| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
,1
* Institute of Animal Nutrition (450), University of Hohenheim, Emil-Wolff-Str. 10, D-70599 Stuttgart, Germany
Animal Nutrition Group, Wageningen University, Marijkeweg 40, 6709 PG Wageningen, the Netherlands
Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta T6G 2P5 Canada
1 Corresponding author: zebeli{at}uni-hohenheim.de
The main objective of this study was to develop practical models to assess and predict the adequacy of dietary fiber in high-yielding dairy cows. We used quantitative methods to analyze relevant research data and critically evaluate and determine the responses of ruminal pH and production performance to different variables including physical, chemical, and starch-degrading characteristics of the diet. Further, extensive data were used to model the magnitude of ruminal pH fluctuations and determine the threshold for the development of subacute ruminal acidosis (SARA). Results of this study showed that to minimize the risk of SARA, the following events should be avoided: 1) a daily mean ruminal pH lower than 6.16, and 2) a time period in which ruminal pH is <5.8 for more than 5.24 h/d. As the content of physically effective neutral detergent fiber (peNDF) or the ratio between peNDF and rumen-degradable starch from grains in the diet increased up to 31.2 ± 1.6% [dry matter (DM) basis] or 1.45 ± 0.22, respectively, so did the daily mean ruminal pH, for which a asymptotic plateau was reached at a pH of 6.20 to 6.27. This study also showed that digestibility of fiber in the total tract depends on ruminal pH and outflow rate of digesta from reticulorumen; thereby both variables explained 62% of the variation of fiber digestibility. Feeding diets with peNDF content up to 31.9 ± 1.97% (DM basis) slightly decreased DM intake and actual milk yield; however, 3.5% fat-corrected milk and milk fat yield were increased, resulting in greater milk energy efficiency. In conclusion, a level of about 30 to 33% peNDF in the diet may be considered generally optimal for minimizing the risk of SARA without impairing important production responses in high-yielding dairy cows. In terms of improvement of the accuracy to assessing dietary fiber adequacy, it is suggested that the content of peNDF required to stabilize ruminal pH and maintain milk fat content without compromising milk energy efficiency can be arranged based on grain or starch sources included in the diet, on feed intake level, and on days in milk of the cows.
Key Words: physically effective fiber • dairy cow • ruminal pH • rumen-degradable starch
This article has been cited by other articles:
|
|
 |
|
  W. Z. Yang and K. A. Beauchemin Increasing physically effective fiber content of dairy cow diets through forage proportion versus forage chop length: Chewing and ruminal pH J Dairy Sci, April 1, 2009; 92(4): 1603 - 1615. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. Kebreab, J. Dijkstra, A. Bannink, and J. France Recent advances in modeling nutrient utilization in ruminants J Anim Sci, April 1, 2009; 87(14_suppl): E111 - E122. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. N. Ametaj, D. G. V. Emmanuel, Q. Zebeli, and S. M. Dunn Feeding high proportions of barley grain in a total mixed ration perturbs diurnal patterns of plasma metabolites in lactating dairy cows J Dairy Sci, March 1, 2009; 92(3): 1084 - 1091. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. AlZahal, M. M. Or-Rashid, S. L. Greenwood, M. S. Douglas, and B. W. McBride The effect of dietary fiber level on milk fat concentration and fatty acid profile of cows fed diets containing low levels of polyunsaturated fatty acids J Dairy Sci, March 1, 2009; 92(3): 1108 - 1116. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Dohme, T. J. DeVries, and K. A. Beauchemin Repeated Ruminal Acidosis Challenges in Lactating Dairy Cows at High and Low Risk for Developing Acidosis: Ruminal pH J Dairy Sci, September 1, 2008; 91(9): 3554 - 3567. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Q. Zebeli, M. Tafaj, B. Junck, V. Olschlager, B. N. Ametaj, and W. Drochner Evaluation of the Response of Ruminal Fermentation and Activities of Nonstarch Polysaccharide-Degrading Enzymes to Particle Length of Corn Silage in Dairy Cows J Dairy Sci, June 1, 2008; 91(6): 2388 - 2398. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
