A STUDY OF DIETARY PROTEIN FOR GROWING CALIFORNIAN RABBITS IN THE MEKONG DELTA OF VIETNAM

MINISTRY OF EDUCATION AND TRAINING
CAN THO UNIVERSITY

TRUONG THANH TRUNG

A STUDY OF DIETARY PROTEIN FOR
GROWING CALIFORNIAN RABBITS IN
THE MEKONG DELTA OF VIETNAM

DOCTORAL THESIS IN ANIMAL SCIENCE

2017
i


MINISTRY OF EDUCATION AND TRAINING
CAN THO UNIVERSITY

TRUONG THANH TRUNG

A STUDY OF DIETARY PROTEIN FOR
GROWING CALIFORNIAN RABBITS IN
THE MEKONG DELTA OF VIETNAM

DOCTORAL THESIS IN ANIMAL SCIENCE

SCIENTIFIC SUPERVISOR

ASSOCIATE PROFESSOR NGUYEN THI KIM DONG

2017

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ACKNOWLEDGMENT
I would like to thank to lectures at Department of Animal Science, Can Tho
University who gave me useful knowledge and encouraged me during the
course.
I want to express particular appreciation to my supervisors, Association.
Professor Dr. Nguyen Thi Kim Dong and Professor Dr. Nguyen Van Thu,
Department of Animal Science, Can Tho University, Vietnam, for all your
support, advice and explanation throughout the research, also for their reading
and correcting my thesis papers. I learnt a lot of useful knowledge and real life
experience from them.
My thanks are extended to my classmates for sharing knowledge and
experience in class. Many thanks to my friends in rabbit farm in Can Tho
University for their help and encouragement to me.
Last but not least, special thanks to my parents, younger brother, sisters, aunt
and my girlfriend for their love and moral support
I would like to thank all the people who contributed to this study
Truong Thanh Trung

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ABSTRACT
This thesis is based on five experiments that were conducted at the
experimental farm in Cantho City to evaluate protein utilization of growing
Californian rabbits in the Mekong Delta of Vietnam. The first experiment was
to identify the nutritional values of some common feedstuffs for feeding
rabbits in the Mekong Delta. The second was to determine the optimum level

of crude protein in diets of growing Californian rabbits. The third was to
compare and choose appropriate protein sources in diets of growing
Californian rabbits. The fourth was to find out optimum level of lysine and
threonine in diets for growing Californian rabbits. And the last experiment was
to determine the optimum ME level in diets of growing Californian rabbits
under feeding conditions in the Mekong Delta of Vietnam.
The results showed that in the first experiment, almost essential and
non-essential amino acid components of water spinach and Psophocarpus
scandens were higher than those of Operculina turpethum and para grass.
Sweet potato vine and water spinach leaves were good feedstuffs with high CP
values and proportional fiber components. Soybean had low values of
essential amino acids and non-essential amino acids than those of fish meal,
feather meal and blood meal with the exception of methionine, glutamic and
arginine concentrations.
In the second experiment, the CP intake increased (P<0.05) while the
NDF, ADF and EE intakes decrease (P<0.05) among treatments. The daily
weight gain were significantly different (P<0.05) among treatments with the
higher values (22.4, 23.3 and 23.2 g/day) for the CP19, CP21 and CP23
treatments. The carcass, thigh meat and lean meat weights were significantly
higher (P<0.05) for the animals fed the 19, 21 and 23% CP treatments and the
highest profit was obtained for the CP21 treatment.
In the third experiment, intakes of DM, OM, CP, EE, NDF, ADF and
ME of the soybean extraction meal (SEM) and water spinach leaves meal
(WLM) treatments were significantly higher (P<0.05) than those the other
treatments. The digestible DM, OM, CP, EE, CF, NDF and ADF were
significantly higher (P<0.05) for the SEM and WLM treatments as compared
to the feather meal (FEM) and blood meal (BM) treatments. Daily weight gain
was significantly different (P<0.05) among treatments with the highest value
for the SEM treatment (22.8 g/day) and the lowest value for the FEM
treatment (14.9 g/day). The carcass weight and carcass percentage of the SEM

