Utilisation of Giant African snail (Achatina fulica) meal as protein source for laying hens

Abstract

A 12-week experiment was carried out to investigate the effects of substituting Giant African snail meal for fish meal in laying hens diet. Four diets were formulated to contain snail meal as replacement for fish meal at 0 (control), 33, 67 and 100 %. A total of 120 Shaver Brown pullets aged 18 weeks were allocated to the dietary treatments in a randomised design. Each treatment consisted of three replicates and ten birds per replicate. Feed intake increased only for the 33 % treatment as compared to the 67 % replacement diet but did not differ from the other treatments. There were no significant treatment effects on egg performance parameters observed (egg production, egg weight, total egg mass, feed conversion ratio and percent shell). The overall feed cost of egg production reduced on the snail meal-based diets. The organoleptic evaluation of boiled eggs revealed no difference between the treatments. Based on these results it was concluded that total replacement of fish meal with cooked snail meat meal does not compromise laying performance or egg quality. The substitution is beneficial in terms of production cost reduction and the reduction of snails will have a beneficial impact especially where these snails are a serious agricultural pest. The manual collection and processing of snails can also become a source of rural income.

Full text

Journal of Agriculture and Rural Development in the Tropics and Subtropics
Vol. 116 No. 1 (2015) 85–90
urn:nbn:de:hebis:34-2015011347178 ISSN: 2363-6033 (online); 1612-9830 (print) – website: www.jarts.info
Utilisation of Giant African snail (Achatina fulica) meal
as protein source for laying hens
Siaka Seriba Diarra∗, Rashmi Kant, Jemarlyn Tanhimana, Patrick Lela
University of the South Pacific, School of Agriculture and Food Technology, Alafua Campus, Apia, Samoa
Abstract
A 12-week experiment was carried out to investigate the effects of substituting Giant African snail meal for fish meal
in laying hens diet. Four diets were formulated to contain snail meal as replacement for fish meal at 0 (control),
33, 67 and 100%. A total of 120 Shaver Brown pullets aged 18 weeks were allocated to the dietary treatments in a
randomised design. Each treatment consisted of three replicates and ten birds per replicate. Feed intake increased only
for the 33% treatment as compared to the 67% replacement diet but did not differ from the other treatments. There
were no significant treatment effects on egg performance parameters observed (egg production, egg weight, total egg
mass, feed conversion ratio and percent shell). The overall feed cost of egg production reduced on the snail meal-
based diets. The organoleptic evaluation of boiled eggs revealed no difference between the treatments. Based on these
results it was concluded that total replacementof fish meal with cooked snail meat meal does not compromise laying
performance or egg quality. The substitution is beneficial in terms of production cost reduction and the reduction of
snails will have a beneficial impact especially where these snails are a serious agricultural pest. The manual collection
and processing of snails can also become a source of rural income.
Keywords: protein sources, feed cost, snail meal, egg production
1 Introduction
The shortage in supply and high cost of traditional
protein feed sources such as fish and soybean meals
have increased research interest in alternative sources
for poultry feeding. In the free range system, chickens
normally obtain an important part of their protein re-
quirement from worms, insects and molluscs. The better
amino acid composition of animal proteins compared to
plant proteins (Ravindran & Blair, 1993) has increased
research into the feeding value ofsuch species normally
eaten by scavenging poultry. Several genera and species
∗Corresponding author
Dr Siaka S. Diarra, Department of Animal Science,
School of Agriculture and Food Technology,
Univ. of the South Pacific, Alafua Campus, Alafua, Apia, Samoa
Email: diarra_s@usp.ac.fj or siakadiarra@yahoo.com
of insects and worms (Johnson & Boyce, 1990; Despins
et al., 1994; Khurso et al., 2012) and molluscs (Ravin-
dran & Blair, 1993; Dragi´
cevic & Balti´
c, 2005) are re-
ported to have nutritional qualities that make them ex-
cellent protein sources for poultry.
Snails, members of the phylum Mollusca, are found
in fresh and sea water, and on land (Thompson & Ch-
eney., 1996). The different species of snail do have
wide differences in nutrient contents. Protein contents
in the dry matter of 53.9% in Pila globosa (Ali & Lee-
son, 1995), 62 % in Pomacea insularis (Serra, 1997) and
54% in Achatina fulica (Diomandé et al., 2008) snail
species have been reported. Snail meal is reported to
have a good (4.35–4.60%) lysine content (Creswell &
Kompiang, 1981; Ali & Leeson, 1995). These nutri-
tional properties have made snail an increasingly impor-
tant dietary protein source for human beings in several
Published online: May 22, 2015 Open access article licensed under a Creative Commons Attribution International License CC BY-NC-ND
http://creativecommons.org/licenses/by-nc-nd/4.0

