The use of ensiled cassava leaves in diets for growing pigs. 3. The effect of graded levels of palm oil on performance traits
Chhayty, T R Preston , J Ly* and Keo Sath
University of Tropical Agriculture
Foundation
Chamcar Daung, PO Box 2423, Phnom Penh 3, Cambodia
chhayty@utafoundation.org
regpreston@utafoundation.org
* Visiting researcher at UTA, Present address: Swine Research
Institute,
PO Box 1, Punta Brava, La Habana, Cuba
jlyca@yahoo.com
Abstract
Sixteen Mong Cai*Large White female and castrate male pigs weighing on average 16 and 12 kg, respectively, were used in a 4*2 factorial arrangement to study the effect of graded levels of crude palm oil (0, 5, 10 and 15%) and sex (castrate male or female) on performance traits with a basal diet formulated with cassava leaf silage, fish meal and broken rice. The pigs were housed in individual pens and allotted at random to the four experimental diets. The feeding trial lasted for 16 weeks (112 days) and was analysed according to three periods (0-8; 9-16 and overall 0-16 weeks).
There was
no significant interaction between treatment and sex. Voluntary DM intake tended
to increase with level of palm oil and to be less for castrate male pigs than for
females. Level of palm oil had no effect on daily live weight gain but tended
to improve the feed conversion ratio.
There
appear to be no advantages in terms of pig growth and feed conversion from adding up to 15% palm oil in a diet based on ensiled cassava leaves
as the main protein source.
Key
words: Crude palm
oil, ensiled
cassava leaves, live weight, pigs, sex
Introduction
In view of the predicted world shortage of cereal grains because of competing needs for the expanding human and livestock populations (Leng 2002), there is an urgent need for research to develop alternative feed resources especially for pigs and poultry.
Cassava (Manihot esculenta Crantz) is a widely grown crop in the tropical regions of Africa, Latin American and Asia (Calpe 1992). The leaves are high in protein (Ravindran and Ravindran 1988) and are a readily available product at the time of harvesting the root. Several reports have shown that cassava leaf protein is rich in lysine but low in sulphur amino acids (Eggum 1970; Gomez and Valdivieso 1984).
Palm oil (Elaeis guineensis Jacq.), palm fruit and by-products of palm oil extraction have been shown to have a high feeding value for growing pigs, and can replace completely the cereal component of the diet (Ocampo et al 1990a,b; Ocampo 1994a,b). An advantage of using vegetable oil as the energy source in pig diets is because it has a very high energy content and no fibre. This creates opportunities for using it as a supplement in diets in which the main source of protein is the leaf biomass from trees and shrubs (Preston and Murgueitio 1992).
The aim of the present study therefore was to determine the effect of graded levels of palm oil on performance traits of pigs fed diets based on ensiled cassava leaves. The feeding trial was a follow up to earlier experiments on digestibility and N retention in pigs fed similar diets (Chhaty et al 2003a,b).
Material and methods
Location and climate
This
experiment was carried out in the ecological farm of the University of Tropical Agriculture Foundation (UTA), located in Chamcar
Daung, at the outskirts of
Experimental animals, treatments and design
Eight
female and eight castrated male crossbred (Mong Cai*Large
Wite) pigs with an average initial body weight of 16.0 kg (females)
and 12.0 kg (males) were allocated to a 4*2 factorial arrangement to study the
effects of level of supplementary crude palm oil (0, 5, 10 and 15%) and
sex. The pigs were housed in individual
pens of 1.2m x 1.4m. The pens had a concrete floor with brick walls and were
provided with feeders and drinking nipples. The pigs were vaccinated against
Salmonella and Swine cholera disease. The pigs were adapted to the feeds and
the housing for a 14 day period before starting the experiment. The pigs were
allocated to 2 blocks according to sex and body weight. The nutritional
treatments were applied
at random within each block.
Feeding and management
The diets were formulated to contain 16% crude protein (N*6.25) in dry basis, with cassava leaf silage as the main protein source and a low level of fish meal to compensate for the low methionine content of the cassava leaves (Table 1).
|
Table 1.