and WLM treatments were significantly (P<0.05) higher than those of the
FEM and BM, while the higher profit was found for the WLM and SEM
treatments (3.07 and 2.63 USD/rabbit), respectively.
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In the fourth trial, almost amino acid digestibility of rabbits were
significantly higher (P<0.05) for the 0.95-Lys treatment as compared to the
0.85-Lys and 1.05-Lys treatments. In term of threonine treatments,
digestibility coefficients of almost amino acids were significantly different
(P<0.05) with the higher values for the 0.75-Thr treatment. Daily weight gain
of rabbit in the 0.95-Lys and the 0.75-Thr treatments (22.4 and 22.2 g/day,
respectively) were significantly higher (P<0.05) than that of the 0.85-Lys and
the 1.05-Lys treatments and the 0.65-Thr treatments, respectively. The carcass,
lean meat and thigh weights of rabbit in the 0.95-Lys treatments were
significantly higher (P<0.05) than others lysine treatments. The carcass, lean
meat and thigh weights were also significantly different (P<0.05) between
threonine treatments and the higher results were found for the 0.75-Thr
treatment.
In the fifth experiment, the DM and CP intakes were not significantly
different among treatments being from 69.4-74.5 and 13.2-14.2
gDM/rabbit/day, respectively. The digestible DM, OM and CP were not
significantly different (P>0.05) among treatments being 39.9-45.4, 35.8-41.3
and 7.65-9.06 g/rabbit/day, respectively. Daily weight gain was significantly
different (P<0.05) among treatments with the highest value (24.5 g/day) for
the ME11.5 treatment. The carcass, lean meat and thigh meat weights were
significantly different (P<0.05) among treatments with the highest values in
the ME11.5 treatment (1.374, 1.049 and 412 g, respectively).
It was concluded that the combination among locally available
feedstuffs in the Mekong Delta of Vietnam could formulate balanced nutrient

diets for Californian growing rabbits. The diets contained 19% CP, 0.95%
Lysine and 0.75% Threonine and 11.5 MJME/kgDM should be fed on
growing Californian rabbits for improving growth performance, nutrient
digestibilities, carcass quality and economic returns. Soybean extraction meal
should be used in the Californian rabbit diets, as a protein supplement source
due to its appetite and high nutrient digestibility.
Keywords: carcass quality, income, nitrogen, nutrient digestibility, rodents

v


DECLARATION
I assure that this thesis is a scientific work that was implemented by myself.
All the figures and results presented in the thesis are true and not published in
any previous theses.
Author

Truong Thanh Trung

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CONTENT
Page
Chapter 1. Introduction .................................................................................... 1
1.1 Problem statement...................................................................................... 1
1.2 Research objectives.................................................................................... 3
1.3 Key findings ............................................................................................... 3
1.4 Sciential and practical values ..................................................................... 3
Chapter II. Literature review ........................................................................... 5

2.1 Californian rabbits ..................................................................................... 5
2.1.1 History .................................................................................................... 5
2.1.2 Appearance ............................................................................................. 5
2.1.3 Temperament .......................................................................................... 5
2.1.4 Californian rabbits in Vietnam ............................................................... 6
2.2 The Understanding of Protein digestion on rabbit..................................... 7
2.2.1 Some features of the protein sources using in rabbit diets ..................... 7
2.2.2 Some characteristics of rabbit diets in Mekong Delta Vietnam ............. 9
2.2.3 Balance of protein and amino acid ......................................................... 10
2.2.4 Crude protein and total amino acids ....................................................... 11
2.2.5 Faecal digestibility .................................................................................. 12
2.2.6 Ileal digestibility ..................................................................................... 13
2.2.7 Nitrogen metabolism in the caecum ...................................................... 19
2.2.8 Protein digestion in young rabbits .......................................................... 21
2.3 Soft faeces and protein digestibility .......................................................... 22
2.4 The enhanced objectives for protein nutrition in rabbits ........................... 26
2.4.1 A documented context ............................................................................ 26
2.4.2 The relation between nitrogen and microbial growth ............................. 29
2.4.3 The interaction of nitrogen ileal flow and intestinal health .................... 31
2.4.4 The trend of using protein in rabbit diets................................................ 35
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Chapter III. Materials and methods ................................................................. 38
3.1 Location and time ...................................................................................... 38
3.2 Animals and housing ................................................................................. 39
3.3 Feed and feeding ........................................................................................ 39
3.4 Experimental design .................................................................................. 45
3.5 Sampling procedure for nutrient digestibility .......................................... 49
3.6 Chemical analyses...................................................................................... 49

