Effects of feeding adult snails Stylosanthes guianensis or Lablab purpureus as substitute for pawpaw leaf

The feeding trial assessed the performance, carcass and sensory evaluation of adult snails fed solely on leaves of Stylosanthes guianensis or Lablab purpureus as substitute for pawpaw leaf. Ninety-six (96) adult snails were used for the trial, and they were shared into three groups. Each group was replicated four times with 8 snails per replicate in a completely randomized design. Parameters measured include weight gain, feed intake and feed conversion ratio, while dressing percent were calculated. The sensory evaluation was also carried out. The results show that snails fed S. guianensis performed better in terms of weight gain and feed intake and compared competitively with snail fed pawpaw leaf (P>0.05). The dressing percent, shell thickness, length and width, taste and general acceptability were not affected by the dietary treatments. Snail farmers are encouraged to cultivate S. guianensis to feed snails which can be used to substitute pawpaw leaf.


INTRODUCTION
Snails have been well known and highly appreciated by Africans and Nigerians in particular for the tasty and delicious nature of the meat (Akegbejo and Akinnusi, 2000).The meat contains 18 -19% crude protein and the calcium content is high (Awah, 1992;Bright 1996;Amusan and Omidiji, 1999).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 rift 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.Lablab purpureus and Stylosanthes guanensis are leguminous plant that are high in protein (Gupta and Singh, 1983;Ruis and Lukewarm, 1998;Yi, 2000).A lot of works have been done on the use of L. purpureus and S. guianensis to feed ruminant such as sheep, goat and cattle without any adverse effect.No information as at present on the use of *Corresponding author.E-mail: omoleboye@yahoo.com.the leaves of these leguminous plants to feed snail.This trial assessed the performance, carcass and sensory evaluation of adult snails fed L. purpureus or S. guianensis as sole feed, compared to conventional pawpaw leaf.

MATERIALS AND METHODS
The experiment was carried out at the Institute of Agricultural Research and Training, Moor Plantation, Ibadan.A total number of ninety-six (96) growing snails of mean weight of 303.67 ± 6.7 g were carefully selected and purchased from a snail farm in Ibadan, Oyo State.The snails were randomly allotted into 3 different groups (GA -GC).Each group was replicated four times with 8 snails per replicate in a complete randomized design.The snails in Group A (GA) were fed S. guanensis while snails in Group B (GB) and Group C (GC) were fed L. purerium and paw paw leaves, respectively.The leaves were cut every fifteen days interval and stored inside refrigerator in order to maintain the freshness of the leaves.The snails were reared in a cage housing type.All management practices were duly observed.The cage has 12 compartments and each compartment had a dimension of 0.25 x 0.25 x 0.5 m 3 .
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 ran- Means with different superscripts along the same row are significantly different (P<0.05).
domly 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 chemical composition of the forages and the meat were done according to the method of A.O. A.C. (1990).All data were subjected to analysis of variance and the means were separated by Duncan Multiple Range Test (SAS, 1997).

RESULTS AND DISCUSSION
The chemical composition of the leaves of stylo (S. guanensis), lab-lab (L.purerium) and pawpaw is shown in Table 1 and their crude protein content were 19.97, 18.18 and 22.53%, respectively.The crude fibre of Lablab is higher than either of stylo and pawpaw leaf.The initial weight of the snails in all the groups were relatively the same, varied between 301.8 and 306.3 g.The mean monthly feed intake of snails in G A and G C was not significantly different from each other but higher than that of G B (P<0.05).The mean monthly weight gain also showed the same trend like that of feed intake.The lowest weight gain of 10.02 (P<0.05) was recorded in snails in G B .The lowest feed intake recorded in G B could be as a result of high fibre content of the diet compared to G A and G C .The lowest weight gain recorded in G B could be due to lowest feed intake coupled with poor utilization of the forage.The weight gain in all the treat-ments was generally low which could be as a result of slow growth nature of snails (Amusan and Omidiji, 1999) and due to the fact that snails used in this experiment were of age (Awah, 1992).It must be noted that snails prefer succulent leaf or forage (Omole and Kehinde, 2005) due to "delicate" nature of the teeth otherwise called "radula".Thus the highest feed intake recorded in G A and G C could also be attributed to succulent nature of stylo and pawpaw leaf compared to Lab-lab (Table 1).The feed conversion ratio was better in G A and G C than G B (P<0.05).It implies that feed was better converted to edible meat in G A and G C .The poor efficiency of feed utilization reported in G B could be due to poor weight gain and high fibre content in the Lab-lab.The shell length, width and thickness were not affected by the feed offered.The mineral content (ash) in all the treatments which is responsible for shell growth and development (Daouda, 1995;Bright, 1996) was relatively the same.
No mortality was recorded during the feeding trial as observed in Table 2.The zero mortality confirmed the safe nature of all leaves of the plant used in the experiment.The proper management practices observed coupled with hardy nature of snail (Cobbinah 1993) could also be attributed to zero mortality recorded.The results of carcass analysis show that the shell, foot and offals weights were affected by the dietary treatments as shown Means with different superscripts along the same row are significantly different (P<0.05).
in Table 3.The dressing percent which is the ratio of the foot (edible portion) to the live weight was not significantly different from one another (P>0.05) in all the treatments.The dressing percent reported in this trial was lower than what was reported by Hamzat et al. (2007) and this could be due to the fact that the snails were fed solely on leaves of plant alone without any supplementation.
The results of sensory evaluation by the panelists show that there were no significant differences in the mean taste, colour, texture and general acceptability of the meat of the snails fed stylo, Lab-lab and pawpaw leaf as observed in Tables 4 and 5.
It could be concluded that snails fed S. guanensis performed better than Lab-lab in terms of feed intake, weight gain and feed conversion ratio although there was no significant differences in the dressing percent, shell thickness, length and width, taste and general acceptability in all the treatments.It is recommended that the farmer should be encouraged to plant S. guanensis for feeding snails rather than cutting pawpaw leaf which is detrimental to pawpaw plant.

Table 1 .
Chemical composition of leaves of L. purpureus, S. guianensis and pawpaw on dry matter basis.

Table 2 .
Summary of performance of adult snails fed experimental diets.

Table 3 .
Carcass analysis of adult snails fed leaves of stylo, lab-lab and pawpaw.

Table 4 .
Sensory evaluation of snail meat fed leaves of stylo, lab-lab and pawpaw.

Table 5 .
Chemical composition of snail meat fed leaves of stylo, lab-lab and pawpaw on dry matter basis.