In vitro cumulative gas production techniques: History, methodological considerations and challenges

Animal Feed Science and Technology

Volumn 123-124 Part 1, Issue , 2005, Pages 9-30

  Rymer, C ^a   Huntington, J A ^b   Williams, B A ^c   Givens, D I ^a  

^a UNIVERSITY OF READING   (United Kingdom)

^b HARPER ADAMS UNIVERSITY   (United Kingdom)

^c WAGENINGEN UNIVERSITY   (Netherlands)

Author keywords

Feed characterisation; Gas production; Rumen in vitro methodology

Indexed keywords

ANIMALIA; BACTERIA (MICROORGANISMS);

EID: 27544493761     PISSN: 03778401     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.anifeedsci.2005.04.055     Document Type: Article

References (90)

1. S. Akhter, E. Owen, A. Fall, F. O'Donovan, and M.K. Theodorou Use of fresh or frozen faeces instead of sheep rumen liquor to provide micro-organisms for in vitro digestibility assays for forages Anim. Prod. 58 1994 452A
2. S. Akhter, E. Owen, S.L. Tembo, M.K. Theodorou, and E.R. Deaville Repeatability of in vitro digestibility assays of forages when using fresh, frozen or freeze-dried cow faeces instead of sheep rumen liquor as sources of micro-organisms Anim. Prod. 60 1995 540A
3. U.R. Altaf, R. Mauricio, F.L. Mould, T. Smith, E. Owen, R.H. Phipps, and M.K. Theodorou Comparison of bovine rumen liquor and bovine faeces as sources of micro-organisms for the in vitro gas production technique for assessing silages of maize and maize plant fractions Proc. Br. Soc. Anim. Sci. 1998 60
4. J.H.T. Barbi, E. Owen, and M.K. Theodorou Use of the rumen simulation technique (RUSITEC) to provide micro-organisms for assessing the rate of fermentation, in vitro, of forages Anim. Prod. 56 1993 462A
5. J.H.T. Barbi, E. Owen, and M.K. Theodorou Use of the rumen simulation technique (Rusitec) to provide micro-organisms for assessing forage rate-of-fermentation in vitro: effect of solid food input to Rusitec Anim. Prod. 58 1994 450A
6. J.H.T. Barbi, E. Owen, and M.K. Theodorou Use of the rumen simulation technique (Rusitec) to provide micro-organisms for assessing forage rate-of-fermentation in vitro: effect of soluble carbohydrate inputs to Rusitec Anim. Prod. 58 1994 450A
7. J.H.T. Barbi, E. Owen, and M.K. Theodorou To test the repeatability of a gas production method for assessing the in vitro fermentation of forages using micro-organisms derived from a rumen simulation technique (Rusitec) or from sheep rumen liquor Anim. Sci. 60 1995 542A
8. E. Bauer, B.A. Williams, M.W. Bosch, C. Voigt, R. Mosenthin, and M.W.A. Verstegen Differences in microbial activity of digesta from three sections of the porcine large intestine according to in vitro fermentation of carbohydrate-rich substrates J. Sci. Food Agric. 84 2004 2097 2104
9. J. Beuvink, and S. Spoelstra Interactions between substrate, fermentation end-products, buffering systems and gas production upon fermentation of different carbohydrates by mixed rumen microorganisms in vitro Appl. Microbiol. Biotechnol. 37 1992 505 509
10. J. Beuvink, S. Spoelstra, and R. Hogendorp An automated method for measuring time course of gas production of feedstuffs incubated with buffered rumen fluid Neth. J. Agric. Sci. 40 1992 401 407
11. M. Blümmel, and E.R. Ørskov Comparison of in vitro gas production and nylon bag degradability of roughages in predicting feed intake in cattle Anim. Feed Sci. Technol. 40 1993 109 119
12. G.A. Broderick Can cell-free enzymes replace rumen micro-organisms to model energy and protein supply? E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 99 114 BSAS Occ. Publ. No. 22
13. I.C.S. Bueno, A.L. Abdalla, S.L.S. Cabral Filho, D.M.S.S. Vitta, E. Owen, R.M. Mauricio, I. Givens, J.D. Sutton, and F.L. Mould Comparison of inocula from sheep and cattle for the in vitro gas production technique under tropical conditions Proc. Br. Soc. Anim. Sci. 1999 151
14. S. Calabrò, B.A. Williams, V. Piccolo, F. Infascelli, and S. Tamminga A comparison between buffalo (Bubalus bubalis) and cow (Bos taurus) rumen fluids in terms of the in vitro fermentation characteristics of three fibrous feedstuffs J. Sci. Food Agric. 84 2004 645 652