Characteristics of the diets (percentage in DM, except for DM% which is on
“as-fed” basis) |
|||||
|
|
Ensiled cassava leaves |
Refined palm oil, % |
|||
|
0 |
5 |
10 |
15 |
||
|
Ingredients,% |
|
|
|
|
|
|
Ensiled cassava leaves |
- |
45.0 |
45.0 |
45.0 |
45.0 |
|
Refined palm oil |
- |
- |
5.0 |
10.0 |
15.0 |
|
Fishmeal |
- |
3.0 |
4.0 |
5.0 |
6.0 |
|
Broken rice |
- |
50.0 |
44.0 |
38.0 |
32.0 |
|
Sugar palm syrup |
- |
0.5 |
0.5 |
0.5 |
0.5 |
|
Vitamins and minerals# |
- |
1.5 |
1.5 |
1.5 |
1.5 |
|
Analysis (%) |
|
|
|
|
|
|
Dry matter |
50.7 |
68.4 |
68.6 |
68.5 |
69.2 |
|
Ash |
14.1 |
8.2 |
8.5 |
8.9 |
9.2 |
|
Organic matter |
85.9 |
91.8 |
91.5 |
91.1 |
90.8 |
|
NDF |
47.0 |
21.1 |
21.1 |
21.1 |
21.1 |
|
Crude fibre |
35.3 |
15.9 |
15.9 |
15.9 |
15.9 |
|
NFE |
11.7 |
52.1 |
46.4 |
40.6 |
34.8 |
|
Crude fat |
14.3 |
7.6 |
13.0 |
18.4 |
23.7 |
|
Crude protein (Nx6.25) |
24.5 |
16.1 |
16.2 |
16.3 |
16.4 |
|
GE, MJ/kg DM## |
20.6 |
18.9 |
20.1 |
21.3 |
23.6 |
|
#According to NRC (1998) recommendations ## Calculated according to Nehring and Haenlein (1973). For further details, see text |
|||||
Leaves were
harvested from 4 to 5 month-old cassava plants grown for root production in farmers’ fields in
The supplements
(crude palm oil, broken rice, mineral/vitamin premix, sugar
palm and fish meal) were mixed together with the cassava leaf silage before
feeding. The pens were
cleaned every day after collecting the feed residue. The pigs were adapted to
the diet and pen for two weeks and thereafter were fed the test diets divided in 3
meals daily.
Data collection and analyses
The pigs were weighed every week.
Individual daily weight gains were calculated by the regression of live weight
on time in days. Individual feed intake was recorded daily from weight of fresh material offered
minus the
residue collected the next morning. Feed conversion ratio was calculated from
individual daily DM intake and live weight gain. Feed samples were taken weekly,
dried and bulked prior to taking sub-samples for chemical
analysis. The
analytical methods were those described in Chhayty et al (2003a).
Statistical analysis
Mean values for effects of supplementation on weight
gain, feed intake and feed conversion were compared using the general linear
model (GLM) option of the analysis of variance, determined with software of
Minitab, release 12.2. The sources of variation in the ANOVA were the
dietary treatments, sex and error
Results
Health
During the experiment the animals were generally in good health but feed intake decreased in the females when they reached 50kg of body weight due to occurrence of oestrous.
Daily feed intake
There was no effect of the level of palm oil on the daily feed intake during the 0-8 week period (Table 2). In the second period (9-16 weeks) feed refusals were observed in all treatments and feed intake, expressed on a live weight basis, was reduced as the level of palm oil was increased. Females ate more DM per day than males but this difference was not apparent when intake was expressed as percent of live weight. The same was true of the differences between blocks.
|
Table 2. Feed DM intake of female and male pigs fed graded level of palm oil and 45% of cassava leaf silage in diet DM |
||||||||||
|
|
Sex |
Crude palm oil |
||||||||
|
Fem. |
Male |
SEM |
Prob. |
0 |
5 |
10 |
15 |
SEM |
Prob. |
|
|
0-8 weeks |
|
|
|
|
|
|
||||
|
Total, g/d |
894 |
672 |
45.9 |
0.01 |
695 |
779 |
763 |
894 |
64.9 |
0.27 |
|
Cassava, g/d |
335 |
246 |
24.7 |
0.04 |
266 |
320 |
256 |
322 |
34.9 |
0.45 |
|
% LW |
4.2 |
4.2 |
0.11 |
0.76 |
4.29 |
4.41 |
3.91 |
4.09 |
0.15 |
0.21 |
|
9-16 weeks |
|
|
|
|
|
|
|
|
|
|
|
Total, g/d |
1387 |
1233 |
50.8 |
0.07 |
1231 |
1392 |
1240 |
1377 |
71.8 |
0.31 |
|
Cassava, g/d |
499 |
448 |
24.6 |
0.19 |
460 |
527 |
447 |
460 |
34.8 |
0.42 |
|
% LW |
3.4 |
3.56 |
0.12 |
0.41 |
3.78 |
3.73 |
3.36 |
3.07 |
0.17 |
0.06 |
|
0-16 weeks |
|
|
|
|
|
|
|
|
|
|
|
Total, g/d |
1166 |
976 |
40.0 |
0.01 |
985 |
1113 |
1019 |
1164 |
56.7 |
0.19 |
|
Cassava, g/d |
431 |
359 |
19.5 |
0.04 |
375 |
436 |
363 |
407 |
27.5 |
0.31 |
|
% LW |
3.82 |
3.89 |
0.09 |
0.67 |
4.06a |
4.09a |
3.64b |
3.59b |
0.13 |
0.05 |
Growth and feed conversion
There was a strong indication (P=0.09) that the female pigs grew slightly faster than castrated males during the first 8 weeks, but this was not apparent over the overall 16 week period (Table 3). Pigs receiving the 15% level of palm oil grew faster than those with 0, 5 or 10% oil during the first 8 weeks, and there was a tendency (P=0.11) to maintain this superiority over the overall 16 week period. There were no differences due to sex or oil supplementation in the 9 to 16 week period. Growth rate was linearly related (R2=0.71) with DM feed intake (Figure 1).
