saliva • (20% of dietary N) • NH3 Microbial • protein • NH3 • Liver • Urea Kidney Excreted CHOs VFAs Microbes

  8. Ruminal degradation of true protein • By ruminal bacteria and protozoa • Not totally desirable • There is always some loss of NH3 • Reduces efficiency • Increases N excretion • Valuable to have protein escape ruminal degradation in animals with high protein requirements • Factors affecting ruminal protein degradation • Protein source • % degraded in 24 hours • Fish meal 51 • Corn (Grain or DDGS) 50 • Cottonseed meal 78 • Soybean meal 89 • Alfalfa (and most other forages) 90 • Heat treatments • 100 C for 4 hours • Soybean meal Reduced protein degradation • Tannins in feeds reduce protein degradation • Example: Birdsfoot trefoil

  9. Factors affecting microbial protein production in the rumen • Ruminal NH3-N concentration • Microbial Ruminal NH3-N • protein • (% of Max) 5 mg% • 12% • Crude protein in diet, % • Rate of ammonia release • Urea • [NH3] Treshold • Biuret • 2 • Time after feeding, hours • Energy level of the diet • Energy and C-skeletons needed by rumen bacteria to produce microbial protein from ruminal NH3

  10. Protein digestion in the abomasum and small intestine • Similar to nonruminants • Proteins are digested to amino acids

  11. OVERVIEW OF AMINO ACID UTILIZATION AFTER DIGESTION Body Protein Non-protein Derivatives Dietary Protein Cellular Amino Acids Glucose Ammonia TCA cycle CO2 + Energy Urea or Uric acid Fatty acids

  12. AMINO ACID METABOLISM • Protein synthesis • Mechanism • Protein synthesis controlled by DNA in the nucleus of cells • DNA is divided into subunits of 3 bases specific for each amino acid • Messenger RNA is produced from DNA • Messenger RNA migrates to ribosomes where it acts as the template for protein • To be used in protein synthesis, amino acids are bound to transfer RNA (specific) • Transfer RNA travels along the messenger RNA to place amino acid in chain • If an given amino acid is not present, synthesis of this protein stops and no more amino acids will be used

  13. Hormonal control • Growth hormone Amino acid • Thyroxine • Increase IGF (Liver) Growth hormone • Transport Testosterone • Insulin • Amino acid • Muscle Testosterone • DNA synthesis Synthesis Degradation • Increase IGF (Muscle) • Protein • Estrogen X

  14. Transamination • Transfer of an amino group from one amino acid to another carbon chain (called a keto acid) to construct a new amino acid • Alpha amino acid1 + keto acid2 keto acid1 + alpha amino acid2 • Importance • A method of synthesizing some specific amino acids from intermediates of carbohydrate metabolism or vis versa • These amino acids are called ‘nonessential’ because they are not needed in the diet

  15. Deamination • Releases amino group from excess amino acids • Mechanism • NH2 O • R C COOH + O R C COOH + NH3 • (C skeleton) • H • Uses of C skeleton • Energy metabolism • Glucose synthesis • New amino acids • Removal of NH3O • Mammals • Synthesis of urea H2N C NH2 • Detoxifies NH3 • Poultry • Synthesis of uric acid; excreted with feces • O • H • C N • H N C • C O • O C C • N N • H H

  16. THE PROTEIN REQUIREMENT • Nonruminants • Not a requirement for protein per se, but really a requirement for 10 essential amino acids • Essential amino acids in the diet • For growth of pigs • Phenylalanine • Valine • Tryptophan • Threonine • Isoleucine • Methionine • Histidine • Arginine • Lysine • Leucine • Additional amino acids for poultry • Arginine • Glycine • Cystine can replace ½ of the methionine • Tyrosine can replace 1/3 of the phenyalanine

  17. Balance of amino acids in a diet is as important as the amounts of individual amino acids • Amino acids can only be used to the extent of the least abundant amino acid relative to the animal’s requirement • Remainder of amino acids will be deaminated and N will be excreted as: • Urea in mammals • Uric acid in poultry • Ammonia in fish • An excess of one amino acid may cause a deficiency of another amino acid • Excess leucine Deficiencies of valine and isoleucine

