Two experiments were carried
out to determine the intake, digestibility and nitrogen retention of ensiled
groundnut leaves (EGL) by growing crossbred (Large White × Mong cai) pigs. In
the first trial the EGL was offered alone during two separate 10 day periods,
and in the second experiment it was included at levels of 0 (EGL0),
10 (EGL10), 20 (EGL20) and 30 (EGL30) % of the
diet, replacing fish meal (FM) and
cassava root meal (CRM) in a traditional diet.
Intake of EGL offered alone ad-libitum
varied considerably among pigs, and ranged from 282 to 370 g DM / pig / day for pigs
from 40 to 60 live weight, with standard deviation (SD) of 39.9. Mean daily
intake was 1393g fresh weight (282g DM) in Period 1 and 1698g fresh weight (370g
DM) in Period 2. The mean daily intake of CP was 59.1g in Period 1 and 76.8 g
in period 2. Coefficients of apparent dry matter (DM), organic matter (
In the second experiment, daily DM intakes of the EGL0, EGL10, EGL20 and EGL30 diets were 1359, 1370, 1268 and 1198 g, respectively, and the corresponding dry matter intakes of EGL were 143, 250 and 336 g. DM digestibility was not different among diets, but OM digestibility decreased significantly with increased inclusion of EGL and CP digestibility decreased from 86.2 % for the EGL0 diet to 80.3, 76.5 and 67.1 % for the EGL10, EGL20 and EGL30 treatments, respectively. N-retention decreased from 12.4 g/day for the EGL0 diet to 10.9, 7.8 and 4.9 g/day for the EGL10, EGL20 and EGL30 diets, respectively.
It can be concluded that ensiled groundnut leaves can be included at a level of up to 10% in growing pig diets.
Of the many types of livestock commonly kept in Central Vietnam, pigs are the most important income source of the farmers. Low inputs is the strategy for pig production in Vietnamese rural conditions, but this results in low outputs. Normally, rice bran, cassava and vegetables are the main feed stuffs. However, these feed resources are low in protein content, and vegetables are often lacking in the dry and rainy seasons. Groundnut (Arachis hypogaea) is a popular cash crop in central Vietnam and groundnut seeds are used for many purposes, but the leaves are not normally used. The chemical composition of groundnut leaves shows that the crude protein content is 16to 20%, and it may be possible to feed them to pigs.
Annually there are about 1.5 million tonnes of groundnut vine available at harvesting in Vietnam (Le Viet Ly and Bui Van Chinh 1996). The groundnuts are harvested from April to May, the harvesting period being only 2 or 3 weeks. Farmers have tried to dry the leaves as feed for pigs, but it is very difficult due to the rain and generally moist conditions during that period. Some previous studies on cassava leaves (Nguyen Thi Loc1998; Nguyen Thi Loc et al 2000) and groundnut leaves (Vo Thi Kim Thanh 1997; Vo Thi Kim Thanh et al 2000) showed that in the natural conditions of central Vietnam, making silage can be applied to preserve these feeds for animals.
The objectives of this study thus were to determine the chemical
composition and nutrient values of groundnut leaves and evaluate groundnut leaf
silage for growing pigs in terms of intake, digestibility and N-balance.
The research was carried out on the Hue University farm and the aims were to determine the nutritive value, intake, digestibility and N-retention of EGL and diets containing EGL by pigs
Four crossbred (Large White X Mong Cai) castrated males pigs from the same litter were used, with an average live weight of 40 kg at the beginning of the study. The pigs were housed individually in metabolism pens. All animals were de-wormed and vaccinated before the experiment. The daily feed intake was restricted to 4% of mean body weight (DM basis) and all animals were fed twice daily at 9:00 and 16:00 h. Feed refusals were recorded daily and water was available at all times.
The diet ingredients, composition of fresh and ensiled groundnut leaves and formulations of the four experimental diets are presented in Tables 1 and 2.
|
Table 1. Diet formulations (DM %) |
||||
|
|
EGL0 |
EGL10 |
EGL20 |
EGL30 |
|
EGL |
0 |
10 |
20 |
30 |
|
FM |
14 |
9 |
4 |
0 |
|
CRM |
86 |
81 |
76 |
70 |
|
CRM: cassava root meal; FM:
fish meal;
EGL: ensiled groundnut leaves |
||||
The groundnut leaves used in this study were the plants left over after harvesting the seeds. The vines were collected and silage was made by separating and then chopping the leaves into pieces with a size of about 5 cm. Then 5.0 % of molasses and 0.5 % salt (NaCl), were mixed in and the resulting mixture stored in a sealed plastic bag. The pigs were fed the EGL after ensiling for 21 days. The pH of the silage was < 4 and the smell was good.
The control diet contained cassava root meal and fish meal as the
sole protein source. In the experimental diets, EGL was included at levels 10, 20
and 30% of DM and replaced fishmeal and cassava root meal
For the EGL intake and digestibility trial, 4 pigs were used as replicates, and the trial started with an adaptation period of one week, followed by 5 days when intake was recorded and 5 days for collecting faeces and urine. This study was divided into 2 periods, starting before and after conducting Exp. 2. The pigs were fed only EGL, and the feed intake and nutrient digestibilities were calculated during the two experimental periods.
