Citation of this paper

Growth of earthworms (Perionyx excavatus) on cattle or buffalo manure with or without water hyacinth

Nguyen Huu Yen Nhi, T R Preston*, Brian Ogle and Torbjorn Lundh

An Giang University, 25 Vo Thi Sau St., Long Xuyen City, Vietnam
nhynhi@agu.edu.vn
* TOSOLY, AA 48 Socorro, Colombia.
** Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences,
PO Box 7024, 750 07, Uppsala, Sweden.

Abstract

The growth of earthworms (Perionyx excavates) was studied in a 2*2 factorial experiment with 4 replicates, in which the treatments were: source of manure (cow or buffalo) and supplementation with water hyacinth at 25% of the weight of manure (DM basis) or none.

Adding chopped water hyacinth to buffalo or cattle manure led a decrease in worm numbers and in productivity per kg DM and crude protein of added substrate. Relative growth in numbers and in weight of the worms was similar on manure derived from buffaloes and cattle. The negative effect of water hyacinth was greater with buffalo than with cattle manure. Residual compost from cattle manure was richer in N and poorer in ash than compost derived from buffalo manure. Water hyacinth added to the substrate resulted in compost with less N but more ash.

Keywords: Ash, chemical composition, compost, earthworms, fermentation, nitrogen, substrate

Introduction

The increase in the population in Vietnam and in the standard of living is creating an increased demand for animal products. However, as livestock production increases so does the environmental pollution through insufficient attention being given to systems of recycling of the excreta.

There are many ways to recycle the organic manure from animals. It can be applied to fish ponds (Prowse 1961), used to feed larvae (Mao Zhang 2004; Latsamy Phounvisouk and Preston 2007), applied to the soil to increase organic matter content (Haynes and Naidu 1998), and especially for raising of earthworms (Hughes et al 1994; Nguyen Quang Suc et al 2000). According to many studies, the earthworms have a diverse role in agriculture. They can be used in breaking down organic wastes (Phan Phuong Loan et al 2009; Edwards and Arancon 2004; Garg et al 2005), to improve the physical structure of the soil, and to enhance soil fertility by providing organic matter, which leads to better crop growth. Earthworms are rich in high quality protein and can be fed to fish (Yaqub 1997; Phan Phuong Loan et al 2009), frogs (Latsamy Phounvisouk and Preston 2007), chickens (Rodríguez et al 1995; Sorn Suheang and Preston 2005; Vu Dinh Ton et al 2009), rabbits (Orozco Almanza et al 1988), ducks and turtles (Bui Xuan Men et al 2007). The many opportunities to use earthworms have created a demand to cultivate them, which creates ways in which farmers in the countryside can raise their income. Thus, raising earthworms is one of the ways of making better use of local resources which are abundant in the rural areas (Keo Sath 2005).

There are many ways to raise earthworms. Different sources of manures (from pigs, cows, buffaloes, goats, chickens and rabbits) have been used (Nguyen Quang Suc et al 2000; Chu Manh Thang 2003; Garg et al 2005; Nguyen Hieu Phuong 2008). According to Garg et al (2005) earthworms grew best on sheep manure, while worms grew fastest on goat manure in the experiments of Nguyen Quang Suc et al (2000) and Nguyen Hieu Phuong (2008). Vegetable wastes (Luu Huu Manh et al 2009), maize stover and rice straw (Tian et al 1997) and water spinach and water hyacinth (Kong Saroeun and Khieu Borin 2007) have been mixed with manure for growing earthworms.

Different species of earthworms have been used. The Califorrnia Red worm (Eisenia foetida) has been the subject of most of the studies. However, Perionyx excavates, an earthworm adapted to living in environments with high levels of organic matter (Edward et al 1998), has been used in a recent study, with good results (Phan Phuong Loan et al 2009).

For the above reasons, this experiment was conducted to find out if there were advantages from incorporating vegetative matter with livestock manure as substrate for earthworms.

Hypothesis

The growth rate and conversion rate of earthworms would be better when water hyacinth was mixed with cow or buffalo manure.

Objective

To record the development of earthworms when using manure from cows or buffaloes supplemented with water hyacinth

Materials and methods

Location and climate

The experiment was conducted in the experimental farm of An Giang University, Long Xuyen City, Vietnam. The climate is tropical monsoon, with a rainy season between May and October and a dry season from November to April. The mean air temperature is 27°C and annual rainfall 1400-1500 mm. The duration of the study was 3 months, from September 2009 to December 2009.

