to banana pseudo-stem and length of time ensiled
to banana pseudo-stem and length of time ensiled
| Livestock Research for Rural Development 26 (6) 2014 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
The objectives of the present study were to evaluate the effect on nutritive value of a diet for growing pigs of silage with increasing proportions (from 0 to 60% as DM) of banana pseudo-stem replacing taro foliage.
Compared with the tara foliage (leaves plus petioles), the banana pseudo-stem had half the crude protein, twice as much NDF and negligible oxalate. Ensiling mixtures of taro forage and banana pseudo-stem for 21 days reduced the oxalate concentration by 43-49% for all the combinations of banana pseudo-stem and taro foliage. Lactic acid concentrations in the silages increased with fermenetation time up to 14 days and were directly related to the proportion of taro foliage in the silage. Intake of the silage, and the crude protein level in the diet, increased linearly as taro foliage replaced banana pseudo-stem in the silage. Coefficients of apparent digestibility of DM, OM, NDF and nitrogen, and retention of nitrogen, increased linearly as taro foliage replaced banana pseudo-stem in the silage. Growth rate was decreased by 26% and feed conversion was poorer by 9% when the silage (which contained [DM basis] 40% banana pseudo-stem and 60% taro foliage) replaced 50% of the ingredients in a control diet based on maize, rice bran, cassava root meal and fish meal.
Key words: ensiling, feed conversion, forages, growth, lactic acid, pH, live weight gain
Taro (Araceae) and Banana (Musaceae ) are important food crops commonly grown in Central Vietnam. Banana is a traditional plant cultivated widely for fruits. After harvesting the fruits, it has been estimated that there is a residual biomass yield of 13-20 tonnes DM/ha/year (Ffoulkes and Preston 1978). Taro is grown as an intercropping plant with sweet potato, maize, cassava and banana. Biomass yields of over 250 tonnes/ha/year have been reported (Ngo Huu Toan and Preston 2008; Du Thanh Hang and Nguyen Trung Kien 2012). The nutritional value of leaves and petioles is high. The crude protein content of taro leaves ranges from 19.5 to 26%, and in petioles from 6.2 to 7.3% (% in DM) (Du Thanh Hang and Preston 2010). The leaves are rich in the essential amino acids lysine, methionine, threonine, valine, phenylalanine and leucine (Lê Đức Ngoan and Dư Thanh Hằng 2011, Rodríguez et al 2006).
The problems with these two feed resources are: the high crude fiber content in banana pseudo-stem and the anti-nutritional factor (oxalate salts) in taro. According to Du Thanh Hang and Preston (2010), the oxalate contain in taro leaves ranges from 768 to 2531 and in petioles from 1324 to 3507 mg/100g DM. It is reasonable to believe that the mixing of banana and taro forage would be advantageous as a means of complementing arrays of nutritional components and reducing the overall concentration of anti-nutritional compounds.
Some research has been done on the use banana pseudo-stem for cattle. Ffoulkes and Preston (1978) measured in vivo digestibility and intake by steers of combinations of leaves and pseudo-stem ranging from 100:0 through to 0:100% (leaf:stem, fresh basis). Digestibility increased and voluntary intake decreased as the proportion of pseudo-stem in the mixture increased.
It has been shown recently that both the banana pseudo-stem and taro foliage are relatively rich in sugars (Dao Thi My Tien et al 2010) and that a mixture of both forages can be ensiled without the need of other additives.
Four treatments (mixtures of the two forages) were compared:
Taro foliage and banana pseudo-stem were harvest from farmers’ gardens and chopped into small pieces (1-2cm) prior to being wilted under shade for 24h. They were mixed according to proposed treatments and ensiled in absence of air in plastic bags with capacity of 1.0 kg. Each treatment was replicated three times. Samples were taken at 0, 7, 14 and 21 days for analysis of DM, crude protein, NH3-N, lactic and acetic acids and pH.
