title: A dynamic mechanistic model of lactic acid metabolism in the rumen.
abstract: Current feed evaluation systems for ruminants are too imprecise to describe diets in terms of their acidosis risk. The dynamic mechanistic model described herein arises from the integration of a lactic acid (La) metabolism module into an extant model of whole-rumen function. The model was evaluated using published data from cows and sheep fed a range of diets or infused with various doses of La. The model performed well in simulating peak rumen La concentrations (coefficient of determination = 0.96; root mean square prediction error = 16.96% of observed mean), although frequency of sampling for the published data prevented a comprehensive comparison of prediction of time to peak La accumulation. The model showed a tendency for increased La accumulation following feeding of diets rich in nonstructural carbohydrates, although less-soluble starch sources such as corn tended to limit rumen La concentration. Simulated La absorption from the rumen remained low throughout the feeding cycle. The competition between bacteria and protozoa for rumen La suggests a variable contribution of protozoa to total La utilization. However, the model was unable to simulate the effects of defaunation on rumen La metabolism, indicating a need for a more detailed description of protozoal metabolism. The model could form the basis of a feed evaluation system with regard to rumen La metabolism.
authors.affiliation: The University of Reading, Centre for Dairy Research, Department of Agriculture, Reading, RG6 6AT, UK.
authors.forename: J A N
authors.initials: JA
authors.lastname: Mills
authors.affiliation: The University of Reading, Centre for Dairy Research, Department of Agriculture, Reading, RG6 6AT, UK.
authors.forename: L A
authors.initials: LA
authors.lastname: Crompton
authors.affiliation: Animal Nutrition Group, Wageningen University, 6708 WD, Wageningen, the Netherlands; Centre for Nutrition Modelling, Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2W1, Canada. Electronic address: jennifer.st-pierre@wur.nl.
authors.forename: J L
authors.initials: JL
authors.lastname: Ellis
authors.affiliation: Animal Nutrition Group, Wageningen University, 6708 WD, Wageningen, the Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Dijkstra
authors.affiliation: Wageningen UR Livestock Research, 8219 PH, Lelystad, the Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Bannink
authors.affiliation: Animal Nutrition Group, Wageningen University, 6708 WD, Wageningen, the Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Hook
authors.affiliation: Dairy and Swine Research and Development Centre, Agriculture and Agri-Food Canada, Sherbrooke, QC J1M 0C8, Canada.
authors.forename: C
authors.initials: C
authors.lastname: Benchaar
authors.affiliation: Centre for Nutrition Modelling, Animal and Poultry Science, University of Guelph, Guelph, ON N1G 2W1, Canada.
authors.forename: J
authors.initials: J
authors.lastname: France
mesh_terms: D000821:Animal Feed; D000818:Animals; D002417:Cattle; D004032:Diet / Q000662:veterinary; D004040:Dietary Carbohydrates / Q000008:administration & dosage; D019344:Lactic Acid / Q000378:metabolism*; D008954:Models, Biological; D012417:Rumen / Q000378:metabolism* / Q000382:microbiology / Q000469:parasitology; D012680:Sensitivity and Specificity; D012756:Sheep
chemical_list: D004040:Dietary Carbohydrates; D019344:Lactic Acid
keywords: lactic acid; mechanistic model; rumen