Experimental treatments and design

The treatments were:

Source of manure: Cow or buffalo
Supplementation with water hyacinth or none

The treatments were arranged as a 2*2 factorial with 4 replications in a completely randomized design (CRD) (Table 1). Individual treatments were:

· C100: Cow manure 100% without water hyacinth

· C75: Cow manure 75% and water hyacinth 25% (DM basis)

· B100: Buffalo manure 100% without water hyacinth

· B75: Buffalo manure 75% and water hyacinth 25% (DM basis)

Table 1. Experimental layout
C100	C75	B100	B100
B75	C75	C100	B75
B75	B100	B75	C100
B100	C100	C75	C75

Experimental feeds

The earthworms (Photo 1) were bought from Cuu Long Delta Rice Research Institute, O Mon District, Can Tho City.


Photo 1. Earthworm (Perionyx excavatus)	Photo 2. Water hyacinth (Eichhornia crassipes)

Cow and buffalo manure were bought from farmers around Long Xuyen City. Water hyacinth (Photo 2) was collected from the canals and rivers in Long Xuyen City.

The earthworms were raised in baskets lined with plastic sheets (Photo 3). The earthworms (100g) were put in the bottom of each basket followed by the manure. Fresh water hyacinth (aerial parts and roots) was chopped and mixed with the manure. At the beginning a total of 500 g DM of substrate was added to each basket. More substrate was added according to the rate at which it was utilized. Weights of fresh manure and water hyacinth that were added were recorded and samples taken for determination of DM, ash, crude fibre (CF) and crude protein (CP). Clean, fresh water was sprayed on the baskets to keep an appropriate moisture level throughout the experiment.

Measurements

Before putting the earthworms into the baskets, a random sample of 30 worms was taken to determine the average length and weight of individual worms. A sample of the worms was analyzed for DM, CP and ash. After 12 weeks the earthworms were separated from the residual substrate (Photo 4). Both worms and substrate were weighed and samples taken for analysis of DM, CP and ash. After harvesting the earthworms, the total weight in each basket was determined. A random sample was chosen of 30 worms for determining average length and weight. From the average weight of the earthworms the total number present in each basket was calculated. A sample of worms from each treatment was analyzed for DM, CP and ash. The residual quantities of residue in each basket were weighed and a sample analyzed for DM, CP, CF and ash.


Photo 3. Feeding the earthworms	Photo 4. Harvesting the earthworms

Chemical analysis

Manure, water hyacinth, compost and earthworms were analyzed for DM, CP, CF and ash according to AOAC (1990) procedures.

Statistical analysis

Data were analyzed using the General Linear Model (GLM) option of the ANOVA program in the Minitab software (Minitab release 13.3, 2000). Sources of variation were: Manure source, water hyacinth, interaction manure*water hyacinth and error.

Results and discussion

Composition of substrate for raising earthworms

The moisture and CP contents of water hyacinth were higher than in the buffalo and cattle manure (Table 2) and were similar to the values reported by Chhay Ty et al (2007) and Nguyen Thi Kim Dong and Nguyen Van Thu (2009). Abdelhamid and Gabr (1991) reported that the water hyacinths collected from a canal had 9.5% DM and 74.3% OM, 20% CP and 18.9% CF in the DM.

Table 2. Composition of manure from cattle and buffalo and water hyacinth
	Buffalo	Cattle	Water hyacinth
DM,%	21.2	16.8	9.16
As % in DM
CP	9.35	10.4	11.6
Ash	35.1	9.50	31.5
CF	15.6	25.4	17.9

Earthworm production

Adding chopped water hyacinth to the manure led to a decrease in worm numbers and in productivity per kg total substrate DM and also per kg of manure DM (Table 3). A similar effect was observed for the utilization of the CP. Thus, incorporating water hyacinth in the manure had a detrimental effect on the efficiency of utilization of the manure by the worms. There was an interaction between the source of manure and addition of water hyacinth (Table 5; Figures 1 and 2). The reduction in earthworm numbers and their growth due to the water hyacinth was greater on buffalo manure than on cow manure. According to Sherman (2003), fresh organic matter added to earthworm beds will cause an increase in temperature of the beds, due to the fermentation of readily degradable carbohydrate. This could result in the death of some of the worms. This could be the explanation for the reduction in worm numbers when the water hyacinth was added to the manure.

