Bioscientifica proceedings最新文献

{"title":"Cloning of embryos","authors":"V. Pursel, D. Bolt, K. Miller, Carl A. Pinkert, Robert E. Hammer, R. Palmiter, R. Brinster","doi":"10.1530/biosciprocs.13.0016","DOIUrl":"https://doi.org/10.1530/biosciprocs.13.0016","url":null,"abstract":"","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86171356","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Factors Affecting Reproductive Efficiency of the Breeding Herd","authors":"G. Tomes, H. E. Nielsen","doi":"10.1530/biosciprocs.11.0025","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.0025","url":null,"abstract":"The great variation that exists in the productivity of sow herds is well illustrated by a Danish survey based on a large number of commercial breeding herds where the number of piglets weaned/sow/year ranged from 10 to 22 (Aagaard and Studstrup, 1977). The financial consequences are clearly demonstrated in Figure 25.1 where overall profitability of the breeding unit rises as the number of pigs weaned/sow/year increases. It is impossible to make a general assessment of financial implications of reproductive efficiency for various countries but such a trend is general. In herds producing small numbers of pigs/sow/year there are often many unproductive sows with the attendant penalties of extra feed, labour and","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43242008","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Establishment and Maintenance of Pregnancy","authors":"F. Bazer, R. Geisert, W. W. Thatchert, R. M. Robertst","doi":"10.1530/biosciprocs.11.0012","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.0012","url":null,"abstract":"In many submammalian species considerable energy is expended by the female to produce liver and/or reproductive tract secretions which are incorporated into ova prior to ovulation. Fertilization of these ova may or may not occur. Females of these submammalian species, therefore, expend energy for the reproductive process regardless of whether offspring result. In mammalian species, such as the pig, restrictions are placed upon the extent to which energy is expended for support of endometrial secretory activity. In the absence of fertilized ova and blastocysts developing in synchrony with the uterine endometrium, the period of endometrial secretory activity is limited primarily to the mid to late luteal phase of the oestrous cycle. In the pig, endometrial secretory activity is dependent upon maintenance of functional corpora lutea (CL). The lifespan of the CL, in turn, is limited during the oestrous cycle by endometrial production of a uterine luteolytic factor which is assumed to be prostaglandin F2a (PGF2a). Release of PGF2c, from non-pregnant uterine endometrium results in morphological regression of CL, progesterone secretion ceases and, therefore, progesterone-dependent endometrial secretory activity is terminated in the late luteal phase of the oestrous cycle. In pigs having normally developing blastocysts, endometrial—blastocyst interactions begin to occur by day 11 of pregnancy. Blastocysts signal their presence, presumably through oestrogen production, which results in CL maintenance and continued endometrial development and secretory activity. Species, such as the pig, that have central or fusion implantation (Schlafke and Enders, 1975) appear to depend upon endonietrial histotroph (Amoroso, 1952) for a major portion of pregnancy. Endometrial secretions of the pig are assumed to contain both a luteolytic factor (PGF20,) and embryotrophic (histotroph) factors. Blastocysts produce oestrogen which is believed to initiate events which result in CL maintenance, i.e. oestrogen acts as a luteostatic factor. This chapter will discuss evidence for the theory that oestrogens, of blastocyst origin, allow for continued secretion of PGF2o and other components of endometrial histotroph into the uterine lumen, i.e. in an exocrine direction, which prevents their release toward the uterine vascular bed, i.e. in an endocrine direction. This mechanism appears to be essential for the establishment and maintenance of pregnancy in pigs.","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47565159","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Controlled Induction of Puberty","authors":"A. M. Paterson","doi":"10.1530/biosciprocs.11.007","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.007","url":null,"abstract":"Puberty, defined as the time at which ovulation and oestrus first occur in association with normal luteal function, usually takes place at about 200 days of age in the gilt (Duncan and Lodge, 1960). As the replacement gilt is reared solely for reproductive purposes, a delay in the attainment of puberty means a delay in the commencement of productive life. With the recent trend towards intensive confinement systems of pig production it has become increasingly desirable to be able to control the onset of puberty in the gilt. As discussed in Chapter 6, age at puberty can be affected by many factors including nutrition, genotype and the environment. Although there are numerous reports in the literature concerning environmental or physiological conditions which may either hasten or retard puberty in the gilt, few include studies of the associated hormonal changes. Therefore in reviewing those methods used in an attempt to control the onset of puberty in the gilt, particular emphasis is given to the endocrinology and mode of action of the technique involved.","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47659628","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Factors Affecting The Natural Attainment of Puberty in The Gilt","authors":"P. Hughes","doi":"10.1530/biosciprocs.11.006","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.006","url":null,"abstract":"Puberty attainment in the gilt represents the onset of reproductive capability, since the first behavioural oestrus normally coincides with the pubertal ovulation. In the wild pig this first oestrus would occur in the late autumn when the gilt is approximately eight months of age (Signoret, 1980). However, in the domestic giff the aim should be to stimulate the precocious attainment of puberty, the gilt being first mated, at second oestrus, at about 200 days of age. It is both desirable and necessary to induce e-arly puberty attainment in the gilt as she is a costly non-productive animal,until the initiation of the first pregnancy. Thus, a review of the major factors influencing puberty attainment in the gilt is of value in identifying those measures which may be taken to reduce pubertal age and hence minimize the cost of introducing replacement gilts.","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45005269","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation and Control of Reproductive Disorders in The Breeding Herd","authors":"A. Wrathall","doi":"10.1530/biosciprocs.11.0027","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.0027","url":null,"abstract":"At a national level there are unceasing efforts through research, technological innovation and education of producers to raise productivity of the pig industry to levels above the contemporary norm. Within this pace-setting framework the