摘要:

SummaryThis paper gives a brief review of the cytogenetic knowlege of equine species, the chromosomal errors currently known to exist, and an account of the interspecific hybrids that have served man during the 4500 years of domestication of horse and donkey.

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04583.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryRecent experiments designed to improve synchronisation and stimulation of ovulation in mares are described. The addition of daily injections of oestradiol benzoate to a routine synchronisation protocol, that utilised intravaginal sponge administration of a progestogen, ally I trenbolone, for seven days followed by an injection of prostaglandin at the time of sponge removal, reduced pituitary follicle stimulation hormone (FSH) secretion during treatment, increased the interval from sponge removal to ovulation but did not improve synchronisation of ovulation. Addition of daily injections of testosterone to the protocol reduced the secretion of pituitary luteinising hormone (LH), but not FSH, during treatment and it did improve synchronisation of ovulation.Attempts to stimulate follicular growth with an anti‐oestrogen, tamoxifen, during late anoestrus or after synchronisation treatment during the breeding season were unsuccessful; FSH and LH secretion rates and follicular growth were not stimulated. Treatment of mares with an extract of horse pituitary glands during successive oestrous cycles to give a total of six treatments per mare during the breeding season induced the growth of a mean of 3.3 mature follicles but only a mean of 1.8 ovulations in each treated cycle. This treatment regime did not seem to exhaust the pool of follicles that can be stimulated in subsequent cycle

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04584.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryAn experiment was undertaken to determine whether the equine conceptus inhibits production of prostaglandin F2αin the pregnant mare. Endometrial tissue was obtained from two normally cycling mares and conceptus membranes were obtained from a further two mares which were pregnant. Endometrial tissue was cultured alone and with conceptus membranes and the prostaglandin F2αconcentrations measured in the incubation medium over a 24 h period. With endometrium alone, prostaglandin F2αconcentrations increased slowly for the first 9 h of incubation but then began to rise sharply. When the conceptus membranes were added, the prostaglandin F2αproduction rate was initially comparable to that of endometrium alone but the sharp increase seen after 9 h was large attenuated. By 18 to 24 h, the prostaglandin F2αconcentration in the endometrium plus conceptus membranes was 63 per cent less than for endometrium alone. The results corroborate previous studies that conceptus membranes can inhibit prostaglandin F2αsynt

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04585.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04586.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryFailure of embryo reinsertion experiments and observation of a high incidence of extended oestrous cycles following transcervical embryo recovery at Day 12.5 (ovulation = Day 0) prompted investigation of the effects of uterine lavage on cycle length and concentrations of progesterone and 15‐keto‐13, 14‐dihydroprostaglandin F2α(PGFM) in peripheral blood. Progesterone profiles confirmed the occurrence of prolonged luteal phases after flushing on Days 12.5 and 13.5 and showed that extended cycles can occur even after flushing as early as Day 7.5. However, almost 40 per cent of the delays in return to oestrus were associated with an initial decline in luteal activity after flushing followed by a reactivation of the corpus luteum and/or the formation of a new one. Profiles of PGFM revealed variable patterns of prostaglandin F2αrelease caused principally by cervical dilatation and uterine manipulation. They also showed that a measure of prostaglandin F2αrelease could be obtained from paired samples taken before and after flushing. Such paired sampling was used on 113 inseminated mares flushed 6.5 to 15.5 days after ovulation. It was shown that flushing could induce prostaglandin F2αrelease after Day 6.5 but probably not before. The presence of an embryo had little effect on the flush‐induced release up to Day 10.5 but its inhibitory effect had become marked by Day 11.5. Oxytocin injection on Days 10.5 or 12.5 also induced prostaglandin F2αrelease. In an ovariectomised mare, uterine flushing and oxytocin injections were similarly effective in inducing prostaglandin F2αrelease after treatment with oestrogen followed by progesterone, but not after oestrogen alone. This suggests a role for oxytocin in normal luteolysis in cycling mares. The fact that the embryo can alter uterine responsiveness to flushing procedures by Day 11.5 calls into question the concept of a ‘critical stage’ for pregnancy recognition in mares. Eight sham transfers in two mares between Days 5.5 and 8.5 had no effect on PGFM concentrations but it is suggested that failure of embryo reinsertion techniques might be associated with prostaglandin F2αrelease provoked b

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04587.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04588.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04589.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryThree different experiments were conducted in which horse embryos were frozen in liquid nitrogen, thawed and transferred surgically to synchronised recipient mares in two countries. In Experiment 1, out of 14 embryos transferred via mid ventral laparotomy, two established normal pregnancies, of which one continued to full term with the birth of a healthy colt foal. In Experiment 2, one of two embryos resulted in a normal conceptus. In Experiment 3, all the transfers were carried out via flank laparotomy and none of the recipients became pregnant. The results from Experiments 1 and 2 indicate that early unexpanded equine blastocysts tolerate cryopreservation better than larger expanded blastocysts. Some other factors associated with the transfer technique, unrelated to the viability of the frozen thawed embryos, are thought to have played a significant role in the failure to achieve any pregnancies in Experiment 3.

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04590.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04591.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

SummaryRepealed examinations of mares with real‐time ultrasound echography demonstrated that the well‐known phenomenon of transuterine migration of the equine conceptus is not a simple one‐way passage. Instead, the embryonic vesicle was shown to bypass its eventual site of attachment many times per day while traversing the full length of each uterine horn and the uterine body.The embryonic vesicle showed limited mobility on Days 9 and 10 post ovulation when it spent more than 60 per cent of the time in the uterine body. Maximum mobility occurred on Days 11 to 14. Location changes within a uterine horn were more likely to be progressive when the vesicle was moving in a caudal direction, whereas location changes within the body were more likely to be progressive when the vesicle was moving in a cranial direction. Individuals of twin conceptuses had mobility patterns similar to those of singletons. Administration of a sympathomimetic blocking agent reduced the extent of mobility, indicating that uterine contractions are the propulsive force for vesicle mobility. Water‐filled balloons acting as simulated vesicles were also mobile when placed in the uterus on Days 12 or 13 of dioestrus, but their rate of movement was less than that of embryonic vesicles. It is suggested that the mobility of the embryonic vesicle may play a role in blocking the uterine luteolytic mechanism.Cessation of vesicle mobility (fixation) occurred on Day 15, 16 or 17 and it remained firm with no further movement between horns. Twin embryos exhibited a preference for unilateral fixation (70 per cent). Fixation may be a function of expansion of the embryonic vesicle combined with intraluminal resistance to mobility resulting from increasing uterine tone. The site of fixation was in the caudal portion of one of the horns, perhaps because of the curvature of the horns at that point. The concept of extensive mobility of the equine conceptus provides rationale for the development of hypotheses concerning the perplexing effects of reproductive status on the site of fixation and the consistency of fixation of the vesicle in the caudal portion of a uterine horn.Orientation is defined as rotation of the vesicle so that the embryonic pole is located ventrally, opposite the mesometrial attachment of the uterus. It is proposed that orientation takes place between the day of fixation and Day 19 when the embryo proper is first detectable by ultrasound. Orientation is attributable to disproportionate encroachment of the dorsal uterine wall, a massaging action by uterine contractions and greater thickness of the vesicle wall at the embryon

ISSN:0425-1644    

DOI:10.1111/j.2042-3306.1985.tb04592.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY