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1.1 Problem statement In recent years, rabbit production has increased considerably in Vietnam because of increasing human consumption. Local rabbits are popularly raised in the Mekong delta due to a good adaptation to the local climate and feeds; however, its productivity is very low. Californian rabbits have been imported into Vietnam to upgrade rabbit production since 1980. In 2000s, rabbit producers in the Mekong delta of Vietnam raised Californian rabbits by feeding locally available feed resources. In initial period, growth and reproductive performances of Californian rabbits were low and unstable. In recent years, Californian rabbits have been adapted to local feeding conditions, thus its productivity has been enhanced. Studies on Californain rabbits was rare, even in the world. In 2000-2012, World Rabbit Science Association published 230 papers including 2 papers research on Pure Californian rabbits, 52 papers for pure New Zealand White rabbits, 35 papers for Californian crossbred rabbits and 141 papers for local rabbits. There were 508 papers that were published in Livestock Research for Rural Development Journal from 1989 to 2016. In which, there was no study on pure Californian rabbits. It had 23 papers for Californian crossbred rabbits, 93 papers for pure New Zealand White rabbits and 392 papers for local rabbits. Shortly, studing on nutritional requirements of pure Californian rabbits has been rarely. It is necessary to study on feed utilization of pure Californin rabbits in local conditions for enhacing rabbit production. Rabbit producers fed natural grasses, wild vegetables and agro-industrial byproducts for both growing and reproductive rabbits. The diets for rabbits usually contain high proportion of fiber and low protein. Protein is needed for growth, reproduction and health of rabbits, and it can be obtained from both plant and animal sources. Protein is an important component for life processes, effects on growth performance, and carcass yield of rabbits. The nutritive value of a protein feed source is determined not only by its amino acid composition, but also by its digestibility of ingested protein. The main factors involved in protein digestibility of rabbits are chemical structure, properties, and accessibility to enzyme activity (McDonald et al., 2010). Rabbits could also utilize more protein resources from microbial activity in caecum by the coprophagy. In recent years, dietary supplementation of protein and amino acids had the major and traditional objective to meet rabbit requirements for production (Carabano et al., 2008). Recent studies in rabbit nutrition have increased the number of criteria included in the nutritional recommendations, especially for fibrous and amino acids components (Gidenne and Fortun, 2003). The most important practical advance was the recommended nutritional needs of growing rabbits for the most frequent limiting amino acids (lysine, methionine and threonine). It is noted that current recommendations are higher for lysine and threonine (Carabano et al., 2008). There is a lot of studies on lysine, methionine and interaction between them on rabbit nutrient requirements, however, researches on interaction between lysine and threonine are rarely. Of all amino acids, lysine is the only one to play a metabolic role almost exclusively to add body protein that is for meat deposition. Lysine is generally related to protein synthesis (Champe and Harvey, 1997). Threonine is an amino acid that is used in the biosynthesis of protein. Threonine also aids in the production of antibodies to strengthen the immune system. Threonine is necessary for creating glycine and serine, two amino acids required to produce collagen, muscle tissue and elastin (Hawwa, 2013). Metabolizable energy (ME) was used by growing rabbits for productive functions as maintenance and growth. Several factors would affect the ME requirement in rabbits including body size, age, gender and breed, vital and productive functions, and feeding environment (De Blas and Wiseman, 2010). Several authors have studied the optimal dietary crude protein, amino acids and metabolizable energy levels for growing rabbits (Carabano et al., 2008) but their studies mainly used commercial pellets for feeding rabbits. Rabbits can be achieved optimum growing performance by supplying a balanced diet of protein, amino acid, fiber and energy. Diet quality has been a major limiting factor of rabbit production in the Mekong Delta of Vietnam, especially Californian rabbit diets. To formulate appropriately rabbit diets, it is necessary to know the nutritional composition of the feedstuffs to be used. However, there is limitary information on the chemical composition of feedstuffs for rabbit diets, especially amino acid components. The researches on suitable protein sources for growing Californian rabbits were not yet implemented. The studies on nutrient requirements, forage feeding and diet digestibility of Californian rabbits under feeding conditions in the Mekong Delta of Vietnam are still limited, especially crude protein levels, lysine and threonine and metabolizable levels in diets. 1.2 Research objectives The objectives of this study were: - To enhance knowledge of the nutritional values of some popular feedstuffs for feeding rabbits in the Mekong Delta of Vietnam. - To identify optimal levels of crude protein in diets for the Californian rabbits - To determine the suitable protein sources in the diets with better uses, growth and benefits of growing Californian rabbits in the Mekong Delta of Vietnam. - To identify optimal levels of lysine and threonine in the Californian rabbit diets - To identify optimal levels of crude protein, lysine and threonine, metabolizable energy in the Californian rabbit diets under feeding conditions in Mekong delta of Vietnam.
