The Journal of endocrinology.
Periodical
Endocrinology
Publisher:
Society for Endocrinology. Bristol, UK : BioScientifica (2011)
Frequency: Monthly
Country: England
Language: English
Author(s):
Society for Endocrinology.
Start Year:1939 -
ISSN:
0022-0795 (Print)
1479-6805 (Electronic)
0022-0795 (Linking)
1479-6805 (Electronic)
0022-0795 (Linking)
Impact Factor
4
2022
| NLM ID: | 0375363 |
| (DNLM): | J19940000(s) |
| (OCoLC): | 01754564 |
| Coden: | JOENAK |
| LCCN: | 64005925 |
| Classification: | W1 JO642 |
Steroids present in the follicular fluid of the mare.
The Journal of endocrinology
April 1, 1960
Volume 20 147-156 doi: 10.1677/joe.0.0200147
SHORT RV.No abstract available Progesterone in blood. IV. Progesterone in the blood of mares.
The Journal of endocrinology
December 1, 1959
Volume 19 207-210 doi: 10.1677/joe.0.0190207
SHORT RV.Progesterone levels have been measured in the peripheral blood of pregnant and non-pregnant
mares, and in umbilical cord blood collected during foaling. It was found that progesterone was
readily detectable in the blood of pregnant and non-pregnant animals provided that there was a
fully developed corpus luteum present in the ovaries. During the second half of gestation, when
the ovaries have become fibrotic, progesterone was no longer detectable in the peripheral blood,
even though it was present in high concentrations in umbilical cord blood.
The reasons for this apparent disappearance... The composition of the stallion’s semen.
The Journal of endocrinology
April 1, 1956
Volume 13, Issue 3 279-290 doi: 10.1677/joe.0.0130279
MANN T, LEONE E, POLGE C.No abstract available Participation of seminal plasma during the passage of spermatozoa in the female reproductive tract of the pig and horse.
The Journal of endocrinology
January 1, 1956
Volume 13, Issue 2 133-140 doi: 10.1677/joe.0.0130133
MANN T, POLGE C, ROWSON LE.No abstract available Hormonal effects in the pregnant mare and foetal foal.
The Journal of endocrinology
October 1, 1951
Volume 7, Issue 4 l-liii
AMOROSO EC, ROWLANDS IW.No abstract available Serum gonadotrophin and ovarian activity in the pregnant mare.
The Journal of endocrinology
October 1, 1949
Volume 6, Issue 2 184-191 doi: 10.1677/joe.0.0060184
ROWLANDS IW.Shortly after Cole & Hart [1930] had reported the discovery of a gonadotrophic hormone in the blood of the mare in early pregnancy they [Cole, Howell & Hart, 1931] described the changes that occur in the ovaries throughout gestation, and associated the unusually active condition of the ovaries between the 40th and 150th day with the presence of the gonadotrophin in the blood. During this period the ovaries are very large and contain numerous follicles and a small number of functional corpora lutea. The authors claim that the latter serve initially to supplement the function of the primary corp... The response of the ovary of the anoestrous goat to pregnant mares’ serum gonadotrophin.
The Journal of endocrinology
October 1, 1949
Volume 6, Issue 2 121-131
FOLLEY SJ, GREENBAUM AL, ROY A.No abstract available Serum gonadotrophin in Welsh and Shetland ponies.
The Journal of endocrinology
February 1, 1947
Volume 5, Issue 1 1-8 doi: 10.1677/joe.0.0050001
DAY FT, ROWLANDS IW.No abstract available The effect of social stress on adrenal axis activity in horses: the importance of monitoring corticosteroid-binding globulin capacity.
The Journal of endocrinology
August 6, 1998
Volume 157, Issue 3 425-432 doi: 10.1677/joe.0.1570425
Alexander SL, Irvine CH.Plasma cortisol is largely bound to corticosteroid-binding globulin (CBG), which regulates its bioavailability by restricting exit from capillaries. Levels of CBG may be altered by several factors including stress and this can influence the amount of cortisol reaching cells. This study investigated the effect of social instability on plasma concentrations of CBG, total and free (not protein bound) cortisol in horses. Horses new to our research herd ('newcomers') were confined in a small yard with four dominant resident horses for 3-4 h daily for 3-4 (n = 5) or 9-14 (n = 3) days. Jugular blood ... Read More
27
Radioimmunoassay of inhibin in various mammals.
