AGR 4501 PASTURE MANAGEMENT1 Nutritive Value of Pastures

AGR 4501 PASTURE MANAGEMENT2 What is nutritive value?  The capacity of a feed to generate animal products if other factors are not limiting

AGR 4501 PASTURE MANAGEMENT3 Animal Feed Products (meat, milk) genetics health environment wastes quantityquality

AGR 4501 PASTURE MANAGEMENT4 Good quality feed  Must be able to supply the nutrients required for growth and body functions of animal

AGR 4501 PASTURE MANAGEMENT5 Nutrients  Energy  Protein  Minerals  Vitamins  Water

AGR 4501 PASTURE MANAGEMENT6 Energy  The most important feed component if all other nutrients are adequate  Determines growth rate and productivity of animals

AGR 4501 PASTURE MANAGEMENT7 Energy in feed  Total energy in feed = Gross Energy (GE) units : MJ (mega joules) per kg  Energy which can be used for growth = net energy (NE)

AGR 4501 PASTURE MANAGEMENT8 Milk Gross Energy Net Energy

AGR 4501 PASTURE MANAGEMENT9 Gross Energy (GE) Digestible Energy (DE) Metabolizable Energy (ME) Net Energy (NE) Faeces Urine, methane Heat

AGR 4501 PASTURE MANAGEMENT10 Types of feed and energy content  Concentrates e.g. corn, wheat – high energy feed >10 MJ/kg  Forages and Roughages including pasture: high fibre <10 MJ/kg

AGR 4501 PASTURE MANAGEMENT11 Measurements of Nutritive Quality  Digestibility  Voluntary Intake  Protein Content  Mineral & Vitamin content

AGR 4501 PASTURE MANAGEMENT12 Digestibility  Estimates the proportion of feed which can be digested (Intake-faeces) Intake - faeces intake X 100= % digestibility

AGR 4501 PASTURE MANAGEMENT13 Factors affecting digestibility  Species Temperate > Tropical C3>C4  Age Digestibility declines with age  Temperature High temperature lowers digestibility  Protein Content If less than 7%

AGR 4501 PASTURE MANAGEMENT14 Effects of cell structure on digestibility  Plant cells are comprised of: Cell contents Cell wall  Cell contents Comprise of soluble carbohydrate, protein, completely digestible  Cell wall Partially digestible

AGR 4501 PASTURE MANAGEMENT15 Cell wall  Cellulose  Hemicellulose  Lignin  Silica

AGR 4501 PASTURE MANAGEMENT16 As plants mature  Amount of cell wall increases  Proportion of cell content decreases  Percentage of indigestible components increase  Digestibility decreases

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AGR 4501 PASTURE MANAGEMENT18 At the plant level  Proportion of stems increases with age  Stems become harder (more lignin) as plant age  Proportion of old and senescing leves increase

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AGR 4501 PASTURE MANAGEMENT20 Methods of measuring digestibility  In vivo  In vitro  Nylon Bag  Van Soest analysis

AGR 4501 PASTURE MANAGEMENT21 In vivo  Use real life animal  Weigh feed and offer to animal  Weigh uneaten feed the next day  Calculate feed intake (feed offered-feed remaining)  Weigh faeces  Calculate digestibility  7 days adaptation 10 days measurement

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AGR 4501 PASTURE MANAGEMENT24 In vitro  (Tilley & Terry, 1963)  Obtain rumen fluid from fistulated animal  Provide anaerobic condition by infusing nitrogen  Incubate ground dried feed sample 39 o C for 48 hrs  Add acid pepsin and incubate in aerobic condition for 48 hrs  Filter and weigh residue (undigested)

AGR 4501 PASTURE MANAGEMENT25 Rumen fistulated cattle

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AGR 4501 PASTURE MANAGEMENT27 Nylon Bag  Use 6 g of dried ground sample  Wrap in nylon bags 15x6 cm  Introduce into rumen via fistula  Leave for 48 hr  Remove bags and incubate further in acid pepsin for 48 hr  Weigh residue

