ABSTRACT
Two experiments were conducted at
the piggery unit of the Department of Animal Science Farm, University of Nigeria,
Nsukka, from July 2007 to March 2009, to determine the effect of nutrition and
body condition at first mating on the reproductive performance of gilts. The
first experiment evaluated the effects of feeding different combinations of
protein and energy diets on age at onset of first observed oestrus, growth
rate, backfat reserve and body condition score of the gilts from weaning to
puberty. Fifty-four (54), eight week old weaner gilts were used for this trial.
They were randomly assigned to nine experimental treatment diets having
different combinations of protein (16%, 18% and 20% crude protein) and energy
(2800 kcal/kg, 3000kcal/kg and 3200kcal/kg) with six (6) gilts per treatment.
The gilts in each treatment were housed in pairs making up three (3) replicates
per treatment. Estrus detection was carried out twice daily at 0800hr and
1600hrs in the presence of mature boar beginning from the age of five months.
Blood samples were collected from two pigs per treatment by humane puncture of
the ear vein for haematological and biochemical analysis. In addition, two (2)
gilts from each treatment were randomly selected, slaughtered and their
reproductive organs excised and examined. Linear body measurements (body
length, chest girth, height at withers and flank-to-flank) were also recorded.
Data collected were analyzed according to factorial arrangement of treatments
in a completely randomized design (CRD) whereas stepwise multiple linear
regression analysis was used to generate prediction equations between body
weight and linear body measurements. In experiment 2, eighteen (18) gilts with
different body conditions and backfat thickness were selected and assigned to
experimental treatments with six gilts per treatment. All the gilts were
weighed and mated twice at the second observed estrus. Pregnancy was confirmed
by the gilt not returning to heat after 21 days of observation for signs of
heat after breeding. Gilts were fed 2.1 kg of an 18% CP diet daily throughout
gestation. Their feed was increased to 3.0 kg of feed daily during lactation
until weaning. Gilts were monitored and their reproductive indices recorded
throughout gestation and lactation. The pre-weaning performances of their
piglets were also recorded until weaning at day 35. Data collected were subjected
to one way analysis of variance (ANOVA) for a completely randomized design
(CRD). Results of the first experiment indicated that diet containing
3000kcal/kg or 3200kcal/kg metabolizable energy and 18% crude protein was the
optimum required for gilts to grow faster and reach the minimum threshold of
age, body weight, backfat reserve and body condition necessary for early
attainment of first oestrus and future reproductive processes. On the other
hand, the result also showed that when pork of a moderate fatness (lean pork)
is in demand, gilts should be fed diets having 2800kcal/kg of metabolisable
energy and either 16 or 18% crude protein. High coefficient of determination (R2)
values of 0.96, 0.95, 0.93 and 0.45, respectively, were recorded between body
(Y) weight and body length (BL), heart girth (HG), flank-to-flank (FF) and
height-at-withers (HW) measurements. Prediction equations for body weight of
the gilts were, Y = 0.83 x BL – 33.53, Y = 1.07 x HG – 37.86, Y = 1.22 x FF –
37.14 and Y = 0.86 x HW – 14.83. Results
of the multiple linear regression showed that with effective management,
farmers, researchers and prospective pig buyers can use the prediction
equations for body length, heart girth and flank-to-flank measurements to
easily estimate the body weight of their pigs especially, during selection,
drug administration and/or determination of market weight and prices. In the
second experiment, results showed that body condition of gilts at mating
affected their gestation weight gain, lactation body weight losses, litter size
at birth and weaning, growth rate of their piglets, pre-weaning mortality and
weaning-to-estrus intervals, etc in favour of gilts with normal and fat body
conditions. It was concluded that in any commercial pig industry where the
management is interested in increasing sow lifetime productivity, replacement
gilts should be scored for body condition both subjectively and objectively
using ultrasonic equipment to determine their readiness to undergo the stress
of growth and reproduction. From an economic point of view, this is an
important factor that should be considered to determine the total value of pigs
produced within a given cycle. Hence, it is recommended that breeding gilts
should have at least between 15mm and 18mm backfat thickness at first mating
for effective and more balanced reproductive processes.
