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1 Animal Nutrition Group, Department of Animal Sciences, Wageningen University, 6700 AH, Wageningen, The Netherlands
2 Crop and Weed Ecology Group, Department of Plant Sciences, Wageningen University, 6700 AK, Wageningen, The Netherlands
Corresponding author: B. Tas; e-mail: tas{at}aninut.uni-kiel.de.
The effects of 8 diploid perennial ryegrass (Lolium perenne L.) cultivars on dry matter (DM) intake, DM digestibility, and milk yield (MY) of dairy cows were evaluated in the summer of 2000 and 2001. Each summer, herbage was harvested daily and stall-fed to 12 dairy cows during six 2-wk periods. Six cultivars were fed in 3 periods (1, 3, and 5) according to a double 3 x 3 Latin square design. In the other periods (2, 4, and 6), 2 cultivars were fed in a repeated measurement design. Herbage mass and leaf blades in the sward canopy varied among cultivars, but differences were not consistent between years. The largest differences in herbage composition were found in water-soluble carbohydrate content, followed by crude protein content. only small differences were found in the neutral detergent fiber (NDF) content. A higher water-soluble carbohydrate content was found in 2 cultivars in both years, whereas ranking of cultivars in crude protein and NDF content was not consistent with years. Dry matter intake and MY were not affected by cultivar. In both years, DM digestiblity was high (>77%), with very small differences among cultivars in 2000 (<0.5%) and larger differences in 2001 (up to 4%). This was associated with a delayed heading date in 2001, resulting in larger differences in leaf blades and NDF content among cultivars. It may be concluded that the 8 cultivars used in our experiments do not provide grass breeders with encouraging evidence to include selection criteria for an increased DM intake, DM digestibility, and MY in their grass breeding schemes.
Key Words: perennial ryegrass • cultivar • intake • milk yield
Abbreviation key: ADL = acid detergent lignin, DMD = dry matter digestibility, FPCM = fat- and protein-corrected milk, LS = Latin square, MPS = microbial protein synthesis, MY = milk yield, NGR = nonglucogenic to glucogenic ratio, WSC = water-soluble carbohydrate
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  B. M. Tas, H. Z. Taweel, H. J. Smit, A. Elgersma, J. Dijkstra, and S. Tamminga Effects of perennial ryegrass cultivars on milk yield and nitrogen utilization in grazing dairy cows. J Dairy Sci, September 1, 2006; 89(9): 3494 - 3500. [Abstract] [Full Text] [PDF]
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 H. J. Smit, S. Tamminga, and A. Elgersma Dairy Cattle Grazing Preference among Six Cultivars of Perennial Ryegrass Agron. J., August 3, 2006; 98(5): 1213 - 1220. [Abstract] [Full Text] [PDF]
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