3.7 Measurements ............................................................................................ 49
3.8 Statistical analysis ...................................................................................... 50
Chapter IV. Results and discussion ................................................................. 51
4.1 Experiment 1: Nutrient evaluation with emphasis on amino acid values of
the common feedstuffs for rabbits in the Mekong delta, Vietnam .................. 51
4.1.1 Nutrient composition of natural plants for feeding rabbits..................... 51
4.1.2 Nutrient composition of agricultural and industrial by-products for
feeding rabbits ................................................................................................
54
4.1.3 Nutrient composition of protein and energy supplemental feed
ingredients for feeding rabbits ......................................................................... 58
4.1.4 Summary ................................................................................................. 64
4.2 Experiment 2: Effects of dietary crude protein levels on growth rate, meat
production, digestible nutrients and economic return of Californian rabbits in
Mekong Delta Vietnam .................................................................................... 65
4.2.1 Feed and nutrient intakes ........................................................................ 65
4.2.2 Daily weight gain and economic returns ................................................ 66
4.2.3 Carcass and meat nutrients ..................................................................... 67
4.2.4 Nutrient digestibility and nitrogen retention........................................... 68
4.2.5 Summary ................................................................................................. 69
4.3 Experiment 3: Effect of different protein sources in the diets on feed
intake, nutrient digestibility, growth and carcass value of Californian rabbits in
the Mekong Delta Vietnam .............................................................................. 70
4.3.1 Feed and nutrient intakes ........................................................................ 70
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4.3.2 Growth performance and economic returns ........................................... 71
4.3.3 Carcass values and meat nutrients .......................................................... 72
4.3.4 Nutrient digestion and nitrogen retention ............................................... 73

4.3.5 Summary ................................................................................................. 75
4.4 Experiment 4: Effect of lysine and threonine levels in the diets on feed
intake, nutrient digestibility, growth and carcass value of Californian rabbits in
the Mekong Delta, Vietnam ............................................................................. 76
4.4.1 Feed and nutrient intakes ........................................................................ 76
4.4.2 Growth performance and economic returns ........................................... 78
4.4.3 Carcass values and meat quality of experimental rabbits ....................... 80
4.4.4 Nutrient digestion and nitrogen retention ............................................... 81
4.4.5 Summary ................................................................................................. 83
4.5 Experiment 5: A response of feed utilization, nutrient digestibility, growth
and carcass value of Californian rabbits to dietary metabolizable energy ..... 84
4.5.1 Feed and nutrient intakes ........................................................................ 84
4.5.2 Growth performance and economic returns ........................................... 85
4.5.3 Carcass values and meat nutrients .......................................................... 86
4.5.4 Nutrient digestion and nitrogen retention ............................................... 87
4.5.5 Summary ................................................................................................. 89
Chapter V. Conclusion and recommendations ................................................ 90
References ........................................................................................................ 92
Appendices..................................................................................................... 109

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LIST OF FIGURES
Page
Figure 2.1 Relative value of some protein sources in rabbit diets in relation to
soybean meal (100) using different nitrogen units (total versus apparent (app.)
faecal digestible . ............................................................................................ 11
Figure 2.2 Apparent (a) and true (b) ileal amino acid digestibility of soybean
meal with respect to its crude protein digestibility. ......................................... 15

Figure 2.3 Relationship between faecal crude protein (CP) digestibility and
amino acid true ileal digestibility .................................................................... 17
Figure 2.4 Caecal nitrogen metabolism ........................................................... 20
Figure 2.5 Effect of the crude protein (CP) concentration of the caecal
contents on the CP of soft faeces ..................................................................... 23
Figure 2.6 Contribution of soft faeces to the total intake of crude protein and
some amino acids ............................................................................................ 26
Figure 2.7 Relationship between mortality (%) and the DP/DE ratio in the
growing period ...……………………………………………………………31
Figure 2.8 Effect of ileal flux of crude protein on mortality from 25 to 60 days
of age
........................................................................................................ 33
Figure 2.9 Relationship between average daily gain (g/d) and the DP/DE ratio
in the growing period ...................................................................................... 36
Figure 3.1 Cages were used in the nutrient digestibility experiment .............. 39
Figure 3.2 Operculina turpethum ..................................................................... 43
Figure 3.3 Water spinach ................................................................................. 43
Figure 3.4 Psophocarpus scandens .................................................................. 43
Figure 3.5 Para grass ........................................................................................ 43
Figure 3.6 Sweet potato vines .......................................................................... 43
Figure 3.7 Water spinach leaves ...................................................................... 43
Figure 3.8 Soybean extraction meal ................................................................ 43
Figure 3.9 Soya waste ...................................................................................... 43
Figure 3.10 Soybean meal ............................................................................... 44
Figure 3.11 Fish meal ...................................................................................... 44
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Figure 3.12 Feather meal ................................................................................. 44
Figure 3.13 Blood meal ................................................................................... 44