TABLE OF CONTENTS
Pages
Title
Page………………………………………………………………………………………….i
Certification………………………………………………………………………………………ii
Dedication………………………………………………………………………………………..iii
Acknowledgement………………………………………………………………………………..iv
Abstract…………………………………………………………………………………………..vi
Table
of Contents………………………………………………………………………………..viii
List
of Tables………………………………………………………………………………….…xiv
List
of Figures……………………………………………………………………………………xvi
CHAPTER ONE 1
1.1 INTRODUCTION 1
1.2 OBJECTIVES OF THE STUDY 4
1.3 JUSTIFICATION 4
CHAPTER TWO 7
LITERATURE REVIEW 7
2.1 GROWTH OF PIGS 7
2.1.1 Measures of postnatal
growth in pigs 7
2.1.2 Allometric growth 8
2.1.3 Nutritional influence on
growth rate 8
2.1.4 Effect of temperature on
growth of pigs 9
2.1.4.1 Effect of temperature on
performance of pigs 10
2.1.4.2 Effect of temperature of growth rate of piglets 11
2.1.5 Physiological effect of
hormones on growth 12
2.1.6 Birth weight in relation
to postnatal growth of pigs 14
2.1.7 Prenatal development of
muscle fibre in the pig 15
2.1.8
Growth rate of pigs relative to their birth and weaning
weights……………………….15
2.2 NUTRIENT REQUIREMENTS OF PIG 16
2.2.1 Protein and amino acids
requirements for growth of pigs 17
2.2.2 Energy intake of gilts
and sows 18
2.2.2.1 Physiological explanation for
small litter size, reduced conception rate and follicular growth 18
2.3 NUTRITION AND REPRODUCTIVE
PERFORMANCE 19
2.3.1 Nutrition and ovulation rate 19
2.3.2 Nutrition and puberty 21
2.3.3 Energy restriction and
length of estrus cycle 21
2.3.4 Influence of diet on
follicular development 22
2.3.5 Influence of diet on
embryo survival 22
2.3.6 Feed intake and
weaning-to-oestrus interval 23
2.4 PHYSIOLOGICAL PATHWAY INVOLVING
NUTRITION AND REPRODUCTION 24
2.4.1 Physiological role of
insulin on reproduction 24
2.4.2 Nutrition and hormonal
mechanisms involved in reproduction. 25
2.4.3 Physiological
relationship between high feed intake and progesterone secretion 25
2.5 MANAGEMENT AND FEEDING OF GILTS
DURING GESTATION 26
2.5.1 Gestational weight gain 29
2.6 FEEDING OF GILTS DURING LACTATION 30
2.6.1 Effect of lactation feed intake on
weaning-to-estrus interval 31
2.6.2 Effect of lactation feed intake on ovulation rate………………………….31
2.6.3 Lactation body weight loss 31
2.7 ONSET OF PUBERTY IN GILTS 32
2.7.1 Factors that influence age at
onset of puberty in gilts 32
2.7.1.1 Nutritional effect on the
puberty attainment in gilts 34
2.7.1.2 Impact of boar exposure on
the onset of puberty 35
2.7.1.3 Effect of season on age at
puberty 35
2.8 CONDITION SCORING IN PIG PRODUCTION 36
2.8.1 Body condition at
breeding 38
2.8.2 Body condition at
farrowing 39
2.8.3 Body condition at weaning 39
2.9 MEASURING BACKFAT 39
2.9.1 Backfat thickness and
reproductive performance in sow 40
2.9.2 Backfat thickness and
body lipid 41
2.10 MILK PRODUCTION OF SOW DURING LACTATION 42
2.10.1 Estimating milk production 44
2.11 SOME MEASURES OF REPRODUCTIVE PERFORMANCE IN FEMALE PIGS 45
2.11.1 Litter size 45
2.11.1.1 Some factors that determine the
size of weaned litter 46
2.11.2 Number of parity 46
2.11.3 Age at weaning 46
2.11.3.1 Advantages of early weaning 49
2.11.4 Liveweight at weaning 49
2.11.5 Litter birth weight 49
2.11.6 Piglet mortality 50
2.11.7 Weaning-to-estrus interval 51
2.11.7.1 Physiological explanation for
prolonged weaning-to-estrus interval 52
CHAPTER THREE 54
MATERIALS AND METHODS 54
3.1 Location and duration of study 54
3.2 Management of experimental animals 54
3.3 Experimental diets 54
3.4 Experimental design 56
3.5 Statistical design 60
CHAPTER FOUR 64
RESULTS 64
EXPERIMENT I 64
4.1 EFFECT OF DIETARY ENERGY AND PROTEIN
ON THE GROWTH AND REPRODUCTIVE PERFORMANCE OF GILTS 64
4.1.1 The effect of dietary
treatments on some reproductive and growth indices of gilts 64
4.1.1.1 Age at first oestrus 64
4.1.1.2 Body weight at first oestrus 65
4.1.1.3 Daily feed intake 65
4.1.1.4 Growth rate 66
4.1.1.5 Feed conversion ratio 66
4.1.1.6 Backfat thickness 67
4.1.1.7 Body condition score (BCS) 67
4.1.2 Relationship between age
at first oestrus, and body weight at first oestrus, growth rate, backfat
thickness and BCS 77
4.1.3 Effect of dietary energy
and protein on weight of reproductive organ, weight of ovary and ovulation rate 78
4.1.3.1 Weight of reproductive organ 78
4.1.3.2 Ovarian weight 78
