Assessment of Growth Rate of Juvenile African Giant Land Snail, Archachatina marginate, Under Three Feeding Treatments

This study assessed the growth rate of snailets of A. marginata under three feed treatment. Ninety snailets divided into thirty snailets per treatment were used for the study. Data collected include Shell Length, Shell Width, Aperture Length and Weight gained. The results indicate that Treatment C (TC) had the highest value for all the growth parameters assessed, while Treatment A (TA) had the least values. The mean Weight gained varied between 16.01±1.92g (TC) and 12.55±0.90g (TA) and was significantly different between the treatments (p<0.01), mean length and shell width varied between TA (4.24±0.40, 6.50±0.40) and TC (4.48±0.13, 6.92±0.30) and were not significantly different (p<0.05). The mean mouth aperture of A. marginata fed with TC (4.90±0.19) was greater than and significantly different form TA (4.35±0.30) and TB (4.58±0.28) at p<0.05. These findings indicate that local farmers who feed their snailets with only vegetable leaves and fruits obtained locally could obtain mature snails with good weight and shell growth even without combination with any other feed material.

In Nigeria and in some West African countries including Ghana, studies have been conducted on the performance of A. marginata on compounded rations in with a view to providing steady snail food supply especially during the dry season for consistent snail farming as well as providing rations for optimal snail growth (Awesu, 1980;Ogogo, 1989;Akinnusi, 2004;Ogogo, 2004;Ukpong et al., 2013;Nyameasem and Borketey-La, 2014). Production of A. marginata can be sustainable and economical when both qualitative and quantitative feed requirements are known and established. This could be made possible by formulating and preparing of nutritionally balanced and least-cost diets for the snails using locally available ingredients. This study therefore aims at evaluating the growth performance of A. marginata hatchlings fed with three different feed materials with a view of making adequate recommendation to farmers to ensure maximization of profit in their business.

Study Area
The experiment was carried out in the Snailery Unit of the Department of Forest and Wildlife. University of Uyo Annex, Town Campus, Uyo. Uyo is located on Latitude; 4° 58 -5° 05'N. Longitude 7°45' -8° 00E in Akwa Ibom State, Nigeria with a mean temperature of 29°C, mean rainfall of 3000 mm and a mean relative humidity of 75%. The state is located in the rainforest agro-ecological zone and covers an area of 15,750  (Ukpong et al., 2013).
Procurement and stocking of samples ninety sample juvenile snails from the snail unit of Akwa Ibom State Agricultural Development Programme (AKADEP), Mbiaobong Etoi, Uyo, Akwa Ibom State and stocked in a concrete pen measuring 2.8 m x 1.5 m x 1 m (length x width x depth). The floor of the pen was filled with sterilized loamy soil collected from the departmental arboretum and the top of the pen was covered with net and mesh wire. They snails were allowed acclimatization period of two weeks. The average temperature, relative humidity and photoperiod during the experimental period (March to June, 2012) ranged from 26°C to 31°C, 50% to 70% and 12 to 18 h respectively.

Feed Treatment
Ninety (90) five weeks old snailets obtained from AKADEP were divided into three sets of twenty (30) snailets each and subjected to three different feed treatments (A, B and C) using completely randomized design with three replications. Each snailet was marked using car paint for identification. Individual snails in T A were indicated using Roman numerals, while T B where indicated using alphabet are T C where indicated by number.
The feed treatment in T A comprised vegetable leaves, fruits, poultry residue, corn mill and soybean residue. T B comprised corn mill, soybean, fruits and vegetable leaves, while T C was made of vegetable leaves and fruits only (control).

Data Collection
Data were collected on the early growth rate of the snails fortnightly for four months. The parameters assessed were; weights of snail, length, width and aperture of each snail. The body weights were measured using electronic weighing balance in grams, Shell length was measured along the axis of the snails using the measuring tape to the nearest centimeter, shell width was measured around the largest position of the shell using also the measuring tape to the nearest centimeter and aperture was measured through the opening apex using also the measuring tape to the nearest centimeter.