AGR 4501 PASTURE MANAGEMENT28 Rumen fistulated cattle

AGR 4501 PASTURE MANAGEMENT29 Nylon bags filled with feed sample

AGR 4501 PASTURE MANAGEMENT30 KN4, 6 and 8 WAPAH and SBM Sampled and driedground CP, OM, NDF and ADF determination In situ DM and CP disappearance using nylon bag technique Insertion of nylon bags into the rumen for 72, 48, 24, 16, 12, 8 and 4h Removed, washed Ruminal degradation study (Nylon bag technique)

AGR 4501 PASTURE MANAGEMENT31 Intestinal digestion study (mobile bag technique) Test samples were incubated in the rumen for 16 and 24h Removed, washed and dried Each dried residual sample was fitted (0.5g) into six mobile bags and sealed Incubated in a Pepsin-HCL solution for 1h at 37 ºC, rinsed and then kept on ice, 4 ºC Introduced into duodenum of canulated steers, 20 min./bag Collected from the feces, stored at -18ºC, washed DM, CP, amino acid* determination Calculation of intestinal DM, CP and amino acid* disappearances * Ruminal and intestinal residues will be analyzed for amino acids later

AGR 4501 PASTURE MANAGEMENT32 Effects of protein on digestibility % protein% digestibility

AGR 4501 PASTURE MANAGEMENT33 Effects of protein on digestibility % protein% digestibility

AGR 4501 PASTURE MANAGEMENT34 Effects of minerals on digestibility % sulfur% digestibility

AGR 4501 PASTURE MANAGEMENT35 Measurements of Nutritive Quality  Digestibility  Voluntary Intake  Protein Content  Mineral & Vitamin content

AGR 4501 PASTURE MANAGEMENT36 Voluntary Intake  The quantity of feed ingested by animals when fed ad libitum  Influenced by animal size, breed, physiology and health  Higher quality feed should have higher intake

AGR 4501 PASTURE MANAGEMENT37 Voluntary Intake  Unit of measure  g/kg liveweight 0.75  eg. Weight of cow 150 kg, consumes 3 kg DM, V.I. = 3000/ = 3000/42.86 = 70 g/kg 0.75

AGR 4501 PASTURE MANAGEMENT38 Factors affecting V.I.  Digestibility  Particle size of feed  Protein content if <7 %  Mineral content

AGR 4501 PASTURE MANAGEMENT39 Mechanism controlling intake  Intake depends on rate of passage through rumen and alimentary tract  Fast rate of passage, more feed can be ingested  Feed of low digestibility and low protein stays longer in rumen

AGR 4501 PASTURE MANAGEMENT40 V.I. can be improved by  Grinding or chopping feed to smaller particles  Adding protein or urea to low protein feed  Adding minerals which are deficient

AGR 4501 PASTURE MANAGEMENT41 Leaf:stem ratio affects V.I. KabulabulaHamil % leaf % digestibility V.I. g/kg

AGR 4501 PASTURE MANAGEMENT42 Sward density effects on V.I.  Short, compact, grasses have higher intake – needs fewer bites compared to loose swards

AGR 4501 PASTURE MANAGEMENT43 Methods of measuring intake  In vivo  Indigestible markers for grazed pasture  NDF is correlated with intake

AGR 4501 PASTURE MANAGEMENT44 Indigestible marker  Chromium oxide  Dose animal with known amount of marker  Analyse the faeces for the marker  Estimate the amount of faeces  Knowing digestibility of feed, can calculate intake

AGR 4501 PASTURE MANAGEMENT45 Measurements of Nutritive Quality  Digestibility  Voluntary Intake  Protein Content  Mineral & Vitamin content

AGR 4501 PASTURE MANAGEMENT46 Protein content  Protein required by animals for growth, milk production and reproduction  Protein requirements vary between stage of growth of animals, dry and lactating  Critical level is at 7% protein, below which feed intake is reduced

