Effects of Degree of Processing and Nitrogen Source and Level on Starch Availability and In Vitro Fermentation of Corn and Sorghum Grain

M. S. Brown, M. L. Galyean, G. C. Duff, D. M. Hallford, S. A. Soto-Navarro

Research output: Contribution to journalArticle

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Abstract

Ruminal fluid from two heifers (384 ± 2 kg) fed an 85% concentrate diet was used to determine effects of degree of processing and N source and level on in vitro DM disappearance (DMD), starch availability, pH changes, and NH3 concentrations of corn and sorghum. In Exp. 1, treatments (× 4 factorial) were unprocessed corn and sorghum (UP) and each grain steam-flaked to bulk densities (BD) of 0.38, 0.33, and 0.28 kg/L (C38, B33, A28, respectively). Treatments in Exp. 2 (× 2 × 3 factorial within grain type) were UP and A28 with 0, 10, or 20 mg of N/g provided by either urea (U) or casein hydrolysate (CH). Starch availability of both grains increased linearly (P<0.001) as BD decreased. In Exp. 1, DMD of sorghum was greater (P<0.10) than that of corn at 24 and 48 h of incubation. For both grains, DMD increased linearly (P<0.02) as BD decreased at 4 and 8 h. Corn culture NH3 was less (P<0.10) than sorghum at 8 h, and as BD decreased at 4, 8, and 12 h, NH3 decreased linearly (P<0.05). Culture pH was less for corn than for sorghum at 8 h and decreased linearly (P<0.04) with decreasing BD at 12, 18, and 24 h. In Exp. 2, source of N did not affect (P>0.10) DMD of corn or sorghum beyond 4 h, but DMD increased linearly (P<0.04) as N level increased at 8, 12, 18, and 24 h for corn and at all incubation times for sorghum. At 8 through 24 h, CH and U increased NH3 of UP and A28 corn linearly (P<0.001), but the magnitude was greater (P<0.001) for U than for CH; the same trends were evident (P<0.001) at 12, 18, and 24 h for NH3 of sorghum treatments. Increasing N level increased pH of corn linearly (P<0.05) at 4, 8, 18, and 24 h, with a greater increase for U than for CH. Increasing N level increased pH of sorghum linearly (P<0.03) at 1 through 24 h, but to a greater extent for U than CH at 1, 2, 12, and 18 h. Degree of processing and level of supplemental N were positively related to in vitro DMD, whereas no benefit was evident from supplementing amino acid N compared to U.

Original languageEnglish
Pages (from-to)83-94
Number of pages12
JournalProfessional Animal Scientist
Volume14
Issue number2
DOIs
StatePublished - Jun 1 1998

Keywords

  • Ammonia
  • PH
  • Starch availability
  • Steam flaking

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