Date of Award
Master of Science
K. M. Barth
C. S. Hobbs, J. B. McLaren
During the spring, summer, and fall of 1965, 1966, and 1967 grazing trials with beef cattle were conducted to study the effects of selective grazing on chemical composition and dry matter digestibility of pasture forage samples. Samples collected from esophageal-fistulated animals were adjusted for losses of leached-out nutrients, mainly nitrogen-free extract and ether extract (NFE + EE), and for artificial increases (due to the loss of other nutrients) in the percentage of acid-detergent fiber (ADF). Two types of pasture species combinations, tall fescue-lespedeza and orchardgrass-Ladino clover, were used in this study. The chemical composition and dry matter digestibility of forage samples selected by grazing animals were compared to the composition and digestibility of forage samples hand-clipped from the same pastures, which represented the average of the available forage. The differences between these two types of pasture samples were attributed to selectivity. The results of this study indicate that grazing animals select forage higher in crude protein and lower in ADF and NFE than the average of the available forage. The differences were significant (P <.05) for all components from tall fescue and lespedeza pastures but differences for ADF from orchardgrass and Ladino clover pastures were significant only at the 90 percent level of probability. The greatest degree of selectivity was observed in June and July and the lowest was observed in August and September for tall fescue and lespedeza pastures. Similar patterns were observed for the orchardgrass and Ladino clover pastures except that the lowest degree of selection occurred in September. Also, the grazing animals exhibited greater selection while grazing fescue and lespedeza pastures.
Coleman, Samuel Winfred, "True selective grazing exhibited by beef cattle as determined after adjusting for esophageal fistula effects. " Master's Thesis, University of Tennessee, 1971.