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 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.

 

CHAPTER ONE

 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

 

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

 

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.

    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 neuro- endocrinological 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

 

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.

 

                      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:

1. Behavioural responses of rabbit does exposed to rabbit bucks at the point of mating

 

1. Productive performance of rabbit does and bucks at different durations of biostimulation

 

1. Reproductive performance and hormonal profile of rabbit does and bucks at varied durations of biostimulation

                      Research hypotheses

H_0: 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 H_o: Biostimulation has no effect on the productive performance of rabbit does and bucks H_1: Biostimulation has an effect on the productive performance of rabbit does and bucks

 

H_o: Biostimulation no effect on the reproductive performance and hormonal profile of rabbit does and bucks

H_1: Biostimulation has an effect on the reproductive performance and hormonal profile of rabbit does and bucks

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ABSTRACT

 

The absorptive nature of S by plants depends on desorption of S from soils. Understanding the kinetics desorption of sulphate as influenced by parent materials and biochar is critical for effective precision of S diagnosis and fertilization recommendations to ensure sustainable and profitable crop production and environmental protection. In this study, soils derived from three

 

• different parent materials namely; Chad formation (CF), Basement complex rock (BCR) and Kerri-Kerri formation (KKF) in the Sudan savanna and biochar soils were investigated on the kinetics of sulphate desorption behaviour. In the desorption experiment, soils were allowed to

 

adsorb sulphate as in the adsorption studies and the adsorbed sulphate was extracted by shaking for 30, 60, 150, 180 and 240 minutes with 15 ml Ca(H₂PO₄)₂ solution containing 500 mg P L^-1 respectively. Five kinetic models first-order, second-order, Elovich, fractional power and parabolic diffusion models were used to test best model for describing S desorption in the soils

 

of varying parent materials. Results indicated that the mean values of both soil pH in water and CaCl₂ were significantly (p>0.05) different between soil parent materials. The soils are low in organic carbon (range; 2.90 to 7.25 g/kg) in all the studied soils. The mean values of exchangeable bases and CEC were not significantly (p>0.05) different by soil parent materials. The mean values of the different forms of oxides were significantly different (p>0.05) by soil parent materials. The mean values of total sulphur and organic in all soils from three parent materials were significantly different (p > 0.05). The values of inorganic sulphur (Org.S) ranged from 18.33 to 123.78 mg/kg in all the soils across three parent materials, however the mean values were not significantly different (p>0.05). The results revealed that sulphate desorption decreased with increasing shaking time (range; 34.96 to 19.09 mg/kg) in all the studied soils. Rate of desorption was also characterized by an initial rapid desorption with > 65% being desorbed in the first 30 minutes which was considered as good index for describing S desorption maximum followed by a slow release that progressed gradually up to 240 minutes. The adsorption-desorption processes were irreversible and hysteretic in nature. The trend of magnitude of rate of desorption by the soil parent materials was in descending order:

 

CF>BCR>KKF. The study showed that the parabolic diffusion and first-order models were found to describe S desorption data satisfactorily as characterized by relatively high R² values and lowest S.E values by soil parent materials, respectively. Comparison of R² values of the best isotherm equations indicated that both Langmuir and Freundlich isotherm models were suitable to describe S desorption data in all the studied soils, as can be seen from R² greater than 0.98. However, in view of the low SE, Langmuir equation gave a better fit to experimental data in this study. Organic matter had a significant influence on modeling of S desorption in these soils. The results also revealed that the BC used in this study did not have significant effect on release of adsorb S (p>0.05). Based on the results, can be concluded that rate of sulphate desorption by these soils are time-dependent and mainly controlled by diffusion-controlled phenomena. It is recommended that sulphur management practice in the farm should be tied up with OM management.