|
Table 3.
Mean values for live weight gain of pigs
fed graded levels of palm oil in a basal diet with 45% (in DM) of cassava
leaf silage |
||||||||||
|
|
Sex |
Crude palm oil |
||||||||
|
|
Female |
Male |
SEM |
P |
0 |
5 |
10 |
15 |
SEM |
P |
|
Live weight, kg |
|
|
|
|
|
|
|
|
||
|
Initial |
16.0 |
12.0 |
- |
- |
12.3 |
12.9 |
14.7 |
15.8 |
- |
- |
|
Final |
53.2 |
46.2 |
|
|
|
50.1 |
48.6 |
57.1 |
|
|
|
Live weight gain, g/d |
|
|
|
|
|
|
|
|||
|
0-8 weeks |
351 |
298 |
19.7 |
0.09 |
264 |
334b |
297bc |
404 |
27.9 |
0.03 |
|
9-16 weeks |
362 |
363 |
26.6 |
0.97 |
328 |
389 |
353 |
379 |
37.6 |
0.67 |
|
0 – 16 weeks |
367 |
352 |
22.1 |
0.64 |
312 |
376 |
340 |
409 |
31.2 |
0.22 |
|
|
||||||||||
Figure 1.
Relationship between live weight gain and feed intake of growing pigs fed a
basal diet
of ensiled cassava leaves, broken rice and graded levels of palm oil
Males had better feed conversion than females in the 9-16 week period and overall from 0 to 16 weeks. There was no apparent effect of level of palm oil on this trait (Table 4). Pigs in block 2 had feed conversion ratio better than those in block 1 in the 0-8 weeks and overall 0-16 weeks periods.
|
Table 4. Mean values for feed DM conversion ratio in pigs fed graded levels of palm oil and ensiled cassava leaves as 45% of diet DM |
||||||||||
|
|
Sex |
Crude palm oil |
||||||||
|
Female |
Male |
SEM |
P |
0 |
5 |
10 |
15 |
SEM |
P |
|
|
0-8 weeks |
2.6 |
2.3 |
0.15 |
0.18 |
2.7 |
2.31 |
2.5 |
2.2 |
0.20 |
0.46 |
|
9-16 weeks |
3.8 |
3.4 |
0.11 |
0.02 |
3.8 |
3.6 |
3.5 |
3.7 |
0.15 |
0.62 |
|
0-16 weeks |
3.2 |
2.8 |
0.14 |
0.04 |
3.2 |
3.0 |
2.9 |
2.8 |
0.17 |
0.56 |
Conversion of gross and digestible energy to live weight was calculated on the basis of the conversion indices proposed by Nehring and Haenlein (1973) and the digestibility data reported by Chhaty et al (2003a). These parameters were poorer in females compared with castrate males in periods 9 to16 and overall from 0 to 16 weeks (Table 5). They were also poorer for the 15% oil level, compared with 0, 5 or 10% added oil, in the 9 to 16 week period. From 0 to 8 weeks and overall from 0 to 16 weeks oil level had no effect on energy conversion. Differences between blocks for energy conversion reflected differences in DM conversion rates.
