 Figure1: Daily intake of broken rice by the chickens in the station trial (means for 14 day periods) |
 Figure2: Daily intake of broken rice by the chickens in the village trial (means for 14 day periods) |
| Livestock Research for Rural Development 11 (1) 1999 | Citation of this paper |
In order to compare the effect of duckweed, soya bean meal and broken rice on the live weight growth of scavenging chickens, 120 native chickens of mixed sexes were bought in the market and randomly allocated into three different treatment groups and two locations (experiment station and village) with 20 chickens in every treatment / location group. In the station (the experimental farm of the Jesuit Service Cambodia) the birds on the three treatments scavenged in the same area of an integrated farm with fruit trees, biodigester and duckweed ponds. In the village, the treatments were in separate, but adjacent, households, each of which had an area with fruit trees, biodigester and duckweed ponds. At night-time the chickens were housed with individual access to the supplements. Three types of supplement were offered daily in the evening when the birds were confined: (Dw) 50g of broken rice and 50 g of duckweed; (Sb) 50g of broken rice and 50g of ground soya beans; and (Br) 50g of broken rice. The trial lasted 70 days.
The amounts of broken rice consumed by chickens in the station and farm locations were very similar: 43, 41 and 43 g/day (SE = 0.35) for the treatments Dw, Sb and Br, respectively on the station and 48, 42 and 48 (SE = 0.23) for the same treatments in the farms in the village. The amounts of fresh duckweed eaten were: 36 ±0.35 and 49 ±0.22 g/day and of ground soya beans 27±0.35 and 28±0.22 g/day for station and farm, respectively. After adjusting by covariance for differences in initial weight the analysis for growth rate showed differences between supplements (P=0.001) and between locations (P=0.001) with an interaction between location and supplement (P=0.001). Overall, the best growth was obtained with broken rice plus soya bean supplement and the worst with broken rice alone; performance on the station was better than in the village. In the station, soya bean supplemented chickens grew faster than those supplemented with duckweed; whereas on the farms, chickens supplemented with duckweed out-performed those given the ground soya bean. On both the station and the farm the margin of income over costs of birds and supplements was highest for the birds supplemented with broken rice and duckweed and lowest for those supplemented with broken rice and ground soya beans
Poverty alleviation of the Cambodian people (mainly farmers), in order to develop the country, is a first priority of the Royal Cambodian government. Agriculture in Cambodia is based on rice and livestock production. Furthermore, it has been found that most Cambodian farmers depend on livestock, because they supply food, draught power for rural transportation and cultivation and manure for crop production. An added feature is their capacity to use non-arable land and agricultural residues. When all these factors are added together, the overall economic value of animal products may account for about half of the total agriculture production (Brumby1987).
According to the Smallholder Livestock Development Project in Bangladesh, chickens play a critical role in increasing family income (Jahangir Alam1993). In Cambodia even a very poor family has at least 5-6 local chickens that scavenge around the household (ARDAHP1993). Thus, poultry are a unique instrument to reach the poorest segment of the rural population.
In a previous study (Hong Samnang 1998), ground whole soya beans were used as the protein supplement for scavenging chickens. In Cambodia, soya beans are grown in a very few areas and the beans are mainly used for human consumption which makes the price too high for poor farmers. It is considered that a better strategy is to reserve the soya beans for human consumption and to search for other protein sources that are higher yielding in tropical ecosystems (Preston1998). There is a wide variety of protein-rich plants in the tropics which could replace soya bean meal in poultry feeds in Asia (Ravindran and Blair 1993). Duckweed is one of the most promising. Results with duckweed in poultry diets in Peru showed that it could replace all the soya bean meal and fish meal for layers and broilers (Haustein et al 1990, 1994) with only slight reduction in performance. However, the process of sun-drying and oven dehydration used by these workers is not feasible for poor farmers.