individual pig producer must set his own herd performance standard or target, and then try to maintain herd output as close as possible to that level with the greatest efficiency. Performance standards in commercial herds include both physical and financial ones. However the latter, because they are so prone to market fluctuations beyond the producer's control, are less useful as criteria of efficiency. Some physical criteria which are extremely precise e.g. feed used per kilogram of pigmeat produced, or weaners (of defined age) per sow place per year, do emphasize important aspects of herd management and are dealt with in other chapters. In this Chapter attention is confined to the area of reproductive failure, i.e. failure by the breeding herd to reproduce adequate numbers of healthy newborn piglets within a specified time period. The term 'control' is used in the broad sense, i.e. any action which is taken to prevent, correct or reduce reproductive failure to a level where it no longer affects herd profitability. It will be apparent from the foregoing remarks that, in the context of modern pig production, any distinction between control of overt diseases of reproduction (the traditional province of the veterinarian) and the control of reproductive failures arising from managemental inefficiency is very blurred. In the past the veterinary role tended to be of the 'firebrigade' type, with intermittent responses to outbreaks of frank reproductive disease. This role is now changing rapidly with emphasis on closer and more regular involvement, not only with disease matters, but also with target setting, monitoring, stockmanship and many other aspects of herd management. Control of reproductive failure should, in fact, be seen as an integral part of the management process, the aim of which is to achieve and maintain a high level of herd health, performance and profitability. The principal steps involved in control of reproductive failure are shown in Figure 27.1 and it is these steps which are the main objects of discussion in this chapter.","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43119099","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Male Sexual Development","authors":"B. Colenbrander, M. Frankenhuis, C. Wensing","doi":"10.1530/biosciprocs.11.001","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.001","url":null,"abstract":"","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44250393","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Management of The Sow and Litter in Late Pregnancy and Lactation in Relation to Piglet Survival and Growth","authors":"P. English, V. Wilkinson","doi":"10.1530/biosciprocs.11.0023","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.0023","url":null,"abstract":"The objectives of management in late pregnancy and lactation are to minimize the incidence of stillbirths, to maximize the number of livebirths at parturition and to improve the viability of these pigs. Thereafter, management must strive to minimize mortality and to produce healthy and well grown pigs at weaning. Treatment imposed in late pregnancy and lactation should be orientated towards achieving prompt conception following weaning and to providing the potential for establishing a large litter of viable piglets in the subsequent gestation. Aspects relating to piglet mortality and its prevention will form the first part of this chapter followed by a consideration of supplementary feeding of the litter.","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49640555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Interrelationships Between Spermatozoa, The Female Reproductive Tract, and The Egg Investments","authors":"Rj Hunter","doi":"10.1530/biosciprocs.11.003","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.003","url":null,"abstract":"This chapter describes some principal physiological events during transport of spermatozoa in the female reproductive tract from the time of ejaculation until penetration of the egg investments at the start of fertilization. The objective is to review our current understanding of the relevant processes and to highlight areas requiring further research; it is also hoped to contrast certain aspects of sperm transport in pigs with those in ruminants. Although much of the material discusses processes not obviously susceptible to manipulation, topics related to the successful practice of artificial insemination are emphasized. Previous reviews of sperm transport in the female reproductive tract of pigs include those of Hunter (1973a; 1975a,b; 1980), Polge (1978) and Einarsson (1980), and a comprehensive coverage of the early literature is found in these works. The volume edited by Hafez and Thibault (1975) compares mechanisms of sperm transport and storage in a wide range of vertebrates, whilst fertilization itself is described in pigs by Thibault (1959), Hancock (1961), Baker, Dziuk and Norton (1967), Hunter (1972a, 1974), Szollosi and Hunter (1973; 1978), Baker and Polge (1976) and Polge (1978).","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48840991","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Endocrine Control of Sexual Maturation In The Female Pig and Sexual Differentiation of the Stimulatory Oestrogen Feedback Mechanism","authors":"F. Elsaesser","doi":"10.1530/biosciprocs.11.005","DOIUrl":"https://doi.org/10.1530/biosciprocs.11.005","url":null,"abstract":"Sexual maturation, culminating in puberty and fertility, is a complex process which may involve maturational changes at all levels of the central nervous system—hypothalamo—pituitary—gonadal axis. It is the purpose of this review, based on published and unpublished work from our own laboratory, as well as the work of others, to summarize our present knowledge of the control of sexual maturation in the female pig. Although several other pituitary hormones and adrenal function may be relevant to the process of sexual maturation, because of the restricted availability of such data in the pig only the control of gonadotrophin secretion and ovarian function will be considered. Where information necessary for the understanding of sexual maturation in the pig is lacking, references will be made to work in other species. However, no attempt is made to integrate these data into a general concept of sexual maturation. The description of the ontogeny of ovarian morphology and steroidogenesis will be followed by a consideration of the developmental pattern of gonadotrophin secretion, attempting to correlate them with the maturation of ovarian function and changes in the responsiveness of the ovary to gonadotrophins. Another aspect to be discussed is the responsiveness of the pituitary to luteinizing hormone (LH) releasing hormone at different stages of development. Special attention will be paid to the ontogeny of negative and positive gonadal steroid feedback control of gonadotrophin secretion as well as to the sexual differentiation of the LH surge mechanism.","PeriodicalId":93083,"journal":{"name":"Bioscientifica proceedings","volume":" ","pages":""},"PeriodicalIF":0.0,"publicationDate":"2020-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44084290","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}