|
Table 5. Mean values for gross and
digestible energy conversion of pigs fed ensiled cassava leaves and crude
palm oil |
|||||||||||
|
|
Sex |
Crude palm oil |
|||||||||
|
|
Female |
Male |
SEM |
P |
0 |
5 |
10 |
15 |
SEM |
P |
|
|
0-8 weeks |
|
|
|
|
|
|
|
|
|
|
|
|
GE
|
53.3 |
47.2 |
3.09 |
0.20 |
50.1 |
46.3 |
52.9 |
51.6 |
4.37 |
0.74 |
|
|
DE
|
39.0 |
34.6 |
2.24 |
0.19 |
37.2 |
34.2 |
38.0 |
37.8 |
3.17 |
0.81 |
|
|
9-16 weeks |
|
|
|
|
|
|
|
|
|
|
|
|
GE
|
80.3 |
71.4 |
2.26 |
0.02 |
71.0 |
71.7 |
73.9 |
86.9 |
3.20 |
0.02 |
|
|
DE
|
58.8 |
52.3 |
1.65 |
0.02 |
52.7 |
53.0 |
53.1 |
63.6 |
2.34 |
0.02 |
|
|
0-16 weeks |
|
|
|
|
|
|
|
|
|
|
|
|
GE
|
66.4 |
58.3 |
2.46 |
0.04 |
60.0 |
59.3 |
63.1 |
66.8 |
3.48 |
0.45 |
|
|
DE
|
48.7 |
42.7 |
2.23 |
0.04 |
44.5 |
43.8 |
45.3 |
49.0 |
2.53 |
0.51 |
|
Discussion
Increasing the digestibility energy content of pig diets through fat addition has been showed have a variety of effects on performance of pigs, including a decrease, no effect or an improvement (Allee et al 1976; Adams and Jensen 1984, 1987; Chiba et al 1985; Howard et al 1990; Brumm and Peo 1994). Similarly, in the study by Olayiwola Adeola and Bajjalieh (1997) weight gain was improved in pigs fed a high-oil maize compared with regular maize; yet in another study, Nordstrom et al (1972) reported that high-oil maize (6.7 to 8.7% ether extract) had no beneficial effect on weight gain compared with regular maize. All these studies used basal diets of cereals. According to the study of Fetuga et al (1975), addition of crude palm oil from 2 to 10% in the diets had no significant effect on performance. Another study in Malaysia, using palm oil from 5 to 30%, showed no effect of level of oil, but the level of palm oil of 10% was superior to the cereal control and feed conversion was improved 17% (Devendra 1977).
The two recent reports on oil addition to forage-based diets indicated a reduction in digestibility when the basal diet was water spinach Prak Kea et al (2003), or ensiled casava leaves (Chhayty et al 2003a). The implication from these findings is that the added energy from the oil is used inefficiently for tissue growth, according to the results of the present experiment and of Chhayty et al (2003a), or that the high level of oil reduces the utilization of other dietary nutrients (Prak Kea et al 2003). Neither of these explanations is supported by the work of Ocampo with high levels of palm oil (Ocampo et al 1994a), palm oil by-products (Ocampo et al 1990a,b) or palm fruit (Ocampo 1994b). Results in all these studies showed that the energy in the oil was used highly efficiently with better DM feed conversion in the diets containing palm oil, palm fruit or palm by-products, compared with control cereal-based diets. The major difference between the diets used by Ocampo and his colleagues and those in the present experiment (and the experiment of Prak Kea et al 2003) is that solvent extracted soya bean meal supplied the major part of the protein in the former case, while in the latter the protein was mainly from green plant tissue.
The results for the control diet (45% DM as ensiled cassava leaf silage, 50% broken rice and 3% fish meal) were encouraging from the point of view of DM conversion (3.2) even though the growth rate (from 12 to 43 kg) was rather low (312 g/day).
Conclusion
The results of the current study indicate that moderate growth rates (312 g/day) and acceptable feed DM conversion ratios (3.2) can be obtained in diets for young growing pigs containing 45% of ensiled cassava leaves (DM basis), but that there are no benefits in performance to be gained from adding palm oil to increase the energy density.
More research is needed to
elucidate possible interactions between the high level of palm oil and the
nature of the rest of the diet and especially the protein component in pig
diets.
Acknowledgments
The present experiment is part of a study on the use of ensiled cassava leaves and palm oil in pigs, supported by the MEKARN project financed by the SIDA-SAREC Agency, and was presented as partial requirement for the MSc degree at SLU, Uppsala, Sweden. The authors express their gratitude to all the personal of the Ecological Farm, of the University of Tropical Agriculture Foundation, for help with the experiment, especially Mr. Keo Saeth for his assistance in taking care of the animals. Thanks are also expressed to Mr. Pok Samkol for analytical assistance in the laboratory of the Ecological Farm.
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Received 30 May 2003; Accepted 19 August 2003