1. THE NITROGEN CYCLE

2. ANIMAL AGRICULTURE’S CONTRIBUTION TO N LOADING OF THE ENVIRONMENT Gaseous emissions % of emissions in the US NH 3 N 2 O NO Total agriculture 80 50 6 Animal agriculture 47-73 25 1 Contribution of different species to atmospheric ammonia

3. Contributions to total N in watersheds

4. Origin of livestock odor Odor compound Large intestine Carbohydrates Protein (Starch, cellulose) Volatile fatty acids (Acetic, Propionic, Butyric acids; may be absorbed or excreted) H 2 S and mercaptans (Passed as gas) Other amines, phenols, and indoles (Absorbed from LI & excreted in urine) Manure Carbohydrates (Secondary Volatile fatty acids and alcohols Protein fermentation Lactic acid greater at: Butyric acid Manure pH > 4.5; High manure moisture; NH 3, H 2 S, mercaptans, branched High ambient temperatures) chain VFAs (Isobutyric, Isovaleric), CH 4 Amines (Putrescine, Cadaverine), Phenols (Phenol, p-Cresol), Indoles (indole, Skatole) Air Emissions increased with increased temperature, moisture, humidity, agitation, dust, pH, wind, surface exposure

5. 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

6. 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 H 2 N 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.

7. AMINO ACIDS FOUND IN PROTEINS 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 NH 2 ) –Lysine –Arginine –Histidine –Glutamine 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

8. Ten amino acids that can’t be synthesized in adequate quantities are called ‘essential amino acids’ –Required in diet on nonruminant animals –Essential amino acids Phenylalanine Valine Tryptophan Threonine Isoleucine Methionine Histidine Arginine Leucine Lysine Other amino acids can be synthesized by animal cells and are called ‘nonessential amino acids’

9. PROTEIN ANALYSIS In applied nutrition, protein content of feeds is normally determined as crude protein Crude protein –Calculation CP% = N% x 6.25

10. Limitations of CP determination –Nitrogen in feeds may come from true protein on 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

11. 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.

12. PROTEIN DIGESTION IN RUMINANTS Rumen Total protein NPN Undegraded Small intestine Metabolizable Degraded protein Recycled via saliva (20% of dietary N) NH 3 Microbial protein NH 3 Liver Urea Kidney Excreted

13. Ruminal degradation of true protein –By ruminal bacteria and protozoa –Not totally desirable There is always some loss of NH 3 –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 50 Cottonseed meal 78 Soybean meal 89 Alfalfa 90 Heat treatments 100 C for 4 hours Soybean meal Reduced protein degradation Tannins in feeds reduce protein degradation –Example: Birdsfoot trefoil

14. Factors affecting microbial protein production in the rumen –Ruminal NH 3 -N concentration Microbial Ruminal NH 3 -N protein (% of Max) 5 mg% 12% Crude protein in diet, % –Rate of ammonia release Urea [NH 3 ] 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 NH 3

15. Protein digestion in the abomasum and small intestine –Similar to nonruminants

16. THE PROTEIN REQUIREMENT Nonruminants –Not a requirement for protein per se, but really a requirement for the 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

19. 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

20. FACTORS AFFECTING PROTEIN REQUIREMENTS Growth –Young, growing animals deposit more protein, but have lower feed intakes than larger animals Swine, kg CP 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

22. DIETARY STRATEGIES TO REDUCE N LOADING OF THE ENVIRONMENT BY NONRUMINANTS Reduce feed waste –Animals can be sloppy eaters –Amounts 5 – 6% of feed contributing 7.5% of the N in manure –May be as high as 20% –Strategies Feed pelleted feeds instead of mash Do not overfill feeders Properly position feeders

23. Maximize the apparent digestibility of N –Feed highly digestible protein sources –Feed processing Grinding Pelleting, expanding, or extruding –Enzyme addition (?)

