School of Agriculture, Food and Ecosystem Sciences - Theses
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ItemInterspecific hybridisation in Clematis L( 2000)Experiments were conducted to evaluate various aspects of the cytology and reproductive biology of selected Clematis species and cultivars. The principal objective of the study was the production of new cultivars suitable for ornamental horticulture by means of intra- and inter-specific hybridisation. The hybridisation studies were mainly focussed on the cultivar C. armandii 'Snowdrift'. The Clematis species and cultivars, C. aristata, C. armandii 'Snowdrift', C. 'Blue Peak', C. X cartmanii 'White Carpet', C. cirrhosa var. balearica, C. cirrhosa 'Lansdowne Gem', C. 'Duchess of Albany', C. tubulosa, C. microphylla var. microphylla, C. ?patens 'Miss Bateman', C. napaulensis and C. recta were studied cytologically and all were found to have a diploid chromosome number of 2n=16. All had a generally similar karyotype morphology consisting of five pairs of m chromosomes, one pair of st chromosomes, and two pairs of t chromosomes. The latter chromosome class was often observed to possess a chromosome satellite. Significant differences in overall somatic chromosome complement length and individual chromosome class length at metaphase were found between some species and cultivars. The possession of an identical chromosome number and similarities in chromosome length were not necessarily indicative of crossability between the Clematis species and cultivars examined in the present study. Seed-set data from artificial (hand) self-pollination of C. armandii 'Snowdrift', C. 'Blue Peak', C. cirrhosa var. balearica, C. cirrhosa 'Lansdowne Gem', C. 'Duchess of Albany', C. ?patens 'Miss Bateman' and C. recta indicated that these species and cultivars show strong self-incompatibility. Seed-set after artificial self-pollination of C. armandii 'Snowdrift' at various stages of floral development, indicated that the level of self-incompatibility in this cultivar did not change substantially during the various stages of floral development, and observation of pollen / pistil interactions revealed that 'self' pollen was rejected after pollen-tubes penetrated the stigma and grew to at least one-third of the style length. This, and other evidence from the scientific literature, indicated that self-incompatibility in this species is likely to be under gametophytic control. The flowers of Clematis armandii 'Snowdrift' have overlapping male and female phases with a bias towards protandry. Stigma receptivity to pollen for this cultivar as indicated by pollen capture, pollen germination and non-specific esterase activity in the stigma pellicle, began approximately one to two days after anthesis and lasted for at least 12 days. The ability of the stigmas to capture pollen and the rate of germination of this captured pollen did not appear to be directly related. Crossability of the Clematis species and cultivars used in this study was generally related to the degree of phylogenetic closeness of the taxa. However, the carpels of C. armandii 'Snowdrift' supported pollen germination and pollen-tube growth to at least one-third the length of the style when either of the distantly related C. aristata or C. X cartmanii 'White Carpet' were used as the male parent. Barriers to crossing between C. armandii 'Snowdrift' and C. X cartmanii 'White Carpet' could not be overcome either by shortening the styles of the former cultivar or by applying a mixture of compatible C. armandii 'Apple Blossom' and incompatible C. X cartmanii 'White Carpet' pollen to the stigmas of this cultivar.
