Protein and Energy Requirements of African Giant Land Snail (Achatina Achatina)
Chapter One
OBJECTIVES
The specific objectives of the study are as follows:
- To investigate the effects of varying dietary energy and protein levels on growth performance of giant land snails.
- To determine the optimum protein and energy levels that will support optimum/normal growth in giant land snails.
- To determine the effects of varying dietary protein and energy levels on carcass yield and organ characteristics of the giant land snails
- To determine the cost of feeding African giant land snail with diets containing varying protein and energy levels.
CHAPTER TWO
LITERATURE REVIEW
In spite of the apparent value of the snail in human diet, not much significant effort has so far been made at large scale production of this “micro livestock” as with other livestock such as cattle, sheep, goats, poultry etc. The main source of supply to the numerous consumers is from people who gather wild snails from nearby bushes and sell along roadside and in the local markets. It is necessary to note that these sellers bring various sizes directly from the bush to the market for sale. With the trend, the possibility of the snails going into extinction may not be far fetched.
However, FAO (1986) encouraged raising one’s own snails, a practice referred to as “snail farming”. The advantage of this being that one will always have a supply of fresh snail meat whenever this is desired and one can sell the excess to neighbours and in the market. For several years, snails have been well known and highly appreciated as a source of protein in many countries. As far back as 1911, snails have been an important item of food in France. By 1970, it was estimated that Paris alone consumed up wards of 100m (million) snails annually. Attempts to introduce snails to United States initially met with stiff opposition even from the government, because snails were seen more as a nuisance than a blessing. They were considered to be serious pests of plant (Dees, 1970). However, with time, the establishment of snail farms was allowed only after the agricultural officials had been consulted. It is also known that the Romans kept snails caught in the wild and fed them with special herbs to improve the taste of snail meat and ensure their availability (Elmslie, 1982).
In many areas in Africa, snails are treasured as a traditional source of protein. In Nigeria, snails constitute an important component of the food of numerous rural dwellers especially in the rain forest belt as well as other areas of the country where snail eating is not regarded as a taboo.
CHAPTER THREE
MATERIALS AND METHODS
LOCATION OF STUDY
The study was conducted at the Snailry Unit of the Department of Animal Science, Teaching and Research Farm, behind Animal Science Analytical Laboratory University of Nigeria, Nsukka.
MATERIALS AND DURATION OF STUDY
Feed Ingredients and Their Sources
Soybean meal, groundnut cake, palm kernel cake and fish meal were main protein sources used to formulate the experimental diets. The other feed ingredients were maize, cassava, wheat offal, palm oil, bone meal, oyster shell and vitamin premix. All the feed ingredients except cassava and palm oil were purchased from Kings Size feed mill at Carmelite Road Onuiyi Nsukka. The cassava and palm oil were bought at Orba and Nsukka main markets respectively.
CHAPTER FOUR
RESULTS
Table 5 shows the proximate composition of the experimental diets; while the performance of snails fed the experimental diets is shown in Table 6.
Body weight gain
There were significant differences (P<0.0.5) among treatments in average daily weight gain. Snails on treatment 16 (24 % CP and 3.2Mcal/Kg ME diet) had significantly (P<0.05) higher daily weight gain than snails on all other treatments. The least body weight gain was observed in snails on treatment 13 (18% CP and 3.2 Mcal/Kg ME diet). There was also a significant (P<0.05) interaction between the protein and energy levels on the average daily weight gain of the snails. Body weight gain was significantly enhanced (P<0.05) at the highest energy and crude protein levels (24% CP and 3.2 Mcal/kg ME).
