ABSTRACT
A 16-week study was conducted to investigate the effect of dietary protein and energy levels on the growth performance of African giant land snail (Achatina achatina). Two hundred and forty eight weeks old African giant land snails were used for the study. The snails were randomly divided into 16 groups of 15 snails each. The groups were randomly assigned to 16 diets in a 4 x 4 factorial arrangement involving four levels ((18%, 20%, 22%, and 24%) of protein and four energy levels (2.6, 2.8, 3.0 and 3.2Mcal/kg ME). Each treatment was replicated 3 times with 5 snails per replicate. Results showed that while body weight gain, feed intake, protein efficiency ratio and carcass yield were significantly (P < 0.05) increased at the 24%CP and 3.2Mcal/Kg ME levels, FCR and cost of feed per kg weight gain were decreased(P < 0.05). There were significant (P < 0.05) interactions between protein and energy levels on final body weight, average daily weight gain, average daily feed intake, feed conversion ratio, protein efficiency ratio, shell length, shell width, feed cost per kg weight gain and carcass yield. Feed intake was significantly (P < 0.05) decreased at the 3.0 Mcal/kg ME and 18%CP levels, and at the 3.2 Mcal/kg ME and 18% CP levels; FCR values were decreased(P < 0.05) at the 3.0 Mcal/kg ME and 24 %CP levels, and at the 3.2 Mcal/kg ME and 24% CP levels; PER was enhanced (P < 0.05) at the 24 %CP level and at the 2.80 Mcal/kg, 3.0 Mcal/kg and 3.2 Mcal/kg energy levels; shell length was enhanced (P < 0.05) at the 3.0 Mcal/kg ME and 22% CP levels, and at the 24% CP and 3.2 Mcal/kg ME levels; shell width was enhanced (P < 0.05) at the 3.0 Mcal/kg ME and 24% CP levels, and at the 24% CP and 3.2 Mcal/kg ME levels. Feed cost per kg weight gain was significantly (P < 0.05) reduced at the 24% CP and 3.2 Mcal/kg ME levels. The results obtained in the present study show that the dietary protein and energy levels of 24% and 3.2Mcal/kg ME are adequate for the growth of African giant land snails (Achatina achatina) in the humid tropics.
TABLE OF CONTENTS
Title page – – – – – – – – – i
Certification – – – – – – – – ii
Dedication – – – – – – – – – – iii
Acknowledgement – – – – – – – iv
Table of contents – – – – – – – – vi
List of tables – – – – – – – – vii
List of figures – – – – – – – – viii
Abstract – – – – – – – – – x
CHAPTER ONE: INTRODUCTION – – – –
1.1 Background – – – – – – – – 1
1.2 Statement of Problem – – – – – – 2
1.3 Objectives – – – – – – – – 3
1.4 Justification of the Study – – – – – – 4
CHAPTER TWO: LITERATURE REVIEW – – – – 5
2.1 Classification of the edible land snails – – – 6
2.2 Morphological and anatomical characteristics – – 6
2.3 Common edible land snails of Africa origin – – – 7
2.4 Common edible snails in Europe – – – – 9
2.5 Differences between the three african giant snails – – 10
2.6 Life cycle development of snail – – – – 11
2.7 Reproduction – – – – – – – 12
2.8 Snail rearing – – – – – – – 14
2.9 Selection of breeding stock – – – – – 16
2.10 Feeds and feeding – – – – – – 16
2.11 Problems associated with snail farming – – – 21
2.12 Special behavioural instincts of the snail – – – 23
2.13 Nutritional and economic importance of snails – – 24
2.14 Snails in international market – – – – – 26
CHAPTER THREE: MATERIAL AND METHODS 28
3.1 Location of study – – – – – – – 28
3.2 Materials and Duration of study – – – – 28
3.3 Experimental diets and design – – – – – 29
3.4 Management of Experimental animals – – – 31
3.5 Parameters determined – – – – – – 32
3.6 Proximate and Statistical Analysis – – – – 33
CHAPTER FOUR: RESULTS – – – – – 34
4.1 Body weight – – – – – – – 34
4.2 Feed intake – – – – – – – – 34
4.3 Feed conversion ratio – – – – – – 35
4.4 Protein efficiency ratio – – – – – – 35
4.5 Shell length – – – – – – – – 36
4.6 Shell width – – – – – – – – 36
4.7 Carcass Analysis – – – – – – – 36
4.8 Feed cost – – – – – – – – 41
CHAPTER FIVE: DISCUSSION 43
5.1 Discussion – – – – – – – – 43
5.2 Summary, conclusion and recommendation – – – 48
REFERENCES – – – – – – – – 50
APPENDIX I – – – – – – – – 58
APPENDIX II – – – – – – – – 59
CHAPTER ONE
INTRODUCTION
- BACKGROUND
The importance of protein in the diet of man cannot be over-emphasized. Protein is required for normal growth and repair of the body tissues. It is the principal constituent of the organs of the animals’ body. Protein can be of plant or animal origin. Most plant protein is deficient in one amino acid or the other and may be associated with one anti- nutritional factor or another. Soyabean for instance is a vegetable protein source that contains trypsin inhibitor and is deficient in methionine.
