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MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources |
Three male cattle (local “Yellow” breed), approximately 2 years of age, were arranged in a 3*3 Latin square design with 3 treatments and 3 replications. The treatments were: CH: rice straw + cassava hay at 1 kg/d, CF: rice straw + fresh cassava foliage at 4 kg/d, CFS: rice straw + fresh cassava foliage at 4 kg/d + NaCl (3kg/100 kg of H2O) sprinkled on the foliage at 0.5 liters/d. All animals were provided with a rumen supplement (65% cassava root chips, 25% rice bran, 3% molasses, 3% urea , 1% sulfur) at 500 g/d.
Spraying salt solution on fresh cassava foliage increased the intake of the foliage and of total DM. Rumen ecology parameters, blood urea and coefficients of apparent digestibility were not affected by the salt solution; live weight gain appeared to be depressed.
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Keywords: Blood urea, HCN, protein, supplementation, urea, VFA
Fresh cassava foliage, as the only source of protein and fibre, supported high growth rates (>800 g/d) in cattle fed a basal diet of molasses and urea (Ffoulkes et al 1978; Ffoulkes and Preston 1978; Ffoulkes and Preston 1979). In Thailand, by contrast, farmers have encountered HCN toxicity when ruminants consumed fresh cassava leaves (M Wanapat, personal communication). For this reason, the technique of sun-drying the foliage (cassava hay) was developed (Wanapat 1999; 2001) as this has been shown to decrease to low levels the concentration of HCN (Bui Huy Nhu Phuc et al 1996).
The objective of the present study was to determine if addition of salt (NaCl) might be beneficial when cassava foliage was fed fresh to cattle.
The experiment was conducted at the Livestock Research Center (Nam Xuang) of the National Agriculture and Forestry Research Institute, situated 44 km from Vientiane City. The climate in this area is divided into 2 seasons: dry and wet. The wet season is from May to October. Annual rainfall is in the range of 1400-1800 mm. The dry season is from November to April. The average minimum and maximum temperatures are about 15oC and 32oC, respectively. The experiment was carried out in June/July, 2006.
Three male cattle (Local “Yellow” breed), approximately two years old, were randomly allotted to three dietary treatments according to a 3*3 Latin square design. Periods were of 21 days: 14 days for adaptation to the diets and 7 days for collection of data.
CH: rice straw + cassava hay (1 kg/day)
CF: rice straw + fresh cassava foliage (4 kg/day)
CFS: rice straw + fresh cassava foliage (4 kg/hd/d) + `salt (NaCl) solution (3kg/100kg of H2O) sprinkled on the foliage at 0.5 liters/d
The layout of the treatments in the Latin square is shown in Table 1.
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Tab le 1. Layout of treatments |
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Periods |
Cattle |
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1 |
2 |
3 |
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1 |
CH |
CFS |
CF |
|
2 |
CFS |
CF |
CH |
|
3 |
CF |
CH |
CFS |
The animals were housed in individual pens with permanent roof. A mineral block and clean, fresh water were available ad libitum during the whole experiment. Feed was offered according to the respective treatments in two equal parts in the morning and in the afternoon.
Rice straw was purchased from the local farmers. Fresh cassava foliage was harvested from plots in LRC. Part of the foliage was sun-dried to produce cassava hay (CH). The rest was chopped (lengths of 7-8cm) and fed as such (CF) or was mixed with salt solution (3kg salt/100kg H2O sprinkled on the cassava foliage at 0.5 liters/day) (CFS). A rumen supplement (65% cassava root chips, 25% rice bran, 3% molasses, 3% urea and 1% sulfur) was given to all the cattle at 500 g/d.