86 S. S. Diarra et al. /
J. Agr. Rural Develop. Trop. Subtrop. 116 -1 (2015) 85–90
regions of the world (Jess & Marks, 1995). Where snails
have no food value however, they could be potential pro-
tein supplements in poultry diets. The use of snail meal
in broilers (Ali & Leeson, 1995; Diomandé et al., 2008)
and laying hens diets (Serra, 1997) has been reported.
All these authors also observed improved feed intake on
diets based on cooked snail meal comparedto raw snail
meal.
Giant African snail (Achatina fulica) which is na-
tive to the east coast of Africa (Mead, 1949) abounds
in Samoa, especially during the months of heavy rains
(November to April), causing serious damages to crops
such as papaya and pineapple (Kant & Diarra, 2014).
Actually, chemical treatments are the main measure to
control snails. Besides the economic aspect, an exces-
sive use of agro-chemicals can have serious environ-
mental and health consequences. Although there are re-
ports on the inclusion of Giant African snail species in
broiler diets (Creswell & Kompiang, 1981; Ali & Lee-
son, 1995; Diomandé et al., 2008), documented infor-
mation on its feeding to laying hens is scanty. It may
therefore be of interest to investigate the feeding value
of this snail species to laying hens, the only form of
commercial poultry in Samoa at the moment. In the
present study it was hypothesised that replacing fish
meal with Achatina fulica meal will have no adverse ef-
fects on egg production and quality.
2 Materials and methods
2.1 Experimental site, source and processing of snail
meal
The study was conducted at the Poultry Unit of the
IRETA institute of the University of the South Pacific
(USP) in Alafua, Samoa (latitude 13.5°S and longitude
172°W). Fresh snails collected from the school cam-
pus and surrounding villages were scraped with an iron
blade to remove the meat from the shell. The meat was
boiled at 100 °C for 20 min and then washed under run-
ning tap water to remove the slime. The boiled snail
meat was sun-dried for 72 hours, ground in a hammer
mill and labelled snail meat meal (SMM). For this study
a total of 227 kg of fresh snails were collected that gave
about 45kg of snail meal, representing a yield of 18 %.
Snail meal and fish meal were analysed for proximate
composition (Table 1) and used for diet formulation.
2.2 Experimental diets
Four layer diets containing 16.5 % crude protein each
were formulated for the experiment (Table 2). Diet 1
(control diet) was based on copra meal and fish meal
as protein sources. Snail meal replaced the fish meal
portion at 33, 67, and 100% in diets 2, 3, and 4, respec-
tively. All the diets were supplemented with lysine and
methionine to compensate for the deficiencies of these
amino acids in copra meal and fortified with vitamins
and mineral premixes to meet the requirements of lay-
ing hens (NRC, 1994).
2.3 Experimental protocol, birds and management
The research was approved by the University of the
South Pacific’s research committeeand birds were man-
aged in compliance with the University’s research ethics
guidelines for animal welfare. A total of 120 Shaver
Brown pullets aged 18 weeks were weighed individu-
ally and allotted to 12 floor pens (2×3m) with the floor
covered with wood shaving as litter material. A trough
feeder and a bell shaped drinker were provided in each
pen. Each of the 4 diets was fed as mash to birds in 3
selected pens in a completely randomised design for a
period of 12 weeks. The diets and drinking water were
supplied ad-libitum throughout the experimental period.
The lighting programme was limited to 13 hours day
light.
Table 1: Analysed composition and calculated ME content of fish and snail meals.
Constituents (g/100g)
Dry matter Crude protein Crude fat Crude fibre Total ash ME*(kcal/kg)
Fish meal 92.1 57.9 4.0 1.3 10.9 3,170
Snail meal 94.4 53.5 0.8 5.9 22.4 2,465
*Metabolisable energy calculated according to Fisher & Boorman (1986)

