Comparative utilization of Centrosema pubescens or Mucuna purensis as a substitute for pawpaw leaf by growing snails

A J Omole, A M Ogungbesan*, J A Fayenuwo and Y A Popoola

Obafemi Awolowo University, Ile Ife, Nigeria
Institute Of Agricultural Research and Training Moor Plantation, Ibadan, Nigeria
omoleboye@yahoo.com
* Olabisi Onabanjo university, Ago- Iwoye, Nigeria.

Abstract

The effect of feeding growing snails (Archachatina marginata) on Centrosema pubescens or Mucuna purensis as a substitute for pawpaw leaf on growth and carcass analysis were carried out. Ninety-six (96) growing snails were used for the trial. The snails were randomly allotted into 3 different groups (G₁ – G₃). Each group was replicated four times with 8 snails per replicate in a completely randomized design. The snails in Group 1  were fed pawpaw leaves (PL) while snails in Group 2 and Group 3 were fed Mucuna purensis (MP) and Centrosema pubescens (CP) solely respectively. Parameters measured or calculated include weight gain, feed intake, feed conversion ratio and dressing percentage.

The results showed that the highest total feed intake of 665g was obtained in   snails fed CP while significant differences were not observed in the snails fed PL and MP. The highest weight gain of 147g was recorded in snails fed CP which was significantly higher than those snail fed PL and MP (P<0.05). The mean shell length, shell thickness and width increments were not significantly influenced by the treatment effect (P>0.05)   The dressing percentage was relatively similar in all the treatments, the values range between 39.5 and 40.5% (P>0.05). Centrosema pubescens and Mucuna purensis compared favourably with the control feed (pawpaw leaf) hence any of the two leguminous plants could be given to snails for feed or use as alternative feed resource for snail.

Keywords: Carcass, dressing percentage, feed utilization, growth, meat, shell

Introduction

Snails have been well known and highly appreciated by African and Nigerian consumers in particular for the tasty and delicious nature of the meat (Ejide 2008; Malik and Dikko 2009). The meat contains 18 – 19% crude protein and the calcium content is high (Bright  1996 ; Amusan  and Omidiji  1998). The low cholesterol level and high iron content of the meat make it good antidote for fat related diseases (Bright  1996). In Nigeria pawpaw leaf is the common feed given to snails of all ages. Cutting of pawpaw leaf by the farmer has affected the pawpaw plant adversely and always lead to rifts between snail and pawpaw farmers in case the snail farmer has no pawpaw plantation of his own. There is need to look for another leaf that is well appreciated by snails. A lot of works have been done on the use of Centrosema pubescens or Mucuna purensis to feed ruminants such as sheep, goat and cattle without any adverse effect. There is no information as of present on the use of the leaves of these leguminous plants to feed snails. This study was designed to determine the effect of feeding growing snails (Archachatina marginata)  on Centrosema pubescens or Mucuna purensis as a substitute for pawpaw leaf on growth and carcass analysis and sensory evaluation.

Materials and methods

The experiment was carried out at the Snail Unit of the Institute of Agricultural Research and Training (I.A.R.& T.), Moor Plantation, Ibadan, which is located on Longitude 03°51E, Latitude 07°23N and Altitude 650” lies in the humid zone of the rainforest belt 0703.25 of Southwestern Nigeria with mean annual rainfall of 1,220 mm and mean temperature of 26°C. The snails were reared under intensive system of production using cages demarcated into 12 compartments and each compartment had dimension of 0.4x0.4x0.5cm³.  The cages were put inside open sided houses covered on all sides with wire netting. The top of the house was roofed with adex asbestos roofing sheets and the floor was concreted. Trees were planted around the house which made the environment cool (FAO 1986; Cobbinah 1993). The cage used for the experiment  was built of wood and wire netting. The bottoms of the cages were perforated to allow free drain of water when wetting the soil. The top was built of mosquito netting reinforced with wire mesh.