15. J.W. Cone The development, use and application of the gas production technique as the DLO Institute for Animal Science and Health (ID-DLO), Lelystad, The Netherlands E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 65 78 BSAS Occ. Publ. No. 22
16. J.W. Cone, A.H. van Gelder, and H. Bachmann Influence of inoculum source on gas production profiles Anim. Feed Sci. Technol. 99 2002 221 231
17. J.W. Cone, A.H. van Gelder, G.J.W. Visscher, and L. Oudshoorn Influence of rumen fluid and substrate concentration on fermentation kinetics measured with a fully automated time related gas production apparatus Anim. Feed Sci. Technol. 61 1996 113 128
18. J.W. Czerkawski, and G. Breckenridge New inhibitors of methane production by rumen micro-organisms. Development and testing of inhibitors in vitro Br. J. Nutr. 34 1975 429 444
19. Z.S. Davies, A.E. Brooks, G.W. Griffith, and M.K. Theodorou Assessment of fermentation characteristics of ruminant foods using an automated pressure evaluation system E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 190 192 BSAS Occ. Publ. No. 22
20. Z.S. Davies, D. Mason, A.E. Brooks, G.W. Griffith, R.J. Merry, and M.K. Theodorou An automated system for measuring gas production from forages inoculated with rumen fluid and its use in determining the effect of enzymes on grass silage Anim. Feed Sci. Technol. 83 2000 205 221
21. F.M.A. Debersaques, B.A. Williams, and S. Tamminga Effect of nitrogen source on fermentation characteristics of citrus pulp Proc. Br. Soc. Anim. Sci. 1998 174
22. M.S. Dhanoa, J. France, L.A. Crompton, R.M. Mauricio, E. Kebreab, J.A.N. Mills, R. Sanderson, J. Dijkstra, and S. Lopez Technical note: A proposed method to determine the extent of degradation of a feed in the rumen from the degradation profile obtained with the in vitro gas production technique using feces as the inoculum J. Anim. Sci. 82 2004 733 746
23. N. Dryhurst, and C.D. Wood The effect of nitrogen source and concentration on in vitro gas production using rumen micro-organisms Anim. Feed Sci. Technol. 71 1998 131 143
24. S. Fakhri, A.R. Moss, D.I. Givens, and E. Owen Comparison of four in vitro gas production methods to study rumen fermentation kinetics of starch rich feeds Proc. Br. Soc. Anim. Sci. 1997 196
25. G. Getachew, M. Blümmel, H.P.S. Makkar, and K. Becker In vitro gas measuring techniques for assessment of nutritional quality of feeds: a review Anim. Feed Sci. Technol. 72 1998 261 281
26. H.K. Goering, and P.J. van Soest Forage fiber analyses (apparatus, reagents, procedures and some applications) USDA Agriculture Handbook No. 379 1970 USDA-ARS Washington, DC, USA
27. L.M.B. Goncalves, and A.E.S. Borba Study of gas production capacity by three sources of inocula J. Agric. Sci. (Camb.) 127 1996 511 515
28. D.M. Harris, A. Barlet, and A.T. Chamberlain The use of dairy cow faeces rather than rumen liquor in the gas pressure transducer techniques for assessing digestion kinetics in vitro Anim. Sci. 60 1995 541A
29. R.E. Hungate The Rumen and its Microbes 1966 Academic Press New York, NY, USA
30. J.A. Huntington, C. Rymer, and D.I. Givens The effect of host diet on the gas production profile of hay and high-temperature dried grass Anim. Sci. 67 1998 59 64
31. N.S. Jessop, and M. Herrero Modelling fermentation in an in vitro gas production system: effects of microbial activity E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 81 84 BSAS Occ. Publ. No. 22
32. J.P. Jouany, and P. Thivend In vitro effect of avoparcin on protein degradability and rumen fermentation Anim. Feed Sci. Technol. 15 1986 215 229
33. P.M. Kennedy, J.B. Lowry, and L.L. Conlan Phosphate rather than surfactant accounts for the main contribution to enhanced fibre digestibility resulting from treatment with boiling neutral detergent Anim. Feed Sci. Technol. 86 2000 177 190
34. J. Lowenadler, and U. Ronner Determination of dissolved carbon-dioxide by colorimetric titration in modified atmosphere systems Lett. Appl. Microbiol. 18 1994 285 288
