Enteric methane : animal scale measurements, uncertainties, indicators

Transcription

1 Training Course Livestock and Climate Change 12 th 14 th January 2015, Dakar Enteric methane : animal scale measurements, uncertainties, indicators Michel Doreau INRA, France

2 N intake CHO intake Amino acids Volatile fatty acids CH4 Enteric methane emission Urinary Faecal N N2O NOx NH3 Faecal CHO CH4 CHO and N losses Manure emission

3 1. Enteric methane emission 1.1. Methods used for CH4 measurement Chambers Indirect SF6 method Other methods 1.2. Evaluation and indicators IPCC calculation Prediction equations Milk fatty acids as markers Other potential markers 2. Faecal and urinary losses and manure emission

4 Chambers A unique word for very different techniques First measurement: Reiset, 1863 Respiratory chambers The most accurate method Simplified chambers Recent adaptation

5 Respiratory chambers Simplifiedchambers For studies of energy metabolism All gaseous exchanges Control of temperature and pressure For gasemissionsonly

6 Respiratory chambers Simplifiedchambers Air entry Gas exit Gas exit CH4 CO2 O2 concentration Gas flow CH4 CO2 O2 concentration Gas flow CH4 (CO2) concentration Air entry

7 Hood Variants Small chamber only for animal s head Only eructated and exhaled Tunnel Several animals (sheep) in a 50 m2 portable greenhouse put on the ground on pasture

8 Portable accumulation chamber Completely closed chamber; gas is accumulated Measurement over 1 or 2 h Animal does not eat during the measures For comparison of feeding or environmental conditions rather that for accurate quantification

9 SF6 tracer technique : on pasture gas collection canister CH 4 SF 6 Halter + filter and capillary tube SF 6 permeation tube Emission of CH 4 and SF 6

10 SF6 tracer technique : in the lab GC - ECD [SF 6 ] [CH 4 ] GC - FID Production CH 4 (l/d) = [CH 4 ] / [SF 6 ] x diffusion rate SF 6

11 Another possible use on pasture Unidirectional wind and flat ground are required

12 Comparison of Tracer and Chamber Measurements SF 6 Chamber Johnson et al (1994) Heifers 165 l/d 164 l/d Steers Boadi et al (2001) Heifers 137 l/d 130 l/d Pinares (unpublished data) Sheep SF 6 /Chamber = 0.95 No significant differences between the two methods

13 Chambers Accurate determination of emitted methane SF6 More variable determination of emitted methane Daily kinetics are possible Daily kinetics are not possible Few animals because of cost Many animals in the same time Animals are not in natural conditions; their training is necessary Animals are in natural conditions

14 A system using cannula Plastic bag to collect ruminal gases Permanent record of ruminal gas flow Electronic module sends information to a computer through satellite Several daily samplings for CH4 concentration

15 The Greenfeed system

16 The Greenfeed system Main source on inaccuracy : Measurements only when animals are present at the bin Estimation of daily emission from spot emissions is necessary Main limit : Only for animals fed significant amounts of concentrates Main interest : Measurements are possible on a large number of animals, in field conditions Variant Similar principle, at milking with a feed bin within a milking robot

17 The Laser Methane Detector The most mobile technique Infrared absorption spectroscopy Wavelength of the light source related to methane absorption Measures every 0.5 sec Scientific publications, but... Questionable at present: Measuremants in [CH4] x m Measures only when animal is not moving Very high variability between measures

18 In vitro determination No direct relation with in vivo response Only for comparing feedstuffs, testing additives, dose response effects

19 In vitro determination Rumen fluid Buffer N and mineral source (optional) Incubation 5 to 24 h Anaerobic conditions Feedstuff Additive (optional) Gas production and methane concentration measurement

20 More complex in vitro methods Rusitec Dual effluent fermenter Better than batch technique Not easy to implement But does not reproduce in vivo conditions

21 1. Methods used for CH4 measurement 2. Evaluation and indicators IPCC calculation : see presentation on Wednesday Prediction equations Milk fatty acids as markers Other potential markers

22 Prediction equations From limited databases (specific to a country, a type of animal, of feeding) to large databases (sometimes less adapted) Fermented OM Digestibility, feed composition (fibre, lipids, ) Feed composition (or digestibility, or energy value), intake, and/or milk yield Examples : CH 4 (MJ/J) = x Metabolizable energy intake (MJ/J) R 2 =0.55; n=159 data (Mills et al, 2003) CH 4 /MSI (g/kgms) = 7,14 + 0,22 MOD (%MS) (n = 976, nexp = 170, R 2 = 0,81, ETR = 2,7) (Sauvant et al., 2011)

23 Milk fatty acids Interest Non invasive marker, easy monitoring when FA are analysed by MIR or NIR spectrometry Principles Acetate and butyrate (hydrogen producers) are precursors of saturated FA with 16 C and less, and are related to minor FA (odd and branched chain) in milk Dietary polyunsaturated FA (mitigating agents) result in specific FA during hydrogenation State of the art Several equations in scientific papers An equation for on farm monitoring Until now, no general equation (additives?)

24 Other markers Faecal archaeol? For the future: metabolomic approach

25 Thank you for your attention