Shelton J N
John Curtin School of Medical Research, Australian National University, Division of Clinical Sciences, Canberra City, ACT.
Rev Sci Tech. 1990 Sep;9(3):825-45. doi: 10.20506/rst.9.3.521.
Research into physiology and embryology has provided a basis for the development of technologies that increase productivity of farm animals through enhanced control of reproductive function. Progestagens, alone or in combination with luteolysins, are used to control the time of oestrus in cattle, sheep and pigs, thus permitting better use of artificial insemination, providing synchronised recipients for embryos and facilitating management strategies. Treatment with progestagens and pregnant mare serum gonadotrophin (PMSG) or with gonadotrophin releasing hormone induces breeding activity in sheep and goats before the commencement of the breeding season and reduces the duration of postpartum anoestrus in cattle. In pigs, gonadotrophins are used to hasten puberty in gilts, control the time of oestrus in sows and gilts and reduce the interval between farrowing and oestrus. Implants of melatonin hasten the onset of the breeding season in sheep and goats. Success in increasing litter size in sheep and cattle with PMSG has been limited because of the large variation in response between animals. Likewise, immunisation against steroids has not given consistent results. Immunisation against inhibin appears to offer the possibility of increasing farm animal fecundity. Induction of twinning in cattle by embryo transfer is practicable, and recent developments suggest that in vitro fertilisation may provide a source of embryos for this purpose. Real-time ultrasonic scanning has proved to be a reliable method for diagnosing pregnancy in small ruminants and pigs. The identification of pregnancy-specific proteins in cattle and sheep may provide a cheap and practical serological test for pregnancy in these species. Partial segregation of spermatozoa into X- and Y-bearing components has been reported, but the method is not yet practicable for use in conventional artificial insemination of farm animals. The sex of bovine and ovine embryos can be determined reliably by DNA probes specific for the Y chromosome. Monozygous twins can be produced in all farm animal species by microsurgical bisection of embryos and techniques for cloning from embryonic cells are rapidly being developed. There is a need to devise strategies to utilise these clones to best advantage in genetic programmes. Chimeric animals can be produced in the common farm animal species and will play an important role in genetic engineering, particularly when embryonic stem cell lines are produced in these species.
生理学和胚胎学研究为开发通过加强生殖功能控制来提高农场动物生产力的技术奠定了基础。孕激素单独使用或与溶黄体素联合使用，可用于控制牛、羊和猪的发情时间，从而更好地利用人工授精技术，为胚胎提供同步受体，并促进管理策略的实施。用孕激素和孕马血清促性腺激素（PMSG）或促性腺激素释放激素进行处理，可在繁殖季节开始前诱导绵羊和山羊的繁殖活动，并缩短牛产后乏情期的持续时间。在猪中，促性腺激素用于加速后备母猪的青春期，控制母猪和后备母猪的发情时间，并缩短产仔与发情之间的间隔。褪黑素植入物可加速绵羊和山羊繁殖季节的开始。由于动物之间反应差异很大，使用PMSG增加绵羊和牛的产仔数的成功率有限。同样，针对类固醇的免疫接种也未取得一致的结果。针对抑制素的免疫接种似乎提供了提高农场动物繁殖力的可能性。通过胚胎移植诱导牛双胎是可行的，最近的进展表明体外受精可能为此目的提供胚胎来源。实时超声扫描已被证明是诊断小型反刍动物和猪妊娠的可靠方法。鉴定牛和羊中的妊娠特异性蛋白质可能为这些物种的妊娠提供一种廉价且实用的血清学检测方法。已报道精子可部分分离为携带X和Y染色体的成分，但该方法尚未适用于农场动物的常规人工授精。通过针对Y染色体的DNA探针可以可靠地确定牛和羊胚胎的性别。通过胚胎显微手术分割，可在所有农场动物物种中产生单合子双胞胎，并且从胚胎细胞克隆的技术正在迅速发展。需要制定策略，以便在遗传计划中充分利用这些克隆。嵌合体动物可在常见的农场动物物种中产生，并将在基因工程中发挥重要作用，特别是当在这些物种中产生胚胎干细胞系时。