35. R.S. Lowman, A.E. Brooks, M.K. Theodorou, M.S. Dhanoa, and D. Cuddeford The effect of head-space pressure on gas production profiles E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 205 206 BSAS Occ. Publ. No. 22
36. R.S. Lowman, M.K. Theodorou, and D. Cuddeford The effect of sample processing on gas production profiles obtained using the pressure transducer technique Anim. Feed Sci. Technol. 97 2002 221 237
37. R.S. Lowman, M.K. Theodorou, J.J. Hyslop, M.S. Dhanoa, and D. Cuddeford Evaluation of an in vitro batch culture technique for estimating the in vivo digestibility and digestible energy content of equine feeds using equine faeces as the source of microbial inoculum Anim. Feed Sci. Technol. 80 1999 11 27
38. R.S. Lowman, M.K. Theodorou, A.C. Longland, and D. Cuddeford A comparison of equine faeces or caecal digesta as sources of inoculum for in vitro fermentation studies using the pressure transducer technique Anim. Sci. 62 1996 683A
39. N.D. Luchini, G.A. Broderick, and D.K. Combs In vitro determination of ruminal protein degradation using freeze-stored ruminal microorganisms J. Anim. Sci. 74 1996 2488 2499
40. D. Machboeuf, M. Jestin, and W. Martin-Rosset Utilization of the gas test method using horse faeces as a source of inoculum E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 187 189 BSAS Occ. Publ. No. 22
41. R. Mauricio, A.L. Abdalla, F.L. Mould, U.R. Altaf, T. Smith, E. Owen, D.I. Givens, M.S. Dhanoa, and M.K. Theodorou Comparison of bovine rumen liquor and faeces as sources of micro-organisms for the in vitro gas production technique assessed using twelve graminaceous forages Proc. Br. Soc. Anim. Sci. 1998 68
42. R.M. Mauricio, F.L. Mould, M.S. Dhanoa, E. Owen, K.S. Channa, and M.K. Theodorou A semi-automated in vitro gas production technique for ruminant feedstuff evaluation Anim. Feed Sci. Technol. 79 1999 321 330
43. R.M. Mauricio, F.L. Mould, E. Owen, M.S. Dhanoa, and M.K. Theodorou Effect of reducing the interval of recording from three to one hour on gas production profiles in the semi-automated technique using a pressure transducer Proc. Br. Soc. Anim. Sci. 1999 148
44. R.M. Mauricio, E. Owen, A.L. Abdalla, I.C.S. Bueno, F.L. Mould, S. Gilmour, and M.K. Theodorou Comparison of rumen liquor and faeces, in UK and Brazil, as sources of microorganisms for in vitro gas production for assessing twelve forages Proc. Br. Soc. Anim. Sci. 1999 147
45. R.M. Mauricio, E. Owen, M.S. Dhanoa, and M.K. Theodorou Comparison of rumen liquor and faeces from cows as sources of micro-organisms for the in vitro gas production technique E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 182 184 BSAS Occ. Publ. No. 22
46. R.M. Mauricio, E. Owen, F.L. Mould, I. Givens, M.K. Theodorou, J. France, D.R. Davies, and M.S. Dhanoa Comparison of bovine rumen liquor and bovine faeces as inoculum for an in vitro gas production technique for evaluating forages Anim. Feed Sci. Technol. 89 2001 33 48
47. R.H. McBee Manometric method for the evaluation of microbial activity in the rumen with application to utilization of cellulose and hemicelluloses Appl. Microbiol. 1 1953 106 110
48. A.Z. Mehrez, and E.R. Ørskov The use of a Dacron bag technique to determine rate of degradation of protein and energy in the rumen J. Agric. Sci. (Camb.) 88 1977 645 650
49. K. Menke, L. Raab, A. Salewski, H. Steingass, D. Fritz, and W. Schneider The estimation of the digestibility and metabolizable energy content of ruminant feedingstuffs from the gas production when they are incubated with rumen liquor in vitro J. Agric. Sci. (Camb.) 93 1979 217 222
50. K.H. Menke, and H. Steingass Estimation of the energetic feed value obtained from chemical analysis and in vitro gas production using rumen fluid Anim. Res. Dev. 28 1988 7 55
51. D.R. Mertens, P.J. Weimer, and G.M. Waghorn Inocula differences affect in vitro gas production kinetics E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 95 98 BSAS Occ. Publ. No. 22