Work in Vietnam has been directed towards the use of duckweed in the freshly harvested state. Results of recent studies show that fresh duckweed can be used to replace all the soya bean for fattening ducks fed broken rice as the energy source (Bui Xuan Men et al 1995) and for growing native (Mong Cai) pigs fed ensiled cassava roots or sugar cane juice (Du Thanh Hang et al 1997; Nguyen Van Lai and Rodriguez 1998). This paper reports the results of a first attempt in Cambodia to use fresh duckweed for scavenging poultry. The hypotheses to be tested were:
The experiment was carried out on the experimental farm of the Jesuit Service Cambodia located in Tropeng veng village, Chock Cheuneng Commune and on farms located in Tram Slek village, Kontok commune of Ang Snul district, Kandal province, about 21 km to the west of Phnom Penh city. The temperature of this region ranges from 28 to 32 ºC. The rainy season usually begins at the end of May but sometimes it can be delayed to the middle of June or the beginning of July and lasts until the end of November or December. The average annual rainfall is 1130 mm. The experiment lasted for 70 days and started at the end of July and finished in the middle of October 1998 during the rainy season.
In order to compare the effect of duckweed, ground soya beans and broken rice on the live weight growth of scavenging chickens, 120 native chickens of mixed sexes were bought in the market and randomly allocated into six different groups according to three dietary supplements and two locations (station and village) with 20 chickens in every supplement / location group. In the station the chickens scavenged in the same area of an integrated farm with fruit trees, biodigester and duckweed ponds. In the village, the supplement treatments were in separate, but adjacent, households, each of which had an integrated farm area with fruit trees, biodigester and duckweed ponds. At night-time the chickens were housed with individual access to the supplements.
The cages where the chickens were confined at night-time were constructed from local materials( bamboo and thatch) on each location. Each cage was 8m long and 0.5m wide and was divided into 20 equal compartments, one for each chicken. A feeder and a water container were available for each chicken. The chickens were trained always to enter the same compartment.
All the chickens were allowed to scavenge in the integrated farm area from 6 am until 5 pm when they were collected to the cages. The supplements offered daily when the chickens were confined were: 50g broken rice and 50 g duckweed in treatment Dw; 50g of broken rice and 50g of ground soya beans in treatment Sb; and 50g of broken rice in treatment Br. All of the chickens were vaccinated against Newcastle, Cholera and Fowl pox before the experiment was started.
The weights of each chicken were measured every 14 days and recorded. The feed offered and refused was recorded every morning for each chicken. Mean feed intakes were calculated for successive 14-day periods throughout the trial. Samples of feed were taken every 14 days and analyzed for dry matter (Undersander 1993) and nitrogen (AOAC 1985).
Liveweight change was determined for individual chickens by regressing liveweight on days in the trial (14 day intervals). The treatment means of liveweight change and feed intake over 14-day periods were analyzed using the General Linear Model for analysis of variance of the Minitab (version 10.2) statistical software. The sources of variation in the ANOVA were supplements, location, supplement*location and error.
The average amounts of broken rice consumed by chickens in the station and farm trials were very similar: 43, 38 and 43 g/day (SE = 0.35) for the treatments Dw, Sb and Br, respectively in the station trial and 48, 42 and 48 (SE = 0.23) for the same treatments in the farm trial (Figures 1 and 2).
Figure1: Daily intake of broken rice by the chickens in the station trial (means for 14 day periods) |
Figure2: Daily intake of broken rice by the chickens in the village trial (means for 14 day periods) |
The intakes of fresh duckweed and ground soya beans are shown in Figures 3 and 4. Intakes increased steadily with time on trial for both soya bean and duckweed in the station while, in the village, the intakes were fairly constant over the entire feeding period. The average amounts of fresh duckweed eaten were: 36 ±0.35 and 49 ±0.22 g/day and of ground soya beans were 27 ±0.35 and 28 ±0.22 g/day for station and farm, respectively.