The Journal of endocrinology
September 1, 1989
Volume 122, Issue 3 697-704 doi: 10.1677/joe.0.1220697
Hamada T, Watanabe G, Kokuho T, Taya K, Sasamoto S, Hasegawa Y, Miyamoto K, Igarashi M.A sensitive radioimmunoassay (RIA) for the determination of inhibin in peripheral plasma and tissue homogenates of different species has been developed using antisera to partially purified bovine follicular fluid (bFF) inhibin and 125I-labelled bFF 32 kDa inhibin. Antisera were produced by immunization of rabbits with partially purified bFF inhibin prepared by immunoaffinity chromatography. Increasing doses of a high titre antiserum could neutralize the suppressing effect of bFF, porcine follicular fluid and rat ovarian homogenate on FSH secretion from rat anterior pituitary cells in culture. ... Read More
26
Proteolytic degradation of IGF-binding protein (IGFBP)-2 in equine ovarian follicles: involvement of pregnancy-associated plasma protein-A (PAPP-A) and association with dominant but not subordinated follicles.
The Journal of endocrinology
September 8, 2004
Volume 182, Issue 3 457-466 doi: 10.1677/joe.0.1820457
Gérard N, Delpuech T, Oxvig C, Overgaard MT, Monget P.In the ovary of mammalian species, terminal follicular growth is accompanied by a decrease in intrafollicular levels of IGF-binding protein-2 (IGFBP-2) and IGFBP-4. The decrease in IGFBP-4 levels is essentially due to an increase in proteolytic cleavage by intrafollicular pregnancy-associated plasma protein-A (PAPP-A) in growing healthy follicles. The decrease in IGFBP-2 levels is partly due to a decrease in mRNA expression by follicular cells. In addition, we have recently shown that IGFBP-2 is also proteolytically cleaved by PAPP-A in bovine and porcine growing follicles. In the present work... Read More
12
Steroids in the follicular fluid and the corpus luteum of the mare. A ‘two-cell type’ theory of ovarian steroid synthesis.
The Journal of endocrinology
March 1, 1962
Volume 24 59-63 doi: 10.1677/joe.0.0240059
SHORT RV.A comparison has been made between the steroids present in equine follicular fluid and luteal tissue. Follicular fluid was found to contain progesterone, 17α-hydroxyprogesterone, androstenedione, epitestosterone, 19-norandrostenedione, oestrone, oestradiol-17β and 6α-hydroxyoestradiol-17β, in confirmation of previous studies. On the other hand, luteal tissue contained large amounts of progesterone and 20α-hydroxypregn-4-en-3-one, and a small quantity of 17α-hydroxyprogesterone. No C18 or C19 steroids could be detected.
These findings are therefore interpreted as evidence in favour of ... Read More
10
Prepartum adrenocortical maturation in the fetal foal: responses to ACTH.
The Journal of endocrinology
September 1, 1994
Volume 142, Issue 3 417-425 doi: 10.1677/joe.0.1420417
Silver M, Fowden AL.The present study was carried out on 19 chronically catheterized mares and fetuses in late gestation (term > 320 days). In six animals which were monitored up to the time of delivery of a live foal, plasma and amniotic fluid cortisol concentrations remained low until 4-5 days before parturition when there was a rapid, significant rise (P < 0.05) which was not accompanied by any corresponding changes in maternal plasma cortisol. Circulating fetal ACTH concentrations became more variable close to delivery and ANOVA revealed no significant increases during this critical period, although a n... Effect of insulin-induced hypoglycaemia on secretion patterns and rates of corticotrophin-releasing hormone, arginine vasopressin and adrenocorticotrophin in horses.
The Journal of endocrinology
June 1, 1997
Volume 153, Issue 3 401-409 doi: 10.1677/joe.0.1530401
Alexander SL, Roud HK, Irvine CH.To study the effect of hypoglycaemia on secretion rates of corticotrophin-releasing hormone (CRH), arginine vasopressin (AVP) and ACTH in a non-ruminant species, a non-surgical method was used to collect pituitary venous (PitVen) blood every 0.5 or 1 min from seven horses before and after insulin administration (0.4 U/kg i.v.). To assess the effect of PitVen cannulation on results, peripheral hormones were also measured before and after insulin in five horses without PitVen cannulae. Insulin administration lowered plasma glucose in all horses (P < 0.0001; paired t-test). Cortisol concentrat... Identification of 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one as endogenous steroids in the fetal horse gonad.
