Assessment of Postruminal Amino Acid Digestibility of Roasted and Extruded Whole Soybeans with the Precision-Fed Rooster Assay

C. G. Aldrich, N. R. Merchen, C. M. Parsons, H. S. Hussein, S. Ingram, J. R. Clodfelter

Research output: Contribution to journalArticle

Abstract

The objectives of these studies were to predict the effects of roasting and extrusion temperatures of whole soybeans (SB) on intestinal protein digestibility in cattle. Intestinal digestibility was assessed with a two-stage in vitro or in situ ruminai incubation/precision-fed cecectomized rooster bioassay. In Exp. 1, whole SB (raw SB or SB roasted to 141, 149, or 157°C exit temperature from a commercial roaster and steeped for 30 min) were incubated in strained ruminal fluid and McDougall's buffer (50:50) at 39°C for 16 h. In Exp. 2, SB (ground raw SB or SB extruded at 116, 138, or 160°C) were placed in polyester bags (20 × 30 cm) and suspended in the ventral rumen of steers for 16 h. Lyophilized residue of the in vitro or in situ incubations and samples of raw SB and most extensively heated SB (roasted SB at 157°C or extruded SB at 160°C) for each respective experiment were crop-intubated to cecectomized roosters. Total excreta were collected for 48 h after intubation and lyophilized, and amino acid (AA) concentrations were determined. In Exp. 1, total AA digestibility was 61.6 and 84.5% for unincubated whole raw SB and 157°C roasted SB, respectively, and 66.2, 88.9, 91.3, and 91.6% for in vitro residues of whole raw SB and SB roasted at 141, 149, and 157°C, respectively. Trypsin inhibitor (TI) activity was 20.09, 1.69, 1.54, and 1.84 mg/g fat-free DM for unincubated whole raw SB and 141, 149, and 157°C roasted SB, respectively, and 30.84, 1.01, .90, and .26 mg/g fat-free DM for in vitro residues of whole raw SB, 141, 149, and 157°C roasted SB, respectively. In Exp. 2, total AA digestibility was 68.5 and 87.7% for unincubated ground raw SB and 160°C extruded SB, respectively, and 81.9, 91.3, 89.7, and 89.4% for in situ residues of ground raw SB and 116, 138, and 160°C extruded SB, respectively. Trypsin inhibitor activity was 17.61, 4.89, 4.08, and 1.56 mg/g fat-free DM for unincubated ground raw SB, 116, 138, and 160°C extruded SB, respectively, and 3.62, .59, .55, and .21 mg/g fat-free DM for incubated ground raw SB, 116, 138, and 160°C extruded SB, respectively. Heat treatment by roasting and extrusion improved AA digestibilities of SB, but there were no differences detected among the roasting or extrusion temperatures. Ruminal fermentation did not eliminate the negative effects of TI activity on intestinal digestibility of AA in whole SB but did reduce TI activity in ground SB.

Original languageEnglish (US)
Pages (from-to)3046-3051
Number of pages6
JournalJournal of animal science
Volume75
Issue number11
DOIs
StatePublished - Nov 1997

Keywords

  • Amino acids
  • Extrusion
  • Fowls
  • Roasting
  • Soybeans
  • Trypsin inhibitors

ASJC Scopus subject areas

  • Food Science
  • Animal Science and Zoology
  • Genetics

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