Masters Theses


Paul Boateng

Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

J. W. Holloway

Committee Members

W.T. Butts, J.B. McLaren


Thirty-five in vivo digestion determinations over one grazing season (from June to September) with three year old, spring-calving cows were made on fresh red clover, orchardgrass-white clover, fescue, N-fertilized fescue, bermudagrass, and bermudagrass-white clover harvested at various maturities to obtain an array of dry matter digestibility (DMD). Fecal samples were analyzed for proximate analysis, detergent fiber fractions and selected minerals, N of fiber fractions, and AIA. Acid soluble ash, NFE, and microbial-N were calculated. Samples were dry-sieved after grinding through a 1 IMM screen and percent finers for 1 MM, .5 MM, .25 MM screens, and smaller than .25 MM particles (MFIMM, MF5MM, MF25MM, MFBOTTOM) calculated. Plots of fecal components against DM intake, DM digestibility, fecal DM output, and digestible DM intake were examined for linearity. Simple linear correlations were used in determining relationships among feed components, intake and digestibility variables. Regression procedures were then used to determine the relationship of the measured variables (DMI, FOUT, DMD, AND DDMI) and counter parts calculated by the method of Holloway et al. (1983). The best method that predicted DM intake employed a regression procedure utilizing fecal output Ca, CF, and DM as independent variables (R2 = .49, RSD = 66 Kg d-1). The best method for predicting DM digestibility was a regression equation using the independent variables fecal DM output, Ca, DM, CF (R2 = .57, RSD = 3.7%). The best model predicting digestible DM intake was a regression equation using the independent variables final weight, cow condition score, Ca, CF (R2 = .46, RSD = .65 Kg d-1). None of the models evaluated was able to accurately predict fecal DM output. The R2 values obtained from some of the models evaluated indicate that those models could be used to adequately predict forage intake and digestibility of extensively grazing beef cows. Lucas test of "ideal" indicators was employed to test the variables used in the predictive equations. ADL, Ca, and N were found to be "ideal" internal indicators.

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