The pigs were fed four experimental diets according to a Latin Square (4 x 4) design. Each period consisted of 5 days adaptation followed by 5 days collection of faeces and urine.
Sample collectionEGL, CRM and FM samples were taken in each experimental period. Feed refusals were collected, weighed and dried at 60°C. Faeces were quantitatively collected and sampled twice a day and kept in a refrigerator at +4°C until analysis. Prior to analysis, faeces were thawed, homogenized, sub-sampled and dried at 60°C and ground to pass a 1 mm screen. The urine was also collected quantitatively and preserved by adding 100 ml of H2SO4 to the collection jar and stored at -20°C.
Dry matter was determined by oven drying at 105°C overnight. Crude protein was determined by the Kjeldahl nitrogen analysis as N*6.25 using Cu as a catalyst. Ash content was determined by ashing for 24h at 550°C. Neutral detergent fibre was determined according to Van Soest et al (1991) and lipids were extracted by diethylether using a Soxhlet apparatus. Amino acids were analysed according to Spackman et al (1958) on an ion exchange column using an HPLC.
The descriptive statistics of Minitab (Version 12) as mean and standard deviation were used to analyse the data of feed intake and nutrient digestibility in the intake trial. The data for each response criterion were analysed as a 4x4 Latin Square using the General Linear Model of Minitab (Version 12).
The model used in the analysis was:
Yijk= µ + Tj + Pj +Aj + eijk
where Yijk: = the dependent variable, µ = overall mean, Tj = effect of replacement level, Pi period effects, Aj = animal effects and eijk = the random error effects.
Results are presented as least square means
on a DM basis with their standard error of mean (SEM). The relationships between
CP and NDF content and the digestibility of CP and N retention were done by the
linear regression analysis procedure in Minitab.
CP of the FGL was rather high and NDF.. However, CP content was reduced by ensiling and was in good agreement with earlier reports on groundnut leaves (Gohl 1981; Bui Huy Nhu Phuc 2000) and higher than reported by NIAH (1995) and Vo Thi Kim Thanh et al (2000). NDF content was not changed after ensiling and was lower than reported by Bui Huy Nhu Phuc (2000).
| Table 2. Composition of the feed ingredients (% in DM, except DM which is on fresh basis) | ||||||
|
Ingredients* |
DM |
CP |
NDF |
EE |
OM |
Ash |
|
CRM |
89.8 |
3.6 |
5.4 |
10.2 |
98.8 |
1.2 |
|
FM |
88.1 |
59.6 |
- |
6.1 |
71.9 |
28.1 |
|
FGL |
18.5 |
24.7 |
21.8 |
9.4 |
92.2 |
7.8 |
|
EGL |
20.2 |
21.2 |
22.6 |
8.5 |
88.3 |
11.7 |
|
*DM = dry matter; CP = crude protein; NDF = neutral detergent fibre; EE: ether extract; OM = organic matter; CRM: cassava root meal; FM: fish meal; FGL: fresh groundnut leaves; EGL: ensiled groundnut leaves. |
||||||
The amino acid (AA) contents of fresh (FGL) and ensiled (EGL) groundnut leaves are shown in Table 3. In FGL, the lowest and highest values were for methionine and leucine (0.55 and 7.37 % of CP, respectively). Leucine and lysine contents were about the same as reported by FAO (1999). After ensiling, the essential and non-essential amino acid concentrations were reduced by on average around 26%, with the exception of methionine which increased slightly. Part of this reduction can be explained by the addition of molasses and salt to the groundnut leaves before ensiling.
|
Table 3. Amino acid composition of fresh (FGL) and ensiled (EGL) groundnut leaves (g per 16 g N) |
|||||
|
Essential amino acids |
FGL |
EGL |
Non-essential amino
acids |
FGL |
EGL |
|
Histidine |
1.99 |
1.13 |
Aspartic |
14.38 |
6.85 |
|
Threonine |
4.70 |
3.72 |
Glutamic |
10.78 |
6.75 |
|
Arginine |
6.44 |
3.21 |
Serine
|
3.11 |
2.14 |
|
Valine |
5.65 |
4.66 |
Glycine |
4.45 |
3.56 |
|
Methionine |
0.55 |
0.69 |
Alanine |
5.53 |
5.78 |
|
Phenylalanine |
6.33 |
4.45 |
Proline |
9.94 |
5.19 |
|
Isoleucine |
4.12 |
3.57 |
S NEAA
|
48.19 |
30.25 |
|
Leucine |
7.37 |
6.14 |
S EAA/S
NEAA |
0.51 |
0.47 |
|
Lysine |
4.57 |
3.54 |
|
|
|
|
Tyrosine |
4.50 |
2.75 |
|
|
|
|
S EAA |
46.23 |
33.86 |
|
|
|
In Period 1, DM intake of EGL varied considerably between pigs and ranged from 189 to 314 g / pig / day. The mean daily intake was only 282g with standard deviation (SD) of 39.9 (Table 4). The low intakes were probably due to the high moisture content and bulkiness of the leaves.
