Barley Processing, Forage:Concentrate, and Forage Length Effects on Chewing and Digesta Passage in Lactating Cows

¹ Livestock Sciences Section, Research Centre, Agriculture and Agri-Food Canada, Lethbridge, AB, T1J 4B1, Canada

Dietary factors that alter fermentability, NDF content, or particle size of the diet were evaluated for their effects on chewing behavior and distribution and passage of feed particles in the digestive tract of dairy cows. A double 4 x 4 quasi-Latin square design with a 2³ factorial arrangement of treatments was used. The dietary factors were: extent of barley grain processing, coarse (1.60 mm) or flat (1.36 mm); forage-to-concentrate ratio (F:C), low (35:65) or high (55:45) (dry matter basis); and forage particle length, long (7.59 mm) or short (6.08 mm). Eight lactating cows with ruminal and duodenal cannulas were offered ad libitum access to total mixed diets. Chewing time, expressed as minutes per day or per kilogram of dry matter or neutral detergent fiber (NDF), was increased with high F:C diets due to increased eating and ruminating times but was decreased when expressed per kilogram of NDF intake from forage. The influence of forage particle length or grain processing on chewing activity was less pronounced than F:C ratio. Chewing activity was positively correlated to proportion of long forage particles in the diet but not to particle length of the diets. Influence of feed particle size on particle size distribution in different sites of the digestive tract was minimal. Particle size distributions of duodenal digesta and feces differed; the proportion of particles retained on the 3.35- or 1.18-mm screens was higher, but proportion of particles that passed through the 1.18-mm screen was lower in duodenal digesta than in feces. Relationships between chewing activities and ruminal pH or fractional passage rate of rumen contents were not significant. These results indicate that particle size of barley-based diets was not a reliable indicator of chewing activity. Forage particle size and NDF content of the diets were more reliable indicators of chewing activity than was the NDF content of forage. Fecal particle size was not an appropriate means of estimating the size of particles exiting the reticulorumen, at least for barley-based diets. Breakdown of coarse particles was necessary, but not a rate-limiting step for particles exiting the rumen. Passage rate of the rumen contents was affected by numerous factors including chewing activity.

Key Words: feed particle size • chewing activity • particle size distribution • dairy cows

Submitted on February 20, 2001
Accepted on July 20, 2001

This article has been cited by other articles:

				S. Seo, C. Lanzas, L. O. Tedeschi, A. N. Pell, and D. G. Fox Development of a mechanistic model to represent the dynamics of particle flow out of the rumen and to predict rate of passage of forage particles in dairy cattle J Dairy Sci, August 1, 2009; 92(8): 3981 - 4000. [Abstract] [Full Text] [PDF]

				Q. Zebeli, J. Dijkstra, M. Tafaj, H. Steingass, B. N. Ametaj, and W. Drochner Modeling the Adequacy of Dietary Fiber in Dairy Cows Based on the Responses of Ruminal pH and Milk Fat Production to Composition of the Diet J Dairy Sci, May 1, 2008; 91(5): 2046 - 2066. [Abstract] [Full Text] [PDF]

				W. Z. Yang and K. A. Beauchemin Altering Physically Effective Fiber Intake Through Forage Proportion and Particle Length: Chewing and Ruminal pH J Dairy Sci, June 1, 2007; 90(6): 2826 - 2838. [Abstract] [Full Text] [PDF]

				Q. Zebeli, M. Tafaj, I. Weber, J. Dijkstra, H. Steingass, and W. Drochner Effects of Varying Dietary Forage Particle Size in Two Concentrate Levels on Chewing Activity, Ruminal Mat Characteristics, and Passage in Dairy Cows J Dairy Sci, April 1, 2007; 90(4): 1929 - 1942. [Abstract] [Full Text] [PDF]

				S. Seo, C. Lanzas, L. O. Tedeschi, and D. G. Fox Development of a Mechanistic Model to Represent the Dynamics of Liquid Flow Out of the Rumen and to Predict the Rate of Passage of Liquid in Dairy Cattle J Dairy Sci, February 1, 2007; 90(2): 840 - 855. [Abstract] [Full Text] [PDF]

				A. Rotger, A. Ferret, X. Manteca, J. L. R. de la Torre, and S. Calsamiglia Effects of dietary nonstructural carbohydrates and protein sources on feeding behavior of tethered heifers fed high-concentrate diets J Anim Sci, May 1, 2006; 84(5): 1197 - 1204. [Abstract] [Full Text] [PDF]

				Q. Zebeli, M. Tafaj, H. Steingass, B. Metzler, and W. Drochner Effects of Physically Effective Fiber on Digestive Processes and Milk Fat Content in Early Lactating Dairy Cows Fed Total Mixed Rations J Dairy Sci, February 1, 2006; 89(2): 651 - 668. [Abstract] [Full Text] [PDF]

				C. Leonardi, K. J. Shinners, and L. E. Armentano Effect of Different Dietary Geometric Mean Particle Length and Particle Size Distribution of Oat Silage on Feeding Behavior and Productive Performance of Dairy Cattle J Dairy Sci, February 1, 2005; 88(2): 698 - 710. [Abstract] [Full Text] [PDF]

				J. C. Plaizier Replacing Chopped Alfalfa Hay with Alfalfa Silage in Barley Grain and Alfalfa-Based Total Mixed Rations for Lactating Dairy Cows J Dairy Sci, August 1, 2004; 87(8): 2495 - 2505. [Abstract] [Full Text] [PDF]

				W. Z. Yang and K. A. Beauchemin Grain Processing, Forage-to-Concentrate Ratio, and Forage Length Effects on Ruminal Nitrogen Degradation and Flows of Amino Acids to the Duodenum J Dairy Sci, August 1, 2004; 87(8): 2578 - 2590. [Abstract] [Full Text] [PDF]

				A. N. Hristov, S. Ahvenjarvi, T. A. McAllister, and P. Huhtanen Composition and digestive tract retention time of ruminal particles with functional specific gravity greater or less than 1.02 J Anim Sci, October 1, 2003; 81(10): 2639 - 2648. [Abstract] [Full Text] [PDF]