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ItemSocial and sexual factors affecting reproduction of the domestic boar( 1978)This thesis describes the results of work in three general areas; (i) the influence 0f the social environment during rearing and after puberty on the sexual behaviour of the boar, (ii) the role of the courting behaviour of the boar in his reproductive performance, and (iii) the influence of sexual stimulation on the spermatozoan output of the boar. The major portion of the work relates to the importance of the social environment. Boars reared from three weeks of age in the absence of visual and physical contact with pigs had markedly lower copulatory performance and level of courting activity compared with those reared from three weeks in either an all-male or mixed-sex group. Lack of physical contact with pigs during rearing was responsible for approximately 70% of this depression in copulatory performance. The copulatory performance of boars reared from 12 weeks of age in the absence of visual and physical contact with pigs was considerably less than that of boars reared in an all-male group, but the difference was not significant. Boars reared from three or 12 weeks- of age individually in adjacent wire-mesh pens had similar copulatory performance to that of group-reared boars. However, an apparently important feature of courting behaviour, 'nosing activity', was significantly reduced for those boars reared from three weeks individually in adjacent wire-mesh pens. These data were interpreted as evidence of the importance of social contact, particularly physical contact with boars or gilts, during rearing on the level of sexual behaviour of the boar. In addition to the social environment during rearing, the social environment after puberty was demonstrated to have a dramatic influence on the level of sexual behaviour of the boar. Isolation of post-pubertal boars from female pigs for six weeks significantly reduced their copulatory performance and level of courting activity. The stimuli received from the presence of sexually receptive or sexually non-receptive female pigs were equally capable of maintaining the level of sexual behaviour of the boar. Two experiments conducted at a commercial piggery revealed the importance of the courting behaviour of the boar on reproductive performance. A significant positive correlation was found between the observed level of nosing activity during courting and the conception rate record of the boar. The proposal that the nosing activity of the boar may stimulate one or more physiological mechanisms leading to fertilisation in the sow is supported by the results of the second experiment. Brief courting of sows by a boar prior to artificial insemination significantly increased the farrowing rate and litter size of group-housed sows. Finally, sexual stimulation of boars prior to semen collection significantly increased the number of spermatozoa . in the sperm-rich fraction of the ejaculate. The technique of sexual stimulation of the boar involved either allowing the boar a false mount and then briefly restraining him or allowing the boar to observe a semen collection. The former technique failed to maintain a significant increase in the yield of spermatozoa from the sperm-rich fraction over a six-week collection period. Prostaglandin F2a, which may be involved in the mechanism by which sexual stimulation increases the number of spermatozoa in the short term, was also studied. Administration of 20 mg of PGF2a 30 minutes before collection significantly increased the number of spermatozoa in the sperm-rich fraction of the ejaculate. The experiments of this thesis demonstrate that sexual and social factors have a major influence on the reproduction of the domestic boar.
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ItemStudies on the reproduction of young ewes( 1973)The experiments described in this dissertation were carried out at the S.S. Cameron Laboratory between January 1971 and December 1973. This study was supported by grants from the Wool Research Trust Fund, and the Victorian Department of Agriculture. I wish to thank Dr. R.H. Watson, Chief, Division of Animal Industry for allowing me the opportunity to submit this thesis and also for his useful comments on the presentation of the experimental data. I would like to express my appreciation to Dr. P.D. Mullaney, Officer-in-Charge, S.S. Cameron Laboratory, for his support throughout the entire period of this project. During the experimental phase of this project, I was under the supervision of Dr. M.A.deB. Blockey. It is to Dr. Blockey that I attribute my interest in the young ewe problem and I wish to sincerely thank him for his guidance, enthusiasm and collaboration in the experiments described in Chapters 2, 4 and 6. During the experimental period much of the technical assistance and field work was ably carried out by Mr. R. Parr to whom I am greatly indebted. The technical assistance of Messrs. P. Langdon, A. Makin, T.Howard, A. Williams, R. Baxter, D. Rizzoli, D. Kearins, W. Chamley, J. Cerini, Mrs. M. Perry, Misses H. Keller, E. Renden, E. Wilson and Mrs. M. Cerini is acknowledged. I wish to thank Dr. I.A. Cumming, Dr. B.J. Restali, Miss H. Hearnshaw and Mr. C.G. Winfield for their. guidance, technical assistance and collaboration. Thanks also is due to the Staff of the Reproduction Research Section, University of Melbourne, S.S. Cameron Laboratory who contributed much technical assistance and carried out the required hormonal assays. Special thanks must go to Drs. J.K. Findlay and Joan Buckmaster for their interest in this project and expertise with the hormone assays. I would like to thank Mr. R. Jardine for his advice in regard to the statistical analyses and for his assistance in the analysis of the experiment described in Chapter 2. I would like to thank Miss Lyn Bourke for her diligence in the typing of this thesis. I wish to acknowledge my indebtness and express my thanks to Drs. R.A.S. Lawson and M.J. Sharkey whose advice has been most appreciated in the preparation of this manuscript. And finally I would like to take this opportunity to thank my parents and. wife. I thank my parents for every sacrifice they made in order to provide for me a secondary and tertiary education and I thank my wife, Hele, for her continual understanding, patience and encouragement.
