 Photo 1: Arrangement of separate feeders holding (right to left): duckweed, rice bran and the 50:50 mixture of fresh duckweed and rice bran |
| Livestock Research for Rural Development 11 (1) 1999 | Citation of this paper |
Eight chickens at point of lay, four of one of the indigenous ecotypes typically used in Vietnam and four of an exotic strain imported orginally from China (the Tam Hoang), scavenged during the day in an integrated farm (planted with cassava, bananas and forage trees with recycling of wastes from pigs and chickens through biodigesters and ponds for duckweed and fish). In the late afternoon until the following morning the chickens were confined individually in bamboo cages with free access to rice bran, fresh duckweed and a 50:50 mixture (fresh weight basis) of the two offered in separate feeders. After a period of 8 weeks of adaptation to the cages and to the scavenging system, records were kept daily of feeds offered and refused during a period of 13 days. The birds were weighed at the beginning and end of the 13 day period and egg production was recorded.
There were major differences (P=0.001) between ecotypes in intake of duckweed offered as a single feed but not (P=0.18) when it was mixed with rice bran. As a consequence, total intake of duckweed (that offered separately plus that in the mixture) was almost twice as high (P=0.001) for the local chickens (65 g/day) compared with the "exotic" Tam Hoang (38 g/day). Calculated levels of crude protein in the total diet dry matter were similar for both ecotypes (15.9 and 15.2%) but the proportion of the protein derived from duckweed was almost 50% higher (20 versus 14%) for the local birds compared with the Tam Hoang.
The success of the family scale poultry project in Bangladesh (Mahfuzar Rahman et al 1997), and the confirmed socio-economic impact of the strategy as a means of poverty alleviation, with women as the primary beneficiaries (Jahangir Alam 1997; Todd 1998), is a stimulus for the development of extension messages relating to this kind of production system. In Vietnam, according to Le Ba Lich (1996), over 80% of the chickens are managed at household level, almost exclusively with indigenous (local) ecotypes in some form of scavenging system. Traditionally these birds are supplemented with energy-rich feeds such as "paddy" rice (whole grains), broken rice or rice bran as these are the available feed resources at household level throughout Vietnam. Protein-rich supplements have been shown to improve dramatically the survival and early growth of chickens (Gunaratne et al 1993). However, protein-rich feeds are scarce and costly in Vietnam, as in most other tropical countries, and poor farmers rarely feed them to their livestock.
The potential of duckweed (Lemnaceae) grown on sewage treatment lagoons as a protein supplement for chickens was conclusively demonstrated in Peru by Haustein et al (1990, 1994). However, the low cost of this material in situ is negated if, because of its high water content (94-96%), it has to be dehydrated (the procedure used by Haustein et al 1990). In our laboratory and that of our colleagues in Cambodia (borin@forum.org.kh), we have therefore concentrated efforts on developing feeding systems using freshly harvested duckweed grown in ponds that form part of an integrated farming system (Preston 1998). Encouraging results have been reported supplementing fresh duckweed to pigs (Du Thanh Hang 1998; Lai 1998) and also to scavenging chickens (Hong Samnang 1999).
The results reported in this short communication are a part of a series of studies to assess the most appropriate way of using this low-cost feed resource. The observations, although preliminary and based on few birds, are thought to be of interest to other researchers studying ways of improving the productivity and economy of rural family poultry.
The experiment was done in an ecological farm on the campus of the College of Agriculture and Forestry of Ho Chi Minh National University in Thu Duc district, some 20 km North of Ho Chi Mnh city. Eight chickens at point of lay, four of one of the indigenous ecotypes typically used in Vietnam http://www.hcm.fpt.vn/inet/~ecofarm/rdpoultry and four of an exotic strain imported orginally from China (the Tam Hoang) were purchased from small scale farms in the area. The Tam Hoang birds had been managed in semi-confinement and supplemented with rice byproducts and kitchen waste. On arrival at UTA the Tam Hoang hens were kept for two months in a semi-scavening system (in a large open pen on soil) and supplemented with rice bran and duckweed. The local birds had been managed in a scavenging system. The periods of accustoming the birds to the cages, to scavenging and collection of data, are shown in Table 1.
