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Effects of Ingestive Mastication on Particle Dimensions and Weight Distribution of Coastal Bermudagrass Hay Fed to Steers at Four Levels^1,2,

North Carolina State University^,5, Raleigh 27695-7621

Abstract

Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay was fed in the long form to four ruminally cannulated steers to evaluate the effects of intake level on the physical reduction of feed particles during ingestive mastication. 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 and fed at 12-h intervals. Boli of ingested, masticated hay were collected at the cardia and separated by wet-sieving into fragments retained on sieves of .0027 to 4.0 mm (mesh aperture). In addition, particles retained on the 4.0-mm and 2.0-mm sieves were scanned by image analysis. Ingestive mastication resulted in a linear decrease (P < .05) in the proportion of boli particles retained on the top (4.0-mm) sieve and linear increases on the 2.0- (P < .02), 1.0- (P < .06) and .25-mm (P < .06) sieves with increasing level of intake. Sixteen to 21% of the ingested hay particles passed through a 1.0-mm sieve. Mean particle size, as determined by sieving data, decreased linearly (P < .05) as feeding level increased. Image analysis showed no differences in length (L) or width (W) of particles retained on the 4.0- and 2.0-mm sieves as feeding level increased, but L/W decreased linearly (P < .05) on both sieves. The frequency of jaw movements following feeding was very similar across feeding levels and averaged 71.3 chews/min. Results indicate that ingestive mastication is an efficient process and suggest that, during eating, feed is chewed to a similar size for bolus formation and ease of deglutition.

¹ Paper No. 11550 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 or criticism of similar products not mentioned.

² The authors wish to thank L. A. Nelson, Dept. of Stat., NCSU, for his assistance with the statistical analyses.

³ Dept. of Crop. Sci. and USDA, ARS.

⁴ Dept. of Materials Sci. and Eng.

⁵ Dept. of Anim. Sci.