The stands of each cage were put inside a container filled with used engine oil to prevent soldier ant infestation. Sandy loam soil was collected from the Southern Farm of the Institute and used as bedding for the snails inside the cages.  A total number of ninety-six (96) growing snails were carefully selected and purchased from a snail farm in Ibadan, Oyo State. The snails were randomly allotted into 3 different groups (G₁ – G₃). Each group was replicated four times with 8 snails per replicate in a completely randomized design. The snails in Group A (PL) were fed pawpaw leaves while snails in Group B (MP) and Group C (CP) were fed Mucuna purensis and  Centrosema pubescens respectively. Feed intake and weight gain were  measured daily and weekly with the use of electric weighing balance. Shell length and width were measured on weekly basis with the use of vernier caliper while shell thickness was measured every week with micrometer screw gauge. Feed conversion ratio was calculated as the ratio of feed intake to weight gain. Twelve snails from each treatment were randomly selected at the end of the feeding trial for carcass analysis. The snails were starved over-night and killed with Iron rod. The shell, foot and offals were then   separated and weighed separately. The cooked feet (edible portion) were placed in different plates based on the treatments and served to panelists. The panelists were trained prior to the serving of the meat for evaluation. The panelists were served with clean drinkable water for rinsing their mouths after tasting each treatment of the meat. Twenty copies of questionnaires were given to the panelists for rating the sample according to the method of Larmond (1977). The rating were 1, 2, 3, 4, 5, 6, 7, 8 and 9 which correspond to Like extremely, Like very much, Like moderately, Like slightly, Neither like nor dislike, Dislike slightly, Dislike moderately, Dislike very much, and Dislike extremely, respectively. The meat was rated for colour, taste, flavour, texture and general acceptability. The chemical composition of the forages and the meat were done according to the Method of AOAC (1990). All data were subjected to Analysis of Variance and the means was separated by Duncan Multiple Range Test (SAS 1999).

Results and discussion

The chemical composition of the experimental feeds is shown in table, Centrosema pubescens had the highest crude protein content and lowest crude fibre content (Table 1). 

The highest feed intake was obtained in CP (Table 2), which could be due to succulency nature of Centrosema pubescens as it has been reported that snail prefers feed that are succulent in nature and this is due to the fact that the teeth of snail otherwise called radulla are delicate in nature (Amusan and Omidiji 1998). Moreover, it has been established that the feed consumption increases with increased protein level. (Mcdonald et al 1987; Bright 1996). The mean total weight gain followed the same trend with the feed intake (Table 2).  It has been reported that there is positive correlation between the feed intake and the weight gain (Cobbinah 1993; Omole et al 2008). The weight gain reported in CP compared favourably with the observation of Aribisala (1998). The feed conversion ratio did not differ among treatments, which implies that snails could be fed with any of the 2 leguminous leaves. 

The values varied between 4.02 and 4.07 mm. Again significant differences were not observed (P>0.05) in the mean monthly shell width increment as observed in Table 2. The values were 1.87, 1.91 and 1.93 mm in PL, MP and CP respectively. The mean monthly shell thickness was not significantly influenced by the treatment effect (P>0.05) as shown in Table 2. The non-significance in the shell growth in all the treatment could be as a result of relatively the same ash content in the feed. The shell of snail is made of calcium which is present in the Ash (Hamzat 2004; Omole et al 2008). Zero mortality was recorded in all the treatments as shown in Table 2. The zero mortality recorded could be due to proper management practices adhered to during the course of the feeding trial. Again it could be due to ‘hardy’ nature of snail. This observation is in line with the report of (FAO 1986; Amusan and Omidiji 1998) that the snail is ‘hardy’ in nature and can tolerate adverse environmental condition better than other livestock. The zero mortality recorded could also be due to saved nature of the test feeds.  The results of carcass analysis and sensory evaluation are presented in Tables 3 and 4 respectively.

The dressing percentage which is the ratio of the foot (edible portion) to the live weight was relatively similar in all the treatments; the values range between 39.49 and 40.5% (P>0.05).   

The dressing percentage observed in this study compared favourably with the report of (Aribisala 1998 and Odukoya 1998). The mean shell to live weight and offal to live weight were not significantly different from one another (P>0.05). No significant differences were observed in the colour, taste, flavour, texture and general acceptability of the snails fed different leguminous plant and this implies that any of the plants could be used as feed resource for the snails

Conclusion

• In conclusion, Centrosema pubescens and Mucuna purensis compared favourably with the control trial (pawpaw leaf) in all parameters measured or calculated hence any of the two leguminous plants could be given to snails for feed or use alternative feed resources for snail.

References

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Received 8 July 2010; Accepted 13 July 2010; Published 6 March 2011

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