title: Short communication: Intestinal digestibility of amino acids in fluid- and particle-associated rumen bacteria determined using a precision-fed cecectomized rooster bioassay.
abstract: Microbial protein represents the majority of metabolizable protein absorbed by ruminant animals. Enhanced understanding of the AA digestibility of rumen microbes will improve estimates of metabolizable protein. The objective of this experiment was to determine the digestibility of AA in fluid- (FAB) and particle-associated bacteria (PAB) using the precision-fed cecectomized rooster bioassay. Bacteria were isolated from 4 ruminally cannulated lactating Holstein cows by differential centrifugation, including particle suspension in 0.1% Tween-80 for increased removal of PAB from ruminal digesta. Samples of FAB and PAB were fed to 9 cecectomized roosters to determine standardized digestibility of AA. Total AA digestibility was 76.8 and 75.5% for FAB and PAB, respectively, but did not differ. Differences existed in AA digestibilities within bacterial type when compared with the mean essential AA digestibility value. Compared with previous literature estimates of AA digestibility in microbes (mean = 76%; range = 57-87%) and relative to National Research Council estimates of total AA from rumen bacteria (80%), the precision-fed cecectomized rooster assay is an acceptable in vivo model to determine AA digestibility of rumen bacteria.
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: A C
authors.initials: AC
authors.lastname: Fonseca
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: S M
authors.initials: SM
authors.lastname: Fredin
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706.
authors.forename: L F
authors.initials: LF
authors.lastname: Ferraretto
authors.affiliation: Department of Animal Science, University of Illinois, Urbana-Champaign 61801.
authors.forename: C M
authors.initials: CM
authors.lastname: Parsons
authors.affiliation: Department of Animal Science, University of Illinois, Urbana-Champaign 61801.
authors.forename: P L
authors.initials: PL
authors.lastname: Utterback
authors.affiliation: Department of Dairy Science, University of Wisconsin, Madison 53706. Electronic address: rdshaver@wisc.edu.
authors.forename: R D
authors.initials: RD
authors.lastname: Shaver
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000821:Animal Feed / Q000032:analysis*; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001419:Bacteria / Q000378:metabolism*; D001681:Biological Assay / Q000662:veterinary; D002417:Cattle / Q000382:microbiology / Q000502:physiology*; D002432:Cecum / Q000378:metabolism / Q000382:microbiology / Q000601:surgery; D002645:Chickens / Q000378:metabolism; D004063:Digestion; D008297:Male; D012417:Rumen / Q000382:microbiology*
chemical_list: D000596:Amino Acids
keywords: digestibility; rumen bacteria