title: Technical note: Methodological and feed factors affecting prediction of ruminal degradability and intestinal digestibility of essential amino acids.
abstract: We hypothesized that ruminal degradability of essential AA (EAA) and the intestinal digestibility of the ruminally undegraded EAA residue in feeds could be evaluated in a meta-analysis. The objective was to characterize methodological factors for ruminal incubation (time of incubation of feed in situ) and method of simulating digestion of the ruminally undegraded AA (incubation of residue in digestive enzymes in vitro or in mobile bags inserted into the duodenum). To increase numbers of observations, feeds were categorized before ANOVA. An approach is described to predict differential ruminal degradability (or undegradability) of individual EAA by normalizing them as a proportion of total AA (TAA) degradability (undegradability) and similarly to normalize the intestinal digestibility of EAA using TAA. Interaction of feed category with individual EAA justifies future studies with a broader range of feeds and more replication within feed to bolster this approach. With broader data, the approach to normalize EAA as a proportion of TAA should allow a better defined EAA library to be integrated with more robust CP databases (that can be updated with specific feed information from more routine laboratory analyses) in dairy supply-requirement models.
authors.affiliation: Department of Dairy Science, Virginia Tech, Blacksburg 24060.
authors.forename: Robin R
authors.initials: RR
authors.lastname: White
authors.affiliation: Department of Animal Science, University of Nebraska, Lincoln 68583.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Kononoff
authors.affiliation: Department of Animal Sciences, The Ohio State University, Columbus 43210. Electronic address: firkins.1@osu.edu.
authors.forename: Jeffrey L
authors.initials: JL
authors.lastname: Firkins
mesh_terms: D000596:Amino Acids / Q000378:metabolism; D000601:Amino Acids, Essential / Q000378:metabolism*; D000821:Animal Feed; D000818:Animals; D004044:Dietary Proteins / Q000378:metabolism; D004063:Digestion; D012417:Rumen / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D000601:Amino Acids, Essential; D004044:Dietary Proteins
keywords: dairy cow; essential amino acid supply; intestinal digestibility; ruminal degradability