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87
Table 2: Ingredient composition and calculated analysis of the experimental diets.
Ingredients (g/kg) Replacement level ofSMM for fish meal (%)
0 33 67 100
Maize 668.5 668.5 668.5 668.5
Copra meal 173.8 173.8 173.8 73.8
Fish meal 86.2 57.75 28.45 0
SMM 0.00 28.45 57.75 86.2
Limestone flour 62.0 62.0 62.0 62.0
Lysine 2.0 2.0 2.0 2.0
Methionine 1.5 1.5 1.5 1.5
Vitamin-mineral premix*2.5 2.5 2.5 2.5
Salt 3.0 3.0 3.0 3.0
Calculated analysis (g/100g)
Crude protein 16.51 16.48 16.47 16.47
Calcium 39.50 39.50 40.00 41.00
Totalphosphorous 9.40 9.43 9.46 9.50
Lysine 0.66 0.64 0.65 0.67
Methionine 0.37 0.37 0.35 0.35
Metabolisable energy (kcal/kg) 2,865 2,851 2,850 2,849
SMM: snail meat meal; * Layer premix supplied/kg: Vitamin A 1.000.000 IU., Vitamin D3
200.000 IU, Vitamin E 1.500 mg, Vitamin K3 200 mg, Vitamin B1 150 mg, Vitamin B2 400 mg,
Vitamin B6 200 mg, Vitamin B12 1.200 mcg, Niacin 2.000 mg, Calcium pantothenate 500 mg,
Biotin 10.000mcg, Folic acid 40.000mcg, Choline chloride 40.000 mg,Vitamin C 2.000mg,
Methionine 30.000 mg, Iron 4.000 mg, Copper 800 mg, Manganese 8.000mg, Zinc 6.000 mg,
Iodine 60.000 mcg, Selenium 15.000mcg, Cobalt 20.000 mcg,Carophyll 2.000 mg, Antioxidant
BHT 10.000 mg
2.4 Data collection
Data were collected on feed consumption, egg pro-
duction and external egg qualities (egg weight and per-
cent shell). A weighed quantity of feed was provided
daily and refusals weighed the next day to account for
quantity consumed. Eggs produced were recorded daily
per pen and mean egg weight taken using a digital
scale. Feed conversion ratio was calculated as unit feed
consumed per unit egg produced. Hen-day production
(HDP) was calculated as:
HDP =eggs produced
hens in the house ×100
Five randomly selectedeggs per pen were weighed fort-
nightly and broken for shell quality measurement. Shell
weight was determined according to the procedures de-
scribed by Kul & Seker (2004) and percent shell calcu-
lated as:
percent shell =dry shell weight
egg weight ×100
On the last day of the experiment five eggs were ran-
domly selected per pen (15 per treatment), boiled for 15
min, peeled, cut transversely into two halves and used
for sensory test at three different locations within the
campus. Four scales (very tasty, tasty, moderate taste,
and poor taste) were used for the test.
Birds in all the pens were weighed individuallyat the
end of the experiment and weight change recorded for
each pen. Mortality was recorded as it occurred.
2.5 Chemical and statistical analyses
Snail meat meal, fish meal and the diets were anal-
ysed for proximate composition in the Central Labora-
tory,USP Alafua Campus, accordingto AOAC (1995).
Performance data (feed consumption, egg production,
egg quality,and weight change) were subjected to anal-
ysis of variance (Steel & Torrie, 1980) using the Statisti-
cal Package for Social Sciences (SPSS Inc., 2013). Sig-
nificant differences were reported at 5 % level of proba-
bility.