4.1.3.3 Number of corpus luteum
(ovulation rate) 79
4.1.4 Relationship between
weight of reproductive organ, ovarian weight and number of corpus luteum 82
4.2 EFFECT OF VARYING ENERGY, PROTEIN AND
ENERGY X PROTEIN INTERACTION ON THE HAEMATOLOGICAL INDICES OF GILTS 84
4.2.1 Packed cell volume 84
4.2.2 Haemoglobin concentration 84
4.2.3 Red blood cell 85
4.2.4 White blood cell 85
4.2.5 Mean corpuscular volume 85
4.2.6 Mean
corpuscular haemoglobin concentration 86
4.2.7 Mean
corpuscular haemoglobin 86
4.2.8 Bilirubin 86
4.2.9 Aspartate transaminase or serum glutamic oxaloacetic acid (SGOT) 87
4.2.10 Alanine
transaminase or serum glutamic pyruvic acid (SGPT) 87
4.2.11 Alkaline phosphatase 87
4.3 Effect of dietary energy and protein
levels on linear body measurements of gilts at first oestrus 91
4.3.1.1 Body length 91
4.3.1.2 Heart girth 91
4.3.1.3 Flank-to-flank 91
4.3.1.4 Height at withers 92
4.3.2 Relationship between body
weight and linear body measurements of gilts 95
EXPERIMENT II 97
4.4 Effect of body condition on the
reproductive performance of gilts 97
4.4.1.1 Gestation length 97
4.4.1.2 Gestation body weight gain 97
4.4.1.3 Gestation backfat gain 97
4.4.1.4 Backfat of gilts at farrowing 97
4.4.1.5 Lactation body weight loss 98
4.4.1.6 Lactation backfat loss 98
4.4.1.7 Sow 21 day milk production 98
4.4.1.8 Weaning-to-oestrus interval 99
4.4.2 Effect of body condition
of gilts on litter performance 101
4.4.2.1 Average litter size at birth 109
4.4.2.2 Average litter size at
weaning 102
4.4.2.3 Average piglet birth weight 102
4.4.2.4 Average piglet weaning weight 102
4.4.2.5 Average piglet growth rate 102
4.4.2.6 Percent survival to weaning 103
4.4.2.7 Pre-weaning piglet mortality 103
CHAPTER FIVE 106
DISCUSSION 106
EXPERIMENT I 106
5.1 Effect of dietary energy and protein on the attainment of puberty
in gilts 106
5.2 Effect of dietary energy and protein on haematological and
biochemical indices of gilts 115
5.3 Effect of dietary energy and protein level on linear body
measurements of gilts at first oestrus 116
5.3.1 Relationship between body weight and linear body
measurements of gilts 117
EXPERIMENT II 118
5.4 Effect of body condition at mating on
the reproductive performance of gilts and pre-weaning growth of their piglets 118
5.5 Summary and conclusion 126
REFERENCES…………………………………………………………………………………128
LIST OF TABLES
Tables
Page
Table 1: Nutrient requirement
of pigs as reported by different authors 17
Table 2: The influence of
premating feed intake on subsequent litter size and piglet performance 21
Table 3: Recommended feeding
levels of sow/gilt during various stages of gestation 29
Table 4: Average age at onset
of puberty of gilts as reported by various authors 33
Table 5: Relationship between
body condition score and backfat thickness 38
Table 6: Relationship between backfat
body condition and feeding intake 38
Table 7: The effect of litter
size on milk yield in the sow 44
Table 8: Estimation of milk production (M), milk
dry matter (DML), Energy (EL) and Nitrogen (NL)
output of gilts during a 21day lactation 45
Table 9: Weaning ages of
piglets as reported by various authors in different countries 48
Table 10: Percentage composition of experimental diets……………………55
Table 11: Proximate composition of experimental diets………………56
Table 12: Relationship between
body condition score and ultrasonic backfat levels 57
Table 13: Pre-mating body
condition score and backfat groups 59
Table 14: Percentage
composition of diet used during gestation and lactation 59
Table 15: Proximate Composition of Gestation and Lactation Diets…………59
Table 16: Analysis of variance
of energy and protein effects on age at first oestrus, weight at oestrus,
growth rate, backfat reserve and body condition score (BCS) 68
Table 17: Least square means
(±SE) of the effects of energy and protein interaction on age at first oestrus,
BW at first oestrus, growth rate, backfat reserves and body condition score 69
Table 18: Pearson correlation
coefficients between age and body weight at first oestrus, growth rate, backfat
thickness and body condition score 78
Table 19: Analysis of variance
of energy and protein effects on weight of reproductive organs, and number of
corpora lutea. 80
