Digestion kinetics of dried cereal grains

Grain fermentability largely determines the feed value of grains for ruminants. Our objective was to evaluate the variation in kinetics of gas production of cereal grains and the relationship among gas production, chemical composition and feed value. Eighteen barley, 99 corn, 23 sorghum, and 57 wheat samples were fermented in vitro for 48 h. Gas production was measured with a computerized system and an exponential model was fitted to the data. The impact of the variation in composition and kinetics on the feed value of grains in feedlot rations was assessed with the Cornell Net Carbohydrate and Protein System (CNCPS). Fractional gas rates were significantly different between grains (P<0.001), with a mean and S.D. of 0.24 (0.029) h−1 for barley (n= 20), 0.15 (0.026) h−1 for corn (n= 98), 0.06 (0.016) h−1 for sorghum (n= 23) and 0.26 (0.039) h−1 for wheat (n= 57). Fermentation rates were more variable than the chemical components. Fractional rates were poorly correlated with chemical composition within grain with the highest correlations for acid detergent insoluble crude protein (ADICP) (r=−0.31, P<0.01) and ADF (r=−0.27, P<0.01) for corn and neutral detergent insoluble crude protein (NDICP) (r= 0.35, P<0.05) for wheat. The impact of the variation in composition and kinetics on the feed value of grains in feedlot rations was assessed. The CNCPS predicted a maximal variation of <2.1 MJ/day and <60 g/day in metabolizable energy (ME) and metabolizable protein (MP) supply from grains, respectively. For sorghum, the fermentation rate was predicted to be a Abbreviations: ADICP, acid detergent insoluble crude protein; CNCPS, Cornell Net Carbohydrate and Protein System; EE, ether extract; ME, metabolizable protein; MP, metabolizable protein; NDICP, neutral detergent insoluble crude protein; SOL CP, soluble crude protein; TDN, total digestible nutrients; VFA, volatile fatty acid ∗ Corresponding author at: 31 Warren Hall, Cornell University, Ithaca, NY, USA. Tel.: +1 607 255 0157; fax: +1 607 255 1005. E-mail address: [email protected] (A.N. Pell). 0377-8401/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.anifeedsci.2006.09.004 266 C. Lanzas et al. / Animal Feed Science and Technology 136 (2007) 265–280 major determinant of the site of starch fermentation. A detailed evaluation of feed values for grains needs to include information on rates of fermentation. © 2006 Elsevier B.V. All rights reserved.