Photo 1: Arrangement of separate feeders holding (right to left): duckweed, rice bran and the 50:50 mixture of fresh duckweed and rice bran |
Adaptation to the cages: The birds of both breeds were confined
individually in raised bamboo cages which later served as housing for the night-time
confinement during the experiment. During this period which lasted two weeks and served to
accustom them to the cages, they had free access to the three experimental feeds offered
in different feeders: rice bran (RB), fresh duckweed (DW) and a 50:50 mixture (fresh
weight basis) of rice bran and duckweed (Photo 1).
Adapation to scavenging: For the next 6 weeks birds of both ecotypes were allowed
to scavenge in the integrated farm (total area of 3,300 m˛ planted with
cassava, bananas and forage trees with recycling of wastes from pigs and chickens through
biodigesters and ponds for duckweed and fish). The scavenging period was from 6 am
until 4 pm when the birds were collected and put in the cages with access to the
experimental feeds. Fresh water was also available at this time.
| Table 1: Design of experiment: length of periods for adaptation to cages and to scavenging and collection of data | ||
Accustom to cages |
Adaptation to scavenging (6 weeks) |
Recording data (2 weeks) |
Data collection: After the 6 week adaptation to scavenging, records were kept of daily amounts and composition (dry matter and nitrogen) of each feed offered and refused, of egg production and changes in liveweight. The experiment was terminated prematurely after 13 days of keeping records as all the chickens were stolen (!!). The daily records for feed intake were grouped in two periods of 7 and 6 days (the offer level of all feeds was increased in the second period) for ANOVA analysis using the General Linear model of Minitab software (version 11). Variables in the ANOVA were ecotype, period, the interaction ecotype*period and error. The data for changes in liveweight and egg production were not analysed but are presented as observations.
Mean values for daily intakes of each feed (fresh basis) and of dry matter and protein, daily egg production and the overall changes in liveweight are shown in Table 2. There were major differences (P=0.001) between ecotypes for intake of duckweed offered as a single feed but not (P=0.18) when it was mixed with rice bran (Figure 1). As a consequence, total intake of duckweed (that offered separately plus that in the mixture) was almost twice as high (P=0.001) for the local chickens (65 g/day) compared with the "exotic" Tam Hoang ecotype (38 g/day). Intakes of the mixture increased in the second compared with the first week (P=0.001) but intakes of rice bran and duckweed offered separately were unchanged. There was no interaction between breed and period for any of the intake measurements. Calculated levels of crude protein in the total diet dry matter were similar for both ecotypes but the proportion of the protein derived from duckweed was almost 50% higher (20 versus 14%) for the local birds compared with the exotics. While little significance can be ascribed to the production data it is interesting to observe that the local chickens laid one egg every second day on average and lost 1.7 g of body weight in the 13-day trial period; in contrast, the Tam Hoang produced no eggs but gained 8.5 g in body weight.
