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Eating and Ruminating Behavior of Steers Fed Coastal Bermudagrass Hay at Four Levels^1,2,

North Carolina State University, Raleigh 27695-7621

Abstract

Effects of feeding level on chewing behavior and physical reduction of particles during ingestive mastication and rumination were examined in four ruminally cannulated steers fed Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay in the long form. The experimental design was a 4 x 4 latin square with 18-d periods. Treatments based on previous intakes were set at 50, 70, 90 and 110% of feed consumed per animal. Steers were fed at 12-h intervals. Chewing behavior was monitored over 4 d with a computerized system. Boli of ingested, masticated hay (MH), collected at the cardia, and serial samples of digesta taken from the ruminal upper strata (RUS) were wet-sieved. Dimensions of MH particles retained on 4.0- and 2.0-mm sieves were determined by image analysis. Increasing feeding level resulted in a linear increase in the number of boli ruminated (P < .01) and in linear increases in eating (P < .01), ruminating (P < .05) and total chewing time (P < .01). Linear increases in number of eating (P < .01), ruminating (P < .01) and total chews (P < .01) also were observed. Feeding level had no effect on bolus duration, number of chews/bolus, number of boli/min rumination time and number of chews/min rumination time. The extent of particle breakdown during ingestive mastication was a determinant of the number of boli ruminated daily and their associated number of chews. Number of boli ruminated daily also was related to the RUS mean particle size. Eating time did not provide a reliable indication of how well feed was chewed. Results suggest that under certain feeding and dietary conditions, eating time could inflate the chewing index (total chewing time/kg DM intake) of feeds.

¹ Cooperative investigation of the USDA, ARS and the North Carolina ARS. Paper No. 11634 of the journal series of the North Carolina ARS, Raleigh, 27695-7601. Use of trade names in this publication does not imply endorsement by the North Carolina ARS and the USDA, ARS or criticism of similar products not mentioned.

² The authors gratefully acknowledge L. A. Nelson, Dept. of Stat., for statistical recommendations.

³ Dept. of Anim. Sci. and Interdept. Nutr. Program.

⁴ USDA, ARS and Dept. of Crop Sci. and Anim. Sci.

⁵ Dept. of Materials Sci. and Eng.