Table 3. Effect of water hyacinth on body length (cm), weight (g) and number of earthworms
	Manure with water hyacinth	Manure without water hyacinth	SEM	Prob.
*Body length, (cm)*
Initial	4.21	4.21
Final	6.50	5.81	0.25	0.07
Length increase	2.29	1.60	0.25	0.07
*Earthworm weight, g*
Initial weight/ basket	100	100
Final weight/ basket	136	215	5.16	0.001
Weight gain/kg DM of added substrate	15.6	38.3	1.86	0.001
Weight gain/kg of added manure DM	20.8	38.3
Weight gain/g CP of added substrate	0.15	0.39	0.02	0.001
Weight gain/g CP from manure	0.20	0.39
*Earthworm number*
Initial number/basket	916	916
Final number/basket	1167	2106	156	0.001
Number increase/kg DM of added substrate	106	389	48.1	0.001
Number increase/g CP of added substrate	1.03	4.00	0.52	0.001


Figure 1. Effect of water hyacinth added to buffalo and cattle manure on earthworm gain in weight per unit added substrate DM	Figure 2. Effect of water hyacinth added to buffalo and cattle manure on earthworm gain in weight per unit added substrate CP

The source of manure had no effect on the growth in numbers and in weight of the worms (Table 4). However, the worms grown on cattle manure were longer than those grown on buffalo manure.

Table 4. Effect of buffalo and cattle manure on the body length (cm), weight (g) and number of earthworms
	Buffalo manure	Cattle manure	SEM	Prob.
*Body length, (cm)*
Initial	4.21	4.21
Final	5.82	6.50	0.09	0.001
Length increase	1.61	2.29	0.25	0.1
*Earthworm weight, g*
Initial weight/basket	100	100
Final weight/basket	175	176	15.7	0.98
Weight gain/kg DM of added substrate	24.3	29.6	4.56	0.43
Weight gain/kg fresh of added substrate	3.70	4.53	0.83	0.49
Weight gain/g CP of added substrate	0.26	0.28	0.05	0.71
*Earthworm number*
Initial number/basket	916	916
Final number/basket	1827	1447	226	0.25
Number increase/kg DM of added substrate	292	203	70.0	0.38
Number increase/g CP of added substrate	3.10	1.94	0.73	0.28

The relative increase in numbers of worms during the trial varied among the treatments, with the highest number on the B100 treatment (Figure 3). At the end of the trial the weights of individual worms on the different treatments did not differ from the weights at the beginning (Table 6). In contrast, the worms at the end were longer than at the beginning, and thus the ratio of weight to length decreased (Figure 4). This was reflected in a tendency (P=0.069) for a decrease in CP content of the worms at the end compared with the beginning. Surprisingly, there were no changes in OM content. There must therefore have been a change in some other component of the body (other than protein and ash) in the worms at the end compared with those at the beginning.

Table 5. Effect of buffalo and cattle manure, with or without water hyacinth, on the growth and reproduction of earthworms
	B75	B100	C75	C100	SEM	Prob.
*Earthworm weight, g*
Initial weight/basket	100	100	100	100
Final weight/basket	125^a	227^d	148^b	204^c	4.07	0.001
Weight gain/kg of added substrate (fresh)	1.22^a	6.19^c	2.77^b	6.30^c	0.23	0.001
Weight gain/kg of added substrate (DM)	9.74^a	38.9^c	21.6^b	37.7^c	1.49	0.001
Weight gain/g CP of added substrate	0.10^a	0.42^c	0.20^b	0.36^c	0.02	0.001
*Earthworm number*
Initial number/basket	916	916	916	916
Final number/basket	1176^a	2478^b	1159^a	1735^ab	185	0.001
Number increase/kg DM of added substrate	104^a	481^b	108^a	298^ab	63.3	0.002
Number increase/g CP of added substrate	1.05^a	5.14^b	1.01^a	2.87^ab	0.64	0.001
^abc Means within rows without common letter are different at P<0.05 B75, 75% buffalo manure and 25% water hyacinth (DM basis) B100, Buffalo manure only (DM basis) C75, 75% Cattle manure and 25% water hyacinth (DM basis) C100, Cattle manure only (DM basis)