Figure 3.14 Maize ............................................................................................ 44
Figure 3.15 Broken rice ................................................................................... 44
Figure 3.16 Sweet potato tuber ........................................................................ 44
Figure 3.17 Amino acids were used in the study ............................................. 45
Figure 3.18 Rabbits for slaughtering ............................................................... 50
Figure 3.19 Experimental rabbit carcass ......................................................... 50
Figure 3.20 Rabbit thigh .................................................................................. 50
Figure 3.21 Rabbit thigh meat ......................................................................... 50
Figure 3.22 Rabbit lean meat ........................................................................... 50
Figure 4.1 DM, CP and ME concentration of para grass, water spinach,
Psophocarpus scandens and Operculina turpethum ....................................... 52
Figure 4.2 Lysine, Threonine and Methionine concentration of para grass,
water spinach, Psophocarpus scandens and Operculina turpethum ............... 54
Figure 4.3 CP, NDF and ME concentration of sweet potato vines, water
spinach leaves, soybean extraction meal and soya waste ................................ 56
Figure 4.4 Lysine, Threonine and Methionine concentration of sweet potato
vines, water spinach leaves, soybean extraction meal and soya waste............ 57
Figure 4.5 DM, CP and ME concentration of soybean, fish meal, feather meal
and blood meal ................................................................................................. 61
Figure 4.6 Lysine, Threonine and Methionine concentration of soybean, fish
meal, feather meal and blood meal .................................................................. 62
Figure 4.7 DM, CP and ME concentration of maize, broken rice and sweet
potato tuber ...................................................................................................... 63
Figure 4.8 Lysine, Threonine and Methionine concentration of maize, broken
rice and sweet potato tuber .............................................................................. 64
Figure 4.9 Effect of CP intake on daily gain of rabbits in the experiment ...... 67
Figure 4.10 Effect of ME concentration in diets on daily weight gain of rabbits
in the experiment ............................................................................................. 86

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LIST OF TABLES
Page
Table 2.1 Proportions of the different types of proteins in total protein of
cereal and legume grains ................................................................................. 8
Table 2.2 Amino acid composition (g/16 g nitrogen) of wheat proteins ........ 8
Table 2.3 Crude protein (g/kg dry matter) of leaves and stems of lucerne hay
and the amino acid composition (as a proportion of total amino acids) of leaf
protein from fresh lucerne................................................................................ 9
Table 2.4 Dietary composition of growing rabbit diets in Mekong delta
Vietnam ........................................................................................................ 9
Table 2.5 The invitro OMD (%) by using rabbit caecum fluid of some
common feeds for rabbit production in the Mekong delta Vietnam................ 10
Table 2.6 Prediction equations for apparent faecal digestible protein (DP,
g/kgDM) from chemical composition (g/kgDM) for different groups of feed
ingredients ....................................................................................................... 12
Table 2.7 Amino acid composition (g/16 g nitrogen) of endogenous flow at the
ileal and faecal levels ....................................................................................... 14
Table 2.8 Total and digestible protein and amino acid content (g/kg dry
matter) using different units for the most important sources .......................... 18
Table 2.9 Effect of age on apparent ileal crude protein (CP) digestibility and
the distribution of protein apparently digested ............................................... 22
Table 2.10 Protein and amino acid recommendations according to several
authors (as-fed basis) ....................................................................................... 27
Table 2.11 Ileal balance in adult rabbits fed alfalfa based diets ..................... 30
Table 2.12 Effect of the level of protein in isofibrous diets (30% NDF) on
pathogenic flora and mortality in early (25 d) weaned rabbits...........…........32
Table 2.13 Effect of level and type of dietary CP on intestinal health and ileal CP
flow ........................................................................................................................ 34

Table 3.1 Chemical composition and metabolism energy concentration of
feeds used in experiment 2 (%DM) ............................................................... 40
Table 3.2 Chemical composition (% DM) and metabolism energy
concentration of feeds used in experiment 3 .................................................. 41
Table 3.3 Chemical composition and metabolism energy concentration of
feeds used in experiment 4 (% DM, with the exception of DM as fed basic) 42
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Table 3.4 Chemical composition and metabolism energy concentration of
feeds in experiment 5 (%DM) ....................................................................... 42
Table 3.5 Dietary feed ingredients and metabolism energy concentration of the
experiment 2 .................................................................................................... 45
Table 3.6 Feed ingredients composition, chemical composition and
metabolism energy concentration of diets in the Exp. 3 (% DM) .................. 46
Table 3.7 Feed ingredients composition, dietary chemical composition and
metabolism energy concentration in the experiment 4 (% DM) .................... 47
Table 3.8 Feed ingredients composition, dietary chemical composition and
metabolism energy concentration in the experiment 5 (% DM) .................... 48
Table 4.1 Nutrient composition of natural grasses for feeding rabbits (Mean ±
SD, n=3) .......................................................................................................... 51
Table 4.2 Nutrient composition of agricultural and industrial by-products for
feeding rabbits.................................................................................................. 54
Table 4.3 Nutrient composition of protein and energy supplemental feed
ingredients for feeding rabbits (Mean ± SD, n=3) .......................................... 58
Table 4.4 The feed, nutrient and metabolizable energy (ME) intakes of rabbits
................................................................................................................. 65
Table 4.5 Daily weight gain, feed conversion ratio and economic returns of
experimental rabbits ........................................................................................ 66

Table 4.6 Carcass and meat quality of rabbits in the experiment ................... 67
Table 4.7 Nutrient intakes, digestible nutrients, and nitrogen retention of
experimental rabbits ........................................................................................ 68
Table 4.8 The feed, nutrient and metabolizable energy (ME) intakes of rabbits
................................................................................................................. 70
Table 4.9 Final live weight, daily weight gain (DWG) and economic returns of
experimental rabbits ........................................................................................ 71
Table 4.10 Carcass values, internal organs and meat quality of rabbits in the
experiment ...................................................................................................... 72
Table 4.11 Nutrient intakes, digestible nutrients and nitrogen retention of
rabbits in the nutrients digestibility trial ......................................................... 73
Table 4.12 Feed and nutrient intakes of experimental rabbits ........................ 76
Table 4.13 Amino acid intakes of experimental rabbits (g/rabbit/day) .......... 77

13


Table 4.14 Final live weight, daily weight gain (DWG) and economic returns
of experimental rabbits ................................................................................... 78
Table 4.15 Carcass values, internal organs and meat quality of rabbits in the
experiment ...................................................................................................... 80
Table 4.16 Nutrient intakes, digestible nutrients and nitrogen retention of
rabbits in the nutrient digestibility trial .......................................................... 81
Table 4.17 Amino acids intake of rabbits in the nutrient digestibility trial
(g/day) .............................................................................................................
82
Table 4.18 Amino acids digestibility of experimental rabbits (%) ................. 82
Table 4.19 The feed and nutrient intakes of rabbits in the experiment ........... 84
Table 4.20 Body weight, daily weight gain, feed conversion ratio and
economic returns of experimental rabbits........................................................ 85

Table 4.21 Carcass values, internal organs and meat quality of rabbits in the
experiment ...................................................................................................... 86
Table 4.22 Nutrient intakes, digestible nutrients and nitrogen retention of
experimental rabbits ...............................................................................................88

14


LIST OF ABBREVIATION

ADF: Acid detergent fiber
AID: Apparent ileal CP digestibility
AOAC: Association of Official Agricultural Chemists
CF: Crude fiber
CP: Crude protein
CPD: Apparent faecal CP digestibility
DM: Dry matter
DWG: Daily weight gain
EE: Ether extract
FCR: Feed conversion ratio
FW: Final live weight
INRA: National Institute for Agricultural Research of France
IW: Initial live weight
ME: Metabolizable energy
N: Nitrogen
NDF: Neutral detergent fiber
NI: Nitrogen intake
NIAS: National Institute of Animal Science of Vietnam
NR: Nitrogen retention
NRC: National Research Council Committee on Animal Nutrition

OM: Organic matter
SD: Standard deviation
VFAs: Volatile fatty acids

15


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 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 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
16


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

17


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
18


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.

19


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
20


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 3 months were 64.0, 707 and 2.840 g, respectively. Feed
conversion ratio from 1 month to 3 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
21


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).

22


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

–

0

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
23


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 <160 to 220–250 g/kg) (De Blas and
Wiseman, 2010)
Table 2.3 Crude protein (g/kg dry matter) of leaves and stems of lucerne hay and the
amino acid composition (as a proportion of total amino acids) of leaf protein from
fresh lucerne
Cytoplasmic Chloroplast
Lucernea
Crude protein Amino acid
proteinb
membraneb
Lucerne hay
191.9

Lysine
0.060
0.051
Leaves (0.82 hay)
277.5
Sulphur aa
0.016
0.013
Stems (0.18 hay)
125.0
Arginine
0.037
0.051
a

Alvir et al. (1987), bMakoni et al. (1993). The ratio of cytoplasmic to chloroplast protein was 0.25:0.75
of total leaf protein

2.2.2 Some characteristics of rabbit diets in the Mekong Delta of
Vietnam
In the Mekong delta of Vietnam, rabbits are fed locally available feed
resources including natural grasses, wild vegetables and agro-industrial
byproducts. Natural and wild feeds were naturally available almost all the year
round in the Mekong Delta. Locally available forages could be provided major
part of protein and fiber requirement of rabbits. The in vitro organic matter
digestibility (% OMD) by using rabbit caecum fluid of these feeds gave good
results and it showed that they had well-potential feed for rabbit production
(table 2.5). However, feeding only forages would not satisfy nutrients for
growth and reproductive performance, thus supplementation of protein and
energy feed sources was needed. Rabbit producers only utilize the local

feedstuffs for feeding rabbits but they do not concern about dietary nutrient
requirement. Dietary composition of growing rabbits in the Mekong delta of
Vietnam was shown in table 2.4
Table 2.4 Dietary composition of growing rabbits in the Mekong delta of Vietnam
Feedstuff

% in diet

Natural grass

63.9

Agro-industrial byproducts

24.6

Concentration

11.5

Source: Chau & Thu., 2014

Chau & Thu. (2014) conducted a research on current status of rabbit
24


production in the Mekong Delta of Vietnam. They concluded that forage
sources such as natural grasses, sweet potato vines and water spinach were
often used as basal diets, while brewery waste, soya waste and concentrates
were used as supplemental feeds for rabbit production. The dietary crude

protein (13.9-14.1%) for growing rabbits was low as compared to the crude
protein requirement of the temperature rabbits (15-19%). The nutrient intakes
per day (58.4 gDM, 7.84 gCP and 680 kJME) and growth rate (13.2
g/rabbit/day) of growing rabbits were lower than domestic data reported (16.724.5 g/rabbit/day). Rabbit production in the Mekong Delta has advantages of
easy sale, yearly available feed sources and adaptable breeds but due to
limited knowledge on nutritional techniques, the production has not achieved
to its potential. They also recommended that more studies on nutrient
requirements and local feeds for rabbits should be considered to serve for
extension activities in raising rabbits.
Table 2.5 The invitro OMD (%) by using rabbit caecum fluid of some common
feeds for rabbit production in the Mekong delta of Vietnam
Feed
Incubation time (hours)
0
24
48
96
Nutural grasses
Wedelia trilobata (Địa cúc)
52.7
65.8
72.4
73.5
Operculina turpethum (Bìm bìm)
52.3
68.1
72.3
72.8
Commelina communis (Rau trai)
53.1

65.0
73.3
77.3
Phyllanthus urinaria (Cây chó đẻ)
62.3
65.9
72.4
76.1
Amaranthus (Rau dền)
70.0
78.4
80.7
85.2
Eichhornia crassipes (Lục bình)
51.8
52.0
56.1
58.4
Brachiaria mutica (Cỏ lông tây)
23.1
40.4
49.4
53.5
Eleusine indica (Cỏ mần trầu)
29.2
45.6
50.6
57.5
Psophocarpus scandens (cỏ đậu)
50.4

64.8
69.4
71.2
Cultivated grasses
Hibiscus rosasinensis (Dâm bụt)
66.7
86.8
87.2
88.0
Cymbopogon citratus (Cỏ sả)
29.5
32.1
36.7
39.0
31.4
38.4
42.1
43.8
Brachiaria ruziziensis (Cỏ Ruzi)
Paspalum atratum
29.0
34.1
37.6
41.8
Agricultural by products
Sweet potato vines
57.8
68.0
88.2
90.6

Water spinach leaves
68.7
82.2
85.8
91.4
Brassica oleracea (Lá bông cải)
58.1
70.8
74.0
77.6
Brassica oleracea (Lá bắp cải)
50.9
71.1
89.0
91.0
Source: Thu & Dong., 2011

2.2.3 Balance of protein and amino acid
The different feedstuffs’ capability to satisfy the protein and amino acid
requirement of rabbits depends on the nitrogen unit used (Carabano et al.,
2000). The relative value of sunflower meal, wheat, wheat shorts, and Lucerne
hay in relation with soybean meal using different units (total CP or
25