52. D.R. Mertens, and P.J. Weimer Method for measuring gas production kinetics E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 209 211 BSAS Occ. Publ. No. 22
53. A.R. Moss, A.N. Pell, and D.I. Givens Use of the Cornell University gas production technique to measure kinetics of carbohydrate degradation in five foods: a comparison between laboratories E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 218 220 BSAS Occ. Publ. No. 22
54. S. Nagadi, M. Herrero, and N.S. Jessop The influence of diet of the donor animal on the initial bacterial concentration of ruminal fluid and in vitro gas production degradability parameters Anim. Feed Sci. Technol. 87 2000 231 239
55. S. Nagadi, M. Herrero, and N.S. Jessop Effect of frequency of ovine ruminal sampling on microbial activity and substrate fermentation Proc. Br. Soc. Anim. Sci. 1999 153
56. H.M. Omed, A. Faza, R.F.E. Axford, I. Ap Dewi, and D.I. Givens A low tech in vitro procedure using faecal liquor for the estimation of digestibility of forages Proc. Br. Soc. Anim. Sci. 1998 59
57. J.S. Payne, A.R. Hamersley, J.C. Milligan, and J.A. Huntington The affect of rumen fluid collection time on its fermentative capacity and the stability of rumen conditions in sheep fed a constant diet Proc. Br. Soc. Anim. Sci. 2002 165
58. A.N. Pell, R.E. Pitt, P.H. Doane, and P. Schofield The development, use and application of the gas production technique at Cornell University, USA E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 45 54 BSAS Occ. Publ. No. 22
59. A.N. Pell, and P. Schofield Computerised monitoring of gas production to measure forage digestion in vitro J. Dairy Sci. 76 1993 1063 1073
60. D.L. Romney, F.C. Cadario, E. Owen, and A.H. Murray Comparison of parameters from the Theodorou gas production technique using nitrogen-free and nitrogen-rich media as predictors of dry matter intake and digestibility. E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 172 174 BSAS Occ. Publ. No. 22
61. M. Rosales, M. Gill, C.D. Wood, and A.W. Speedy Associative effects in vitro of mixtures of tropical fodder trees E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 175 177 BSAS Occ. Publ. No. 22
62. J.B. Russell Strategies that ruminal bacteria use to handle excess carbohydrate J. Anim. Sci. 76 1998 1955 1963
63. J.B. Russell, and H.J. Strobel Microbial energetics J.M. Forbes J. France Quantitative Aspects of Ruminant Digestion and Metabolism 1993 CABI Wallingford, UK 165 186
64. C. Rymer, A.E. Brooks, M.K. Theodorou, and D.I. Givens The effect of shaking on the gas production profile of high temperature dried grass Proc. Br. Soc. Anim. Sci. 1998 65
65. C. Rymer, and D.I. Givens A comparison of different types of apparatus used for measuring gas production in vitro Proc. Br. Soc. Anim. Sci. 1997 193
66. C. Rymer, J.A. Huntington, and D.I. Givens Effects of inoculum preparation method and concentration, method of inoculation and pre-soaking the substrate on the gas production profile of high temperature dried grass Anim. Feed Sci. Technol. 78 1999 199 213
67. C. Rymer, A.R. Moss, E.R. Deaville, and D.I. Givens Factors affecting the amount of indirect gas produced by the in vitro gas production technique E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 89 91 BSAS Occ. Publ. No. 22
68. C. Rymer, C.R. Stewart, T.F. Garstang, and D.I. Givens The use of mixtures of pure bacterial cultures as an alternative inoculum to rumen fluid in the in vitro gas production technique Gas production: fermentation kinetics for feed evaluation and to assess microbial activity. EAAP Satellite Symposium, Wageningen International Conference Centre Wageningen, The Netherlands 2000 Br. Soc. Anim. Sci. Penicuik, UK 29 30
69. C. Rymer, B.A. Williams, and A.E. Brooks The inter-laboratory variation in the in vitro gas production profiles of feeds Anim. Feed Sci. Technol. 2005 (this issue)
70. R. Sanderson, S.J. Lister, A. Sargeant, and M.S. Dhanoa Effect of particle size on in vitro fermentation of silages differing in dry matter content Proc. Br. Soc. Anim. Sci. 1997 197