88 S. S. Diarra et al. /
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3 Results
3.1 Chemical analysis
Results of proximate composition of fish meal, snail
meal and the experimental diets (Tables 1 and 3) showed
lower protein and fat but higher fibre and total ash in
snail meal compared to fish meal. The proximate com-
position of the diets (Table 3) showed a linear increase
in dietary fibre and a decrease in metabolisable energy
(ME) content with increasing level of replacement of
fish meal with snail meal.
3.2 Laying performance
The performance data of the hens are presented in Ta-
ble 4. Daily feed intake (g/bird) significantly increased
(P<0.05) on the 33 % diet comparedto the 67 % replace-
ment diet. There was no significant dietary effect on
feed intake among the control, 33% and 100 % replace-
ment of fish meal with snail meal diets as well as among
the control, 67% and 100% replacement diets. No di-
etary effects were observed on egg performanceparam-
eters (hen-day production, egg weight, egg mass, feed :
egg, and percent shell). However, feed cost of egg pro-
duction(WST$/kg egg) reduced on the snail meal-based
diets as compared to the control fish meal based diet. A
total of three birds died within the 33 % replacementdiet
groups during the investigation.
The results of the sensory evaluation of eggs (Table 5)
showed no significant dietary effects on consumer pref-
erence for the scales very tasty and moderate taste. Ex-
cept for the scale poor taste which recorded the highest
(P<0.05) value on the 33% replacement diet, the con-
trol fish meal-based diet was not superior to the snail
meal-based diets for any other taste preference scale.
Table 3: Analysed composition and calculated ME content of the experimental diets.
Constituents (g/100g) Replacement level of SMM for fish meal (%)
0 33 67 100
Dry matter 88.30 89.70 89.10 90.14
Crude protein 16.26 16.24 16.19 16.14
Crude fat 7.59 7.54 7.09 7.04
Crude fibre 5.40 5.76 5.83 6.39
Totalash 14.87 15.61 15.10 16.21
Metabolisable energy*(kcal/kg) 2,785 2,772 2,769 2,742
SMM: snail meat meal
* Calculated according to Fisher & Boorman (1986)
Table 4: Performance of laying hens fed graded levels of snail meat meal as replacement for fish meal.
Variables Replacement level of SMM for fish meal (%)
0 33 67 100 SEM P value
Initial weight (g/hen) 1,418.7 1,419.0 1,417.7 1,415.0 7.64 0.981
Final weight (g/hen) 1,851.0 1,786.0 1,839.0 1,806.0 17.98 0.112
Daily feed intake (g/hen) 79.56ab 81.14 a77.37b79.33 ab 1.05 0.016
Hen-day production (%) 38.06 44.36 41.31 43.00 2.82 0.478
Mean egg weight (g) 53.03 53.45 51.15 52.40 1.10 0.514
Egg mass (kg) 16.97 19.91 17.73 18.93 1.28 0.430
Feed : egg 3.97 3.56 3.77 3.54 0.30 0.740
Feed cost of production (WST$/kg eggs) 4.29a3.06b3.13 b2.83 b0.26 0.019
Percent shell 10.51 10.69 10.67 10.88 0.24 0.752
Mortality (%) 0 10 0 0 NA
a,b: means within the row bearing different superscripts are significantly different (P<0.05);
SMM: snail meat meal; SEM: standard error of the mean; WST$: Western Samoan Dollar (WST$1 =US$ 0.424 @ period of experiment).