Plastic bags with capacity of 50 kg were used to ensile the same mixtures of taro foliage and banana pseudo-stem as in experiment 1. After 21 days the silages were mixed with rice bran, maize and rice wine byproduct (Table 1) for feeding to experimental pigs.
|
Table 1: Proportions and proximate composition of the ingredients in the diets (DM basis) |
||||
|
|
T100B0 |
T80B20 |
T60B40 |
T40B60 |
|
Mix of ensiled forage |
50 |
50 |
50 |
50 |
|
Rice bran |
20 |
20 |
20 |
20 |
|
Maize |
20 |
20 |
20 |
20 |
|
Rice wine-by product |
10 |
10 |
10 |
10 |
|
Nutritional value of experimental diets (on DM basis except for DM which is on fresh basis) |
||||
|
DM, % |
44.3 |
41.2 |
40.5 |
39.8 |
|
Crude protein, % |
14.8 |
16.1 |
15.6 |
15.1 |
|
Crude fiber, % |
8.6 |
9.2 |
11.3 |
16.1 |
|
Lignin, % |
8.0 |
6.8 |
6.5 |
6.4 |
|
ME, kcal/kg |
2860 |
2956 |
2953 |
2950 |
|
Oxalate, mg/100 g |
1670 |
1502 |
1480 |
1334 |
Four castrated male pigs (Mong Cai x Large White)) with initial weight of 50 kg were housed individually in metabolism cages that allowed the separate collection of urine and feces. They were fed the experimental diets according to a 4*4 Latin square. Periods were of 10 days; 5 for adaptation to the change of diet and 5 for collection of feces and urine. Urine and feces of each pig were collected separately twice daily, weighed and stored at -20ºC. Urine was collected in a bucket via a funnel below the cage. The pH was kept below 4 by collecting the urine in 50 ml of 25 % sulfuric acid. At the end of each period, the feces were mixed, dried (in a drying oven at 60-65 ºC), ground and representative samples taken for analysis. DM, N, NDF and ADF of feed offered and refused, and in feces, and N in urine, were determined according to AOAC (1990).
Sixteen crossbred pigs (Mong Cai x Large White) with body weight of 20 ± 1.2 kg were housed in individual cages and allocated to two treatments (Control and T60B40). The control diet was based on rice bran, maize, cassava root meal, rice wine by-product and fish meal (Table 2). The test diet (T60B40) was formulated by replacing 50% of the DM of the control diet by ensiled forage of taro and banana (60% taro foliage plus 40% banana pseudo-stem in DM). The feed offer level was 4% (DM basis) of body weight. All diets had the same level of crude protein.
|
Table 2: Proportions and proximate composition of the ingredients in the diets (DM basis) |
||
|
Ingredients in the feeds |
Control |
T40B60 |
|
Rice bran |
35 |
15 |
|
Maize |
32 |
14 |
|
Cassava root meal |
10 |
5 |
|
Fish meal |
12 |
6 |
|
Ensiled forage |
0 |
50 |
|
Rice wine by-product |
10 |
10 |
|
Premix of ash & vitamin |
1 |
1 |
|
|
||
|
Crude protein, % |
15 |
15 |
|
ME, kcal/kg |
3100 |
3010 |
|
Crude fibre, % |
5.6 |
8.3 |
|
Oxalate, mg/100g DM |
52 |
568 |
The pigs were weighed in the early morning at the beginning and at 30 day intervals until the end of the trial, which lasted for 90 days. Feeds offered and refused were recorded before and after each meal (3 times a day). Samples of feed offered (refusals were expected to be close to zero) were taken at weekly intervals and stored at -180C until the end of the trial when they were bulked for each pig and sub-samples taken for determination of DM, N and crude fiber, using the procedures of AOAC (1990). Economic analysis was done using current data on feed cost, and value of the live weight.
The data that were collected during the experiment were analyzed using the GLM option in the ANOVA program of the Minitab software (Minitab 2010). Sources of variation in the model were treatment, replicates and error.