71. L.D. Satter, and L.L. Slyter Effect of ammonia concentration on rumen microbial production in vitro Br. J. Nutr. 32 1974 199 208
72. P. Schofield Gas production methods J.P.F. D'Mello Farm Animal Metabolism and Nutrition 2000 CABI Publishing Wallingford, UK 209 232
73. Schöner, F.J., 1981. Schätzung des energetischen Futterwertes von Milchleistungsfuttern (Ergänzungsfutter für Milchkühe) unter besonderer Berücksichtigung des Hohenheimer Futterwerttestes. Dissertation, Bonn University, Bonn, Germany.
74. T. Senshu, K. Nakamura, A. Sawa, H.A. Miura, and T. Matsumoto Inoculum for in vitro rumen fermentation and composition of volatile fatty acids J. Dairy Sci. 63 1980 305 312
75. Steingass, H., 1983. Bestimmung des energetischen Futterwertes von wirtschaftseigenen Futtermitteln aus der Gasbildung bei der Pansenfermentation in vitro. PhD Thesis, University of Hohenheim, Hohenheim, Germany.
76. A. Stevenson, C.J. Buchanan, R. Abia, and M. Eastwood A simple in vitro fermentation system for polysaccharides - the effects of fermenter fluid surface area/fluid volume ratio and amount of substrate J. Sci. Food Agric. 73 1997 101 105
77. M.K. Theodorou A new laboratory procedure for determining the fermentation kinetics of ruminant feeds Ciencia e investigación agraria 20 1993 332 344
78. M.K. Theodorou, R.S. Lowman, Z.S. Davies, D. Cuddeford, and E. Owen Principles of techniques that rely on gas measurements in ruminant nutrition E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 55 64 BSAS Occ. Publ. No. 22
79. M.K. Theodorou, B.A. Williams, M.S. Dhanoa, A.B. McAllan, and J. France A simple gas production method using a pressure transducer to determine the fermentation kinetics of ruminant feeds Anim. Feed Sci. Technol. 48 1994 185 197
80. J. Trei, W. Hale, and B. Theurer Effect of grain processing on in vitro gas production J. Anim. Sci. 30 1970 825 831
81. J.S. van Kessel, and J.B. Russell The Effect of Amino Nitrogen on the Energetics of Ruminal Bacteria and its Impact on Energy Spilling 1995 US Dairy Forage Research Center Research Summaries Madison, WI, USA pp. 78-80
82. J.S. van Kessel, and J.B. Russell The effect of amino nitrogen on the energetics of ruminal bacteria and its impact on energy spilling J. Dairy Sci. 79 1996 1237 1243
83. J. Wilkins Pressure transducer method for measuring gas production by microorganisms Appl. Microbiol. 27 1974 135 140
84. B.A. Williams Poster discussion session report E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 282 284 BSAS Occ. Publ. No. 22
85. B.A. Williams Cumulative gas production techniques for forage evaluation D.I. Givens E. Owen R.F.E. Axford H.M. Omed Forage Evaluation in Ruminant Nutrition 2000 CABI Publishing Wallingford, UK 189 213
86. B.A. Williams, L.J.M. van Osch, and P. Kwakkel Fermentation characteristics of the caecal contents of broiler chickens fed fine and coarse particle diets Br. Poult. Sci. 38 S 1997 S41 S42
87. B.A. Williams, C. Voigt, and M.W.A. Verstegen The faecal microbial population can be representative of large intestinal microfloral activity Proc. Br. Soc. Anim. Sci. 1998 165
88. C.D. Wood, A.H. Murray, A.R. Moss, and D.I. Givens Use of the gas production technique to investigate responses of supplementing low quality forages: 1. In vitro interactions E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 92 94 BSAS Occ. Publ. No. 22
89. C.D. Wood, N.S. Prathalingam, A.M. Murray, and R.W. Matthewman Use of the gas production technique to investigate supplementation of nitrogen-deficient foods E.R. Deaville E. Owen A.T. Adesogen C. Rymer J.A. Huntington T.L.J. Lawrence In Vitro Techniques for Measuring Nutrient Supply to Ruminants 1998 BSAS Edinburgh, UK 202 204 BSAS Occ. Publ. No. 22
90. G.Y. Zhao, and X.J. Chen The suitability of a faecal suspension of sheep as inocula for the estimation of utilizable crude protein of feeds by in vitro incubation Arch. Anim. Nutr. -Arch. Tierernahr. 58 2004 137 148