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Chris Regan |
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Northern Territory Department of Primary Industry and Fisheries (NT DPIF) |
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Darwin, Australia |
E-mail: [email protected] |
EXPERIMENT LOCATION
This small study was conducted at Humpty Doo, approximately 40 km SE of Darwin, Northern Territory, Australia (12°24' S, 131°15' E). The area receives a mean annual rainfall of between 1 500 and 2 000 mm, 80% of which falls in four months: December to March.
DESCRIPTION OF THE EXPERIMENT
The nutritive values of cavalcade (Centrosema pascuorum) and pangola grass (Digitaria eriantha subsp. eriantha) were compared with those of the same species preserved as 7-month old hays and silages. The materials were cut when cavalcade and pangola were 125 days and 45 days old, respectively (cavalcade by slashing and pangola with a disc mower) and wilted. The materials were wilted to DM contents ranging from 221 to 865 g/kg and made into small cylindrical bales (800 mm long × 450 mm wide), which were wrapped in plastic film for preservation as silage, or left unwrapped as hay. Each bale was sampled and analysed for nutritive value (DM, DDM, ME, and CP).
The results are given in Table1.
The nutritive values of the cavalcade and the pangola grass forages decreased as DM content increased, but nutritive values during storage were maintained. Silages had better nutritive value than hays. Silage quality was good. The cavalcade silage had high lactic acid content, lower acetic, and minor butyric acid production associated with low pH. Spoilage was generally low (11.5%). In the pangola grass silage, the main fermentation product was ethanol, but the silage quality was still good, with lactic acid content higher than acetic acid content, minor butyric acid production being associated with high pH (4.95). Spoilage was consistently low (2.82%). Ammonia-N production, which was always less than 60 g/kg total N, was highest for low-DM-content silages for both species.
Table 1. A comparison of the nutritive value of cavalcade pasture and pangola grass preserved as wilted silage or as hay(1)
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Silage |
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Pasture |
Minimum Wilt |
Wilted |
Heavily Wilted |
Hay |
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Cavalcade |
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DM (%) |
23.3 |
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41.4 |
61.8 |
92.2 |
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Digestibility (%DM) |
55.1 |
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53.4 |
50.1 |
42.5 |
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ME (MJ/kg DM) |
8.2 |
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7.8 |
7.3 |
6.1 |
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CP (%DM) |
20.4 |
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16.1 |
16.1 |
13.1 |
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Bale Weight (kg) |
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25.7 |
15.9 |
9.7 |
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pH |
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4.50 |
4.60 |
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Ethanol (g/kg DM) |
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2.49 |
1.44 |
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Acetic acid (g/kg DM) |
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13.99 |
5.10 |
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Butyric acid (g/kg DM) |
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1.79 |
0.34 |
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Lactic acid (g/kg DM) |
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16.61 |
13.44 |
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Ammonia N (g/kg total N) |
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52.30 |
32.20 |
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Pangola grass |
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DM (%) |
22.1 |
44.3 |
55.4 |
63.7 |
91.9 |
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Digestibility (%DM) |
59.8 |
60.8 |
57.0 |
55.5 |
48.7 |
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ME (MJ/kg DM) |
9.0 |
9.0 |
8.4 |
8.1 |
7.1 |
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CP (%DM) |
13.0 |
10.7 |
10.8 |
11.3 |
9.8 |
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Bale weight (kg) |
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24.8 |
22.3 |
18.4 |
10.7 |
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pH |
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4.50 |
4.90 |
5.40 |
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Ethanol (g/kg DM) |
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16.27 |
12.52 |
7.38 |
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Acetic acid (g/kg DM) |
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4.12 |
1.87 |
1.30 |
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Butyric acid (g/kg DM) |
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0.45 |
0.06 |
0.04 |
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Lactic acid (g/kg DM) |
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11.74 |
5.05 |
2.52 |
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Ammonia N (g/kg total N) |
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40.00 |
30.70 |
28.90 |
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Notes: (1) The data present the nutritive values of the silages and hays after 7 months in storage. This corresponded to a complete dry season. Other data are available on request showing the nutritive values of the silages and hays at the time of formation (i.e. at the beginning of the storage period).
