* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Nitrogen lectures (Part 2)
Gene expression wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Nucleic acid analogue wikipedia , lookup
Ancestral sequence reconstruction wikipedia , lookup
List of types of proteins wikipedia , lookup
Protein moonlighting wikipedia , lookup
Magnesium transporter wikipedia , lookup
Ribosomally synthesized and post-translationally modified peptides wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
Western blot wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Bottromycin wikipedia , lookup
Cell-penetrating peptide wikipedia , lookup
Peptide synthesis wikipedia , lookup
Metalloprotein wikipedia , lookup
Two-hybrid screening wikipedia , lookup
Point mutation wikipedia , lookup
Protein adsorption wikipedia , lookup
Protein (nutrient) wikipedia , lookup
Genetic code wikipedia , lookup
Protein structure prediction wikipedia , lookup
ANIMAL AGRICULTURE’S CONTRIBUTION TO N LOADING OF THE ENVIRONMENT • Gaseous emissions Total agriculture Animal agriculture % of emissions in the US NH3 N 2O NO 80 50 6 47-73 25 1 • Contribution of different species to atmospheric ammonia • Contributions to total N in watersheds – Distribution of total manure N in relation to ability to apply at agronomic rates in US % of farms w/ % of manure N % of counties w/ % of manure N adequate land produced on adequate land produce in land to apply farms with land to apply counties with produced N adequate land produced N adequate land at agronomic to apply manure at agronomic to apply manure rates N produced rates N produced____ 78 40 95 80 – Distribution on excess manure N by species in the US % of manure N produced in excess of land available % of % of manure N for application at Species AFOs excreted agronomic rates Beef 9 48 18 Dairy 49 22 7 Swine 27 9 15 Poultry 15 20 60 ROLE OF PROTEIN NUTRITION IN N MANAGEMENT OF LIVESTOCK • Proteins are the basic unit of life • Average composition of protein Carbon Hydrogen Oxygen Nitrogen Possibly sulfur and phosphorus % 53 7 23 16 1 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 H2N C OH 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 200 amino acids of which 22 are commonly found in proteins in varying amounts 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 NH2) – – – – 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 – Peptide linkage is the bond that hold amino acids together in proteins H CH2 N H O + HO COOH H O C CH2 CH2 NH2 N C COOH CH2 NH2 • Most proteins will have chains of 350 to 5000 amino acids • Amino acid chains with less than 100 amino acids are called peptides • Secondary structure – Hydrogen bonding that occurs with a chain producing helixes or sheets • Tertiary structure – Folding and twisting of protein chains held together by disulfide linkages between and within chains • Quaternary structure – Aggregates of two or more amino acid chains IMPORTANCE OF PROTEIN STRUCTURE • Determines biological activity • Determines digestibility LOSS OF PROTEIN STRUCTURE • Denaturation – Loss of secondary, tertiary, and quaternary structure – Caused by heat, UV light, alkali or organic solvents – Effects • Loss of biological activity • May increase digestibility • Browning or Maillard reaction – Results from overheating of feeds – Causes • Over-cooking of feeds • Over-drying of grains • Over-heating of feeds during storage – Mechanism Protein + Carbohydrate Indigestible protein-carbohydrate complex (Acid detergent insoluble N; ADIN) PROTEIN ANALYSIS • In applied nutrition, protein content of feeds is normally determined as crude protein • Crude protein – Calculated from the N content of the feed determined by the Kjeldahl analysis Digested in H2SO4 Sample Distill into boric acid (NH4)2SO4 (NH4)borate Titrate with acid – CP% = N% x 6.25 • The factor 6.25 comes from the fact that most proteins contain 16% N or 16 gm N/100 gm protein – 100 gm protein/16 gm N = 6.25 • Limitations of CP determination – Nitrogen in feeds may come from true protein on nonprotein nitrogen sources • True protein – Example » Chains of amino acids – Only source of protein that can be used by nonruminant (monogastric) animals • Nonprotein nitrogen (NPN) – Examples » Free amino acids » Nucleic acids » Ammonia » Urea » Biuret – 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 – Crude protein says nothing about the digestibility of the protein • Individual amino acids can be analyzed by chromatographic procedures – Expensive – Slow • Near infrared reflectance spectroscopy may have the potential for real-time amino acid analysis – Procedures still need to be developed PROTEIN DIGESTION IN NONRUMINANTS • Digestion