 Figure 3: Daily intakes of duckweed and ground soya beans in the station |
 Figure 4: Daily intakes of duckweed and ground soya beans in the village |
The protein content in the dry matter of duckweed (27%) was less than that in the ground soya bean (38%). This together with the much lower dry matter content of the duckweed (6% in duckweed versus 90% in soya beans), resulted in very large differences in the intakes of protein between the two supplements (see Figures 5 and 6).
 Figure 5: Daily intakes of protein from duckweed and ground soya beans in the station |
 Figure 6: Daily intakes of protein from duckweed and ground soya beans in the village |
| Table 1: Mean values for initial and final weights of chickens in the station and farm locations | ||||
Dw |
Sb |
Br |
SE |
|
| Initial weight, g | ||||
| Station | 607 |
692 |
551 |
± 25.3 |
| Farm | 542 |
523 |
499 |
|
| Final weight, g | ||||
| Station | 1567 |
1814 |
1255 |
± 28.7 |
| Farm | 1424 |
1344 |
1241 |
|
There were differences (P=0.001) in final weight at 70 days between supplements and between locations (Table 1). After adjusting by covariance for differences in initial weight the analysis for growth rate showed differences between supplements (P=0.001) and between locations (P=0.001) and with an interaction for "location*supplement" (P=0.001). Overall the best growth was with broken rice plus soya bean supplement and the worst with broken rice alone. Performance on the station was better than in the village (Figure 7). However, the relative ranking between duckweed and soya bean differed according to the location (Figure 8). In the station, soya bean supplemented chickens grew faster than those supplemented with duckweed; whereas on the farms, chickens supplemented with duckweed out-performed those given the ground soya bean.
 Figure 7: Adjusted (for differences in initial weight) daily weight gains of scavenging chickens fed broken rice alone (Br) or complemented with duckweed (Dw) or ground soya beans (Sb) on station or on farm. Comparisons are among supplements and between locations |
 Figure 8: Adjusted (for differences in initial weight) daily liveweight gains of scavenging chickens fed broken rice alone (Br) or complemented with duckweed (Dw) or ground soya beans (Sb) on station and on farm |
 Figure 9: Growth curves of scavenging chickens fed broken rice alone (Br) or complemented with duckweed (Dw) or ground soya beans (Sb) on station. |
 Figure 10: Growth curves of scavenging chickens fed broken rice alone (Br) or complemented with duckweed (Dw) or ground soya beans (Sb) on farm. |
The chickens in treatment groups Dw and Sb consumed broken rice in greater quantities than was observed for the other supplements. Intakes of broken rice in these groups were similar to those in the group that received only broken rice. This confirms the opinion of Ravindran and Blair (1991) that scavenging chickens have energy as their first priority rather than protein. Broken rice is an excellent energy source with a nutritive value similar to that in maize (Yoshida and Hoshii 1970; Syed et al 1975; Sinha et al 1980; Maner1985; Shrivastav et al 1990). Tadelle Dessie (1996) observed that there were few sources of energy available to scavenging chickens in the rainy season in Ethiopia, therefore energy-rich supplements were most appropriate in this time of the year. The experiment reported in this paper was carried out in the wet season.
It has been argued that chickens given free access to energy-rich and protein-rich feeds will select the combination of ingredients that best satisfy their nutritional needs (Cumming 1992,1994; Becchi 1997). However, it appears that most work on choice feeding has been done with caged "exotic" strains of broilers and layers and with whole cereals, complete feeds and protein concentrates. Thus a search of the CABI (1989-1999) data base (Gueye F, 1999 personal communication) revealed that of 32,914 references on poultry only three related to feed intake in free range or scavenging, while the restriction to "chickens (or poultry) + village + intake" yielded only one reference. Even in this restricted field the evidence is equivocal. In two studies, turkeys were given a control "balanced" diet or free access to a high energy-low protein mixture and to a low-protein-high energy one. In both cases, the diet combination that was consumed by self selecting birds was lower in protein than the control diet. Egg production and feed conversion were not affected but fertility and hatchability were less on self-selection in one of the studies (Emmerson et al 1991) but not in the other (Emmerson et al 1990). Broiler lines, selected for differing body size, were given free access to contrasting diets in terms of protein:energy ratios in a trial reported by Huey et al (1982). The authors concluded that the composition of the diets selected did not appear to reflect the nutrient requirements of these particular populations. In the Ivory Coast, the preferences od 14-day old broilers, previously adapted to choice feeding of energy and protein, were dictated more by the physical nature of the feeds offered (whole, cracked or ground maize and a protein contentrate as pellets or meal) than by their nutritive value (Yo et al 1997).
