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RUMEN MOTILITY AS INFLUENCED BY PHYSICAL FORM OF OAT HAY H. W. COLVIN, J[~. ~D L. B. DANIELS Departmen~ of Animal Industry and Yeterinary Science University of Arkansas, ]~ayetteville ~ ABSTRACT The effect of oat hay, fed in the long condition and after grinding through l~-inch or %2-inch Hammermill screens, on the tureen motility of steers was studied. In one experiment all bedding was removed from the steers when the %2-inch hay was fed. Significant differences (P < .01) in rumen contraction amplitude existed between the steers on all the diets except between those on the two %2-inch hay diets. The difference in the rumen contraction frequency of the steers on diets of long and ¼-inch hay was not statistically significant; however, both of these diets produced rmnen contractions significantly (P < .05) more rapid than those for the steers on the ~2-inch hay diets. The average time required for the rumen contraction amplitude to become uniform when the diet was changed from long hay to :~2-inch hay was 4 wk; a/~-inch hay to ~e-ineh hay, 5 wk; :~-ineh hay to long hay, 6 wk; and when the sawdust bedding was removed from the calves on the %2-inch hay, 2 wk. Frothy tureen ingesta and frequent bloating were observed in steers receiving the %2-inch hay diets; one death occurred. Scabrous materials in the diet may maintain or reinforce the tonic activity of the motor neurons responsible for nlmen motility. A lack of scabrous materials in the diet of ruminants has been reported to result in di- gestive abnormalities. Heifers fed a roughage- free diet for 18 months were found to be normal in size and showed no abnormalities except for frequent bloating and lack of rumination (16). Mead, Cole, and Regan (15) observed 21 cases of bloat over a 15-day period in four cows receiving ground alfalfa hay and only one case of bloat in the cows receiving the unground diet. Colvin, Musgrave, and Williams (9) fed a non- scabrous diet consisting of an ahnost pure wood cellulose product, Solka-Floe BW 20, and a ground grain mixture to bulls from 6 to 41 months of age. Rumen motility was greatly de- pressed and highly abnormal; however, when long prairie hay was added to the diet, rumen motility returned to normal within 6 wk. On the other hand, Lindahl et al. (14) found no de- pression of rumeu motility in one steer fed a bloat-provoking diet for 1 yr. With the exception of Johns' (11) observa- tions with young succulent rye grass, grass pas- ture or hay has not been considered as bloat- provoking. In fact, long grass hays have been used as bloat preventives (5, 7). Based on their studies in which Sudan grass hay was used to l%ceived for publication February 24, 1965. 1 Published with the approval of the Director of the Arkansas Agricultural Experiment Station. prevent acute legmne bloat, Cole and Mead (4) proposed their physical deficiency theory. Al- though this theory has been ahnost abandoned because of the evidence in favor of the frothy bloat theory, the findings of Colvin, Musgrave, and Williams (9) suggest the need of scabrous material in the diet to maintain or reinforce normal rumen motility and eructation. If scab-
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