| Table 4. Intakes, digestibility and N retention by pigs fed ensiled groundnut leaves offered ad libitum (n=4) | |||
|
|
Period 1 |
Period 2 |
SD |
|
Intake (g) |
|
|
|
|
Fresh leaves |
1393 |
1698 |
227 |
|
DM |
282 |
370 |
39.9 |
|
OM |
245 |
324 |
35.1 |
|
CP |
59.1 |
76.8 |
8.3 |
|
NDF |
74 |
97.2 |
10.5 |
|
Digestibility (%) |
|
|
|
|
DM |
74.4 |
78.7 |
1.7 |
|
OM |
75.6 |
80.0 |
1.8 |
|
CP |
69.0 |
74.6 |
2.1 |
|
NDF |
65.5 |
75.0 |
3.5 |
|
N retention |
|||
|
g/day |
3.6 |
3.7 |
0.6 |
|
% |
38.8 |
29.4 |
3.4 |
|
% of N digested |
56.2 |
39.5 |
4.9 |
Dry matter and organic matter digestibility coefficients were quite high, and increased by approximately four percentage units in Period 2 compared to Period 1, due to the higher live weight of the pigs and perhaps that their digestive tracts would have adapted to the high intakes of groundnut leaves. N retention and N utilization values were found to be rather low , probably as a result of the poor amino acid balance of the leaves, in particular the low methionine content.
Feed intake and total tract apparent digestibility of nutrients (Expiment 2)Although the feed DM
intake was not significantly different among diets, it
deceased slightly as the level of EGL was increased (Table
5).
|
Table 5. Effect of level of inclusion in the diet of ensiled groundnut leaves on daily intake and nutrient digestibility of growing crossbred pigs |
|||||
|
|
EGL0 |
EGL10 |
EGL20 |
EGL30 |
SEM/P |
|
Intake, g/day |
|||||
|
DM |
1359 |
1370 |
1268 |
1198 |
56.2 / ns |
|
CP |
155 |
142 |
119 |
106 |
|
|
EGL DM |
|
143 |
250 |
336 |
|
|
Digestibility, % |
|||||
|
DM |
91.9 |
91.1 |
91.0 |
89.3 |
0.37 / ns |
|
OM |
95.0a |
93.1ab |
92.8ab |
91.1bc |
0.72 / 0.05 |
|
CP |
86.2a |
80.3ab |
76.5ab |
67.1c |
2.49/0.01 |
|
EE |
98.3a |
97.0ab |
96.6ab |
95.3bc |
0.41 / 0.01 |
|
NDF |
53.6 |
57.0 |
63.9 |
66.9 |
3.03 / ns |
|
N retention |
|||||
|
g / day |
12.3a |
10.9ab |
7.81c |
4.88d |
0.40 / 0.01 |
|
% of digested N |
49.8 |
48.0 |
41.0 |
28.8 |
4.97 / ns |
|
|
|||||
Digestibility coefficients for organic matter, crude protein
and ether extract decreased significantly as the level of EGL was increased. However, NDF digestibility was not different among diets even though
the NDF content increased from 5.3 % in the control diet to 10.2 % in the EGL30
diet. N retention was reduced significantly on the EGL20 and EGL30 diets as a result of the lower CP content of these diets compared to the
control diet, and the poor amino acid balance of EGL, especially of
methionine.
The replacement of fishmeal and cassava
root meal by ensiled groundnut leaves at the level of 20 % of DM resulted in
nutrient digestibilities only slightly lower than those of the control diet.
However N retention was reduced significantly at the 20% inclusion level.
It is recommended that no more than 10 % EGL is included in
diets for growing pigs.
Bui Huy Nhu Phuc 2000 Tropical Forages for Growing Pigs,
Digestion and nutritive value. PhD Thesis. Paper III.
FAO
2000 Tropical feeds. Groundnut, Arachis hypogaea. FAO\home page\DOCS\TFEED8\DATA\201.HTM
Le Viet Ly and Bui Van Chinh 1996 Development
of Animal Production in Sustainable Agricultural Systems. Agricultural
Publishing House,
National
Nguyen Thi Loc, Nguyen Thi Hoa Ly, Vo Thi
Kim Thanh and Hoang Nghia Duyet 2000 Processing, preserving and using cassava
leaf silage for Mong Cai sows in
Vo
Thi Kim Thanh, Nguyen Thi Loc, Dao Thi Phuong and Phung Thi Luu 2000 Evaluation of ensiled groundnut leaves for fattening pigs. Workshop-seminar
"Making better use of local feed resources” SAREC-UAF, January 2000 http://www.mekong.org/sarpro/cover.htm
Vo Thi Kim Thanh 1997 Using ensiled groundnut leaves for fattening pigs. Scientific paper of Hue University of Agriculture and Forestry.