Compared with the tara foliage, the banana pseudo-stem had half the crude protein, twice as much NDF and negligible oxalate (Table 3).
|
Table 3 : The chemical composition of diet ingredients |
|||||
|
|
DM |
OM |
CP |
NDF |
Oxalate |
|
|
% |
As % of DM |
mg/100gDM |
||
|
Taro forage |
19.8 |
86.1 |
16.3 |
33.8 |
2100 |
|
Banana pseudo-stem |
5.8 |
88.0 |
5.5 |
69.2 |
387 |
|
Rice Bran |
90.4 |
90.9 |
11.3 |
38.8 |
|
|
Maize |
87.8 |
98.5 |
7.9 |
46.4 |
|
|
Rice wine-by product |
10.2 |
96.4 |
12.8 |
20.5 |
|
Increasing proportions of banana pseudo-stem in the silage led to reduction in content of DM and of crude protein (Table 4). There were decreases in both these elements with increasing time of ensiling. The pH decreased markedly afte 7 days of ensiling with a tendency to increase slightly in the subsequent 14 days (Table 5; Figure 1).
|
Table 4. DM and crude protein (in DM) in the silages |
||||||||
|
Day-0 |
Day-7 |
Day-14 |
Day-21 |
|||||
|
DM |
CP |
DM |
CP |
DM |
CP |
DM |
CP |
|
|
T100B0 |
19.7a |
21.5b |
13.8a |
19.8a |
11.7a |
19.0a |
11.2a |
18.2c |
|
T80B20 |
16.4b |
18.9a |
11.7b |
18.2a |
10.0b |
17.3ab |
9.60b |
16.8b |
|
T60B40 |
15.9 b |
16.2a |
11.0b |
15.9a |
9.23b |
15.2a |
9.20b |
14.8b |
|
T40B60 |
14.4b |
13.6a |
10.5b |
13.1a |
9.12b |
12.7a |
9.01b |
12.1b |
|
SEM |
0.13 |
0.11 |
0.11 |
0.23 |
0.14 |
0.12 |
0.11 |
0.32 |
|
P |
0.04 |
<0.01 |
0.03 |
<0.01 |
0.05 |
<0.01 |
<0.05 |
<0.01 |
|
abc Means in the same column without common letter differ at P<0.05 |
||||||||
|
Table 5. Mean values for pH in the mixtures of taro foliage and banana pseudo-stem according to time ensiled |
||||||
|
Day 0 |
Day 7 |
Day 14 |
Day 21 |
SEM |
p |
|
|
T100B0 |
6.73 |
3.67 |
3.87 |
4.00 |
||
|
T80B20 |
6.73 |
3.70 |
3.83 |
4.03 |
||
|
T60B40 |
6.77 |
3.60 |
3.83 |
4.10 |
||
|
T40B60 |
6.73 |
3.53 |
3.90 |
4.17 |
||
|
Mean |
6.74 |
3.63 |
3.86 |
4.08 |
0.034 |
<0.001 |
Oxalate levels decreased as banana pseudo-stem replaced the taro foliage. On all treatment combinations the oxalate decreased with length of time ensiled (Table 6; Figure 2). These results are similar to those reported by Du Thanh Hang and Preston (2010) when ensiling taro foliage for 14 days reduced the oxalate level by 50%. High oxalate concentrations in feeds consumed regularly are of concern because of the harmful health effects associated with the intake of high amounts of oxalates. A diet high in soluble oxalates is widely known to cause an excessive urinary excretion of oxalate (hyperoxaluria) with an increased risk of developing kidney stones (Coet et al 2005).