CHAPTER FIVE
DISCUSSION
As shown in Table 6, body weight gain, feed intake, the efficiency of feed conversion and protein efficiency ratio were significantly increased at the 24%CP and 3.2Mcal/Kg metabolizable energy levels (treatment 16). This could be attributed to the synergistic effect of the levels of protein and energy on performance. Sunde (1955) and Jackson et al.(1982) had earlier reported the importance of calorie to protein ratio in the diets of animals, precisely broiler birds. According to these authors, high protein-low energy diet caused reduction in growth rate , whereas O’ Neil et al.(1968) showed that excess energy in relation to protein depressed feed efficiency. Similarly, Jackson et al. (1982a) showed that body weight and feed efficiency were improved with higher amount of dietary protein and energy indicating the importance of balanced calorie- protein ratio. Snails are also known to utilize high energy and protein foods for good weight gain and optimum production (Hodasi, 1982). The higher performance observed in snails fed the 24%CP and 3.2Mcal/kgME diet was not surprising, therefore, since this diet contained the highest protein and energy levels and this would have met the snails’ optimal requirement for growth. Moreover, the snails could have utilized the available protein very efficiently for enhanced growth performance. A similar report had been documented (Adegbola and Akinwande, 1981). Considering the superior performance of the snails fed the 24%CP and 3.2Mcal/kgME diet, it does appear therefore, that the 24%CP and 3.2Mcal/kgME diet produced a better energy: protein ratio. This suggestion corroborates earlier report by Jackson et al. (1982a). Although feeding snails with diets containing 22. 60%CP and 23% CP had resulted in increased growth rate (Radrizzani, 1992; Bright, 1996), decreasing the crude protein level to 18% as in the present study led to reduction in performance. The implication of the present observation is that growing snails require more than 18% dietary protein and 3.0 Mcal/kg ME for optimum performance. The result obtained in the present study contradicts the report of Sang-Min and Tae- Jun (2005) that a diet containing 22% and 3.3kcal/g diet was optimal for snail growth. The result also contradicts the reports of Hodasi (1979) and Omole (2001a) that diets containing 28% CP and 2200Kcal/kgMe were optimal for the growth of snail. Observation also revealed that the average shell length and width of snails which consumed the diet containing 24%CP and 3.2Mcal/kgME were superior to the average shell length and width of snails which consumed other diets. This could be attributed to the enhanced growth performance of snails that consumed the 24%CP and 3.2Mcal/kgME diet. Perhaps there is a positive correlation between live weight gain, shell length gain, and shell width gain. Odunaiya and Akinnusi (2008) had earlier reported the positive correlation between live weight gain (g/day), shell length gain (cm/day) and shell width gain (cm/day) of growing snails. The shell has been found to account for as much as 26% of the body weight (Ajayi et al; 1978). However, the highest average shell length and width (2.19cm and 1.64cm, respectively) obtained in this study compare favourably with the shell length (2.92cm) and shell width (2.48cm) reported by Adu et al. (2002) for growing snails fed 24.91% dietary protein. However the values differ from the shell length (5.85cm) and shell width (4.38cm) reported by Oluokun et al. (2005) for snails fed 24.2 % CP diet. The significant interactions between the protein and energy levels on average daily weight gain, average daily feed intake, feed conversion ratio(FCR) and protein efficiency ratio (PER) had marked effects on these performance parameters. The significant interactions contributed enormously to the enhancement of the body weight gain at the 24% CP and 3.2 Mcal/kg ME levels. The enhancement observed in body weight gain corroborates earlier report (Donaldson et al., 1956; Jackson et al., 1982) that maximum growth among flocks is realistic at high dietary energy and protein levels. While daily feed intake was significantly decreased at the 3.0 Mcal/kg ME and 18 %CP levels, and at the 3.2 Mcal/kg ME 18% CP and levels, it increased at the24% CP and 3.2 Mcal/kg ME levels. Feed conversion ratio was also enhanced at the 3.0 Mcal/kg ME and 24 %CP levels, and at the 3.2 Mcal/kg ME and 24% CP levels. Protein efficiency ratio was significantly enhanced at the 24 %CP and 2.80 Mcal/kg, 3.0 Mcal/kg and 3.2 Mcal/kg ME levels. Shell length was significantly enhanced at the 3.0 Mcal/kg ME and 22 % CP and at the 24% CP and 3.2 Mcal/kg ME levels, while shell width was significantly enhanced at the 3.0 Mcal/kg ME and 24 % CP levels, and at the 24% CP and 3.2 Mcal/kg ME levels. The observed effects of energy and protein levels on feed intake, FCR and PER in the present study support earlier reports(Hill and Dansky,1954; Elliot., 2002) that when the protein level of the diet is increased in relation to the energy, there is increase in feed consumption thereby resulting in better efficiency of feed conversion. On the other hand, an excess of energy over that of protein in the diet depressed feed consumption and eventually results in the deficiency of protein, amino acids, minerals and vitamins.
Summary, Conclusion and Recommendation:
The results of the experiment have shown the relative effectiveness of different protein and energy combinations in promoting the growth of African giant land snail (Achatina achatina). It was observed that the growth performance of the snails in terms of body weight gain, shell length and shell width differed significantly (P<0.05) among the treatments. However, snails fed diet containing 24% CP and 3.2Mcal/kgME dietary energy levels had better growth performance than others. There were also significant (P<0.05) differences among treatments in feed intake, feed conversion ratio, protein efficiency ratio, edible weight, average shell weight and average visceral weight. The diet containing 24% CP and 3.2Mcal /kg ME supported higher growth rate, feed intake and produced better feed conversion ratio and protein efficiency ratio, higher edible weight, shell weight and visceral weight than other diets. This tends to suggest that 24% CP and 3.2 Mcal/kg ME may be the optimum crude protein and energy requirement of A. achatina for normal growth.
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