Table 6. Effect of buffalo and cattle manure, with or without water hyacinth, on the number, mean weight and composition of earthworms
	Initial	B75	B100	C75	C100	SEM	Prob.
No./basket	916^b	1176^b	2478^a	1159^b	1735^ab	222	0.001
Weight, g/worm	0.109^ab	0.106^ab	0.094^b	0.129^a	0.124^a	0.008	0.003
Length, mm	42.1^c	63.0^a	53.4^b	67.1^a	62.8^a	1.50	0.0001
W/L, g/mm	0.259^a	0.166^b	0.173^b	0.189^ab	0.191^ab	0.014	0.011
DM, %	18.2^b	21.0^a	20.9^a	20.7^a	20.5^a	0.37	0.02
As % of DM
CP	75.0	66.5	59.1	67.0	65.2	2.88	0.069
OM	92.3	93.6	93.7	93.2	93.2	0.41	0.41
^abc Means within rows without a common letter are different at P<0.05 B75, 75% buffalo manure and 25% water hyacinth (DM basis) B100, Buffalo manure only (DM basis) C75, 75% Cattle manure and 25% water hyacinth (DM basis) C100, Cattle manure only (DM basis)


Figure 3. Effect of buffalo and cattle manure, with (B75 and C75) or without water hyacinth, on the number of earthworms per basket at the end compared with initial values	Figure 4. Effect of buffalo and cattle manure, with (B75 and C75) or without water hyacinth, on weight/length ratio of the earthworms at the end compared with initial values

Characteristics of residual “compost”

Addition of water hyacinth reduced the DM, increased the ash, and decreased the CP and the CF contents (Table 7). Buffalo manure resulted in higher DM, higher ash and lower CP and CF than when cattle manure was the substrate. There were interactions between the main treatments (Table 8), with the differences between buffalo and cattle manures being less pronounced when water hyacinth had been added to the worm beds.

Table 7. Mean values (main effects) for composition of residual compost after earthworm culture on manure from buffalo and cattle, with (25WH) or without (0WH) water hyacinth
	25WH	0WH	Prob.	Buffalo	Cattle	Prob.	SEM
DM, %	16.3	21.5	0.001	22.9	14.9	0.001	0.23
As % in DM
CP	1.97	2.22	0.001	1.69	2.51	0.001	0.029
Ash	37.5	32.8	0.001	46.6	23.7	0.001	0.19
CF	10.1	11.2	0.001	9.22	12.0	0.001	0.12

Table 8. Composition of residual compost after earthworm culture on manure from buffalo and cattle, with or without water hyacinth
	B75	B100	C75	C100	SEM	Prob.
DM, %	19.2^c	26.6^d	13.3^a	16.5^b	0.32	0.001
As % in DM
N	1.65	1.73	2.30	2.72	0.042	0.001
Ash	46.3^c	47.0^c	28.7^b	18.6^a	0.27	0.001
CF	9.31^a	9.14^a	10.9^b	13.2^c	0.17	0.001
^abcd Means within rows without a common letter are different at P<0.05

The influence of the treatments on the overall fertilizer value of the residual compost depends mainly on the relative values of the contents of N, ash and organic matter. Compost from cattle manure was richer in N and poorer in ash (but richer in OM) than compost derived from buffalo manure. Water hyacinth added to the substrate resulted in compost with less N but more ash (and less OM). Evaluation of the fertilizer value of the compost, for example by means of the “biotest” (Boonchan Chantaprasarn and Preston 2004; Tran Thi Bich Ngoc and Preston 2006) is a topic meriting future research.

Conclusions

· Adding chopped water hyacinth to buffalo and cattle manure led to a decrease in worm numbers and in productivity per kg DM and crude protein of added substrate.

· Relative growth in numbers and in weight of the worms was similar on manure derived from buffaloes and cattle.

· The negative effect of water hyacinth was greater with buffalo than with cattle manure.

· Residual compost from cattle manure was richer in N and poorer in ash than compost derived from buffalo manure. Water hyacinth added to the substrate resulted in compost with less N but more ash.

Acknowledgements

The senior author would like to express gratitude to the SIDA- SAREC program, which provided the funds for conducting this experiment - a part of the MSc course through the regional MEKARN project. Thanks also to An Giang University and students who helped to conduct the experiment.