|
|
| Figure 1. Trends in pH of the silage according to ratio of taro foliage to banana pseudo-stem and length of time ensiled |
Figure 2. Trends in oxalate content of the silage according to ratio of taro foliage to banana pseudo-stem and length of time ensiled |
|
Table 6. Oxalate content (mg/100g DM) of the ensiled mixtures of taro foliage and banana-pseudo according to time ensiled |
|||||
|
Day-0 |
Day-7 |
Day-14 |
Day-21 |
% Reduction |
|
|
T100B0 |
2156a |
1888 |
1376a |
1103a |
48.8 |
|
T80B20 |
1802b |
1606b |
1289a |
1025a |
43.0 |
|
T60B40 |
1448c |
1244c |
889b |
738b |
49.0 |
|
T40B60 |
1095d |
976d |
684c |
578c |
47.2 |
|
SEM |
37.8 |
28.9 |
32.7 |
20.5 |
|
|
p |
0.01 |
0.01 |
0.03 |
0.03 |
|
|
abcd Means in the same column without common letter differ at P<0.05 |
|||||
|
Table 7. Lactic and acetic acid levels in the ensiled mixtures of taro foliage and banana pseudo-stem according to time ensiled |
||||||||
|
|
Day-0 |
Day-7 |
Day-14 |
Day-21 |
||||
|
|
Lactic |
Acetic |
Lactic |
Acetic |
Lactic |
Acetic |
Lactic |
Acetic |
|
T100B0 |
0.93 |
1.32 |
1.32 |
0.76 |
1.75b |
0.57c |
1.83b |
0.54c |
|
T80B20 |
0.87 |
1.41 |
1.2 |
0.87 |
1.56b |
0.61bc |
1.57b |
0.65b |
|
T60B40 |
0.81 |
1.53 |
1.13 |
0.88 |
1.32b |
0.72b |
1.24ab |
0.77b |
|
T40B60 |
0.75 |
1.56 |
0.98 |
0.91 |
1.15a |
0.81a |
1.01ab |
0.90a |
|
SEM |
0.041 |
0.067 |
0.09 |
0.04 |
0.11 |
0.03 |
0.024 |
0.020 |
|
p |
0.07 |
0.1 |
0.15 |
0.2 |
0.02 |
0.02 |
0.001 |
0.001 |
|
abc Means in the same column without common letter differ at P<0.05 |
||||||||
 |
 |
| Figure 3. Trends in lactic acid content of the silage according to ratio of taro foliage to banana pseudo-stem and length of time ensiled |
Figure 4. Trends in acetic acid content of the silage according to ratio of taro foliage to banana pseudo-stem and length of time ensiled |
The lactic acid content of the silage decreased as the banana pseudo-stem replaced the taro foliage and increased with time ensiled, reaching peak values after 14 days ensiled for the three treatments containing banana pseudo-stem. For the 100% taro foliage the lactica cid content continued to increase up to 21 days although at a slower rate (Table 7; Figure 3). The trends for acetic acid were the opposite with a rapid drop from 0 to 7 days, with no differemce among treatments. From 14 to 21 days acetic levels increased slightly and were higher for silages containing banana pseudo-stem (Figure 4).
The pigs had free access to the silage (in one feed trough) and the rest of the diet (in a separate trough). Intake of the silage, and the crude protein level in the diet, increased linearly as the banana pseudo-stem was replaced by taro foliage (Table 8; Figure 5).
|
Table 8. Mean values for feed intake of the pigs with ensiled mixtures of taro foliage and banana pseudo-stem |
||||||
|
|
T40B60 |
T60B40 |
T80B20 |
T100B0 |
SEM |
P |
|
Feed intake, kg/d |
|
|
|
|
|
|
|
Fresh silage |
3.92c |
4.58b |
5.02b |
5.83a |
0.418 |
|
|
Silage DM |
0.57b |
0.72b |
0.83ab |
1.09a |
0.071 |
|
|
Total DM |
1.56b |
1.69ab |
1.73ab |
1.94a |
0.097 |
|
|
Silage as % of total DM intake |
36.7b |
43.4b |
46.6a |
54.7a |
2.41 |
|
|
CP in silage as % of total CP |
44.4d |
55.5c |
62.4bc |
72.4a |
2.35 |
|
|
CP, % in DM |
11.1d |
12.5c |
14.0b |
16.2a |
0.187 |
|
|
Live weight gain, g/d |
538 |
500 |
438 |
581 |
86.1 |
|
|
abcd Means in the same column without common letter differ at P<0.05 |
|
|||||
 |
| Figure 5: Trends in relative intake of silage and of the level of crude protein in the diets consumed, as taro foliage replaced banana pseudo-stem in the silage |
The pigs gained in live weight during the trial with no apparent difference among treatments. However, the lack of difference among treatments is of little significance for measurements over such short periods (10 days).
