Enteric Fermentation: origin of gases, variations, predictions and mitigation Michael Blümmel
Outline of Presentation � Origin of ruminal CO 2 and CH 4 from fermentation products � Causes and implications of variations in ruminal CO 2 and CH 4 � Stochiometry of CO 2 and CH 4 production � Prediction of CO 2 and CH 4 production in vitro and in vitro � Enteric mitigation options
Principles Generalization of ruminal microbial feed degradation OMTDR SCFA = + MBP + GAS Short chain fatty acids (C 2 , C 3 , C 4 ) �� SCFA supply energy to host animal Microbial biomass supplies MBP �� protein to host animal ( but also CHO, lipids) CH 4 und CO 2 ,losses to rumen �� GAS Microbes and host animal alike
Carbon Utilization from Hexose in Microbial Short-Chain Fatty Acid (SCFA) Production HEXOSE SCFA C-C-C-C-C-C 2 Acetate (2 X C-C) C-C-C-C-C-C 2 Propionate (2 X C-C-C) C-C-C-C-C-C 1 Butyrate (1 X C-C-C-C )
Stoichiometrical calculation of CO 2 and CH 4 from SCFA ratio (C 2 :C 3 :C 4 ) according to Wolin (1960) Principle: balance of net oxidation values is zero Example 1 mol of SCFA with 0.65a; 0.25p; 0.1b CO 2 = a/2 + p/4 + 1.5 * b CO 2 = 0.65/2 + 0.25/4 + 1.5 * 0.1 CO 2 = 0.54 (see Van Soest, 1994, pp 272 – 275)
Generally, CH 4 is produced from CO 2 CO 2 + 8H > CH 4 + 2* H 2 0 Stoichiometrically (Wolin, 1960) CH 4 = a + 2*B - CO 2 CH 4 = 0.65 + 0.2 – 0.54 CH 4 = 0.31
Comparisons of stoichiometrically calculated and observed in vitro gas volumes 24 h measured gas volumes (ml) after 125 Diets and compound feeds N = 38 Components N = 27 115 Forages and roughages N = 57 pressure correction 105 95 85 75 65 55 45 SBM 35 25 2 y= -3.1 + 1.03x; R = 0.96 Sy.x = 4.2; P < 0.0001 15 15 25 35 45 55 65 75 85 95 105 115 125 24 h gas volumes (ml) stoichiometrically calculated (Blümmel et al 1999)
Stochiometry � Powerful, simple and inexpensive tool to predict gases from SCFA amount and proportion � Generally good agreement between lab / in vitro and in vivo data � More complex with substrates/feeds high in protein and anti-nutritive factors � Limited application to hindgut fermentation
Variations in ratios of products of ruminal microbial feed degradation Low E fficiency of M icrobial P roduction (EMP) + + GAS MBP OMTDR SCFA = High E fficiency of M icrobial P roduction (EMP) = + + GAS MBP SCFA OMTDR
EMP in vivo: data from literature review Mean EMP Range in EMP Stern & Hoover 30 g 10 – 50 g (1979) MN /OMTDR MN / OMTDR Lebzien (1996) 10.3 g 7.1 – 14.0 g MP / MJ MEI MP / MJ MEI � Many feeding systems treat microbial production as a constant, despite acknowledged variation in EMP � Lack of simple techniques to detect and predict variations in EMP
Relevance of EMP for Carbon Emissions Assumptions: EMP Diet 1 = 0.10 and EMP Diet 2 = 0.40 Digestibility 63% Pansen 10 kg Futter mikrobiell 5 kg degraded in abgebaut the rumen 8 kg DM intake 11
Diet 1 (8 kg) CO 2 : 513 l (1008 g) CH 4 : 296 l (211 g) 4.5 kg: C 2 , C 3 , C 4 , CO 2 , CH 4 0.5 kg: Microbial biomass Urine-N Diet 2 (8 kg) CO 2 : 324 l (673 g) 3.0 kg: C 2 , C 3 , C 4 , CO 2 , CH 4 CH 4 : 197 l (140 g) 2.0 kg: Microbial biomass Urine-N
Efficiency of microbial production � Variations in EMP are real and have significant effects on variations in enteric GHG emissions � Maximizing EMP regardless of specific P: E host animal requirement � Not applicable to hindgut fermentation � How to detect variations in EMP?
