Analysis of Dietary Protein • Crude protein (CP %) = total N (%) 6.25 • Factor is based on 16% N in protein. • True protein varies between 13 to 19% N. Source %N in protein Conversion factor oilseed proteins 18.5 5.40 cereal proteins 17.0 5.90 meat or fish 16.0 6.25 alfalfa 15.8 6.33 true microbial protein 15.0 6.67 • Not all N in protein is present as true protein.
Classification of protein and nitrogen fractions in feedstuffs Total Borate Buffer Neutral Detergent Acid Detergent Sol A B1 Insol B2 B3 C Sol A1 B1 B2 Insol B3 C Sol A1 B1 B2 B3 Insol C
Crude Protein True protein (60 to 80%) Non-protein nitrogen Lignified nitrogen Essential amino acids Arginine (Arg) Histidine (His) Isoleucine (Ile) Leucine (Leu) Lysine (Lys) Methionine (Met) Phenylalanine (Phe) Threonine (Thr) Tryptophan (Trp) Valine (Val) Non-essential amino acids Alanine (Ala) Asparagine (Asn) Aspartic acid (Asp) Cysteine (Cys) Glutamic acid (Glu) Glutamine (Gln) Glycine (Gly) Proline (Pro) Serine (Ser) Tyrosine (Tyr) Amides Amines Amino acids Peptides Nucleic acids Nitrates Ammonia Urea
Calculations Protein Fraction A, B1 B2 B3 C Log of % nutrient remaining Hours Calculate slope (change per hour) of each line. Slope = kd, has units of % of pool remaining that is lost per hour.
Terms for describing nitrogen components of feedstuffs • Degradable Intake Protein (DIP): dietary crude protein degraded in the rumen. • Undegraded intake protein (UIP): dietary crude protein that is not degraded in the rumen and escapes or bypasses the rumen to the intestine. It is largely true protein but also contains ADFIP. • Soluble protein (SolP): Contains non-protein nitrogen, amino acids and peptides. Soluble protein is degraded instantaneously in the rumen.
Terms for describing nitrogen components of feedstuffs • Non-protein nitrogen (NPN): Includes amides, amines, amino acids, some peptides, nucleic acids, nitrates, urea, ammonia. Degraded instantaneously in the rumen. • Acid detergent fiber insoluble protein (ADFIP): Consists of heat damaged protein and nitrogen associated with lignin. Resists ruminal fermentation and is indigestible in the small intestine.
Protein content of common feedstuffs CP DIP UIP SolP NPN ADFIP Feedstuff %DM %CP %CP %CP %SolP %CP Alfalfa silage 19.5 92 8 50 100 15 Barley silage 11.9 86 14 70 100 6.1 Corn silage 8.6 77 23 50 100 9 Alfalfa hay 22 84 16 28 93 14 Timothy hay 10.8 73 27 25 96 5.7 Barley straw 4.4 30 70 20 95 65 Barley grain 13.2 67 33 17 29 5
Protein content of protein supplements CP DIP UIP SolP NPN ADFIP Plant sources %DM %CP %CP %CP %SolP %CP Canola meal 40.9 67.9 32.2 32.4 65 6.4 Soybean meal 52.9 80 20 33 27 1 Soypass* 52.6 34 66 6.8 50 1 Brewer’s grains 29.2 34.1 65.9 4 75 12 Corn distiller’s gr. 30.4 26.6 73.7 6 67 18 Corn gluten meal 66.3 41 59 4 75 2 *Commercial product: LignoTech USA, Inc.
