ABSTRACT
A 16-week study was conducted to evaluate the effect of biostimulation on behaviour, growth,
and reproduction of rabbits. Seventy five (crossbreds) mature rabbits (2.6 -2.70 kg), comprising
of 50 nulliparous does aged, 6-7 months old and 25 bucks, (8-10 months old), were used for this
study. The rabbits were allocated into five treatment groups in a completely randomised design
(CRD). Each treatment consisted of 10 nulliparous does and five bucks. The study plan involved
an exposure ratio of one buck to two does, implying five replications per treatment and each
replicate containing two does and one buck. However, the does in the control group were not
exposed to any buck. The does in the treatment groups were placed in opposite cages separated
by a distance of 2.5 cm to the bucks at a ratio of 2 does: 1 buck for 7,14,21 and 28 days of
exposure. The results showed that the behavioural response of the does ranging from flattening at
a corner, circling, mounting without lordosis and mounting with lordosis differed significantly
(P<0.05) across treatments. The frequency of vulva colour occurrence varying from white, red to
pink across treatments were observed. The reproductive performance of the biostimulated does
also differed significantly (P<0.05) as gestation length, pregnancy rate and average litter weight
at weaning were higher in the treatment groups. Reaction time, sperm motility, percentage live
sperm, percentage dead sperm and percentage coiled tails of the exposed bucks differed
significantly (P<0.05) from the control. There were evidence of linear increase in hormonal
profiles (estradiol and testosterone), as duration of exposure advanced to 7 and 14 days,
respectively. Therefore, this study suggests that biostimulation can be a veritable tool for
improving reproductive performance in rabbits. Also, it was noted that exposing rabbit does to
rabbit bucks longer than 7-14 days prior to mating may adversely affect their reproductive
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performance. Hence, it is recommended that farmers should expose rabbit does to rabbit bucks 7
days prior to mating or artificial insemination for higher reproductive performance.
TABLE OF CONTENTS
Title Page …………………………………………………………………………………………………………………………. i
Declaration ……………………………………………………………………………………………………………………… ii
Certification ……………………………………………………………………………………………………………………. iii
Acknowlegdements ………………………………………………………………………………………………………….. iv
Dedication ………………………………………………………………………………………………………………………. v
Abstract …………………………………………………………………………………………………………………………. vi
Table of Contents …………………………………………………………………………………………………………… viii
List of Tables …………………………………………………………………………………………………………………. xii
List of Figures ……………………………………………………………………………………………………………….. xiii
CHAPTER ONE
1.0 Introduction ……………………………………………………………………………………………………………….. 1
1.1 Justification ………………………………………………………………………………………………………………… 3
1.2. Objectives …………………………………………………………………………………………………………………. 4
1.3 Research hypothesis————————————————————————————–4
CHAPTER TWO
LITERATURE REVIEW
2.1. Brief History and Origin of Domestic Rabbits ……………………………………………………………………. 6
2.2 Breeds of Rabbit ………………………………………………………………………………………………………….. 6
2.3. Physiology of the Rabbit Doe…………………………………………………………………………………………. 7
2.3.1 Puberty and sexual maturity in rabbit Does ……………………………………………………………………… 7
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2.3.2 Estrus and estrous cycle in rabbit does ……………………………………………………………………………. 8
2.3.3 Mating in rabbits ……………………………………………………………………………………………………….. 8
2.3.4 Sexual receptivity in rabbits …………………………………………………………………………………………. 9
2.3.5 Mechanism of ovulation in rabbit does………………………………………………………………………….. 10
2.3.6 Gestation and pseudo-pregnancy in rabbit does ………………………………………………………………. 12
2.3.7 Testing for pregnancy ……………………………………………………………………………………………….. 12
2.4 Physiology of the Rabbit Buck ………………………………………………………………………………………. 13
2.4.1 Anatomy of the rabbit bucks reproductive system ……………………………………………………………. 13
2.4.2 Puberty and sexual maturity in rabbit bucks …………………………………………………………………… 16
2.4.3 Spermatogenesis and sperm production in rabbit bucks …………………………………………………….. 16
2.5. Semen characteristics of rabbit bucks …………………………………………………………………………….. 19
2.5.1 Gel plug…………………………………………………………………………………………………………………. 19
2.5.2 Seminal plasma ……………………………………………………………………………………………………….. 20
2.5.3. Sperm motility ……………………………………………………………………………………………………….. 21
2.5.4. Sperm morphology ………………………………………………………………………………………………….. 22
2.5.5 Semen volume and sperm concentration ……………………………………………………………………….. 23
2.5.6 Semen colour ………………………………………………………………………………………………………….. 24
2.6 Behaviours in rabbits———————————————————————————–24
2.7 Buck Effect ………………………………………………………………………………………………………………. 25
CHAPTER THREE
MATERIALS AND METHODS
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3.1. Experimental site ………………………………………………………………………………………………………. 27
3.2. Experimental Animals and Design ………………………………………………………………………………… 27
3.2.1 Experimental diets and management …………………………………………………………………………….. 27
3.3 Data Collection ………………………………………………………………………………………………………….. 28