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DEPLETION OF STRATOSPHERIC OZONE

ABSTRACT

Depletion of stratospheric ozone emerged as a political concern in the early 1970s in the United States in the debate over the devel­opment of a commercial fleet of supersonic transports. In the mid- 1970s it became a major political issue with regard to the use of CFCs in aerosol spray cans, and in 1978 the United States banned the nonessential use of CFCs as aerosol propellants. Efforts at ne­gotiating an international agreement controlling CFC use began in the 1980s and culminated in the 1987 Montreal Protocol. This paper traces the evolution of policy responses to stratospheric ozone de­pletion. The evolution of stratospheric ozone depletion policy can best be understood as a two-stage process. The first stage involves the emergence of stratospheric ozone depletion as a domestic issue in the United States and several other countries in the 1970s, while the second stage focuses on its transformation to an international issue in the 1980s. In addition to the emergence of stratospheric ozone depletion as an international political issue, three other factors are important in understanding the sources of the Montreal Protocol: (/) the evolving scientific understanding of the problem, (2) increas­ing public concern over the problem based on the threat of skin cancer and the discovery of the Antarctic ozone hole, and (3) the availability of acceptable substitutes for CFCs.

CHAPTER ONE/INTRODUCTION

Representatives from 24 nations, meeting in Montreal in September 1987, signed the “Montreal Protocol on Substances that Deplete the Ozone Layer,”¹ an international agreement designed to reduce the world­wide production and use of chlorofluorocarbons (CFCs). This protocol is the result of years of negotiation fostered by the United Nations En­vironment Programme (UNEP) among the major CFC producing coun­tries. Its formulation was a response to a growing international consensus on the need to protect stratospheric ozone from depletion by CFCs. The Montreal Protocol is a landmark agreement in that it is the first inter­national treaty for mitigating a global atmospheric problem before serious environmental impacts have been conclusively detected. As such, the Montreal Protocol has stirred much interest, and both scientists and pol­icymakers have suggested that it can be used as a model for international agreements on other global environmentalproblems, especially the prob­lem of CO2 and trace-gas induced global warming.

Before such a comparison to other environmental problems can be made, however, it is useful to understand the Montreal Protocol in its historical and political context. Depletion of stratospheric ozone is an example of both the complicated and the global nature of contemporary environmental problems, and the Montreal Protocol shows that innovative approaches to such global environmental problems are possible. During the past two decades concern over stratospheric ozone has evolved from a fringe environmental issue to a major policy issue of national and international importance. An analysis of this evolution is important for understanding both the value of the Montreal Protocol and its implications for other global atmospheric problems.

The evolution of stratospheric ozone policy can be understood as a two-stage process: (1) the development of domestic regulations controlling CFC use in aerosol spray cans in the United States and several other countries in the mid- and late-1970s, and (II) the development of an international policy response to the problem of global stratospheric ozone depletion in the 1980s. These are not separate issues. The development of an international response clearly followed from the concern raised in the United States, Canada, Sweden, and other countries which had taken unilateral action to control CFCs in the 1970s. However, many important differences between stage 1 and II make this distinction a useful tool for analysis. I argue that four key factors are important in understanding the evolution of stratospheric ozone policy: (1) the recognition that ozone depletion is a global problem requiring an international response; (2) the evolving scientific understanding of stratospheric ozone depletion and its influence on policymakers; (3) increasing public concern based on the threat of skin cancer and the perception of the potential for global catas­trophe associated with the discovery of the Antarctic ozone hole; and (4) the availability of acceptable substitutes for CFCs.

This paper analyzes the evolution of stratospheric ozone policy. The first section reviews the science behind the problem of CFC-induced stratospheric ozone depletion. The next two sections discuss the emerg­ence of stratospheric ozone depletion as a national political issue in the United States during stage I, and its evolution to an international political issue during stage II. This is followed by a discussion of how the evolving scientific understanding of the problem, the catastrophic nature of the risks, and the availability of alternatives to CFCs influenced the final negotiations on an international agreement. The last section examines the Montreal Protocol and discusses its prospects for success.

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