Approaches: detecting variations in EMP OMTDR SCFA = + MBP + GAS Possible measurements: 1. All three degradation products 2. Two products and OMTDR like: MBP = OMTDR – [SCFA + GAS] 3. One product and OMTDR if firm linkage exists between this and one other product
Exemplary: One mmol of SCFA in proportion 0.65a: 0.25p: 0.10b results in 1. 0.54 mmol CO 2 (23.4 mg) 2. 0.31 mmol CH 4 ( 5.0 mg) 3. 0.65 mmol a (39.0 mg) 4. 0.25 mmol p (18.5 mg) 5. 0.10 mmol b ( 8.8 mg) 6. 2x0.35 mmol H 2 O (11.2 mg) 105.9 mg Gas volume: 0.54 mmol CO 2 13.8 ml 0.31 mmol CH 4 7.9 ml 1.00 mmol CO 2BUFF 25.6 ml 47.3 ml SF = 105.9 mg: 47.3 ml = 2.24 mg/ml
Accepting a stoichiometric factor (SF) of 2.2 mg H, C, O for 1 ml of gas, MBP can be calculated as: MBP = OMTDR – [GAS * 2.2] Requirements: 1. Gas volume 2. OMTDR Observe: SF at high propionate (>40%) equals 2.34 mg/ml (Bl � mmel et al. 1997
Predicting in EMP in vitro by gas volumes, OMTDR and SF EMP EMP 0.1 0.4 EMP = (325 – [130.6 * 2.2])/325 EMP = (325 – [87.5 * 2.2])/325 EMP = 0.41 EMP = 0.12 87.5 ml gas 130.6 ml gas 500 mg substrate supplied 325 mg feed degraded as determined by ND- solution treatment 175 mg 175 mg (Goering and Van Soest (Blummel et al 1997) (1970)
Partitioning Factor: high degradability but proportionally low gas production EMP EMP 0.1 0.4 PF = 325 mg/130.6 ml PF = 325 mg /87.5 ml PF = 3.74 mg/ml PF = 2.49 mg/ml 87.5 ml gas 130.6 ml gas 500 mg substrate supplied 325 mg feed degraded as determined by ND- solution treatment 175 mg 175 mg (Goering and Van Soest (1970)
Partitioning Factor: actually measured after 24-h of incubation Wheat Straw Wheat Straw Trifol. PF = 264.2 mg / 90.8 ml PF = 264.0 mg / 68.5 ml PF = 2.91 mg/ml PF = 3.85 mg/ml 90.8 ml gas 68.5 ml gas 500 mg substrate Residue 236.0 mg Residue 235.8 mg
Comparison of predicted and measured CH 4 production 40 (l) measured in respiration Untreated straws NaOH treated straws 35 NH treated straws 4 chambers 30 25 20 4 CH 15 2 = 0.88; P<0.0001; Sy.x=2.5 y=3.8 + 0.82x; R 10 10 15 20 25 30 35 40 CH (l) predicted based on in vitro variables and 4 voluntary feed intake (Blümmel et al 2005)
Relations between digestible organic matter intake and methane production in sheep 40 Methane production in sheep (l/d) 35 30 25 20 15 10 2 y = 5.6 + 0.037x, R = 0.82, P<0.0001 HOWEVER: 35.4 to 63.7 l/kg DOMI 5 0 0 100 200 300 400 500 600 700 800 900 Digestible organic matter intake in sheep (g/d)
Predicting GHG in vivo � Major driver intake, feed quality next � With intake and diet quality known, GHG can be predicted with reasonable accuracy � Intake and quality often unknowns, opportunistic, variable in small holder systems
Mitigation of enteric GHG 1. Feed manipulation (SCFA/ EMP) 2. Feed allocation, intensification
Combined SCFA and EMP effects on methane production 67.5 CH 4 (l) produced per kg feed digested 62.5 57.5 52.5 47.5 high roughage (high acetate) high concentrate (high propionate) 42.5 37.5 32.5 27.5 22.5 17.5 100 150 200 250 300 350 400 Microbial biomass produced per kg feed digested (g/kg) Blümmel and Krishna 2003
Across herd milk yields (3.61 kg/d) in India and scenario-dependent ME needs for total milk production (81.8 million t/y) ME required (MJ x 10 9 ) Milk (kg/d) Maintenance Production Total 3.61 (05/06) 1247.6 573.9 1821.5 6 (Scenario 1) 749.9 573.9 1323.8 9 (Scenario 2) 499.9 573.9 1073.8 12 (Scenario 3) 374.9 573.9 948.8 15 (Scenario 4) 299.9 573.9 873.9 25
Effect of increasing average daily milk yields on overall methane emissions from dairy in India 2.5 current herd average milk yield of 3.61 l/d Methane produced (Tg) 2.0 1.5 1.0 0.5 0.0 0 3 6 9 12 15 Daily milk yield per animal (liter) (Bl � mmel et al. 2009) 26
Mitigation of enteric GHG 1. Feed manipulation (SCFA/ EMP) Biologically feasible, however, multiple trade-offs involved, economically largely untested, difficult to apply to small holder systems 2. Feed allocation, intensification Feasible and bound to happen. However , important non-technical support required such as credit, insurance, labor issues etc
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Efficiency of Microbial Production LEGENDS SCFA: 0.65 a: 0.25 p : 0.10 b MBP Gases EMP = 0.1 EMP = 0.4 SCFA 1 kg OMTDR MBP: 100 g 400 g Gases: 338g 225 g 375 g SCFA : 562 g � (Bl � mmel et al. 2001)
Efficiency of Microbial Production LEGENDS SCFA: 0.50 a: 0.40 p : 0.10 b MBP Gases EMP = 0.1 EMP = 0.4 SCFA 1 kg OMTDR MBP: 100 g 400 g Gases:289 g 193 g SCFA : 611 g 407g � (Bl � mmel et al. 2001)
EMP and host animal requirement of protein: energy Problem: If MBP > protein requirement of host MBP used for energy � EMP 0.4 – 0.1 300 g MBP 3.3 MJ from SCFA 2.94 MJ NE (f) 1.94 MJ NE (f) HOWEVER ↑ ↑ ↑ RENAL N EXCRETION ↑
Predicting GHG in vivo � Major driver intake, feed quality next � With intake and diet quality known, GHG can be predicted with reasonable accuracy � Intake and quality often unknowns, opportunistic, variable in small holder systems
Release of N and OM during 24 hrs incubation in five iso-nitrogenous diets 25 g N: kg OM 25 LEGENDS 24 D I (0.778) D II (0.788) 23 Ratio N: OM D III (0.817) D IV (0.780) 22 D V (0.830) 21 20 19 18 17 0 2 4 6 8 10 12 14 16 18 20 22 24 Release of N: OM during 24 hrs
Relationship between synchronization Indices and EMP in sheep Efficiency of microbial production ( g 38 2 MBP/100 g OMTDR) in sheep) y = - 29.3 + 78.8 x; R = 0.89; P = 0.02 37 36 35 34 33 32 31 30 0.76 0.77 0.78 0.79 0.80 0.81 0.82 0.83 0.84 0.85 0.86 Synchronization Index
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