Data Analysis
Data collected were subjected to analysis of variance (ANOVA) and means separated using least significant difference (LSD) as outlined by Steel and Torrie (1980) and Ukpong et al. (2013) at 5% probability level.

Results and Discussion Mean weight gain for the sample Snails
The results of growth morphology of the juvenile snailets are shown in Table 1. The result indicates that the mean weight gained by each of snailets where significantly different (p>0.05) for each treatment. Moreover, there was significant difference between the means weight gained. Snailets fed with T C had the highest weight gain (16.01±1.92 g), followed by T B (14.45±1.20 g), while snailets fed with T A had the least weight gain (12.55±0.90). The above mean weight obtained for the feed treatments are higher than those obtained by Ukpong et al. (2013), implying that the present feed gives a better growth rate in terms of weight gained than those used by Ukpong et al. (2013) whose feed treatments indicated a mean weight gain of between 5.86 g and 8.58 g. Also, a correlation of the weight gained and age showed all the three treatments had positive correlation. T C had the highest correlation coefficient of 0.946 7 and T A had the least coefficient of 0.654 2 (Figure 1). The above results indicate the weight gained and shell growth rate were significantly higher for snailets treatment C and lower for treatment A. This could be attributed to the level of nutrients in the feed diets (Nyameasem and Borketey-La, 2014). The higher performance of snailets fed with T C implies the diet contained the essential nutrient and energy levels and met the snailets optimum requirement for growth (Radrizzani, 1992;Bright, 1996). Nyameasem and Borketey-La (2014) and Ani et al. (2013) observed that decrease in dietary protein below 18% resulted in reduced performance in snails. However, Sang-Min and Tae-Jun (2005), Omole et al. (2000) and Hodasi (1979) reported that a diet containing between 22% to 28% and 2 200 Kcal/kgME -3.3 Mcal/kgME was optimal for snail growth. The energy content of the compounded diets in the present study could be said to compare favorably with above values. Table 1 also indicates the growth response of the snailets to the varying feed treatment. The mean shell length varied between 4.24±0.40cm in T A , treatment B (4.29±0.30) to 4.48±0.13 cm in treatment C, although they were not significantly different from each other (p>0.05). The same trend was followed by the mean shell width as it from 6.50±0.60cm in T A to 6.52±0.95 cm in T B and 6.92±0.30 cm in T C (p<0.05). There was significant difference between the feed treatments with regards to mean mouth aperture growth (p>0.05). Snailets feed with T C had the highest mean mouth aperture (4.90±0.19) against 4.58±0.28 observed in T B and T A gave the least mouth aperture growth of 4.35±0.30.

Shell growth rate of the sample snailetss
The higher shell length, width and aperture increments observed among snailets fed with T C over T B and T A ( Table 2, 3 and 4) could also be attributed to the growth performance of the diet which had a high correlation between weight gained (-0.7212), shell width (0.965 6) and mouth aperture (0.958 0). A positive correlation between weight gained, shell length, and shell width has been established growing snails (Odunaiya and Akinnusi, 2008;Ani et al., 2013). The fortnightly range of increment of shell length and width (4.24 to 4.48 and 6.50 to 6.92 mm, respectively) obtained in the present study compares favorably with the values (17.0 to 19.8 and 11.9 to 13.2 mm) reported by Nyameasem and Borketey-La (2014) and above the values (8.77 to 11.4 and 3.67 to 6.60 mm) reported by Omole et al. (2004) for growing snails. Also, the shell mouth aperture for T C had a correlation with weight gained (-838 1), shell length (0.958 9) and shell width (0.980 8) in Table 4 than T A (Table 2) and T B (Table 3). The mouth aperture values compared favorably with the values (4.69±0.11 -5.07±0.19 cm) obtained by Aluko et al. (2014). The variant in values of measured parameters between the authors and the present study could be attributed to factors such as differences in age of snail, species, management as well as environment.

Conclusion
The growth rate of juvenile snails can be enhanced by the combination of fruits and vegetables, in the absence of corn and soybeans residues as feed ingredient. This will have no adverse effect on the snail growth rate as the combination of fruits and vegetables still contain an appreciable amount of vital ingredients needed by the snailets for growth.