CHAPTER I INTRODUCTION 1.1 Problem statement In recent years, rabbit production has increased considerably in Vietnam because of increasing human consumption Local rabbits are popularly raised in the Mekong delta due to a good adaptation to the local climate and feeds; however, its productivity is very low Californian rabbits have been imported into Vietnam to upgrade rabbit production since 1980 In 2000s, rabbit producers in the Mekong delta of Vietnam raised Californian rabbits by feeding locally available feed resources In initial period, growth and reproductive performances of Californian rabbits were low and unstable In recent years, Californian rabbits have been adapted to local feeding conditions, thus its productivity has been enhanced Studies on Californain rabbits was rare, even in the world In 2000-2012, World Rabbit Science Association published 230 papers including papers research on Pure Californian rabbits, 52 papers for pure New Zealand White rabbits, 35 papers for Californian crossbred rabbits and 141 papers for local rabbits There were 508 papers that were published in Livestock Research for Rural Development Journal from 1989 to 2016 In which, there was no study on pure Californian rabbits It had 23 papers for Californian crossbred rabbits, 93 papers for pure New Zealand White rabbits and 392 papers for local rabbits Shortly, studing on nutritional requirements of pure Californian rabbits has been rarely It is necessary to study on feed utilization of pure Californin rabbits in local conditions for enhacing rabbit production Rabbit producers fed natural grasses, wild vegetables and agroindustrial byproducts for both growing and reproductive rabbits The diets for rabbits usually contain high proportion of fiber and low protein Protein is needed for growth, reproduction and health of rabbits, and it can be obtained from both plant and animal sources Protein is an important component for life processes, effects on growth performance, and carcass yield of rabbits The nutritive value of a protein feed source is determined not only by its amino acid composition, but also by its digestibility of ingested protein The main factors involved in protein digestibility of rabbits are chemical structure, properties, and accessibility to enzyme activity (McDonald et al., 2010) Rabbits could also utilize more protein resources from microbial activity in caecum by the coprophagy In recent years, dietary supplementation of protein and amino acids had the major and traditional objective to meet rabbit requirements for production (Carabano et al., 2008) Recent studies in rabbit nutrition have increased the number of criteria included in the nutritional recommendations, especially for fibrous and amino acids components (Gidenne and Fortun, 2003) The most important practical advance was the recommended nutritional needs of growing rabbits for the most frequent limiting amino acids (lysine, methionine and threonine) It is noted that current recommendations are higher for lysine and threonine (Carabano et al., 2008) There is a lot of studies on lysine, methionine and interaction between them on rabbit nutrient requirements, however, researches on interaction between lysine and threonine are rarely Of all amino acids, lysine is the only one to play a metabolic role almost exclusively to add body protein that is for meat deposition Lysine is generally related to protein synthesis (Champe and Harvey, 1997) Threonine is an amino acid that is used in the biosynthesis of protein Threonine also aids in the production of antibodies to strengthen the immune system Threonine is necessary for creating glycine and serine, two amino acids required to produce collagen, muscle tissue and elastin (Hawwa, 2013) Metabolizable energy (ME) was used by growing rabbits for productive functions as maintenance and growth Several factors would affect the ME requirement in rabbits including body size, age, gender and breed, vital and productive functions, and feeding environment (De Blas and Wiseman, 2010) Several authors have studied the optimal dietary crude protein, amino acids and metabolizable energy levels for growing rabbits (Carabano et al., 2008) but their studies mainly used commercial pellets for feeding rabbits Rabbits can be achieved optimum growing performance by supplying a balanced diet of protein, amino acid, fiber and energy Diet quality has been a major limiting factor of rabbit production in the Mekong Delta of Vietnam, especially Californian rabbit diets To formulate appropriately rabbit diets, it is necessary to know the nutritional composition of the feedstuffs to be used However, there is limitary information on the chemical composition of feedstuffs for rabbit diets, especially amino acid components The researches on suitable protein sources for growing Californian rabbits were not yet implemented The studies on nutrient requirements, forage feeding and diet digestibility of Californian rabbits under feeding conditions in the Mekong Delta of Vietnam are still limited, especially crude protein levels, lysine and