24. Precision feeding of protein –Avoid feeding protein in excess of requirements Example (Feeding regimes for swine giving equal performance) %CP in diets Grower phase 17.8 17.8 16.2 Finisher phase 17.1 15.4 13.5 lb/pig Manure N 6.3 5.8 4.9 Gaseous N 2.4 2.1 1.8 % reduction Manure N - 9 23 Gaseous N - 12 25 Advantages –Reduces feed costs –Reduces environmental N load Strategies –Feed proteins for optimal gain, not necessarily maximum gain –Minimize safety margins in dietary formulation

25. –Balance for available amino acids Strategy –Utilize high quality protein sources or synthetic amino acids to feed an ‘ideal’ protein –An ideal protein has all of the essential amino acids in amounts proportional to their requirements relative to lysine –Potential (200 lb swine) 14% CP 12% CP 10% CP Corn-soybean meal + lysine + lysine threonine tryptophan _______ _______ methionine g/d Retained N 26 26 26 Fecal N 7 7 7 Urinary N 34 25 17 Total N excreted 41 32 24 % reduction - 22 42 –Amino acids currently economically produced »Lysine »Methionine »Threonine »Tryptophan

26. –Separate animals by sex and feeding phase Separate sex feeding –Protein requirements »Intact males>Castrated males>Females Phase feeding –As animal grows, protein requirement decreases as a percentage of diet –Potential of phase feeding (Swine) Feeding system Single feed Two feeds Three feeds Diet CP, % 17 (55-220 lb) 17 (55-120 lb) 17 (55-110 lb) 15 (120-230 lb)15 (110-165 lb) 12 (165-230 lb) N excretion, lb/pig/day.07.064.059 Reduction - 8.6 15.8 –Typical number of phases »Swine 3-4 »Broilers 4 »Turkeys 6 –Limited by feed storage and handling

27. Enhance lean growth (Swine) –Mechanism Increases incorporation of amino acids into protein Reduces the effects of the maintenance requirement –Strategies Genetically lean pigs Feed Ractopamine –Sold as Paylean for pigs –Used at 18 g/T for 150 to 240 lb (5 weeks) »Effect decreases after 4 weeks »Can’t be used longer than 90 days –Mechanism »Shifts energy from fat deposition to muscle growth in ham, loin, belly and shoulder –Effects »Increases feed efficiency – 12% »Increases daily gain – 10% »Increases lean gain – 25- 37% »Decreases N excretion by 11 to 34% –Greatest improvement in genetically lean pigs

28. STRATEGIES TO REDUCE N EXCRETION BY RUMINANTS Increase microbial protein production in the rumen –Maximize feed intake –Supply adequate, but not excess degradable protein –Feed highly digestible grains Grain species Grain variety Grain processing –Feed forages with high digestibility

29. Balance supply of rumen degradable protein and undegraded protein –Supplemental protein source dependent on forage protein degradability and energy level Ruminal degradability of protein Ruminal degradability of protein, % Forages Alfalfa 90 Cool season grasses 90 Corn silage 60 Grains and protein supplements Dry corn 50 High moisture corn 55-60 Soybean meal 65 Expeller soybean meal (Soyplus) 40 Corn gluten meal 25 Dry corn gluten feed 70 Dried distillers grains 50 Urea 100 With proper balance of RDP and RUP, dietary N can be reduced by 10 to 15% and N excretion can be reduced by 20%

30. –Optimal balance of degradable and undegradable protein is dependent on the animals’ body weights (growing-finishing cattle) or stage of lactation (dairy cows) In young, light-weight cattle or dairy cows in early lactation, metabolizable protein requirements exceed the amounts of microbial protein produced –Therefore, feed a supplement that is high in undegraded protein In feedlot cattle near finish or dairy cows in late lactation, microbial protein is adequate for metabolizable protein needs –Therefore, no supplemental protein needed if degradable N needs are met. Implications –Phase feed

31. Balance diets for essential amino acids by supplementing amino acids that are protected from ruminal degradation –Ruminal degradation of some amino acids are protected by binding with minerals or poorly degraded proteins –Protected amino acids currently economically viable Lysine Methionine –Only economically viable for lactating dairy cows –Reduces N excretion by 13 to 20%