Protein content of protein supplements CP DIP UIP SolP NPN ADFIP %DM %CP %CP %CP %SolP %CP Animal sources Blood meal 93.8 25 75 5 0 1 Feather meal 85.8 30 70 9 89 32 Fishmeal 67.9 40 60 21 0 1 Meat and bone 50 47 53 16.1 93.8 4.9 Non-protein nitrogen sources Urea 291 100 0 100 100 0
Ruminally Protected Protein • A nutrient(s) fed in such a form that provides an increase in the flow of that nutrient(s), unchanged, to the abomasum, yet is available to the animal in the intestine • Methods to decrease the rate and extent of ruminal degradation involved the use of heat, chemical agents, or combination of both
Heat Processing • Heat processing decrease rumen protein degradation by denaturation of proteins and by the formation of protein-CHO (Millard reactions) and protein cross-links. Commercial methods that rely solely on heat include: cooker-expeller, roasting, extrusion, pressure toasting, and micronization. • Heat processing reduced fraction A, increases fraction B, and C, and decreases in the fractional rates of degradation of the fraction B
Heat Processing cont. • Over heating also causes significant losses of lysine, cysine, and arginine. • Among those AA, lysine is the most sensitive to heat damage and undergoes both destruction and decreased availability
Chemistry of the Maillard reaction between reducing sugars and lysine residues during heat treatment of proteins
Heat Processing • Careful control of heating conditions is required to optimize the content of digestible RUP. • Under heating results in only small increase in digestible RUP. . Over heating reduces the intestinal digestibility of RUP through the formation of indigestible Millard products and protein complexes.
Chemical Treatment • Chemical treatment of feed proteins can be divided into three categories: 1) chemicals that combine with and introduce cross-links in proteins, (2) chemicals that alter protein structure by denaturation (e.g., acids, alkalis, and ethanol), and (3) chemicals that bind to proteins but with little or no alteration of protein structure (e.g., tannins).
Chemical Treatment cont. • For a variety of reasons, often including less than desired levels of effectiveness, use of chemical agents as the sole treatment for increasing the RUP content of feed proteins has not received commercial acceptance. • A more effective approach involving “chemical” agents has been to combine chemical and heat treatments. • An example of this approach is the addition of lignosulfonate, a byproduct of the wool pulp industry that contains a variety of sugars (mainly xylose), to oilseed meals before heat treatment.
Chemical Treatment cont. • The combined treatments enhance non-enzymatic browning (Millard reactions) because of the enhanced availability of sugar aldehydes that can react with protein.
Characterization of Protein Sources • Common protein supplements that are high in RUP are: • Fish meal • Meat and bone meal (MBM) • Feather meal (FtM) • Blood meal (BM) • Corn gluten meal (CGM) • Distillers dried grains (DDG) • DDG with solubles (DDGS) • Brewers dried grains (BDG) • Brewers wet grains (BWG)
Nitrogen transactions in the rumen Sources of nitrogen in the rumen • Dietary crude protein (true protein and NPN). • Recycled microbial protein (bacteria and protozoa). • Endogenous N (urea, abraded epithelial cells, salivary proteins).
Degradation of nitrogenous compounds by ruminal microorganisms Bacteria • 30 to 50% of the bacteria are proteolytic. • Most species have some activity with the exception of the main cellulolytic bacteria (Fibrobacter succinogenes, Ruminococcus flavefacians, R. albus). • Major proteolytic bacteria: Ruminobacter amylophilus, Butyrivibrio Fibrisolvens and Prevotella ruminicola. • P. ruminicola is the most numerous proteolytic bacteria (> 60% of ruminal bacteria) with strains that occur on both roughage and mixed roughage-concentrate diets.
Bacteria cont’d • R. amylophilus is the most active proteolytic bacteria. Important on starch-based diets. • Breakdown of both soluble and insoluble protein in the rumen. Protozoa • Minor involvement in soluble protein breakdown. • Engulf and hydrolyze particulate proteins and bacteria. • Predatory activity of protozoa against rumen bacteria contributes to bacterial protein degradation and turnover in the rumen. Fungi • Minor role in protein degradation.
PROTEIN D. ruminantium, B. fibrisolvens, E. caudatum Clostridium spp, E. simplex, E. budayi E. caudatum ecaudatum, E. ruminantium, E. maggii Fusobacterium spp., E. medium L. multipara O. caudatus, P. ruminicola P. multivesiculatum, R. amylophilus, S. ruminantium O. joyonii, N. frontalis, S. bovis, P. communis OLIGOPEPTIDES Dipeptidyl peptidase S. bovis, R. amylophilus, P. ruminicola DIPEPTIDES D. ruminantium, E. caudatum F. succinogenes, M. elsdenii, P. ruminicola Isotricha spp., L. multipara, S. ruminantium Dipeptidase AMINO ACIDS C. aminophilum, C. sticklandii P. anerobius, B. fibrisolvens, P. ruminicola M. elsdenii, S. ruminantium, E. caudatum Isotricha spp. AMMONIA