Proteins • In stomach – HCl secreted by gastric glands • Denatures protein • Converts pepsinogen into pepsin – Pepsinogen secreted • Converted into pepsin by HCl • Pepsin is an endopeptidase that preferentially degrades peptide linkages next to aromatic amino acids Peptides Peptides Amino acids • In small intestine – Pancreatic proteases Proenzyme Active enzyme Activated by Bonds hydrolyzed Trypsinogen Trypsin Enterokinase Bonds next to lysine and arginine ChymoChymotrypsin Trypsin Bonds next to trypsinogen phenyalanine, tyrosine, leucine, histidine, methionine and tryptophan Procarboxy Carboxypeptidase Trypsin Amino acids w/ peptidase free carboxyl group – Small intestinal peptidases – Digestion is normally high, but variable Corn Soybean meal Wheat Wheat bran Meat and bone meal Poultry byproduct meal Protein digestion, % (swine) 85 84-87 89 75 84 77 • Amino acid absorption – Most protein is absorbed as amino acids, but small amounts of peptides are absorbed – Amino acid absorption occurs by active transport • Requires energy and a carriers on the intestinal membranes • Carrier systems – Neutral amino acids (Leucine, Isoleucine, Valine) – Neutral amino acids (Glycine, Alanine, Serine) – Basic amino acids (Lysine, Arginine) – Imino acids (Proline, Hydroxyproline) • Amino acids compete for carrier systems – Excess leucine inhibits absorption of valine and isoleucine absorption – Excess lysine inhibits arginine absorption – Excess methionine inhibits lysine absorption • Requires vitamin B6 – Amino acid can be transported in blood plasma without a carrier THE RUMINANT STOMACH PROTEIN DIGESTION IN RUMINANTS • Rumen Total protein NPN Undegraded Small intestine Metabolizable protein Degraded Recycled via saliva (20% of dietary N) NH3 Microbial protein NH3 Liver Urea Kidney Excreted • 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 50 Cottonseed meal 78 Soybean meal 89 Alfalfa 90 • Increasing rate of passage decreases ruminal protein degradation • Heat treatments 100 C for 4 hours Soybean meal Reduced protein degradation • Tannins in feeds reduce protein degradation – Example: Birdsfoot trefoil • Coating proteins with materials resistant to degradation • Factors affecting microbial protein production in the rumen – Ruminal NH3-N concentration Microbial protein (% of Max) Ruminal NH3-N 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 – Sulfur level of diet • Sulfur needed to synthesize S-containing amino acids • Particularly important when NPN fed • Required N:S ratio – 10:1 • Advantage of ruminant CP digestion – Ability to utilize NPN • Limitations of ruminant CP digestion – Loss of ruminal NH3 • Inefficient • Increases environmental N loading – Urea toxicity • Occurs when blood NH3>60 mg% • Causes – Feeding excess urea (> 1% of ration dry matter) – Inadequate energy fed with urea – Poor mixing of urea in diet • High blood NH3 toxic to brain cells • Protein digestion in the abomasum – The abomasum is the fourth compartment of the ruminant stomach – Functionally it is similar to the stomach on nonruminant animals – Abomasum secretes hydrochloric acid and pepsinogen • Hydrochloric acid converts pepsinogen into the active protease, pepsin • Peptides hydrolyzes ruminal undegraded protein and microbial protein into peptides • Small intestinal protein digestion in ruminants – Pancreas secretes proenzymes of proteases • • • • Trypsinogen converted to the protease, Trypsin Chymotrypsinogen converted to the protease, Chymotrypsin Procarboxypeptidase converted to the protease, Carboxypeptidase Pancreatic proteases degrade proteins to peptides and amino acids – Intestinal mucosa secretes peptidases that degrade peptides to amino acids • Digestibility of ruminal undegraded protein and microbial protein normally high – 80% TRANSPORT OF PLASMA AMINO ACIDS INTO CELLS • Amino acid transport into cells by active transport • Transport enhanced by certain hormones Tissue Liver Uterus Muscle Hormones Epinephrine Glucocorticoids Estradiol Growth hormone Insulin Testosterone • Amino acid pool in cells for metabolism comes from dietary amino acids and protein degradation in the animal AMINO ACID METABOLISM • Protein synthesis – Mechanism • Protein synthesis controlled by DNA in the nucleus of cells • DNA composed of chains on nucleotides composed of: – Deoxyribose – Phosphoric acid – 1 of 4 purine or pyrimidine bases: » Adenine » Cytosine » Guanine » Thymine • Three nucleotides represent the codon for one amino acid in a protein chain • Messenger RNA is produced from DNA – If DNA has mRNA will have Adenine Uracil Cytosine Guanine Guanine Cytosine Thymine Adenine • 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 • 