Coefficients of apparent digestibility of DM, OM, NDF and nitrogen increased as taro foliage replaced banana pseudo-stem in the silage (Table 9; Figure 6). Similar trends were observed for N retention (Figure 7) which was almost doubled when the silage was 100% taro foliage compared with the mixtureof 40% taro silage and 60% banana pseudo-stem.
|
Table 9: Mean values for apparent digestibility and nitrogen retention in pigs fed silage in which taro foliage was replaced by banana pseudo-stem |
||||||
|
T100B0 |
T80B20 |
T60B40 |
T40B60 |
SEM |
p |
|
|
Apparent digestibility coefficients, % |
||||||
|
DM |
83.9a |
79.4b |
83.5a |
81.7ab |
0.972 |
<0.01 |
|
OM |
84.9a |
83.2a |
84.8a |
80.8b |
0.907 |
<0.01 |
|
NDF |
60.7a |
55.6b |
56.4b |
48.4c |
2.58 |
<0.01 |
|
N |
76.8a |
66.38c |
70.20a |
58.0c |
2.36 |
<0.001 |
|
N retention, g/d |
28.7a |
21.40b |
20.8b |
13.6c |
1.99 |
<0.001 |
|
abc Means in the same row without common letter differ at P<0.05 |
||||||
 |
 |
| Figure 6. Trends in apparent digestibility coefficients of the diets, as taro foliage replaced banana pseudo-stem in the silage |
Figure 7. Trends in daily N retention as taro foliage replaced banana pseudo-stem in the silage |
The results from the feeding trial showed that, replacing 50% of the ingredients in the control diet (Table 1) with silage containing 60% taro foliage and 40% banana pseudostem, led to 26% slower growth rates and 9% poorer feed conversion (Table 10).
|
Table 10. Mean values for live weight change, feed intake and feed conversion in growing pigs fed the control diet with no silage (see Table 1) compared with the experimental diet containing 50% (as DM) of mixed silage that had 60% taro foliage and 40% banana pseudo-stem |
||||
|
Control |
T60B40 |
SEM |
p |
|
|
Initial weight, kg |
18.8 |
19.1 |
0.32 |
0.51 |
|
Final weight, kg |
61.2 |
53.4 |
1.22 |
0.001 |
|
LWG, g/d |
807 |
638 |
20.40 |
0.01 |
|
Feed intake, kg/d |
||||
|
Fresh silage |
5.5 |
6.4 |
0.12 |
0.26 |
|
Total DM |
2.11 |
1.83 |
0.07 |
0.042 |
|
DM conversion |
2.61 |
2.86 |
0.068 |
0.07 |
The overall findings show clearly the superior feeding value for pigs of silage made from 100% taro foliage compared with ensiled mixtures of taro foliage and banana pseudo stem. To some degree these findings are confounded by the fact that the taro foliage was a combination of petioles and leaves while the banana component was exclusively pseudo-stem. Thus the protein content was higher in the taro foliage component and decreased as the taro foliage was substituted by banana pseudo-stem. As a result, the crude protein of the diets fed in the digestibility-N retention trial increased from 11.1% in DM when the silage contained 60% banana pseudo-stem to 16.2% when the silage contained only taro foliage. This diference in crude protein content could also explain the preference shown by the pigs for the silage with 100% taro foliage compared with the silage mixtures containing banana pseudo-stem. Future studies should be with silage in which only the petiole of the taro is used so as to avoid the confounding effect of the leaves which are known to have a high nutritive value (Rodríguez et al 2006). Similar reservations should be made with respect to the digestibility of the cell wall fraction (NDF), which was 25% lower for the diets with silage made only from taro foliage compared with those having silage made from 40% taro foliage and 60% banana pseudo-stem.
The fact that, in the feeding trial, growth rates were 638 g/day with a DM feed conversion of 2.86 is nevertheless encouraging, bearing in mind that the banana pseudo-stem is almost invariably wasted when the plant is grown exclusively for fruit production. Further evidence for the potential of banana pseudo-stem as a feed resource for pigs is to tbe found in the recent study by Duyet and Preston (2013) in which ensiled mixtures of taro foliage and banana pseudo-stem provided 90% of the diet of pregnant and lactating Mong Cai sows with satisfactory performance as measured by litter size and weight of the offspring, days from weaning to estrus and overall feed conversion (DM feed consumed by the sow in pregnancy and lactation per unit weight of piglets at weaning).
The authors would like to thank the Vietnam National Foundation for Science and Technology Development (NAFOSTED) (Grant number 106-NN.05-2013.31), and MEKARN (Sida), for the funding of this research.
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Received 24 April 2014; Accepted 29 April 2014; Published 1 June 2014