References

Abdelhamid A M and Gabr A A 1991 Evaluation of water hyacinth as a feed for ruminants. Archives of Animal Nutrition. 41: 7, 745 -756 http://dx.doi.org/10.1080/17450399109428519

AOAC 1990 In Helrick (Ed.), Official Methods of analysis. Association of Official Analytical Chemists 15^th edition. Arlington. pp 1298 pp.

Boonchan Chantaprasarn and Preston T R 2004 Measuring fertility of soils by the bio-test method. Livestock Research for Rural Development. Vol. 16, Art. No. 78. http://www.lrrd.org/lrrd16/10/chan16078.htm

Bui Xuan Men, Brian Ogleand T R Preston 2007 Recycling organic wastes to produce earthworms as a protein supplement in diets for poultry and fish. International workshop. Matching livestock systems with available resources http://www.mekarn.org/prohan/menbx.htm

Chhay T, Borin K and Preston T R 2007 Effect of mixtures of water spinach and fresh water hyacinth leaves on growth performance of pigs fed a basal diet of rice bran and cassava root meal. Livestock Research for Rural Development. Volume 19, Article #194. http://www.lrrd.org/lrrd19/12/chha19194.htm

Chu Manh Thang 2003 Effects of different substrates and levels of seeding on reproductive rate of earthworms. http://www.mekarn.org/msc2003-05/miniprojects/webpage/thang.htm

Edwards C A Dominguez J and Neuhauser E F, 1998 Growth and reproduction of Perionyx excavatus (Perr.) (Megascolecidae) as factors in organic waste management. Biol Fertil Soils, volume 27, pages 155–161. http://login.oaresciences.org/whalecomwww.springerlink.com/whalecom0/content/gn49nvlgj9v9pknx/fulltext.pdf

Edwards C A and Arancon N Q 2004 The use of earthworms in the breakdown of organic wastes to produce vermicomposts and animal feed protein. Eathworm ecology. 345p http://www.google.com/books?hl=vi&lr=&id=7mHvxY-1BKsC&oi=fnd&pg=PA345&dq=Recycling++organic++wastes++to++produce++earthworms+as+a+protein+supplement+in+diets+for+poultry+and+fish&ots=FJiQIJJ6YL&sig=bRumJDeuD0C3_BEfgy07i2rmtxo#v=onepage&q&f=false

Garg V K Chand S, Chhillar A, Yadav A, 2005 Growth and reproduction of eisenia foetida in various animal wastes during vermicomposting. http://www.ecology.kee.hu/pdf/0302_051059.pdf

Haynes R J and Naidu R, 1998 Influence of lime, fertilizer and manure applications on soil organic matter content and soil physical conditions: a review. Nutrient cycling in agroecosystems. Issue: Volume 51, number 2 / June, 1998. http://login.oaresciences.org/whalecomwww.springerlink.com/whalecom0/content/n263q181t541777j/fulltext.pdf

Hughes M S, Bull C M, and Doube B M 1994 The use of resource patches by earthworms. In: Earth and Environmental Science. Biology and Fertility of soils. Issue: Volume 18, Number 3 / September, 1994. http://login.oaresciences.org/whalecomwww.springerlink.com/whalecom0/content/w068132801460152/fulltext.pdf

Keo Sath 2005 Effect of spraying different levels of biodigester effluent on cow and buffalo manure used as substrate for growth of earth worms, Center for Livestock and Agriculture Development (CelAgrid-UTA Cambodia). http://www.mekarn.org/MSC2005-07/protocols/sath.htm

Kong Saroeun and Khieu Borin 2007 Evaluation of different ratios of manure and water plants on the production of earthworms and humus. International workshop. Matching livestock systems with available resources. http://www.mekarn.org/prohan/abstracts/saroeun2.htm

Latsamy Phounvisouk and Preston T R 2007 Fly larvae, earthworms and duckweed as feeds for frogs in an integrated farming system. MSc Thesis, MEKARN-SLU http://www.mekarn.org/MSC2005-07/thesis07/lats2.htm

Luu Huu Manh, Nguyen Nhat Xuan Dung, Ngo ngoc Hung and Lam Kim Ngan 2009 Vegetable by-product disposal and animal manures as a feed source to raise earthworm (Perionyx excavatus). International workshop. Livestock, climate change and the environment. http://www.mekarn.org/workshops/environ/Abstracts/manh01.htm

Mao Zhang 2004 Rearing fly larvae and animals in space for waste recycling and food supplying. United states Patent application publication. Pub. No.: US 2004/0089214 A1. Pub. Date: May 13, 2004. http://www.google.com.vn/patents?hl=vi&lr=&vid=USPATAPP10619130&id=9BmJAAAAEBAJ&oi=fnd&dq=maggot+raising+by+manure&printsec=abstract#v=onepage&q=maggot%20raising%20by%20manure&f=false

Minitab 2003 Statistical software Version 13.31.