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 stop and no more amino acids will be used – Hormonal control Growth hormone Thyroxine Amino acid Increase IGF (Liver) Growth hormone Testosterone Insulin Transport Amino acid Muscle DNA synthesis x Synthesis Increase IGF (Muscle) Protein Estrogen Degradation Testosterone • 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 – Importance keto acid1 + alpha amino acid2 • A method of synthesizing amino acids from intermediates of carbohydrate metabolism Carbohydrate metabolism intermediate Amino acid Pyruvate Alanine Oxalacetate Aspartic acid Alpha-ketoglutarate Glutamic acid 3-phosphoglycerate Serine – Animals can synthesize Glycine Alanine Serine Aspartic acid Asparagine Glutamic acid Glutamine Cysteine Cystine Tyrosine Proline Hydroxyproline – Although these amino acids are needed metabolically, they aren’t needed in the diet; called Nonessential amino acids – Amino acids that can’t be synthesized in adequate quantities are called ‘essential amino acids’ – Essential amino acids Phenylalanine Valine Tryptophan Threonine Isoleucine Methionine Histidine Arginine Leucine Lysine • Decarboxylation – Removal of the carboxyl producing amino NH2 R C NH2 COOH H – Examples Amino acid Histidine Tyrosine Tryptophan R CH2 CO2 Amine Histamine Tyramine Hydroxytryptamine Physiological effects Inflammation, dilates capillaries, depresses blood pressure Constricts capillaries, Increased blood pressure Constricts capillaries, Increased blood pressure • Deamination – Releases amino group from excess amino acids – Mechanism NH2 R C O COOH + O R C COOH + NH3 (C skeleton) H – Uses of C skeleton • Energy metabolism • Glucose synthesis • New amino acids – Removal of NH3 O • Mammals – Synthesis of urea – Detoxifies NH3 H2N C NH2 • Poultry – Synthesis of uric acid; excreted with feces O H N C H N C C O C C N H N H O 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 – 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 • An excess of one amino acid may cause a deficiency of another amino acid Excess leucine Deficiencies of valine and isoleucine • The term “protein quality” refers to the amino acid balance of a protein relative to an animal’s requirement for each of the essential amino acids – A “high quality protein” called an “ideal protein” has the essential amino acids present in proportions equal to an animal’s requirements. » It says nothing about the concentration of protein in the diet – A ration with a “high quality protein” may be composed from two or more feeds if they complement each other’s deficiencies 20 kg pig Corn Soybean meal Corn/soybean meal mix Amino acid requirements of pigs (% of protein) Leucine Lysine S-containing AAs Tryptophan 3.8 4.4 2.8 .7 12.5 2.3 3.0 1.1 7.4 6.3 2.6 1.3 11.5 4.4 2.7 1.2 – An “ideal” protein can be synthesized by adding individual amino acids to a diet • Measures of protein quality – Chemical score » The chemical score is the percentage of the requirement of the most limiting amino acid » Example Amino acid, Requirement (% of protein) Chemical A B C D E score Reqt. 4 10 8 12 5 Protein 1 3 12 3 8 4 % of AA reqt. 75 120 37.5 67 80 37.5 Protein 2 4 14 6 0 6 % of AA reqt. 100 140 75 0 120 0 – Biological value » % of digested and absorbed N that is retained by the body » Range in value High > 70 (means good amino acid balance) Low < 70 (means poor amino acid balance) » Feeds BV Egg albumen 97 Milk 85 Beef 76 Cereal proteins 50-65 Gelatin 12 » A ration with a dietary protein with a high BV can be made from feeds with low BV if their amino acid compositions complement each other (or if individual amino acids) • 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 FACTORS AFFECTING PROTEIN REQUIREMENTS • Growth – Young, growing animals deposit more protein, but have lower feed intakes than larger animals Swine, kg 1-5 5-10 10-20 20-35 35-60 CP reqt. % 27 20 18 16 14 • Sex – Males deposit more protein at a given weight than females 300 kg large frame gaining 1 kg/d Bulls Steers Heifers gm protein/day 807 804 735 • Production of milk, eggs, or wool • Balance of protein and energy – As energy increases, feed intake decreases • Should increase the percentage of protein in the diet • Environmental temperature – As temperature increases, feed intake decreases • Should increase the percentage of protein in the diet PROTEIN DEFICIENCY • • • • • • • • Reduce feed intake Reduced growth rate Reduced feed efficiency Fat accumulation in liver Reduced fertility Reduced birthweight Reduced production of milk or effects Reduced fiber digestion (in ruminants) PROTEIN EXCESS • • • • Reduced feed intake Reduced growth rate Reduced fertility in cattle Excess N excretion