The Journal of endocrinology
October 1, 1983
Volume 99, Issue 1 87-92 doi: 10.1677/joe.0.0990087
Tait AD, Santikarn S, Allen WR.The 5,7-dienes, 3 beta-hydroxy-5,7-pregnadien-20-one and 3 beta-hydroxy-5,7-androstadien-17-one were extracted from fetal horse gonads and purified by solvent partition, thin-layer chromatography and high performance liquid chromatography. The isolated steroids were identified by comparison with the synthetic steroids using ultraviolet and mass spectroscopy and by gas chromatography-mass spectroscopy. The identification of these compounds as endogenous steroids, together with the data on their biosynthesis reported previously, support the proposal that in the fetal horse gonad there is a 5,7-d... Postnatal insulin secretion and sensitivity after manipulation of fetal growth by embryo transfer in the horse.
The Journal of endocrinology
June 3, 2004
Volume 181, Issue 3 459-467 doi: 10.1677/joe.0.1810459
Forhead AJ, Ousey JC, Allen WR, Fowden AL.This study examined the effects of intrauterine growth on insulin secretion and resistance in newborn foals. Embryo transfer between small pony and large Thoroughbred mares was used to produce four groups of foals with different birth weights (pony in pony n=7; pony in Thoroughbred n=7; Thoroughbred in Thoroughbred n=8; Thoroughbred in pony n=8). On day 2 after birth, glucose (0.5 g/kg) was administered intravenously to the foal and blood samples were taken for 2 h to determine plasma glucose and insulin concentrations. On day 3, insulin sensitivity was assessed by giving insulin (0.75 U/kg i.... The influence of maternal size on placental, fetal and postnatal growth in the horse. II. Endocrinology of pregnancy.
The Journal of endocrinology
February 9, 2002
Volume 172, Issue 2 237-246 doi: 10.1677/joe.0.1720237
Allen WR, Wilsher S, Stewart F, Stewart F, Ousey J, Ousey J, Fowden A.Within-breed artificial insemination and between-breed embryo transfer were carried out in small pony (P) and large Thoroughbred (Tb) mares to create 4 types of horse pregnancy in which the fetus experienced spatial and nutritional deprivation (Tb-in-P; n=8), luxury (P-in-Tb; n=7) or normality (Tb-in-Tb; n=7 and P-in-P; n=7) in utero. Measurement of equine chorionic gonadotrophin (eCG), total conjugated oestrogens and progestagen concentrations in serial peripheral serum samples recovered from all the mares throughout gestation showed that the amount of eCG produced during the first half of ge... Effect of isolation stress on concentrations of arginine vasopressin, alpha-melanocyte-stimulating hormone and ACTH in the pituitary venous effluent of the normal horse.
The Journal of endocrinology
March 1, 1988
Volume 116, Issue 3 325-334 doi: 10.1677/joe.0.1160325
Alexander SL, Irvine CH, Livesey JH, Donald RA.A non-surgical, non-stressful technique was used for collection of pituitary venous blood from five conscious horses every minute for two 10-min periods before and during isolation from the herd, which caused a predictable, yet humane and physiological, emotional stress. Pituitary blood was also sampled every 5 min for two approximately 90-min periods before and after isolation, while jugular blood was sampled every 15 min throughout the experiment. During isolation, all horses became agitated, hyperventilating and sweating. Packed red cell volume increased, as did pituitary venous concentrati... Pathways of steroid biosynthesis in the intact Graafian collicle of mares in oestrus.
The Journal of endocrinology
July 1, 1970
Volume 47, Issue 3 321-331 doi: 10.1677/joe.0.0470321
Younglai EV, Short RV.No abstract available Development of insulin and proinsulin secretion in newborn pony foals.