threonine and metabolizable levels in diets 1.2 Research objectives The objectives of this study were: - To enhance knowledge of the nutritional values of some popular feedstuffs for feeding rabbits in the Mekong Delta of Vietnam - To identify optimal levels of crude protein in diets for the Californian rabbits - To determine the suitable protein sources in the diets with better uses, growth and benefits of growing Californian rabbits in the Mekong Delta of Vietnam - To identify optimal levels of lysine and threonine in the Californian rabbit diets - To identify optimal levels of crude protein, lysine and threonine, metabolizable energy in the Californian rabbit diets under feeding conditions in Mekong delta of Vietnam 1.3 Key findings Key findings of this study were: - Supplying the nutritional values, especially amino acid compostion, of the popular feeds for rabbits in the Mekong Delta of Vietnam - Identifying appropriate protein source in the diets for growing Californian rabbits in the Mekong Delta of Vietnam - Determining optimal levels of crude protein, lysine and threonine, metabolizable energy in the diets for Californian rabbits under feeding conditions in the Mekong delta of Vietnam 1.4 Sciential and practical considerations Sciential consideration This thesis supplies the scientific knowledge about nutrient compositions of some common feedstuffs in the Mekong Delta for feeding Californian rabbits with emphasis to amino acid values Finding a better protein source in rabbit diets in the Mekong Delta of Vietnam is very informative for scientists who study on rabbits This thesis researched on the protein utilization of Californian rabbits by systematic method and found the optimal levels of crude protein, lysine and threonine, metabolizable energy in diets It is profitably scientific information for further studies on Californian rabbits in the Mekong Delta of Vietnam Practical consideration The findings of this study can be applied in the practice for feeding Californian rabbits to enhance productivity and economic returns for rabbit producers in the Mekong Delta of Vietnam CHAPTER II LITERATURE REVIEW 2.1 Californian rabbits-introduction The Californian rabbits is a medium to large domestic animals that is the result of a Himalayan crossbred with a Chinchilla, before making kits to a New Zealand white, developed in Southern California in the early years of the 1920s George West, breeder who are seeking an animal that has good coverage as well as a high quality of meat At the initial time, Californian failed to arouse the interest of American fanciers and it was not until the 1930s when it became popular Today, Californian is one of the most common meat production rabbit in the world (Pets4home, 2010) 2.1.1 History The Californian rabbit was originally developed by George West in Southern California such as meat and feather production animal The country has experienced a boom in rabbit breeding to meet the needs of a hungry population, and Californian was intended to help meet the growing demand for food By putting together a Himalayan and a standard Chinchilla, West was partway to achieve their goals By breeding the New Zealand White, he finally realized his ambition of creating a new rabbit that had great muscle cover and lovely body, silky soft fur (Pets4home, 2010) 2.1.2 Appearance Californian's main color is white with dark brown markings on the nose, tail, feet and ears The average live weight is 3.5 to 4.75 kg for adult Californian rabbit ears is big, which was held up, and is a moderate to largesized animals The coat is silky and soft and white, with a dark brown almost ear, tail, nose and feet This unusual colors make Californian look very similar to its ancestors of the Himalaya The breed is well rounded and compact, with a short neck It is muscular, plump and firm The nose markings continue below the jaw and up towards the eyes, while the leg markings run well up the limbs towards the body and the nails and feet are dark Ears up from base to tip the tail is also a dark chocolate brown (Pets4home, 2010) 2.1.3 Temperament The California is an animal calm, friendly and kind that makes a great pet They can sometimes be sensitive, but with the careful handling and encourages, they can learn to adapt in human conditions It is important to remember though, that is a prey animal, any rabbit can pale and may show fear Any rabbit producers should learn how to pick up and keep a rabbit correctly, if the rabbit feels unsafe or uncomfortable, they will struggle Rabbits are much stronger than they appear and have powerful hind legs If they struggle while being held, they can cause injury to themselves or their keeper As a first breed developed in warmer climates, Californian is known for not thrive at low temperatures (Pets4home, 2010) Figure 2.1 Californian rabbit 2.1.4 Californian rabbits in Vietnam Rabbit meat production has been more developed recently in Vietnam due to suitable production conditions such as low investment, labor saving, good income and low risks Local rabbits are mainly raised because of their good adaptation to the local conditions, however, productivity is very low Thanks to National Institute of Animal Science of Vietnam, Californian rabbits have been imported two times in 1980 and 2000 from Hungary to upgrade rabbit production Up to now they have adapted to Vietnamese ecological condition in the North Vietnam (Binh et al., 2008) The performance of Californian rabbits in the