Feed offered and refused was measured daily during each period. During the last two days of each period, rumen fluid was obtained by stomach tube before and at 2h and 4h after feeding. Rumen pH was measured immediately using a digital pH meter. Rumen fluid was prepared for later analysis of NH3-N using a KJELTEC AUTO 1030 analyzer (Bromer and Keeney 1965), and volatile fatty acids (VFA) using HPLC model Water600 with UV Detector (Millipore Corporation) (Samuel et al 1997). Blood was collected from the jugular vein from each animal before and at 2h and 4h post-feeding, and was analyzed for blood urea nitrogen (BUN) by the method of Crocker (1967). Fecal samples were collected directly from the rectum during the last 5 days of each period and bulked for later chemical analysis. Samples of feeds and feces were analyzed for DM, ash and nitrogen, using procedures of AOAC (1990). Analysis of NDF, ADF and ADL was according to the method of Goering and Van Soest (1970). Acid insoluble ash (AIA) was determined by the procedure described by Van Keulen and Young (1977) and used to calculate coefficients of apparent digestibility of DM, OM, crude protein, NDF and ADF.
The experimental data were
analyzed according to the General Linear Model (GLM) option of the ANOVA program
in the Minitab software (MTAB 2000). Treatment means which showed significant
differences at p<0.05 were compared by the Tukey test in the Minitab software.
The sources of variation were: treatments, animals, periods and error.
These are shown in Table 2.
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Table 2. Composition of the rice straw and cassava foliage |
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Rice straw |
Cassava hay |
Fresh cassava foliage |
Fresh cassava foliage + salt |
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DM, % |
83.0 |
85.8 |
21.8 |
22.1 |
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As % of DM |
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|
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OM |
86.7 |
89.4 |
87.8 |
88.2 |
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CP |
5.4 |
19.9 |
21.6 |
21.6 |
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Ash |
13.3 |
10.6 |
12.3 |
11.8 |
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NDF |
77.6 |
56.0 |
61.6 |
51.6 |
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ADF |
57.1 |
34.1 |
34.1 |
38.4 |
Intakes of rice straw and of total DM were highest on treatments with fresh cassava foliage with or without addition of salt (Table 3). Adding salt to the fresh cassava foliage increased intake of the foliage to the same level recorded for cassava hay. Total DM intake was highest for the treatment of cassava foliage sprayed with salt, with no differences between the cassava hay and the fresh cassava foliage treatments. Despite the higher DM intakes with fresh cassava foliage sprayed with salt solution, the gain in live weight was lowest on this treatment (Table 3).
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Table 3. Mean values for DM intake and changes in live weight for cattle fed of rice straw supplemented with fresh cassava foliage (CF), fresh cassava foliage with salt (CFS) or cassava hay (CH) |
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CH |
CF |
CFS |
SEM |
P |
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DM intake, kg/day |
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Rice straw |
2.21a |
2.65b |
2.86b |
0.083 |
0.001 |
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Cassava foliage |
0.82a |
0.37b |
1.05a |
0.029 |
0.001 |
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Total |
3.03a |
3.02a |
3.90b |
0.083 |
0.001 |
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% BW |
2.55a |
2.41a |
3.09b |
0.075 |
0.001 |
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Live weight change, kg |
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Initial |
123 |
128 |
127 |
1.6 |
0.078 |
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Final |
127 |
132 |
131 |
1.5 |
0.070 |
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Daily gain |
0.179a |
0.184a |
0.159b |
0.0051 |
0.002 |
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a,b,c Means in the same row with different superscripts differ (P<0.05) |
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There were no differences in the coefficients of apparent digestibility among treatments (Table 4)..
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Table 4. Mean values for coefficients of apparent digestibility for cattle fed of rice straw supplemented with fresh cassava foliage (CF), fresh cassava foliage with salt (CFS) or cassava hay (CH) |
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CH |
CF |
CFS |
SEM |
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Apparent digestibility, % |
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DM |
61.3 |
60.6 |
61.9 |
2.82 |
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OM |
55.0 |
63.5 |
62.6 |
3.43 |
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CP |
58.1 |
58.7 |
67.4 |
6.35 |
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NDF |
58.5 |
59.5 |
58.5 |
4.67 |
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ADF |
62.1 |
63.4 |
62.1 |
1.81 |
There were no differences among treatments in rumen pH, ammonia and VFA, nor in blood urea nitrogen (Table 5).