3.3.1 Behavioural responses of the does ……………………………………………………………………………….. 28
3.3.2 Productive performance of the does and bucks ……………………………………………………………….. 29
3.3.3 Blood sampling and hormonal assay …………………………………………………………………………….. 29
3.3.3 Testosterone assay procedure ……………………………………………………………………………………… 29
3.3.4 Estradiol assay procedure …………………………………………………………………………………………… 31
3.3.6 Reproductive performance of the does ………………………………………………………………………….. 32
3.4 Model and data analyses ………………………………………………………………………………………………. 35
CHAPTER FOUR
RESULTS
4.1 Behavioural Characteristics of Rabbit Does Exposed to Rabbit Bucks at Different Durations of
Biostimulation——————————————————————————————-37
4.2 Productive Performance of Rabbit Does Exposed to Rabbit Bucks at Different Durations of
Biostimulation——————————————————————————————-37
4.3 Productive Performance of Rabbit Bucks Exposed to Rabbit Does at Different Durations of
Biostimulation——————————————————————————————-37
4.4. Vulva Colour of Rabbit Does Exposed to Rabbit Bucks at Different Durations of Biostimulation … 37
4.5 Sexual Receptivity of Rabbit Does Exposed to Rabbit Bucks at Different Durations of
Biostimulation——————————————————————————————-38
4.6 Hormonal Profile of Rabbit Does and Bucks under Different Durations of Biostimulation ………….. 38
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4.7 Reproductive Performance of Rabbit Does Exposed to Rabbit Bucks at Different Durations of
Biostimulation——————————————————————————————-39
4.8 Reproductive Performance of Rabbit Bucks Exposed to Rabbit Does at Different Durations of
Biostimulation——————————————————————————————–40
CHAPTER FIVE
DISCUSSION
5.1 Behavioural characteristics of rabbit does exposed to rabbit bucks at different durations of
biostimulation——————————————————————————————-49
5.2 Vulva colour of rabbit does exposed to rabbit bucks at different durations of biostimulation ……….. 49
5.3 Sexual receptivity of rabbit does exposed to rabbit bucks at different durations of biostimulation …. 50
5.4 Hormonal profile of rabbit does and bucks under different durations of biostimulation ………………. 51
5.5 Reproductive performance of rabbit does exposed to rabbit bucks at different durations of
biostimulation——————————————————————————————-52
5. 6 Reproductive performance of rabbit bucks exposed to rabbit does at different durations of
biostimulation——————————————————————————————-53
CHAPTER SIX
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS
6.1 Summary ………………………………………………………………………………………………………………….. 55
6.2 Conclusions ………………………………………………………………………………………………………………. 56
6.3 Recommendations ………………………………………………………………………………………………………. 57
References …………………………………………………………………………………………………………………….. 58
CHAPTER ONE
1.0 INTRODUCTION
The increasing demand for animal protein has aroused so much interest in the production of
animals with short generation intervals like rabbits (Obinne and Okorie, 2008). The expansion of
the livestock industry in Nigeria can hold great promise to bridge the gap in the supply and
demand of animal protein in the country (Apantaku et al.,1998) if attention is given to
microlivestock such as rabbit. The composition and quality of rabbit meat is comparable to
poultry and superior to meat of larger animals (ruminants), It is highly palatable with less fat,
sodium and cholesterol (Atteh, 2004). Rabbits are commonly raised to provide tender meat for
human consumption. Besides, high prolificacy is the most important economic factor in rabbit
production (Belhadi, 2004; Nofal et al., 2005). In addition to this, rabbits have a number of other
good characteristics that are advantageous to subsistence farming, such as their small body size
and short gestation period of 30-31 days. The daily weight gain is directly proportional to the
body weight which gives them rapid growth rate and early sexual maturity. These factors are
responsible for rabbits attaining the weight of sexual maturity 30 % faster than other animals and
makes them suitable as meat producing small livestock in developing countries (Arijeniwa et al.,
2000, Ajayi et al., 2005).
The profitability of rabbit production depends on the reproductive intensity and the number of
kits weaned from a litter (Castellini et al., 2010). Although rabbits are reflex ovulators, the
ovulation following instant mating sometimes does not result in successful conception. The
inherent prolificacy in rabbits is currently facing biochemical, biophysical and environmental
challenges which depresses their performance, therefore there is need for the application of some
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biological strategies to enhance their reproductive efficiency. Biostimulation methods are natural
and cheaper alternatives to improve the reproductive performance of animals. Such methods
have been found or tested in bulls (Bailey et al., 2005), bucks (Bonanno et al., 2011), hamsters
(Cooke et al., 2001) and rams (Kasimanickam et al., 2007). Other approach to promote a steady
reproductive performance in animals is the application of hormonal protocols (Rebollar et al.,
2006). This however, increases labour cost and possible adverse effects on health due to residual
effects.
