| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
* Institute of Grassland and Environmental Research, Plas Gogerddan, Aberystwyth SY23 3EB, U.K.
Trawsgoed Research Farm, Aberystwyth SY23 4LL, U.K.
North Wyke Research Station, Okehampton EX20 8SB, U.K.
Corresponding author:
R. J. Dewhurst; e-mail:
Richard.Dewhurst{at}bbsrc.ac.uk.
Two experiments were conducted to investigate the basis for higher voluntary intakes and increased 
-linolenic acid content in milk from cows offered clover silages. Six cows with rumen and duodenal cannulae were used in a four-period changeover-design experiment. Cows received 8 kg/d of dairy concentrate and had ad libitum access to one of six silage treatments: grass, red clover, white clover, alfalfa, and 50/50 (dry matter basis) mixtures of grass with red clover or white clover. The rumen fermentability of grass, red clover, white clover, and grass/red clover silages was also evaluated in a nylon bag study. Legume silages led to increased dry matter intake and milk production in comparison with grass silage. There was no significant effect of legume silages on rumen pH and volatile fatty acid concentrations, but a significant increase in rumen ammonia concentration with the legume silages, reflecting their higher protein content. The inclusion of white clover or alfalfa silage, but not red clover silage, in diets led to an increase in molar proportions of iso-butyric, iso-valeric, and n-valeric acids in comparison with diets based on grass silage. Rumen fill was significantly lower, and rumen passage rates were significantly higher for cows offered alfalfa or white clover silages. However, the markedly different particle size distribution of rumen contents with these feeds suggests very different mechanisms for the high intake characteristics: high rates of particle breakdown and passage with alfalfa, and high rates of fermentation and passage with white clover. Microbial energetic efficiency (grams microbial N per kilogram organic matter apparently digested in the rumen) was highest for cows offered alfalfa silage, intermediate for clover silage, and lowest for cows offered grass silage. These differences reflect the higher rumen outflow rates for legume silages in comparison with grass silage. However, the effect of these differences on N-use efficiency (feed to milk) was probably quite small in comparison with effects of N intake. Although the biohydrogenation of -linolenic acid was still high for red clover silage (86.1% compared with 94.3% for grass silage), there was a 240% increase in the proportion of -linolenic acid passing through the rumen. This explains the increased recovery of -linolenic acid from feed into milk with diets based on red clover silage.
Key Words: legume • silage • rumen biohydrogenation • digesta kinetics • fatty acid
Abbreviation key: A = alfalfa silage, G = grass silage, GRC = mixture of G and RC, GWC = mixture of G and WC, RC = red clover silage, WC = white clover silage, RUN = rumen undegraded N
This article has been cited by other articles:
|
|
 |
|
  J. A. Voelker Linton and M. S. Allen Nutrient Demand Interacts with Forage Family to Affect Intake and Digestion Responses in Dairy Cows J Dairy Sci, July 1, 2008; 91(7): 2694 - 2701. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. F. Lee, S. A. Huws, N. D. Scollan, and R. J. Dewhurst Effects of Fatty Acid Oxidation Products (Green Odor) on Rumen Bacterial Populations and Lipid Metabolism In Vitro J Dairy Sci, August 1, 2007; 90(8): 3874 - 3882. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. A. Broderick, A. F. Brito, and J. J. O. Colmenero Effects of Feeding Formate-Treated Alfalfa Silage or Red Clover Silage on the Production of Lactating Dairy Cows J Dairy Sci, March 1, 2007; 90(3): 1378 - 1391. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. F. Brito, G. A. Broderick, J. J. O. Colmenero, and S. M. Reynal Effects of Feeding Formate-Treated Alfalfa Silage or Red Clover Silage on Omasal Nutrient Flow and Microbial Protein Synthesis in Lactating Dairy Cows J Dairy Sci, March 1, 2007; 90(3): 1392 - 1404. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 R. J. Merry, M. R. F. Lee, D. R. Davies, R. J. Dewhurst, J. M. Moorby, N. D. Scollan, and M. K. Theodorou Effects of high-sugar ryegrass silage and mixtures with red clover silage on ruminant digestion. 1. In vitro and in vivo studies of nitrogen utilization J Anim Sci, November 1, 2006; 84(11): 3049 - 3060. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. R. F. Lee, P. L. Connelly, J. K. S. Tweed, R. J. Dewhurst, R. J. Merry, and N. D. Scollan Effects of high-sugar ryegrass silage and mixtures with red clover silage on ruminant digestion. 2. Lipids J Anim Sci, November 1, 2006; 84(11): 3061 - 3070. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Moorby, R. J. Dewhurst, R. T. Evans, and J. L. Danelon Effects of dairy cow diet forage proportion on duodenal nutrient supply and urinary purine derivative excretion. J Dairy Sci, September 1, 2006; 89(9): 3552 - 3562. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
E. J. Kim, R. Sanderson, M. S. Dhanoa, and R. J. Dewhurst Fatty Acid Profiles Associated with Microbial Colonization of Freshly Ingested Grass and Rumen Biohydrogenation J Dairy Sci, September 1, 2005; 88(9): 3220 - 3230. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. J. Bradford and M. S. Allen Milk Fat Responses to a Change in Diet Fermentability Vary by Production Level in Dairy Cattle J Dairy Sci, November 1, 2004; 87(11): 3800 - 3807. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. M. Al-Mabruk, N. F. G. Beck, and R. J. Dewhurst Effects of Silage Species and Supplemental Vitamin E on the Oxidative Stability of Milk J Dairy Sci, February 1, 2004; 87(2): 406 - 412. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
V. Fievez, B. Vlaeminck, M. S. Dhanoa, and R. J. Dewhurst Use of Principal Component Analysis to Investigate the Origin of Heptadecenoic and Conjugated Linoleic Acids in Milk J Dairy Sci, December 1, 2003; 86(12): 4047 - 4053. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. J. Dewhurst, W. J. Fisher, J. K. S. Tweed, and R. J. Wilkins Comparison of Grass and Legume Silages for Milk Production. 1. Production Responses with Different Levels of Concentrate J Dairy Sci, August 1, 2003; 86(8): 2598 - 2611. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