Animal protein is of high biological value and possesses all the essential amino acids in desirable quantities. The sources of animal protein include macro and micro livestock. The macro livestock are the conventional big animals such as sheep, goat, cattle, etc. However, the cost of production of macro livestock in term of housing, feeding, space and disease control is high. Micro livestock are excellent and cheaper sources of animal proteins (Akinnusi, 1998; NRC, 1991). The term micro livestock refers to a group of livestock associated with small body size, moderate nutrition and management (Oji, 2000). It includes snails, rabbits and cane rat, among others.
Snails are invertebrate, shell bearing animals that are passive or inactive during the day, but very active in the night, at dusk or when it rains. They are usually found in cool environment (Segun 1975; FAO, 1986).
Snail meat tastes good and it is also consumer friendly. When eaten, it serves as a special delicacy in the diet. Snail meat is particularly rich in protein (Ajayi et al., 1978). According to Imevbore and Ademosun (1988) indicated that snail meat has a protein content of 88.37 (dry weight, basis) low total fat content (1.64 percent), saturated fatty acids (28.71 percent) and cholesterol content (20.28mg/100g fresh sample). The analysis also showed that snail meat is a rich source of mineral particularly calcium and phosphorous with values of 185.70mg/100g and 61.24mg/100g dry sample respectively. Snail meat is rich in essential amino acids like lysine, leucine, isoleucine and phenylalanine and also high in iron to about 45-50mg/kg (Imeivbore, 1990; Stievenat, 1975).
In West Africa, the common breeds of snail reared are the African giant land snail: Archachatina Marginata, Achatina achatina and Achatina fulica (Awesu, 1980; FAO, 1986 and Akinnusi, 1997). These breeds vary in their adaptability to environment, size at day old, size at maturity, egg size, and growth rate (Amusan and Omidiji, 1999).
The two giant land snails common in Nigeria are Achatina achatina and Archachatina marginata. Achatina achatina has a brown shell with conspicuous zigzag streaks and a narrow apex. The foot (the fleshy part) is grey in colour. Archachatina marginata has a wide bulbous apex and the foot is usually dark brown to black in colour.
According to Amusan and Omidiji (1999) Archatina achatina species has been found to be more difficult to breed in Nigeria they do not eat well and the growth rate is very slow compared to Archachatina marginata species.
- STATEMENT OF PROBLEM
According to Nisbet (1974), Hodasi (1979), Awesu (1980), FAO (1986), Akinnusi (1998), Amusan et al (1998) and Ayodele and Asimalowo (1999), the conventional feeds of snail comprises bread fruit, water leaf, pawpaw leaf, sweet orange, mango fruits, ripe fruits of plantain and banana, pineapple. These feedstuffs are mainly of plant origin, seasonal, perishable, and relatively scarce during the dry season and cannot supply all the nutrients needed for the optimum performance of snail. In commercial production of snail especially in the urban area, it is very difficult to source for these feeds. However, the major causes of slow growth and mortality in snail production may be as a result of improper stocking rate and poor nutrition. To ameliorate the problem of feed shortage, it is pertinent to formulate ration that are balanced in nutrients for optimum performance of snails. Before formulated ration could be compounded, information on nutrient requirement for that particular animal is essential: protein, energy, mineral etc. However, formulated ration is not widely used in snail production. This is because much work has not been done in this area (Omole, 1999). Therefore, there is need for research studies to be conducted on the use of compounded ration for the feeding of snails in order to solve the problem of scarcity of fruit, tubers and leaves during the dry season. Moreover, there are lots of arguments on whether salt (NaCl) should be included in the diet of snails or not. Amusan and Omidiji (1999) recommended that salt should not be included in snail diet. Nevertheless, farmers are supplementing snails’ feeds with compounded ration (Layers, growers, and broiler starter mashes) and these compounded rations contain between 0.2% to 0.5% salt (Arthur, 1975; NRC, 1980).
It has been reported that feed particle size has significant effects on consumption, weight gain and nutrients digestibility (Ohn et al., 1983; Reece et al., 1986). Due to the fact that the teeth of snails (radula) are very tiny and delicate, there is need to determine the feed particle size effects on performance of snails.
- 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.
- JUSTIFICATION OF THE STUDY
The cost of conventional protein food like beef, pork, mutton and chicken has been on the increase in Nigeria due to high cost of production. It is therefore necessary to explore non-conventional sources of animal protein supply. The protein deficiency that is endemic in the developing nations can be reduced through the domestication of micro livestock like snail. Snails are food rich in protein and Iron (Ajayi, et al., 1978).
Snails are noiseless and have potential for very high returns on investments with extremely low level of capital inputs. Besides snailry requires little technical know how or experience.
However, formulated ration is not widely used in snail production. This is because much work has not be done in this area (Omole, 1998); therefore there is need for research studies to be conducted on the use of compounded ration for the feeding of snails in order to solve the problem of scarcity of fruit, tuber and leaves during the dry season. Also, the availability of formulated snail feed will enhance large-scale production of snails thereby making them available all year round. It is anticipated that the use of formulated ration would possibly improve the growth performance of snails.
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