Nguyen Hieu Phuong 2008 Effects of goat, pig and cattle manure suspensions as feed for earthworm on their performance in recycling excreta. Miniproject, Mekarn MSc 2008-10. http://www.mekarn.org/msc2008-10/miniprojects/minpro/phuong.htm.

Nguyen Quang Suc, Le Thi Thu Ha and Dinh Van Binh 2000 Manure from rabbits, goats, cattle and buffaloes as substrate for earthworms. Workshop-seminar "Making better use of local feed resources" SAREC-UAF, January , 2000. http://www.mekarn.org/sarpro/sucew.htm

Nguyen Thi Kim Dong and Nguyen Van Thu 2009 Study of water hyacinth (Eichhornia crassipes L,) as feed for growing rabbits. International workshop. Livestock, climate change and the environment. http://www.mekarn.org/workshops/environ/PDF/kdong.pdf

Orozco Almanza M S, Ortega Cerrilla M E, Pérez-Gil Romo F 1988 Use of earthworms as a protein supplement in diets for rabbits http://www.ncbi.nlm.nih.gov/pubmed/3154302

Phan Phuong Loan, Nguyen Huu Yen Nhi, Tran Thi Thanh Van and Tran Phong Phu 2009 Earthworm (Perionyx excavatus) as a main protein source for growing zig-zag eel (Mastacembelus armatus) in small-household aquaculture-based farming systems in the Mekong river delta. International workshop. Livestock, climate change and the environment. http://www.mekarn.org/workshops/environ/PDF/loan.pdf

Prowse G A, 1961 The use of fertilizers in fish culture. Indo-Pacific fisheries council. Technical paper. http://www.apfic.org/Archive/techpapers/1961.pdf#page=76

Rodríguez Lylian, Salazar Patricia y Arango María Fernanda 1995 Lombriz roja californiana y azolla-anabaena como sustituto de la proteina convencional en dietas para pollos de engorde. . Livestock Research for Rural Development. Volume 19, Article #194. http://www.lrrd.org/lrrd7/3/5.htm

Sherman R 2003 Raising Earthworms Successfully. Published by: North Carolina Cooperative Extension Service http://www.worms.com/worm-pdfs/raising%20earthworms.pdf

Sorn Suheang and T R Preston 2005 Use of sugar cane fibre/pig excreta as substrate for cultivation of earthworms (Eisenia foetida) http://www.mekarn.org/msc2003-05/theses05/content/suheang2.pdf

Tian G, Kang B T and Brussaard L 1997 Effect of mulch quality on earthworm activity and nutrient supply in the humid tropics. Soil biology and biochemistry. Volume 29, issue 3-4, pages 369-373. http://login.oaresciences.org/whalecomwww.sciencedirect.com/whalecom0/science?_ob=MImg&_imagekey=B6TC7-3RH6DCP-1G-1&_cdi=5163&_user=5062602&_pii=S0038071796000995&_orig=browse&_coverDate=04%2F30%2F1997&_sk=999709996&view=c&wchp=dGLbVzb-zSkzS&md5=8a76c1e9b010b2bbcb3db3688522ab86&ie=/sdarticle.pdf

Tran Thi Bich Ngoc and Preston T R 2006 Soil bio-test to evaluate comparative fertility of soils and effects of adding earthworm compost. Livestock Research for Rural Development. Volume 18, Article No. 42. http://www.lrrd.org/lrrd18/3/ngoc18042.htm

Vu Dinh Ton, Han Quang Hanh, Nguyen Dinh Linh and Nguyen Van Duy, 2009 Use of redworms (Perionyx excavatus) to manage agricultural wastes and supply valuable feed for poultry. http://www.lrrd.org/lrrd21/11/ton21192.htm

Yaqub H B 1997 Earthworm and maggot meals as a potential fish meal replacement http://www.oceandocs.org/bitstream/1834/1268/1/paper1feed.pdf

Received 14 August 2010; Accepted 21 August 2010; Published 1 September 2010

Go to top