  18. Ruminant protein requirements • Ruminants have no essential amino acid requirements in their diets • The rumen microbes can synthesize all of the amino acids • Ruminants require • Degradable N up to 12% crude protein in the diet dry matter • To meet the N needs of the rumen bacteria • Undegraded protein above 12% crude protein

  19. FACTORS AFFECTING PROTEIN REQUIREMENTS • Growth • Young, growing animals deposit more protein, but have lower feed intakes than larger animals • Swine, kgCP reqt. % • 1-5 27 • 5-10 20 • 10-20 18 • 20-35 16 • 35-60 14 • Sex • Males deposit more protein at a given weight than females • 300 kg large frame gaining 1 kg/d gm protein/day • Bulls 807 • Steers 804 • Heifers 735 • Production of milk, eggs, or wool

  20. METHODS TO MINIMIZE NITROGEN EXCRETION BY LIVESTOCK • Nonruminants • Do not overfeed protein • Separate sexes • Phase feed • Balance amino acids • Use individual amino acids • Ruminants • Do not overfeed protein • Phase feed • Properly balance rumen undegraded and degraded proteins • Undegraded proteins • Young cattle and dairy cows in early lactation • Degraded proteins • All other cattle • Feed high energy diet with degraded proteins • Growth promotants and BST

  21. MANURE HANDLING AND STORAGE TO MINIMIZE N LOADING OF THE ENVIRONMENT • Reason to store manure • Preserve and contain manure nutrients until it can be spread onto the land at a time compatible with climate and cropping system • Goals • Maintain excreted N in non-volatile organic forms • Undigested protein • Microbial N • Urea • Minimize volatilization of NH3 • Minimizes PM2.5 • Minimizes N deposition in terrestial and aquatic ecosystems • Reduces manure odors • If N is volatilized, it should be in the form of N2 • Prevent losses of N into surface and ground water sources • Provide adequate storage until it can be safely spread

  22. N TRANSFORMATIONS IN LIVESTOCK PRODUCTION AND MANURE STORAGE FACILITIES Manure N Anerobic microbial C skeletons H2S degradation (slow) VOCs Fecal N (20-40% of N) Microbial N NH4+ Slow Urine N aerobic Anerobic (60-80% of N) Microbial NH3 NO2 N2 O urease (rapid) pH (volatile) H2N C NH2 + H+ + H2O 2NH4+ 2HCO3- • In poultry • Urinary N is secreted as uric acid with the feces

  23. FACTORS AFFECTING NH3 LOSS FROM LIVESTOCK HOUSING AND MANURE STORAGE FACILITIES • NH3 volatilization increased by: • Increasing manure pH • Increased by increased HCO3 and NH3 • Increased difference in NH3 concentration between air at manure surface and ambient air • Ambient air NH3 NH3 NH3 NH3 • Manure surface NH3 NH3 NH3 NH3 NH3 NH3 (Gay and Knowlton, 2005)

  24. Increased surface area • Increased air velocity at surface • Increased ambient temperature • Increases urease activity • Increases NH3 mass transfer coefficient • Increases ventilation from confinement buildings • Decreased ambient temperatures increase NH3 concentrations in confinement buidings • Increased moisture

  25. N LOSSES FROM DIFFERENT MANURE HANDLING AND STORAGE SYSTEMS N loss, %N retention, % Daily scrape and haul from barn 20-35 65-80 Open lot 40-70 30-60 Pile (Cattle/Swine) 10-40 60-90 Pile (Poultry) 5-15 85-95 Compost 20- 50 50-80 Deep pit (Poultry) 25-50 50-75 Litter 25-50 50-75 Pit under floor (Swine) 15-30 70-85 Tank above ground top loaded 20-35 65-80 Tank above ground bottom loaded 5-10 90-95 Tank above ground with cover 2-30 70-98 Holding basin 20-40 60-80 Anerobic lagoon w/ no cover 70-80 15-30 Constructed wetlands 15 85

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