AGR 4501 PASTURE MANAGEMENT47 Factors affecting protein content  Species: legumes 18-30% protein grasses 6-15% protein  Age – protein declines as plant mature decline is greater with grasses  Nitrogen Fertiliser

AGR 4501 PASTURE MANAGEMENT48 Measurement of Protein  Protein contains ~ 16% N  To determine protein content, analyse N content and multiply by 6.25 (100/16=6.25) eg. 2% N = 12.5% protein  Measurement of N by Kjeldahl method

AGR 4501 PASTURE MANAGEMENT49 Mineral content  Lack of minerals will results in metabolic disorder  Supply mineral lick or supplements to overcome deficiency  Plants usually have low P and Na compared to animal needs

AGR 4501 PASTURE MANAGEMENT50 Indirect Measurement of Nutritive Value  Based on fibre content and composition  Can be correlated with digestibility and intake  The method is faster and less expensive

AGR 4501 PASTURE MANAGEMENT51 Proximate Analysis  Has been in use for more than 150 years  Sample is analysed for the following components:  Dry matter  Ether Extract  Crude Fibre  Crude Protein  Nitrogen-free extract (NFE)

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AGR 4501 PASTURE MANAGEMENT53 Ether extract  Measures amount of fat  Sample refluxed in ether to remove lipids (fats)

AGR 4501 PASTURE MANAGEMENT54 Crude fibre  Fat-extracted residue refluxed in 1.25% sulfuric acid for 30 mins  Followed by reflux in 1.25% sodium hydroxide for 30 mins

AGR 4501 PASTURE MANAGEMENT55 Crude Protein  Measured by analysis of N using Kjeldahl Method.  %N x 6.25 = Crude Protein

AGR 4501 PASTURE MANAGEMENT56 NFE  Calculated by DM – Crude Fibre – Crude Protein - EE

AGR 4501 PASTURE MANAGEMENT57 Weakness of Proximate Analysis  Don’t know what the analysis is actually measuring, especially, CF, EE and NFE

AGR 4501 PASTURE MANAGEMENT58 Van Soest Detergent System  To replace the Crude Fibre component  Plant sample divided into the following components: Cell Wall (Neutral Detergent Fibre NDF) Cellulose + lignin + (others, pectin, tannin, silica) (ADF) Hemicellulose = NDF – ADF Lignin Ash (minerals)

AGR 4501 PASTURE MANAGEMENT59 Cell contents (soluble in neutral detergent)  Lipids  Sugars, organic acids, water-soluble matter  Pectin  Non-protein N  Soluble protein  Almost completely digestible – not lignified

AGR 4501 PASTURE MANAGEMENT60 Cell wall constituents (fibre insoluble in neutral detergent)  Soluble in acid detergent (NDF) Hemicellulose Fibre bound protein  Acid detergent fibre (ADF) Cellulose Lignin Lignified N

AGR 4501 PASTURE MANAGEMENT61 Basic Scheme of Forage Analysis Using Detergents FractionReagentTreatmentYield NDF ADF Lignin Cellulose Hemicellulose Na lauryl sulphate, EDTA, pH 7.0 Cetyl trimethylammonium bromide in 1N H2SO4 72% H2SO4 treatment on ADF None Boil 1 h 3 h, 20 o C Ash residue from lignin step NDF-ADF Plant cell wall less pectins Lignocellulose + insoluble minerals Crude lignin Loss in weight

AGR 4501 PASTURE MANAGEMENT62 Sample NDF: Cellulose, hemicellulose, lignin, ADF: cellulose + lignin hemicellulose 72% H 2 SO 4 Lignin + minerals 550 o C Ash (minerals)

AGR 4501 PASTURE MANAGEMENT63 Correlations of various forage components with in vivo voluntary intake and digestibility of 187 forage species ComponentDigestibilityIntake Digestibility in vivo Digestibility in vitro Lignin ADF NDF CP Cellulose Hemicellulose

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