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Table 5. Mean values of rumen traits in cattle fed of rice straw supplemented with fresh cassava foliage (CF), fresh cassava foliage with salt (CFS) or cassava hay (CH) |
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CH |
CF |
CFS |
SEM |
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pH |
0h post-feeding |
7.6 |
7.7 |
7.5 |
0.04 |
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2 |
7.6 |
7.7 |
7.6 |
0.06 |
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4 |
7.6 |
7.7 |
7.5 |
0.07 |
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NH3-N, mg% |
0h post-feeding |
9.3 |
6.3 |
7.6 |
1.35 |
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2 |
9.0 |
8.2 |
8.1 |
1.36 |
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4 |
5.3 |
5.0 |
3.8 |
1.39 |
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BUN, mg% |
0h post-feeding |
16.8 |
14.0 |
14.5 |
3.95 |
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2 |
19.0 |
17.7 |
16.8 |
4.12 |
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4 |
12.8 |
12.4 |
12.4 |
2.32 |
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VFA, mM/liter |
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Total |
0h post-feeding |
111 |
100 |
94.7 |
5.44 |
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|
2 |
98.1 |
106 |
110 |
3.93 |
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4 |
107 |
104 |
109 |
3.48 |
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Acetate |
0h post-feeding |
72.1 |
72.0 |
70.5 |
0.42 |
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|
2 |
69.7 |
69.5 |
68.7 |
1.24 |
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4 |
68.3 |
69.2 |
69.2 |
0.50 |
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Propionate |
0h post-feeding |
19.0 |
18.9 |
19.6 |
0.64 |
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2 |
18.9 |
18.8 |
19.5 |
0.22 |
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|
4 |
21.0 |
19.5 |
20.2 |
0.79 |
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Butyrate |
0h post-feeding |
8.9 |
9.1 |
9.9 |
0.58 |
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|
2 |
11.4 |
11.7 |
11.8 |
1.24 |
|
|
4 |
10.7 |
11.3 |
10.7 |
1.04 |
The only apparent effects of spraying salt on the fresh cassava foliage was to increase the intake of the foliage and of the total DM. In contrast, the rate of live weight gain was lowest for this treatment. There is no obvious explanation for these contrasting findings. It can be hypothesized that the salt solution could have raised the osmotic pressure in the digestive tract. Such an effect would be expected to increase the rate of passage and therefore the DM intake. Measurements of live weight over periods of 21 days are not very reliable; however, the apparent negative change is the opposite of what might have been expected.
Use of fresh and sun-dried cassava foliage and leaves, as a protein supplement for ruminants fed basal diets of high and low nutritive value, has been reported extensively (Preston 2001; Wanapat 2001; Keo Sath et al 2008; Ho Thanh Tham et al 2008) but never together in the same experiment. Such comparisons are urgently needed, as are further studies on the effects of supplements of NACl.
· Spraying salt (NaCl) solution on fresh cassava foliage increased the intake of the foliage and of total DM.
· Rumen ecology parameters, blood urea and coefficients of apparent digestibility were not affected by the salt solution; however, live weight gain appeared to be depressed
The authors are extremely grateful to the Swedish International Development Agency (Sida), Department for Research Cooperation with Developing Countries (SAREC), through the MEKARN regional project for supporting this thesis research. Thanks also to the National Agriculture and Forestry Research Institute (NAFRI), Livestock Research Center (LRC) and Tropical Feed Resources Research and Development Center (TROFREC), Department of Animal Science, Faculty of Agriculture, Khon Kean University, Thailand, for permission to use their research facilities and for their cooperation.
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