Grazing behaviour and pattern of intake of dairy cows grazing kikuyu (Pennisetum clandestinum) grass pastures in relation to sward height and length of grazing session
R. C. Dobos A E , W. J. Fulkerson B , K. Sinclair C and G. N. Hinch DA New South Wales Department of Primary Industries Beef Industry Centre, Armidale, NSW 2351, Australia.
B MC Franklin Laboratory, University of Sydney, Camden, NSW 2570, Australia.
C New South Wales Department of Primary Industries, Wollongbar Agricultural Institute, Wollongbar, NSW 2477, Australia.
D School of Environmental and Rural Science, University of New England, Armidale, NSW 2351, Australia.
E Corresponding author. Email: robin.dobos@dpi.nsw.gov.au
Animal Production Science 49(3) 233-238 https://doi.org/10.1071/EA08212
Submitted: 1 August 2008 Accepted: 10 November 2008 Published: 2 March 2009
Abstract
To investigate how grazing time, herbage dry matter intake (DMI) and intake rate (IR) are influenced by intensive grazing management, dairy cows strip-grazing subtropical grass pastures (Pennisetum clandestinum) at two compressed sward heights (10 and 13 cm) and at five grazing durations (1, 2, 4, 8 and 15 h) and replicated over 3 days were studied. The study was conducted in summer and the cows were observed every 20 min from 1600 to 0700 hours to calculate the time spent (min/h) grazing, ruminating and resting. Total time spent grazing was 45 min longer for cows grazing the 13-cm sward than for those grazing the 10-cm sward over the 15-h grazing period. The rate of increase in grazing time was 0.64 h/h grazing duration up to 4 h after introduction to fresh pasture. IR of cows grazing the 13-cm sward was significantly higher than those grazing the 10-cm sward (0.17 v. 0.12 kg DM/min spent grazing). The difference in IRs between sward height treatments resulted from the higher DMI in the 13-cm sward within the first 4 h of grazing compared with the 10-cm sward, although following the first 4-h grazing period IR was similar for both sward heights. Grazing time increased with sward height up to a maximum of 4 h after introduction to fresh pasture and had also maximised herbage DMI by this time. These results have important practical implications for dairy cow grazing management systems because they show that dairy managers could remove cows after 4 h with little compromise in production and will help in developing optimum supplementary feeding strategies when pasture availability limits DMI.
Acknowledgements
The authors are indebted to Messrs Scott Petty, Bill Davis and Dick Bryant for technical assistance in the conduct of this experiment. Funding from Dairy Australia as part of a larger project (DAN097) is also gratefully acknowledged.
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