ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02298.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02299.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02300.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTPractical and reliable methods for assessing reproductive status are essential for any work designed to enhance fertility in captive endangered species. This paper described recent advances in the development and application of such methods and their implications for the management of captive breeding. Since non‐invasive procedures are necessary when working with animals that are easily stressed, urinary hormone analysis provides the most feasible approach to long term studies on most endangered species. Simplified hormone assay methods have been developed and applied to the detection of ovulation and pregnancy in a variety of animals, including primates, the Giant Panda and ungulates. The possibility now exists for extending the application of these methods to studies in the field. Finally, the ability to monitor reproductive status in endangered animals provides the basis for future attempts to accelerate captive breeding by artificial mean

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02301.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTSeasonally‐breeding deer living in cool temperate environments exhibit pronounced seasonal rhythms of voluntary food intake, growth rate and fattening and the growth and development of the coat. All of these rhythms are considered to be entrained by photoperiod and melatonin, although so far this has only been demonstrated to be the case in one species, the red deer. This paper reviewed current data on seasonal rhythms in several species of deer. A comparison of two species with different breeding seasons, the red deer and the Pere David's deer, indicated that seasonal reproduction, appetite and coat growth rhythms are linked and may be controlled by a single circannual rhythm generator. All of these seasonal rhythms should be considered as adaptive for species living in cool temperate environments with marked fluctuations in food supply and climatic condition

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02302.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Captive breeding plays an increasingly important role in species conservation, but special problems are encountered in achieving the ideal of a demographically stable but genetically diverse population. Breeding programmes involving co‐operation among a number of centres are now being developed which will overcome some of these difficulties by identifying individual animals, genetic lineages or age cohorts from which to breed. Application of techniques such as artificial insemination, embryo transfer and semen collection and storage, as well as the monitoring of reproductive status will contribute to the success of such programmes. The usefulness of these procedures for various population problems is discussed and criteria for their appropriate implementation within breeding programmes is outline

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02303.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Whilst the rate of displacement and migration of sperm cells in the female reproductive tract of rodents, farm animals and humans has attracted attention for at least 50 years, the overriding purpose of sperm transport has not always been kept in focus. This report is concerned with spermatozoa that can penetrate the egg investments and promote formation of a zygote, judgements involving a surgical approach and subsequent phase‐contrast microscopy. A minimum period of 6–8 hours was required for such spermatozoa to be established in the oviducts in sheep and cows mated at the onset of oestrus. Sperm were then arrested in the caudal 12 cm of the isthmus for 17–18 hours or more until just before the moment of ovulation, when they were activated and displaced onwards to the site of fertilization at the ampullary‐isthmic junction. The time‐scale of these events differs in pigs as a result of the intra‐uterine site of ejaculation and the 40‐hour interval between the onset of oestrus and ovulation, but the pre‐ovulatory sequestering of viable spermatozoa in the caudal tip of the oviduct is conspicuous for 36 hours or more. This function of the oviduct appears to be under local control from ovarian follicular hormones and, as judged by sperm motility and membranous changes, so does the process of capacitation. Completion of capacitation is interpreted as a peri

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02304.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The diverse techniques used to successfully regulate reproduction in domestic farm species involve both the direct and indirect manipulation of the endocrine system. Rapid advances in our understanding of the endocrine control of reproduction provides for an expansion and improvement of the techniques available to control fertility. A failure to appreciate even subtle species differences in physiological control mechanisms frequently limits the success of otherwise effective treatments. Changes in the social environment, acting through pheromonal signals, and changes in the physical environment such as light and temperature, may be effective in regulating reproductive function. Likewise changes in suckling intensity and nutritional availability can be used to alter the fertility and fecundity of farm species. Direct intervention to modify reproductive activity is practised at all stages of the reproductive cycle. The range of compounds currently used exert their effects at all levels of the reproductive axis and may promote or inhibit the synthesis and release of hormones, as well as their action in target tissues. Regulation of the bioavailability of hormones has also proved to be an effective means of controlling fertility. In contrast to the application of fertility control in the human and in non‐domesticated species, in the socio‐economic climate of the modern animal husbandry industry, long term control of the timing of reproductive activity may be as economically important as an increase in fertility or fecund

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02305.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

ABSTRACTFor many years artificial insemination has been widely used for the manipulation of fertility in farm animals and more recently methods for the synchronization of oestrous cycles, superovulation and embryo transplantation have been increasingly applied. These techniques now provide new opportunities for the manipulation of gametes and embryos which might further enhance reproductive potential through the production of embryos in vitro, their preservation by deep freezing, cloning from embryonic cells or genetic manipulation to increase fecundity.

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02306.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The seasonal reproductive cycle in rams was monitored in Mouflon (wild‐type), Soay (feral type) and a variety of domesticated breeds of sheep (Shetland, Blackface, Herdwick, Norfolk, Wiltshire, Portland and Merino) by measuring the changes in the diameter of the testes (first three years of life in all breeds) and the blood plasma concentrations of FSH and testosterone (first four to six years of life in Mouflon and Soay rams). In the Mouflon rams there was a pronounced seasonal cycle in all the reproductive parameters from one to six years of age. The plasma concentrations of FSH increased from June to September associated with redevelopment of the testes; maximum testicular size and plasma concentrations of testosterone occurred in October at the onset of the rut. In the Soay and domesticated breeds the seasonal maximum in testicular size occurred in late September or October except in two of the southern breeds (Portland and Merino) which showed an earlier peak to the sexual cycle in August. The change in size of the testes from the minimum to the maximum was less in the domesticated breeds (135–157%) compared to the Soay (171%) and Mouflon (160%). Crossbred rams produced by mating Soay ewes (highly seasonal breed) with Portland or Merino rams (less seasonal breed) had a seasonal testicular cycle intermediate in timing compared to the pattern characteristics of the parent breeds; this is consistent with the involvement of multiple genes in the mechanism controlling the sexual cycle in the ram. The earlier seasonal onset of full testicular activity in the southern breeds is assumed to be the result of selection for a prolongation of the breeding season for early lamb

ISSN:0024-4082    

DOI:10.1111/j.1096-3642.1989.tb02307.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY