ABSTRACT
A total of 65 Yankasa, 23 Uda and 16 Balami ewes were mated to 4 Yankasa, 3 Uda
and 3 Balami rams in a diallel breeding pattern to produce 192 lambs that were used to
genetically analyse growth and some reproductive traits. Weight records and linear
body measurements were obtained from lambs at birth, 90-Day (weaning weight), 180-
Day and 360-Day (yearling weight). Blood samples (5 ml) were collected from all the
ewes and rams used for the study. The blood samples were subjected to cellulose acetate
electrophoresis to obtain distinct bands of haemoglobin genotypes (AA, BB and AB).
Daily growth of the lambs was calculated using average daily gain (ADG) and relative
growth rate (RGR). The haemoglobin type HbAB was the most predominant in the
studied population and allele A of the haemoglobin type was the most numerous. Breed
and haemoglobin types had significant (P<0.05) effect on lamb weight. Crossbred lambs
of Yankasa rams and Uda ewes (YK X UD) were the heaviest at birth. Pure Balami
lambs were superior to all other lamb genotypes in body weight at 90 and 180-Day. The
heaviest 360-Day weight (18.73±1.53 kg) was recorded for lambs of HbBB. The ADG
and RGR of lambs were affected (P<0.05) by dam’s haemoglobin type, lamb genotype,
type of birth and sex of lambs. Yankasa rams and ewes produced lambs with the
shortest gestation lengths (151.84±0.23 days and 151.85±0.20 days, respectively). The
highest litter size was recorded in UD X YK or BL X UD crosses. All the lamb
genotypes had very high mortality from 180 to 360 days. However, there was no
mortality recorded for BL X BL lambs from birth to 180 days. The HbBB genotype
however had the highest percent mortality from 90 to 180-Day. The coefficients of
phenotypic correlations between body weight and linear body measurements increased
in proportion as Yankasa lambs grew from birth to 360-Day.Heritability estimates for
body weight and some linear body measurements for Yankasa lambs were high at 180-
Day (0.765±0.514) and 360-Day(0.805±0.961) indicating low effect of the environment
on the traits in the studied population. Linear body measurements that considered
volume of animal in terms of circumference (chest girth and loin girth) and body length
(back length, neck length and height at wither) tended to give better accuracy of
prediction of liveweight of lambs. Balami sheep (used as either sire or dam) expressed
its superior genetic potential in terms of faster growth rate than Uda and Yankasa in the
Northern Guinea Savannah agro-ecological zone. Selection for improved growth traits
in the population of Yankasa sheep should be based on individual records of the lambs
at 180-Day because of high heritability for 180-Day body weight of Yankasa lambs.
Weighing chart and bands should be produced for all the sheep breeds considered on the
basis of prediction equations.
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TABLE OF CONTENTS
TITLE PAGE……………………………………… ERROR! BOOKMARK NOT DEFINED.
DECLARATION …………………………………………………………………………………………… II
CERTIFICATION………………………………………………………………………………………….III
ACKNOWLEDGMENTS……………………………………………………………………………… IV
ABSTRACT……………………………………………………………………………………………….. VII
TABLE OF CONTENTS ……………………………………………………………………………..VIII
LIST OF FIGURES……………………………………………………………………………………..XIV
LIST OF TABLES ……………………………………………………………………………………. XVII
LIST OF PLATES……………………………………………………………………………………….XXI
LIST OF APPENDICES ……………………………………………………………………………. XXII
CHAPTER ONE ……………………………………………………………………………………………..1
INTRODUCTION……………………………………………………………………………………………1
1.0 BACKGROUND INFORMATION………………………………………………………..1
1.1 STATEMENT OF RESEARCH PROBLEM ……………………………………………3
1.2 JUSTIFICATION OF RESEACH…………………………………………………………..3
1.3 GENERAL OBJECTIVE ……………………………………………………………………..5
1.4 SPECIFIC OBJECTIVES……………………………………………………………………..5
CHAPTER TWO …………………………………………………………………………………………….6
LITERATURE REVIEW ………………………………………………………………………………….6
2.1 SHEEP IN ANIMAL AGRICULTURE…………………………………………………..6
ix
2.2 SHEEP PRODUCTION IN THE TROPICAL ENVIRONMENT…………………7
2.3 DISTRIBUTION AND PRODUCTIVE POTENTIALS OF NIGERIAN
SHEEP BREEDS………………………………………………………………………………………….9
2.4 MANAGEMENT SYSTEMS IN SHEEP PRODUCTION………………………..14
2.4.1 Housing……………………………………………………………………………………..14
2.4.2 Feeding ……………………………………………………………………………………..16
2.4.3 Breeding and Reproductive Management ………………………………………..17
2.5 TRAITS OF ECONOMIC IMPORTANCE IN SHEEP PRODUCTION………18
2.6 GROWTH RATE OF FARM ANIMALS ………………………………………………19
2.6.1 Birth Weight of Sheep………………………………………………………………….21
2.6.2 Weaning Age and Weight of Sheep………………………………………………..25
2.6.3 Yearling Weight of Sheep …………………………………………………………….27
2.6.4 Pre-Weaning and Post-Weaning Average Daily Gain ………………………..27
2.7 REPRODUCTIVE PERFORMANCE OF SHEEP…………………………………..28
2.7.1 Gestation Length in Sheep…………………………………………………………….29
2.7.2 Fecundity, fertility and prolificacy of sheep……………………………………..30
2.7.3 Sex Ratio of Lambs at Birth ………………………………………………………….34
2.8 MORTALITY RATES IN SHEEP PRODUCTION…………………………………35
2.9 BREEDING SYSTEMS IN SHEEP PRODUCTION ……………………………….37
2.9.1 Out-Crossing and Crossbreeding ……………………………………………………37
2.9.2 Inbreeding………………………………………………………………………………….38
2.9.3 Line Breeding …………………………………………………………………………….38
2.9.4 Genetic Basis of Heterosis…………………………………………………………….39
2.10 LINEAR BODY MEASUREMENTS IN SHEEP ……………………………………40
2.11 GENETIC PARAMETER ESTIMATES FOR SHEEP …………………………….42
x
2.11.1 Heritability Estimates for Growth and Reproductive Traits…………………42
2.11.2 Repeatability Estimates for Growth and Reproductive Traits………………44
2.11.3 Genetic and Phenotypic Correlation for Growth and
Reproductive Traits ………………………………………………………………………………….46
2.12 HAEMATOLOGICAL PARAMETERS OF LIVESTOCK………………..47
2.13 BIOTECHNOLOGY IN ANIMAL PRODUCTION ………………………………..50
2.14 HAEMOGLOBIN POLYMORPHISM IN SHEEP ………………………………….51
CHAPTER THREE………………………………………………………………………………………..53
MATERIALS AND METHODS………………………………………………………………………53
3.1 EXPERIMENTAL LOCATION…………………………………………………………..53
3.2 ANIMALS AND THEIR MANAGEMENT …………………………………………..54
3.2.1 Housing……………………………………………………………………………………..54
3.2.2 Feeding ……………………………………………………………………………………..55
3.2.3 Health ……………………………………………………………………………………….56
3.3 SHEEP BREEDS AND BREEDING PLAN …………………………………………..56
3.3.1 Heat (estrus) Detection and Breeding Pattern …………………………………..56
3.4 BLOOD COLLECTION AND ANALYSIS……………………………………………58
3.4.1 Electrophoretic Analysis of Blood Samples……………………………………..59
3.5 DATA COLLECTION AND MANAGEMENT ……………………………………..60
3.5.1 Measurements of Body Weights…………………………………………………….61
3.5.2 Linear Body Measurements…………………………………………………………..62
3.5.3 Average Daily Gains of Body Weights and Linear
Body Measurements…………………………………………………………………………………64
3.5.4 Relative Growth Rate …………………………………………………………………..64
xi
3.5.5 Genotypic Frequency of Haemoglobin ……………………………………………65
3.5.6 Allelic Frequency of Haemoglobin…………………………………………………65
3.6 STATISTICAL ANALYSIS ……………………………………………………………….65
CHAPTER FOUR………………………………………………………………………………………….68
4.1 RESULTS………………………………………………………………………………………..68
4.1.1 Diallel Breeding Pattern, Lamb Genotype and Dam’s
Haemoglobin Type…………………………………………………………………………………..68
4.1.2 Effect of Breed of Sire and Dam on Growth Traits ……………………………72
4.1.3 Effect of Lamb Genotype and Dam’s Haemoglobin
Type on Growth Traits ……………………………………………………………………………..75
4.1.4 Effect of Type of Birth and Sex of Lamb on Growth Traits ………………..78
4.1.5 Effect of Lamb Genotype on Linear Body Measurements of
Lambs 82
4.1.6 Body Average Daily Gains (ADG) of Body Weight of
Sheep of Northern Nigeria and their Crosses ………………………………………………..90
4.1.7 Body Relative Growth Rate (RGR) of Sheep of Northern
Nigeria and their Crosses…………………………………………………………………………..98
4.1.8 Variability of Gestation Length and Litter Size among
Sheep of Northern Nigeria……………………………………………………………………….107
4.1.9 Mortality Rates of Sheep of Northern Nigeria and their Crosses ………..112
4.19.1 Mortality rates in relation to lamb genotype ……………………………….112
4.1.9.2 Mortality rates in relation to dam’s haemoglobin type………………….116
4.1.9.3 Mortality rates in relation to type of birth and sex of lambs…………..120
4.1.9.4 Distribution of dam’s haemoglobin type within lamb genotype……..123
xii
4.1.9 Genetic parameter estimates of growth traits and linear body
measurements for Yankasa lambs……………………………………………………………..128
4.1.10 Prediction of Body Weight using Linear Body Measurements …………..136
CHAPTER FIVE………………………………………………………………………………………….142
5.0 DISCUSSION…………………………………………………………………………………142
5.1.1 Population of the Experimental Animal…………………………………………142
5.1.2 Frequency of Dam’s Haemoglobin Type ……………………………………….142
5.1.3 Effect of Breed of Sire and Dam on Growth Traits ………………………….143
5.1.4 Effect of Lamb Genotype on Growth Traits……………………………………143
5.1.5 Effect of Dam’s Haemoglobin Type on Growth Traits……………………..144
5.1.6 Effect of Type of Birth and Sex of Lambs on Growth Traits……………..145
5.1.7 Average Daily Gains (ADG) and Relative Growth Rate (RGR)…………146
4.1.8 Variability of Gestation Length and Litter Size……………………………….147
5.1.9 Mortality Rates of Sheep …………………………………………………………….149
5.1.10 Heritability Estimates for Growth Traits and Linear
Body Measurements of Yankasa Lambs …………………………………………………….151
5.1.11 Phenotypic and Genetic Correlation for Growth Traits
and Linear Measurements of Yankasa Lambs……………………………………………..151
5.1.12 Prediction of Body Weights using Linear Body Measurements…………153
CHAPTER SIX……………………………………………………………………………………………155
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS…………………………..155
6.1 SUMMARY……………………………………………………………………………………155
6.2 CONCLUSIONS……………………………………………………………………………..157
6.3 RECOMMENDATIONS ………………………………………………………………….158
xiii
REFERENCES…………………………………………………………………………………………….160
APPENDICES …………………………………………………………………………………………….193
CHAPTER ONE
INTRODUCTION
1.0 BACKGROUND INFORMATION
Genotypic variations between and within breeds are great resource for improvement of
animals (Akpa et al., 2010). Variations in the ability of one breed of domestic animals
to perform better than the other in productive and reproductive traits arise from the
combined effects of genetic components and adaptation to the prevailing environmental
conditions in which such animals are being raised (Adebambo, 2003). Adaptation
enables individual animals to survive in the environment in which they are managed
(Willmer et al., 2005; Van der Werf et al., 2009). Sheep breeds in various tropical
agro-ecological zones have adapted to the prevailing climates having survived in such
environment over many generations. Wilson (1991) stated that there aresome reasons in
Africa to attempt an improvement of sheep by utilizing non-African breeds. However,
the use of non-African breeds of sheep should be under ideal climatic or management
conditions for such breeds.
Sheep are kept all over Nigeria (Akpa et al., 2002b), with a broad distinction between
their importance and ubiquity in the north and the more dispersed populations of the
humid zone. Improvement of productivity in Nigerian indigenous sheep is important
because of the demand for this species (Adu and Ngere, 1979). Farm animals are
improved through health, feeding, breeding, reproductive management and
crossbreeding (Akpa et al., 1994a; Akpa, 2001 and Tibbo et al., 2006). Many
crossbreeding schemes, some highly complex, have been developed to meet particular
needs. The main objective in crossbreeding programmes is to exploit non-additive
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genetic variance (heterosis or hybrid vigour). Crossbreeding can also be used as a
supplement to a programme for additive genetic improvement (Gjedrem, 2005).
Not many attempts have been made at the improvement of sheep breeds found
predominantly in Northern Nigeriausing the genetic resources within and between
breeds. This is partially due to genotype-environment interactions, which can be
regarded as the adaptation of a breed to its environment. Osinowo and Adu (1985)
advised farmers in the different agro-ecological zones to concentrate their efforts in
rearing sheep breeds that predominate in their particular agro-ecological zone because
the productive capability of such breeds is at its best in such zones.
There are four main breeds of sheep in Nigeria: Balami, Uda, Yankasa and West
African Dwarf (WAD). Balami, Uda and Yankasa are predominant breeds in Northern
Nigeria while the West African Dwarf (WAD) is adapted to the humid climate of
southern Nigeria. These breeds differ considerably in size, coat-colour and other
characteristics (Adu and Ngere, 1979). The Balami is the largest in size (live weight)
and is confined to the most arid areas of the country (Sudan savannah) while Yankasa,
which is the smallest among the three breeds in the Northern part of the country, is
adapted to the areas with relatively more rainfall (Northern Guinea Savannah). Thus,
any strategy for improving breeds (Yankasa, Uda and Balami) adapted to the semi-arid
and arid climate (water and feed scarce areas) needs to consider their unique attributes
and focus on improving within breed, with some level of crossbreeding with those that
are adapted to such harsh climates (Tibbo et al., 2006).
3
1.1 STATEMENT OF RESEARCH PROBLEM
Yankasa sheep have been bred and selected by National Animal Production Research
Institute (NAPRI) for large litter size, high birth weight, rapid growth rate and good
performance of offspring. The same cannot be said for Balami and Uda sheep breeds
which are known to grow faster naturally than any other breed in the country. There is
paucity of information on detailed genetic diversity and the combining ability (additive
and non-additive genetic variation) of Nigerian sheep breeds and their crosses.
Concerted efforts at establishing the proficiency of each of the breeds in the country is
also lacking. The question that formed the basis of this study tried to find out if it is
possible for offsprings of Balami sheep to competefavourably with those of Yankasa
and Uda in the Northern Guinea savannah zone of Nigeria.
1.2 JUSTIFICATION OF RESEACH
Growth rate and prolificacy are important traits in most systems of sheep production,
since both affect the share of ewe overheads carried by each lamb (Adu and
Buvanendran, 1982). Kosgey (2003) concluded that litter size and lambing frequency
are the most important traits in a breeding objective for smallholder production.
Performance evaluation of these traits is a logistical complement to genetic
improvement schemes.
Genetic information available for the assessment of genetic variation has been
commonly based on variations at the protein and deoxyribonucleic acid (DNA) levels.
These proteins or regions of the genome are treated as genetic markers and variations
detected at these loci are assumed to reflect the level of variation that influences
adaptation or individual fitness (Ibeagha-Awemu and Erhardt, 2004). Several
4
livestock breeds, including the domestic sheep (Ovis aries), have been characterized for
variations in the major blood proteins and enzymes which are used as genetic
markers.Such proteins are albumin (Margetin and Malik, 1982), ceruloplasmins
(Graetzer et al., 1964; Bhat, 1986), vitamin D-binding protein (Ibeagha-Awemu and
Erhardt, 2004), haemoglobin and transferrin (Braend, 1972; Baruah and Bhat, 1980;
Margetin and Malik, 1982; Bhat, 1986; Henkes et al., 1994; Di Stasio, 1997). Some of
the enzymes are amylase (Bhat, 1986), carbonic anhydrase (Margetin and Malik, 1982),
malic enzyme, NADH diaphorase and catalase (Tsunoda and Douge, 1990; Henkes et
al., 1994).
Several studies in sheep have already linked these markers to production traits and
environmental adaptation (Dally et al., 1980; Vicovan and Rascu, 1989; Charon et al.,
1996, Salako et al., 2007). Information on blood proteins has also been extensively used
for parentage control (Francois et al., 1992) and to study the genetic relationships
among sheep breeds (Buis and Tucker, 1983; Ordas and San Primitivo, 1986;
Mwacharo et al., 2002). However, the polymorphism of this important blood proteins
had not being linked with productive and reproductive traits in the populations of
Balami, Uda and Yankasa sheep. Study of the influence of variations in haemoglobin
genotype, lamb genotype, breed of sire and dam on growth traits such as birth weight,
90, 180 and 360-Day weight and some reproductive traits can help in selection of sheep
on the basis of lambs with the best performing haemoglobin genotype along with other
sources of variations.
5
1.3 GENERAL OBJECTIVE
The general objective of this study was to evaluate the genetic potential for improved
growth rate and some reproductive traits in Balami, Uda and Yankasa sheep in the
Northern Guinea Savannah zone of Nigeria.
1.4 SPECIFIC OBJECTIVES
The specific objectives are to:
(1.)Evaluate the effect of breed of sire and dam on the growth rate of lambs of
Northern Nigeria.
(2.)Evaluate the effect of dam’s haemoglobin type on the growth rate and
reproductive traits of sheep of Northern Nigeria and their crosses.
(3.)Measure the level of survivability of lambs of Balami, Uda and Yankasa sheep
in the Northern Guinea Savannah zone of Nigeria.
(4.)Estimate genetic parameters (heritability, genetic and phenotypic correlations) of
growth traits of sheep of Northern Nigeria.
(5.)Generate prediction equation for body weight of sheep of Northern Nigeria
through linear body measurements.
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