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89
Table 5: Sensory evaluation of eggs from hens fed graded levels of snail meal as replacement for fish meal.
Taste preference scale (%) Replacement level of SMM for fish meal (%)
0 33 67 100 SEM P value
Very tasty 25.60 22.89 26.67 24.84 1.56 0.482
Tasty 24.00 ab 22.11 b25.89 ab 28.00 a1.34 0.013
Moderate taste 25.00 26.00 25.00 24.00 1.16 0.693
Poor taste 25.40 b29.00 a22.44 c23.16 bc 0.88 0.001
a,b,c: means within the row bearing different superscripts are significantly different (P<0.05);
SMM: snail meat meal; SEM: standard error of the mean
4 Discussion
4.1 Chemical analysis
The ash content of the snail meat used in the present
study compares favourably with the 22.7% reported in
Achatina fulica meal by Diomandé et al. (2008). The
protein and fat contents (62.4% and 4.30 % respec-
tively) observed by these authors are however higher
than our values. As snails are mainly foragers, the
species of foraging materials available will greatly in-
fluence their body composition. The effect of the en-
vironment in which the snail lives on its body compo-
sition has earlier been reported by Gomot (1998). As
older animals forage more efficiently than younger ones,
the age of the snail may also be a factor of variation in
body composition. Dietary protein levels met the re-
quirements of brown egg laying hens (NRC, 1994; ISA,
2005). The decrease in dietary ME observed with in-
creasing level of snail meal was a result of differences
in ME content between fish and snail meals. Despite
this linear decrease with increasing level of SMM, the
ME content of all the diets was comparable to the 2,800
kcal/kg recommended for the breed (NRC, 1994; ISA,
2005).
4.2 Laying performance
Birds normally consume feed to meet their energy re-
quirement. The reason for the decreased intake on the
67% compared to the 33% diet despite the steady de-
crease in ME content was not understood. The pattern
of feed intake in the present study did not support the
finding of Venugopalan et al. (1976) that feed intake of
broiler chicks increased on diets based on snail meal
compared to fish meal. The body of foraging snails is
known to contain different anti-nutrients associated with
the foraging substrates (Ravindran& Blair, 1993; Chuk-
wuka et al., 2013). Differences in feed processing meth-
ods and temperatures during processing might influence
feed intake pattern of poultry fed snail meal.
In the present study,100 % replacement or 8.62% di-
etary snail meal did not affect performance compared
to the control fish meal-based diet. This is in agree-
ment with an earlier report by Serra (1997) that 10%
cooked dietary snail (Pomacea insularis) meal did not
affect performance of laying hens. However, feeding up
to 12% dietary cooked snail (Pila leopoldvillensis) did
reduce feed consumption but without adversely affect-
ing weight gain in broilers grown to 28 days (Barceló
& Barceló, 1991). All mortalities recorded in the group
fed 33% replacement were the result of bleeding and
pecking of cloacae following the laying of very large
eggs.
Fish meal used for the experiment was imported form
Fiji at the cost of WST$ 6.00 per kg dry matter. The
cost of snail meal was estimated from collection and
processing to be WST$ 1.42 per kg dry matter. This
price difference of WST$ 4.58 between the two ingredi-
ents resulted in reduced feed costs of egg production on
the snail meal-based diets compared to the control.
Based on the results it is concluded that a complete re-
placement of dietary fish meal with Giant African snail
meal has no adverse effects on egg production, egg qual-
ity and egg taste. This substitution is not only beneficial
in terms of reducing cost of egg production but the man-
ual collection and processing of snail can also become
a source of local income. In this way snails can be con-
trolled to some extent and crop damage reduced. Fur-
ther research into snail meal processing methods with
the goal to improve its utilisation by poultry should be
considered.
Acknowledgements
The study was funded by the research office of the
University of the South Pacific (6D303-111-Acct-00).
Undergraduate students in agriculture (Rasch Isabell,
Oikali Selina, and Taro Lenior)were very helpful during
data collection.

90 S. S. Diarra et al. /
J. Agr. Rural Develop. Trop. Subtrop. 116 -1 (2015) 85–90
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