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ItemAcute prenatal androgen treatment in sheep( 1994)The steroid environment of the cell nucleus in differentiating mammals is a major determinant of subsequent cellular function. The exogenous manipulation of this environment has resulted in permanent changes in metabolism, behaviour, reproduction, endocrinology and growth. The experiments described in this thesis suggest that an acute exposure to exogenous androgen, established as an intramuscular depot in the gravid ewe, can effect these changes. The growth responses resulting from acute prenatal androgen treatment (APAT) are similar to those reported for chronic androgenization.The undesirable side effects of androgenization, e.g. reduced birthweight, deformed external female genitalia and masculine urination posture, can be avoided with APAT. The literature and the experimental data indicate that mammalian development is strongly influenced by tissue steroid status. Furthermore, the literature and the experimental data suggest that both the timing and duration of the modification of mammalian developmental steroid status (MDSS) affect the response of ovine tissues to androgens. Some of the observed responses appear refractory in nature. The periods of sensitivity to MDSS manipulation differ between tissues and between species. MDSS manipulation via APAT is capable of effecting changes to tissues not normally considered sexually dimorphic, including the ovine pancreas, liver, brain, kidney, bone and wool follicle.
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ItemGenetic studies of reproduction in four species of domestic animals( 1975)The objectives of this study are to determine the most effective technique of assessing reproductive performance, to analyse factors influencing the performance and the problems involved in analysing data from records of performance from commercial farms, and to make recommendations for improving the reproductive performance, in meat-producing species of farm animals using genetics methods. The study consists of a review of the present status of knowledge on the genetics of reproduction, a series of analyses of reproductive performance using records of performance of three meat-producing species of farm animals (beef cattle, pigs and sheep) and one species of laboratory mammal (mice) and concludes with some suggestions of steps that may be taken for recording performance and improving breeding programs in meat producing farm animals to raise reproductive performance. The review discusses the concepts of reproduction and growth, identification and measurement of reproductive traits, factors affecting reproductive performance and alternative strategies for improving the level of reproduction in domestic animals. Reproduction is considered to be a function of fertility, survival and growth and the success of reproduction depends on the total contribution made by the sire, the dam and the progeny resulting from specific matings. Studies on the reproductive performance in beef cattle cover two chapters. The first (Chapter 2) describes an analysis of reproductive performance of beef cattle from 13 properties in Victoria. The overall data gave a mean age at first calving of 863.5 days, mean calving interval of 361 days, calving rate of 88.7%, mortality rate at birth of the calves of 4.3%, preweaning mortality of 1.5%, postweaning mortality of 0.3% and twinning rate of 1.5%. At this level of performance the rate of reproduction of beef cattle from commercial properties in Victoria is better than that in northern Queensland and comparable if not better than those reported in the United States. The heritability estimates of reproductive traits calculated from the records of performance in many cases gave values beyond the theoretical limits (from 0 to 1). This was attributed to confounding effects of management practices. The next chapter (Chapter 3) consists of studies on the effects of crossbreeding between British breeds of beef cattle (Angus, Hereford and Shorthorn) and the crossing of these breeds with Friesian sires and Friesian-cross heifers. Traits analysed include growth rates from birth to yearling age. Factors affecting these traits are examined and their heritability is estimated. Calving performance of the dams and twinning are also studied. Crossbred calves generally showed superior preweaning growth rate than the purebred calves and even better performance occurred if one of the parents was a Friesian. There were no significant differences among the crossbred calves produced by the crossbred dams and the purebred dams when both were mated to Shorthorn sires indicating that in the material available maternal heterosis had little influence on growth compared to F1 heterosis as expressed in the crossbred progeny. Birthweight and postweaning growth rate generally were moderately heritable but preweaning growth rate generally gave negative estimates of heritability indicating greater influence of environmental variations on the latter trait. Data obtained from crossbred progeny tended to give lower estimates of heritability than those from the purebred progeny. It was not possible to analyse traits related to fertility and postnatal survival because of imcomplete recording of performance from the farm. The analysis of reproductive performance of Corriedale sheep (Chapter 4) gave an overall conception rate of 91%, lambing rate of 112%, twinning rate of 37%, mortality of lambs at birth of 5%, mean period between start of mating and lambing of 166 days and lambing interval of 369 days. This level of reproductive performance is slightly higher than generally reported by other workers for various breeds of sheep. Selection for wool and twinning made in the flock did not seem to have produced any effect on reproduction. Ewes born twins were lighter at birth, had high rate of mortality, lower rate of preweaning growth and wool production, had a lower rate of conception, rate of lambing and rate of twinning at first mating, and reached their peak level of reproductive performance at an earlier age than those born as singles. Females born co-twin to a male in the same litter showed effects of being at a disadvantage in their prenatal and