The Journal of endocrinology
June 3, 2004
Volume 181, Issue 3 469-476 doi: 10.1677/joe.0.1810469
Holdstock NB, Allen VL, Bloomfield MR, Hales CN, Fowden AL.At birth, the endocrine pancreas must assume a glucoregulatory role if the neonate is to survive the transition from parenteral to enteral nutrition. In species like the horse, neonatal hypoglycaemia is common, which suggests that the glucoregulatory mechanisms are not always fully competent at birth. Hence, this study examined pancreatic beta cell function in newborn foals during nutritional adaptation over the first 10 days post partum. Over a 48 h period at three time intervals after birth (days 1-2, 5-6 and 9-10 post partum), the beta cell responses to suckling and to intravenous administr... Ontogeny and ultradian rhythms of adrenocorticotropin and cortisol in the late-gestation fetal horse.
The Journal of endocrinology
February 1, 1995
Volume 144, Issue 2 271-283 doi: 10.1677/joe.0.1440271
Cudd TA, LeBlanc M, Silver M, Norman W, Madison J, Keller-Wood M, Wood CE.Fetal maturation and the timing of parturition in both sheep and primates are thought to be controlled by the hypothalamic-pituitary-adrenal axis but little is known about the endocrinology of the equine fetus. We investigated the ontogeny of plasma concentrations of adrenocorticotropic hormone (ACTH), cortisol and corticosteroid binding capacity in the late-gestation fetal horse. We also wished to determine whether there is ultradian rhythmic release of ACTH and cortisol in fetal horses and we compared fetuses to maternal and non-pregnant adult horses. Six fetuses, 278-304 days gestation (ter... Thyroxine secretion rate in the horse in various physiological states.
The Journal of endocrinology
November 1, 1967
Volume 39, Issue 3 313-320 doi: 10.1677/joe.0.0390313
Irvine CH.No abstract available Anti-Müllerian hormone and ovarian aging in mares.
The Journal of endocrinology
November 8, 2018
Volume 240, Issue 2 147-156 doi: 10.1530/JOE-18-0391
Uliani RC, Conley AJ, Corbin CJ, Friso AM, Maciel LFS, Alvarenga MA.Anti-Müllerian hormone (AMH) is used as a marker of follicle population numbers and potential fertility in several species including horses but limited data exist across the lifespan. No one has decreased ovarian reserve experimentally to investigate whether a corresponding, quantitative decrease in AMH results. Concentrations of AMH across the lifespan were compiled from 1101 equine females sampled from birth to >33 years of age. Young and old mares (averaging 6 and 19 years) were hemi-ovariectomized and circulating AMH was assessed before and daily thereafter for 15 days. The remaining o... The immunological measurement of pregnant mare serum gonadotrophin.
The Journal of endocrinology
April 1, 1969
Volume 43, Issue 4 593-598 doi: 10.1677/joe.0.0430593
Allen WR.No abstract available Diurnal variation in plasma gluco-corticosteroid levels in the horse (Equus caballus).
The Journal of endocrinology
July 1, 1966
Volume 35, Issue 3 249-253 doi: 10.1677/joe.0.0350249
Zolovick A, Upson DW, Eleftheriou BE.No abstract available The dynamics of gonadotrophin-releasing hormone, LH and FSH secretion during the spontaneous ovulatory surge of the mare as revealed by intensive sampling of pituitary venous blood.
The Journal of endocrinology
February 1, 1994
Volume 140, Issue 2 283-295 doi: 10.1677/joe.0.1400283
Irvine CH, Alexander SL.Conflicting views exist on the mode of gonadotrophin-releasing hormone (GnRH) secretion during the ovulatory LH surge and the relative importance of changes in pituitary responsiveness to GnRH in generating the LH surge. This disagreement may stem from species differences and/or methodological problems. To provide data on the exact relationship between GnRH and gonadotrophin secretion during the spontaneous LH surge, we collected pituitary venous (PV) blood every 30 s for 3-4 h from eight mares and then assayed GnRH (in six of the mares), FSH and LH. Jugular blood was also collected from twelv... beta-Subunit 102-104 residues are crucial to confer FSH activity to equine LH/CG but are not sufficient to confer FSH activity to human CG.