Table 20: Least square means (±SE) of the effects dietary treatments on weight of reproductive organ, ovarian weight and number of corpora lutea of gilts at first oestrus………………………………81
Table 21: Pearson correlation
coefficient between weight of reproductive organ, ovarian weight and number of
corpora lutea 83
Table 22: Analysis of variance
of energy, protein and energy x protein interaction on the haematological
indices of gilts 89
Table 23: Least square means (±SE)
of the effect of dietary treatments (energy and protein) on the haematological
indices of gilts 90
Table 24: The analysis of
variance of energy and protein effects on linear body measurements of gilts at
first oestrus 93
Table 25: Least square means ± SE
of the effects of energy and protein interaction on linear body measurements of
gilts at first oestrus 94
Table 26: Correlation
coefficients showing interrelationships between various measurements and body
weight (kg) 96
Table 27: Relationship between
live weights and linear measurements of pigs 96
Table 28: Stepwise multiple
regression prediction of body weight from body measurements; regression
coefficients. 96
Table 29: Analysis of variance
and descriptive statistics of the effect body condition on reproductive
performance of sow 100
Table 30: Effect of Duncan mean
on the reproductive performance of sows with different body condition 101
Table 31: Analysis of variance
of the effect of body condition on litter performance 104
Table 32: Effect of Duncan mean
on the litter performance of gilts with different body condition 105
LIST OF FIGURES
Figures Page
Fig. 1: Interaction of energy
and protein on average age at first oestrus of gilts 70
Fig. 2: Interaction of energy
and protein on average body weight of gilt at first oestrus 71
Fig. 3: Interaction effect of
energy and protein on average daily feed intake 72
Fig. 4: Interaction of energy
and protein on average growth rate of gilts at first oestrus 73
Fig. 5: Interaction of energy
and protein on average feed conversion ratio of gilts at first oestrus 74
Fig. 6: Interaction of energy
and protein on average backfat thickness of gilts at first oestrus 75
Fig. 7: Interaction of energy
and protein on average body condition score of gilts at first oestrus 76
CHAPTER ONE
1.1 Introduction
Recent report (Spore, 2007) showed
that pork is the world most widely consumed meat making up about 40 per cent of
the total meat consumed worldwide. The high pork consumption has been
attributed to the high cost of beef and the fear of avian influenza for poultry
(Spore, 2007). In Africa, however, it barely
accounts for 10% of meat consumed. From 1990 to 2005, its production has risen
from 500,000 to 800,600 tonnes, probably as a result of rapid urbanization
which interestingly has boosted production (Spore, 2007). In Nigeria, FAO
(2005) reported a 4 per cent increase in the annual growth rate for pig
production from 1990 to 2000 and this was adjudged to be the highest among
other livestock species.
These
reports are an indication that swine production has the potential for bridging
the protein deficiency gap in this country. This is because pigs are endowed
with natural genetic potentials that support rapid growth and high reproductive
performance. For instance, pigs have a rapid growth rate and demonstrate
excellent capacity for reproduction being litter-bearing in nature (Holness,
2005). They are characterized also by the best efficiency of nutrient
transformation into high quality animal protein (Spore, 2007). These attributes
have not been completely harnessed in this country thus leading to the slow
increase in the supply of pork.
The performance of the breeding herd
is fundamental to the financial success of any pig enterprise. According to
White (1996) and Whittemore (1998), pig production is often assessed based on
the number of litters produced per sow per year, the number of piglets produced
per litter, and the viability of those piglets. Also, the lifetime productivity
of the female within the herd is taken into account. Thus, the young gilt
represents the future of any pig enterprise and if not fed properly, is
unlikely to achieve her reproductive potential of rearing 60 to 70 pigs over 6
to 7 parities (Scharlach, 1998). It is therefore necessary to provide gilts
with adequate nutrition in order to maximize litter growth rate, and minimize
empty sow-d