preweaning development. Preweaning body growth had fairly high estimates of heritability while fertility of the dam had very low estimates of heritability. Measurement of overall reproductive performance gave the highest estimate of heritability suggesting greater accuracy of this measurement as a measure of reproductive performance of female ruminants. The analysis of reproductive performance in pigs gave an overall estimate of 78.8% success at mating, total litter-size at birth of 9.4 of which 6.5% were stillbirths, total litter-weight of 12.2 kg., average weight of piglet of 1.43 kg. and gestation length of 115 days. Except for the rather low conception rate, the level of reproductive performance is comparable to those reported for various breed in Britain, Canada and the United States. The reproductive performance was mainly affected by parity of sow while traits related to fertility of sows and survival of progeny were improved by using crossbred dams. Development of a new breed through selection for high litter-size did not result in significant improvement in reproductive performance. The analysis also indicated that there was little to be gained by having a litter-size of over 12. Most of the reproductive traits had low estimates of heritability except for average conception rate of the individual boar which was shown to be moderately heritable and should therefore be included in a selection program. The analysis of the effect of selection for high litter weight at 9 weeks of age in two lines of mice when compared with a control line indicated that there was very little direct or correlated response except perhaps for some initial improvement in the average bodyweight of the individuals selected. On the other hand there was an overall decline in production towards the end of the selection culminating in the extinction of both the selected lines. This was associated with a rapid rise in inbreeding coefficient in the small populations. Heritability estimates of traits related to litter production in the control line indicated that these traits have low heritability, particularly if measurement was based on litter-size rather than on litter-weight. Estimation of heritability using data from the selected lines produced incredibly high estimates. Possible genetic implications of the results are discussed. The difficulties involved in analysing data recorded in commercial farms were discussed, particularly, the insufficiency of information being recorded in the performance records. Genetic factors influencing the various components of reproduction and the overall reproductive performance in domestic animals based on the results of the various analyses were also examined. The feasibility of applying the different methods for improving the reproductive performance was considered and some recommendations were put forward for, the improvement of reproductive performance in meat-producing species of farm animals in southern Australia. The recommendations may be summarised as the encouragement of mating of crossbred females derived from breeds of superior maternal ability and efficiency of reproduction to males derived from breeds of superior growth rate and selected for good records of success at mating.
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ItemLocal immunity in the reproductive tract of female pigs( 1993)The subject of this thesis concerns the local immune system of the reproductive tract of the female pig and the role it may play in the success of reproduction. The specific aims of this study were; (i) to localise and characterise immune cells in the reproductive tract of non-pregnant and pregnant pigs to allow a basis for an understanding of the local immune system in the reproductive tract of the pig; and (ii) to investigate the immunological influence of seminal plasma on the local uterine environment and explore the possibility of immunological involvement in the phenomenon of uterine priming to improve reproduction in gilts. Histological and immunohistochemical studies undertaken in pre-cycling and cycling gilts established the cellular basis for the local immune response in the reproductive tract. The major leukocyte cell types in the uterus of the pig are T lymphocytes, macrophages and neutrophils and their tissue migration and distribution is strongly influenced by the oestrous cycle. These studies show that the reproductive tract of the pig has a local immune system that provides an environment capable of mounting an immune response, and the various leukocyte phenotypes identified probably play an important interactive role in the cyclic cellular changes in structure and function of the endometrium. The work presented here showed that during pregnancy in the pig there are distinct changes in the presence and distribution of immune cells in the endometrium which may be evoked by exposure to paternal antigens. Further studies revealed marked differences when comparing the uterine lymph node of pregnant and non-pregnant pigs. Since the uterine node exclusively drains the uterus and the oviduct, these results provide strong evidence of a cellular immune response to pregnancy. In a study of the immunological influence of seminal components on the local uterine environment it was shown that mating with a vasectomised boar transiently induces an acute inflammatory response that includes dramatic changes in the tissue and cellular components in the endometrium. It was further revealed in vivo that seminal plasma induces the activation of lymphocytes in the uterine lymph node, while in vitro, seminal plasma fractions were shown to have a non-specific immunostimulatory effect on uterine lymph node cells. Together, these results demonstrate that pronounced immunological and physiological changes are induced by seminal plasma in utero. The results of field trials (Appendix A) indicated that pre-exposing the uterus with seminal plasma (prior mating with a vasectomised boar) can improve reproductive performance in gilts. The work presented in this thesis indicates that there is an important role for the local uterine immune system in porcine reproduction, and that the local uterine response to seminal plasma may play a key role in the success of reproduction in pigs.