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Rumen Function. Kenneth Bruerton PhD 11 August 2011. Rumen Function. Rumen Fermentation. Breaks down Protein Digested to amino acids by rumen micro-organisms and resynthesized into microbial protein.
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Rumen Function Kenneth Bruerton PhD 11 August 2011
Rumen Fermentation • Breaks down • Protein • Digested to amino acids by rumen micro-organisms and resynthesized into microbial protein. • This is digested in the small intestine to amino acids which are absorbed and used for growth (enzymes, immune proteins, muscle protein). • Some amino acids can be used to make glucose for energy production in specialized tissues such as brain and formation of rapid energy stores (liver and muscle glycogen). • Fibre (cellulose, hemicellulose, lignin). • Only digested in the rumen by certain micro-organisms. What is undigested is excreted in the faeces. • Producing volatile fatty acids (VFAs) such as propionate and butyrate which are absorbed in the small intestine and used for energy production and fat synthesis. • Starch, sugars • Digested rapidly in the rumen to form lactate or acetate. Excess fermentation of starch can cause acidosis, particularly in lotfed cattle receiving grain.
Rumen Fermentation • Urea • Supplies Nitrogen (N). • Contrary to common belief Urea is not protein. Urea is a simple N compound. Urea is ~45% N = 281% crude protein equivalent. • Rumen microorganisms can convert N to ammonia which is converted to amino acids and microbial protein. • Urea can supply up to 1/3 of the total protein requirement of cattle. However at these levels sufficient fermentable energy must be supplied to allow utilization of available N
Rumen Fermentation Urea Microbial Urease NH3 + CO2 Carbohydrates Microbial Enzymes FA + Keto Acids KetoAcids + NH3 Microbial Enzymes AminoAcids AminoAcidsMicrobial Enzymes MicrobialProtein Microbial Protein Small Intestine Enzyme Free Amino Acids Free Amino Acids Absorbed Toxic dose generally regarded as 0.5grams/kg LWT in a single feeding episode.
Rumen Fermentation • Sulphate of Ammonia (NH4)2SO4 • Supply N as with urea. Contains approx ½ the level of N as urea • Important source of Sulphur(S) • Sulphur required as a precursor to the production amino acids • N:S ratio should be in the range of 12-15:1 • SO4 often used to control intake (more bitter than urea ) • More expensive source of N than urea
Rumen fermentation • Elemental Sulphur • Source of S. • Less available source of S than SO4. • Protein Meal • Source of Rumen Escape Protein • Source of Energy to aid utilization of Urea. • Used to manipulate intake. • Commonly used meals include • Cotton Seed Meal 43% • Copra Meal 20% • Canola Meal 35% • Soybean meal 48% • PKE 15% • Very important to calculate the input cost of the protein.