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Poster 4.4: Kikuyu grass composition and implications for silage production - A.G. Kaiser, J.W. Piltz, E.J. Havilah and J.F. Hamilton

Alan G. Kaiser and John W. Piltz

Euie J. Havilah and John F. Hamilton

NSW Agriculture

NSW Agriculture

Wagga Wagga Agricultural Institute

Pasture Research Unit

PMB Wagga Wagga

PO Box 63, Berry

NSW, 2650, Australia

NSW, 2535, Australia


Kikuyu grass (Pennisetum clandestinum), often top-dressed with nitrogen (N) fertilizer, is an important summer-growing pasture along the east coast of Australia, especially in new South Wales (NSW) and SE Queensland. Cutting surplus summer and autumn growth for silage would improve forage utilization and the management of these pastures (Kaiser et al., 1993). Strategic silage cuts could be integrated with grazing to maintain the grass at a more vegetative, higher quality stage of growth for dairy and beef cattle. In order to ensile Kikuyu grass with an organic matter digestibility of 0.60 to 0.70, a regrowth interval of 20 to 50 days would be required. This interval would vary with the prevailing growing conditions. There are few data on the ensiling characteristics of Kikuyu grass when cut at this stage of growth.


Fresh Kikuyu grass samples were collected at silage cutting in 11 experiments conducted in the Nowra district of coastal NSW. Regrowth intervals varied from 20 to 50 days and N fertilizer was applied at 50 or 100 kg N/ha at the commencement of the regrowth period. Samples were dried in a forced-air oven at 80°C for 24 h to determine DM content, and were then ground prior to analysis for WSC, starch and total N content. Buffering capacities were determined on fresh forage using the method of Playne and McDonald (1966). A summary of the data from the 11 experiments is presented in Table 1.

Table 1. Composition of Kikuyu grass at the time of cutting for silage (summary of results from 11 experiments)

DM content

(g/kg DM)

(g/kg DM)

Total N
(g/kg DM)

Buffering capacity(2)
(meq/kg DM)








108.5 - 323.0

23.4 - 68.4

14.2 - 57.8

17.4 - 35.1

224.7 - 495.7

Notes: (1) Starch data from four experiments. (2) Buffering capacity from two experiments


Although there was some variation in Kikuyu grass composition, it generally had low DM content, low WSC content, high N concentration and intermediate buffering capacity. Low DM content in the range 100 to 160 g/kg is common, and it is only under dry conditions, when Kikuyu grass is moisture stressed, that DM content can reach 300 g/kg at cutting. The mean buffering capacity - an indicator of the ability of the forage to resist pH change - was similar to published values for temperate grasses (McDonald et al., 1991).

The results from four experiments indicate that Kikuyu grass contains an appreciable quantity of starch. While starch will not contribute directly to the silage fermentation, as silage bacteria cannot ferment starch, hydrolysis of starch to sugars during wilting and prior to the establishment of anaerobic conditions in the silo could boost the supply of sugars available for fermentation, provided there are not significant losses due to respiration.

The low WSC content, low DM content and intermediate buffering capacity indicate that there is a significant risk of a poor fermentation if Kikuyu is ensiled without wilting or with only a minimal wilt (<300 g/kg DM content). Data based on UK studies with temperate grasses have shown that the critical sugar level for successful (low risk) silage production is 25-30 g/kg fresh crop (Wilkinson, 1990). In our experiments, the mean sugar content of Kikuyu grass on a fresh crop basis was only 8.7 g/kg, well below this critical level.


Because of its low DM content, low WSC content and intermediate buffering capacity, farmers ensiling Kikuyu grass will need to rely on wilting or silage additives to improve the probability of achieving a satisfactory lactic acid fermentation.


We are greatly indebted to the Australian Dairy Research and Development Corporation and NSW Agriculture for funding this research, and for assistance from local dairy producers who provided access to land and equipment.


Kaiser, A.G., Havilah, E.J., Chopping, G.D. & Walker, R.G. 1993. Northern dairy feedbase 2001. 4. Feeding systems during winter and spring. Tropical Grasslands, 27: 180-211.

McDonald, P., Henderson, N., & Heron, S. 1991. The Biochemistry of Silage. 2nd edition. Marlow, UK: Chalcombe Publications.

Playne, M.J., & McDonald, P. 1966. The buffering constituents of herbage and of silage. J. Sc. Food and Agric., 17: 264-268.

Wilkinson, M. 1990. Silage UK. 6th edition. Marlow, UK: Chalcombe Publications.

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