North Vietnam has achieved 5.12 kg for adult female and 5.65 kg for adult male Body live weights at birth, at 30 days and at months were 64.0, 707 and 2.840 g, respectively Feed conversion ratio from month to month was 5.05 kgDM/kg weight gain (Binh et al., 2008) In 2000s, rabbit producers in the Mekong delta of Vietnam raised Californian rabbits by using locally available feed resources In initial period, growing and reproductive performance of Californian rabbits were low and unstable In recent years, Californian rabbits have been adapted to local feeding conditions, thus its productivity was enhanced Californain rabbits become an important breed for rabbit production in the Mekong Delta of Vietnam 2.2 The Understanding of Protein digestion on rabbit 2.2.1 Some features of the protein sources using in rabbit diets Proteins, as we know, are macromolecules which are made up of long amino acids chains linked by peptide bonds to form a polypeptide chain The polypeptide chains are folded in three dimensions to form a characteristics tertiary structure for each protein The chain structure of each amino acid (size and electric charge) decides its properties Nutrition experts consider eight of them (isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine) essential since their carbon skeletons cannot be synthesized in higher animals (De Blas and Wiseman, 2010) A protein’s nutritive value is determined by both its amino acid composition and its digestibility proportion of ingested protein digested in the gut and absorbed as free amino acids It is chemical structure and properties (the insoluble proteins are more resistant to digestion) and accessibility to enzyme activity that involved in protein digestibility in rabbits, as in other non-ruminant species (De Blas and Wiseman, 2010) There are two major classes of plant proteins: seed and leaf proteins The main seed proteins are a part of the reserve material needed for the development of the future plant’s embryo Therefore, the cereal endosperm holds around 0.7 of total cereal protein; the rest is in the germ and in the outer bran The proportions of the different types of proteins (Table 2.1) are divergent between cereals: the soluble albumins and globulins derive from the cell’s cytoplasm, and the insoluble prolamins and glutelins are storage proteins Since the bran includes the aleuronic layer of endosperm (inner bran), its proportions of both crude protein (CP) and cell walls are higher than those of the whole grain The storage proteins’s nonessential amino acids (especially glutamic acid and proline) are richer and their lysine and threonine are lower in comparison to cytoplasmic proteins (Table 2.2) Consequently, cereals’ amino acid composition depends on the relative proportions of the various types of proteins While protein from cereals represents about 0.13 of the total protein of rabbit diets, it is about 0.2 for cereal byproducts, mainly wheat bran (De Blas and Wiseman, 2010) Table 2.1 Proportions of the different types of proteins in total protein of cereal and legume grains Cytoplasmic or saltsoluble protein Albumins Storage or insoluble protein Globulins Prolamins Glutelins Wheat (Triticum aestivum) 0.03–0.05 0.10–0.15 0.50–0.65 0.10–0.20 Barley (Hordeum vulgare) 0.03–0.04 0.10–0.20 0.45–0.50 0.25–0.35 Oats (Avena sativa) 0.01 0.60–0.65 0.10–0.15 0.25–0.30 Maize (Zea mays) Trace 0.05–0.06 0.65–0.75 0.15–0.20 Bean (Vicia faba) 0.04 0.67 – 0.29 Peas (Pisum sativum) 0.21 0.66 – 0.12 Soya (Glycine max) 0.10 0.90 – Sources: Boulter and Derbyshire, 1978; Larkins, 1981; Miflin and Shewry, 1981 In general, proportions of albumins and globulins in the grains of legumes and oil seeds are higher than in cereal grains Therefore, the proteins of legumes’ essential amino acids (especially lysine) are richer and these proteins should be more digestible than those of cereals The value of these seeds, however, is limited by the presence of various antinutritive factors (e.g trypsin inhibitors, lectins or tannins) when they are used unprocessed The mostly used protein concentrates in rabbit diets in Europe are soybean and sunflower meals whose inclusion levels are 80–90 g/kg comprising from 0.35 to 0.4 of total dietary protein (De Blas and Wiseman, 2010) Table 2.2 Amino acid composition (g/16 g nitrogen) of wheat proteins Albumins Globulins Prolamins Glutelins Methionine 1.8 1.7 1.0 1.3 Lysine 3.2 5.9 0.5 1.5 Threonine 3.1 3.3 1.5 2.4 Tryptophan 1.1 1.1 0.7 2.2 Glutamic acid 22.6 15.5 41.1 34.2 Source: Bushuk and Wrigley, 1974 The leave is where the proteins of forage plants are concentrated (Table 2.3) Unlike grains’ storage proteins, leaf proteins are concerned with the growth and biochemical functions of the cells The amino acid composition of plant leaf proteins varies within narrow limits (Makoni et al., 1993) and this is due to their enzymatic nature Even though a comparatively small fraction of insoluble protein remains tightly bound to the cell wall’s cellulose, leaf proteins’ major portion are separated from the cell wall Lucerne hay (0.90 of diets; Villamide et al., 2009) with inclusion levels from 200 to 400 g/kg is the forage most extensively used in rabbit diets Lucerne protein hence represents at least 0.25 of the dietary protein Lucerne hay’s protein content is very variable as it mainly depends on the maturation state and drying process Therefore, INRA (2002) tables classify dehydrated Lucerne into four groups according to protein content (from