Factors affecting the in vitro production of volatile fatty acids by mixed bacterial populations from the bovine rumen

• Published in: Journal of animal science Vol. 67; no. 6; p. 1593
• Main Authors: Peters, J.P. (The Upjohn Company, Kalamazoo, MI), Leedle, J.A.Z, Paulissen, J.B
• Format: Journal Article
• Language: English
• Published: United States 01.06.1989
• Subjects: Acetates - biosynthesis; ACETIC ACID; ACIDE ACETIQUE; ACIDE GRAS VOLATILE; ACIDE PROPIONIQUE; ACIDO ACETICO; ACIDO GRASO VOLATIL; ACIDO PROPIONICO; Animals; BACTERIA; Bacteria - metabolism; BACTERIE; BOEUF; BUEY; BULLOCKS; Cattle - microbiology; Colony Count, Microbial - veterinary; DIGESTIBILIDAD; DIGESTIBILITE; DIGESTIBILITY; EXPERIMENTACION IN VITRO; EXPERIMENTATION IN VITRO; Fatty Acids, Volatile - biosynthesis; Hydrogen-Ion Concentration; IN VITRO EXPERIMENTATION; Methane - biosynthesis; OSMOTIC PRESSURE; PRESION OSMOTICA; PRESSION OSMOTIQUE; Propionates - biosynthesis; PROPIONIC ACID; RUMEN; Rumen - microbiology; VOLATILE FATTY ACIDS
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/jas1989.6761593x

Factors affecting in vitro ruminal bacterial VFA production were examined. Treatments consisted of high and low initial pH (6.7, 5.7), osmolality (600, 400 mOsm) and concentrations of acetic (40, 0 mM) and propionic acids (20, 0 mM). Response variables measured included the production of acetic, propionic and total VFA, total gas and methane. Initial pH affected (P less than .05) most variables either independently or in combination with one or more of the other factors. Acetic acid production was reduced 40% (P = .03) when initial acetic acid concentrations were 40 mM compared with 0 mM. Also, acetic acid production was less (P less than .01) at low initial pH (5.7) than at high initial pH (6.7). Propionic acid production was greater (P = .05) at high vs low initial acetic acid concentrations. Propionic acid production was greater in response to low vs high initial osmolality, although the magnitude of this difference depended on initial pH (interaction P = .02). Total production of VFA was greater (P less than .01) at high than at low initial pH; however, at low initial pH, no difference (P greater than .05) was observed due to initial osmolality, whereas at high pH, production was greater (interaction P = .04) for low than for high initial osmolality. The diminished production of total VFA at pH 5.7 occurred primarily due to reduced acetic acid production, although increased production of propionic and butyric acids was noted.