The use of exogenous products such as hormones and antibiotics to improve livestock production
goes against the perception of the consumers. Castellini et al. (2006) reported that the European
Community Policy might impose a restriction on the use of hormones in relation to their residues
in meat, animal welfare and the desire to preserve a natural meat quality. For these reasons,
serious efforts have been made by the International Rabbit Reproduction Group (IRRG, 2005) to
set up alternative methods which do not require the use of hormones in rabbit production in order
to increase sexual receptivity at the time of insemination or natural mating. Several
biostimulation approaches such as animal manipulation (doe-gathering) at the time of semen
collection, dam-litter separation, evaluation of different reproductive rhythms or re-mating
intervals, adoption of different feeding programs, buck effect and photoperiods have been tried
in an attempt to obviate the use of hormones in animal reproduction (Ojeda and McCann, 2000).
These biostimulation methods are believed to stimulate the release of gonadotropins, luteinizing
hormone (LH) and follicle stimulating hormone (FSH) through visual, olfactory (pheromonal)
and tactile cues from the anterior pituitary gland under the influence of some releasing factors
from the hypothalamus (Ojeda and McCann, 2000). The release of LH and FSH provides
steroidal feedback to the hypothalamus which ensures the continuation of normal ovarian
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cyclicity (Frink, 1998). However, the exact effects and mechanism of biostimulation techniques
and the subsequent behavioural responses on the reproductive performance of rabbit does and
bucks have not been properly elucidated. Therefore, the present study was designed to evaluate
the effect of biostimulation on the reproductive performance of nulliparous rabbit does as well as
to ascertain its effects on semen characteristics of the bucks.
1.1 Justification
In order to contain the pressure of increased human population on the demand for meat and meat
products, rabbit (Oryctolagus cuniculus) production is a viable option, because of their
prolificacy, early maturity, fast growth rate, high genetic selection potential, high feed
conversion efficiency and economic utilization of space (Hassan et al., 2012). To ensure a
sustained rabbit production and development of the sector, rabbit breeds and breeding practices
should be explored and challenges identified. However, poor response of rabbit does during
service and subsequent decrease in ovulation and/or conception has necessitated the emergence
of possible and cost effective techniques in improving reproduction in rabbits. Sexual responses
of female rabbits to visual, acoustic/auditory and olfactory stimuli from the male have not been
properly investigated, but ovulation is believed to be induced by mating through a neuroendocrinological
reflex which provokes an LH surge (Bakker and Baum, 2000).
Frank (1966) reported the possibility of certain pheromones secreted by the sebaceous glands of
rabbit bucks to induce sexual receptivity in the does. It has also been suggested that rabbit does
emit specific signals containing information on her sexual state that attracts male rabbits
(Hudson and Distel, 1990). Till date, the precise nature of the pheromones or signals supposedly
exchanged between the male and female rabbits remain obscure. However, it appears that male
presence is beneficial to receptivity and fertility in nulliparous does (Berepudo et al., 1993) but
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not in lactating does (Kustos et al., 2000; Eiben et al., 2001; Bonanno et al., 2003).
Biostimulation is one of the techniques which has been tested on other species and appears to be
promising in enhancing fertility in animals (Theau-Clement, 2005). In addition, several
evidences have shown that the use of exogenous gonadotropic hormones such as equine
chorionic gonadotropin (eCG) to improve reproductive performance in rabbits has resulted in
resistant effects, with subsequent decrease in conception rate and increase in mortality rate
following frequent and/or high dosage treatment (Theau-Clément, 2007). Therefore, a practical
and potent non-hormonal approach in improving fertility in rabbits remains imperative. This
study aimed at evaluating the effect of different durations of exposure on the reproductive
performance of rabbit does and bucks towards finding the best duration of exposure for optimum
performance.
1.2. Objectives
The broad objective of this study was to evaluate the effect of different durations of exposure on
the reproductive performance of rabbit does and bucks. The specific objectives were to
determine the:
a. Behavioural responses of rabbit does exposed to rabbit bucks at the point of mating
b. Productive performance of rabbit does and bucks at different durations of biostimulation
c. Reproductive performance and hormonal profile of rabbit does and bucks at varied durations
of biostimulation
1.3. Research hypotheses
H0: Biostimulation has no effect on the behavioural response of rabbit does and bucks
H1: Biostimulation has an effect on the behavioural response of rabbit does and bucks
Ho: Biostimulation has no effect on the productive performance of rabbit does and bucks
H1: Biostimulation has an effect on the productive performance of rabbit does and bucks
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Ho: Biostimulation no effect on the reproductive performance and hormonal profile of rabbit does
and bucks
H1: Biostimulation has an effect on the reproductive performance and hormonal profile of rabbit
does and bucks
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