Table 2: Mean values (4 chickens of each ecotype), standard error of mean (SEM) and level of significance for effects of ecotype, period (weeks 1 and 2) and interaction (ecotype*period) on intakes of rice bran and duckweed offered alone or mixed (50/50 fresh basis) when the chickens were confined over-night. |
||||||||
Ecotype |
Period |
Probability |
||||||
Local |
Tam Hoang |
1 |
2 |
SEM |
Ecotype |
Period |
Eco*Per |
|
| Intake, g/day | ||||||||
| Rice bran | 16.1 |
13.9 |
15.4 |
14.6 |
2.0 |
0.43 |
0.78 |
0.12 |
| Duckweed | 36.0 |
11.3 |
22.4 |
24.8 |
2.5 |
0.001 |
0.51 |
0.47 |
| Mixture | 58.2 |
53.2 |
41.8 |
69.6 |
2.6 |
0.18 |
0.001 |
0.12 |
| DW in mixture | 29.1 |
26.6 |
20.9 |
34.8 |
1.3 |
0.18 |
0.001 |
0.12 |
| RB in mixture | 29.1 |
26.6 |
20.9 |
34.8 |
1.3 |
0.18 |
0.001 |
0.12 |
| Total DW | 65.1 |
37.8 |
43.3 |
59.6 |
3.0 |
0.001 |
0.001 |
0.95 |
| Total RB | 45.2 |
40.5 |
36.3 |
49.4 |
2.5 |
0.19 |
0.001 |
0.70 |
| Total dry matter | 44.1 | 38.3 | ||||||
| Total protein | 7.00 | 5.84 | ||||||
| Protein % in | ||||||||
| Dry matter | 15.9 | 15.2 | ||||||
| From duckweed | 19.5 | 13.6 | ||||||
| Production | ||||||||
| Eggs/day | 0.43 | 0.00 | ||||||
| Weight change, g/13 days | -1.74 | 8.5 | ||||||
Discussion of the results of this study must be tempered by the small number of birds in each ecotype and the short period during which
data were recorded. Furthermore the comparison between ecotypes is subordinate to the
observations on feed intake, and in no way is meant to demonstrate valid differences
between them. As reported by Samnang (1999) there appear to be few data in the
literature on feed selection by scavenging chickens, although many experiments have been
reported for caged birds in industrial systems. Thus, the observations on feed
selection we consider to be of interest.
The apparent greater capacity of the indigenous (local) chickens to eat duckweed (when this was offered as a separate meal), as compared with the exotic Tam Hoang breed, is similar to the response noted by Nguyen Van Lai (1998) in indigenous (Mong Cai) compared with exotic (Large White) pigs when fresh duckweed was the only protein supplement in a mixed diet of rice bran and ensiled cassava roots. It is logical to think that natural selection pressure on indigenous birds scavenging in tropical ecosystems would favour traits reflected in the ability to consume protein-rich vegetative matter. The contrasting behaviour of the two ecotypes in the present study appears to confirm this hypothesis. It remains to be seen if these observations are confirmed in subsequent studies with greater numbers of birds, and whether such traits are reflected in greater economic benefits for the indigenous ecotypes in view of the demonstrated protein-producing potential of duckeed cultivated in integrated farming systems (Rodriguez and Preston 1996; Chara et al 1999). Of more immediate relevance is the observation that the intake of duckweed by the Tam Hoang birds was more than doubled when it was offered as a 50:50 mixture with the rice bran. This form of offering the duckweed is now standard practice in ongoing experiments, the preliminary observations from which (Rodriguez Lylian, 1999, unpublished) confirm that highest intakes of duckweed are obtained with this feeding system.
Jahangir Alam 1997 Impact of smallholder livestock development project in some selected areas of rural Bangladesh. Livestock for Rural Development, Volume 9, Number 3: http://www.cipav.org.co/lrrd/lrrd9/3/bang932.htm
Mahfuzar Rahman, Sorensen Poul, Jensen Askov and
Dolberg F 1997 Exotic hens under semi-scavenging conditions
in Bangladesh. Livestock Research for Rural Development. Volume 9, Number 3: http://www.cipav.org.co/lrrd/lrrd9/3/bang931.htm
Nguyen Van Lai 1998 On-farm comparison of Mong Cai and Large White pigs
fed ensiled cassava root, rice bran and duckweed. Livestock Research for Rural
Development. Volume 10, Number 3: http://www.cipav.org.co/lrrd/lrrd10/3/lai103.htm
Preston T R 1998 Animal production and use of
natural resources. Proceedings 8th World Conference on Animal Production. (In press)
Rodríguez Lylian and Preston T R 1996 Use of effluent from low cost
plastic biodigesters as fertilizer for duckweed ponds. Livestock Research for Rural
Development. Volume 8, Number 2: http://www.cipav.org.co/lrrd/lrrd8/2/lylian2.htm