The highly significant differences in protein intakes between birds on the three treatments in the present trial, set against similar intakes of broken rice, imply that the supplements were not selected according to nutritive value but for physical consistency. The chickens only consumed half of the duckweed offered, giving them a protein intake (from duckweed) of slightly over 1 g/day compared with the 10 g/day of protein consumed by the birds having access to the ground soya beans. The moisture content of fresh duckweed was cited by Haustein et al (1990) as being the constraint to intake. In this respect the results of Rodriguez and Preston (1999) are relevant. They reported intakes of fresh duckweed by laying hens of over 200 g/day when the duckweed was offered in a mixture of equal parts of duckweed with rice bran compared with only 32 g/day of duckweed when these two feeds were offered on free access basis.
In the present experiment there was a highly significant improvement in growth rate of the birds when they were offered duckweed plus broken rice compared with broken rice alone. It is difficult to believe that this was due to the additional intake of protein from the duckweed which was small (<1 g/day). Duckweed is also rich in minerals, especially phosphorus (Nguyen Duc Anh et al 1997) and in carotene the precursor of vitamin A (Dewanjii 1993). However, the same argument applies as with protein; that the increased amounts of these nutrients resulting from the duckweed were small and unlikely to have been of nutritional significance. Furthermore, the birds on all the treatments were scavenging during the day in areas rich in green biomass and where presumably there was considerable opportunity to find fauna and flora rich in protein and trace nutrients. It this regard, it is interesting to recall the reports of Haustein et al (1990, 1994) that the addition of small amounts (5%, dry matter basis) of dehydrated duckweed to diets supposedly balanced for all required nutrients led to significantly better performance in both broilers and laying hens. Thus the results of the present experiment, plus those of Haustein et al (1990, 1994) suggest strongly that even small amounts of duckweed in the diet may have nutritional significance at least for poultry.
Data on the amounts of supplement dry matter consumed per unit gain in liveweight, the sale value of the birds and the costs of feed plus purchase price of the birds, are in Table 2. On both the station and the farm the difference (profit) between income and variable costs was highest for the birds supplemented with broken rice and duckweed and lowest for those supplemented with broken rice and ground soya beans. On the farms the soya bean treatment resulted in a net loss.
| Table 2: Mean values of dry matter conversion (supplement dry matter consumed per unit liveweight gain), and costs and returns on the different treatments | |||
| Duckweed | Soya bean | Broken rice | |
| DM conversion | |||
Station |
2.8 |
3.3 |
3.5 |
Farm |
3.6 |
6.0 |
4.1 |
| Costs (Riels) | |||
Initial chicken (Riels 3,510/kg) |
|||
Station |
2134 |
2432 |
1937 |
Farm |
1905 |
1838 |
1754 |
Feed supplement 70 days |
|||
Station |
2160 |
6000 |
2032 |
Farm |
2456 |
7050 |
2400 |
Final sale value (Riels 5000/kg) |
|||
Station |
7835 |
9070 |
6275 |
Farm |
7550 |
7650 |
7750 |
Net income |
|||
Station |
3541 |
638 |
2306 |
Farm |
2759 |
-2168 |
2051 |
| Riels 2,500=USD1.00 | |||
It is concluded that:
I would like to thank the Jesuit Service Cambodia organization and the representative members of Cambodian Women's Association of Tramslek village, Kantok commune for their help in carrying out this experiment; and the Catholic Committee Fund for Development (France) and the University of Tropical Agriculture Foundation (UTA) for financial support.
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