The Journal of endocrinology
March 16, 2001
Volume 169, Issue 1 55-63 doi: 10.1677/joe.0.1690055
Chopineau M, Martinat N, Galet C, Guillou F, Combarnous Y.Horse LH/CG (eLH/CG) and donkey LH/CG (dkLH/CG) are strictly LH-specific in their respective homologous species. However, both bind to the FSH receptors from non-equid species, whereas the zebra hormone (zbLH/CG) does not. The FSH/LH ratio of eLH/CG and of the alphadkbetae hybrid is about tenfold higher than that of dkLH/CG and of the alphaebetadk hybrid, showing that the betae subunit contains the structural features responsible for the high FSH activity of eLH/CG. Only six amino acid positions (51, 94, 95, 102, 103 and 106) are unique to the betae subunit when compared with the betadk and be... Postnatal decline in gonadal secretion of dehydroepiandrosterone and 3 beta-hydroxyandrosta-5,7-dien-17-one in the newborn foal.
The Journal of endocrinology
January 1, 1998
Volume 155, Issue 2 277-282 doi: 10.1677/joe.0.1550277
Raeside JI, Renaud RL, Christie HL.Dehydroepiandrosterone (DHEA) and 3 beta-hydroxyandrosta-5,7-dien-17-one (7-dehydro-DHEA) are secreted in large quantities by the remarkably hypertrophied fetal gonads of both sexes in the pregnant mare. Their secretion serves as the fetal component of a feto-placental unit for oestrogen production in equine pregnancies. They are secreted in large amounts but show a decline in late pregnancy when the fetal gonads regress and levels of oestrogens in the mare fall as a consequence. We have examined the levels of these precursor steroids in the newborn foal in the first days after birth. DHEA and... Ovarian steroids affect prostaglandin production in equine endometrial cells in vitro.
The Journal of endocrinology
January 30, 2014
Volume 220, Issue 3 263-276 doi: 10.1530/JOE-13-0185
Szóstek AZ, Galvão AM, Ferreira-Dias GM, Skarzynski DJ.This study aimed to evaluate the influence of ovarian steroids on equine endometrial epithelial and stromal cells, specifically i) prostaglandin (PG) production in a time-dependent manner, ii) specific PG synthases mRNA transcription and protein expression, and iii) cell proliferation. After passage I, cells were exposed to vehicle, oxytocin (OT, positive control, 10(-7) M), progesterone (P4, 10(-7) M), 17β estradiol (E2, 10(-9) M), or P4+E2 for 12, 24, 48, or 72 h. Following treatment, PG concentration was determined using the direct enzyme immunoassay (EIA) method. Alterations in PG synth... Pancreatic beta-cell function in the fetal foal and mare.
The Journal of endocrinology
November 1, 1980
Volume 87, Issue 2 293-301 doi: 10.1677/joe.0.0870293
Fowden AL, Barnes RJ, Comline RS, Silver M.Insulin secretion and the factors influencing beta-cell function were investigated in the chronically catheterized fetal foal and mare during the second half of gestation. The response of the fetal beta cells to exogenous glucose was also examined. The mean concentration of insulin in the fetal foal was 7.5 +/- 0.5 (S.E.M.) microunit./ml (n = 20) which was significantly less than the corresponding maternal value of 49.0 +/- 5.0 microunit./ml (n = 20, P < 0.01). The insulin concentration in non-pregnant horses was 24.5 +/- 1.5 microunit./ml (n = 5) which was significantly less than the value... Immortalization of equine trophoblast cell lines of chorionic girdle cell lineage by simian virus-40 large T antigen.
The Journal of endocrinology
September 27, 2001
Volume 171, Issue 1 45-55 doi: 10.1677/joe.0.1710045
Thway TM, Clay CM, Maher JK, Reed DK, McDowell KJ, Antczak DF, Eckert RL, Nilson JH, Wolfe MW.Immortalized cell lines have many potential experimental applications including the analysis of molecular mechanisms underlying cell-specific gene expression. We have utilized a recombinant retrovirus encoding the simian virus-40 (SV-40) large T antigen to construct several immortalized cell lines of equine chorionic girdle cell lineage - the progenitor cells that differentiate into the equine chorionic gonadotropin (eCG) producing endometrial cups. Morphologically, the immortalized cell lines appear similar to normal chorionic girdle cells. Derivation of the immortalized cell lines from a cho... Changes in plasma cortisol concentrations during the ovulatory cycle of the mare.
The Journal of endocrinology
November 1, 1983
Volume 99, Issue 2 329-334 doi: 10.1677/joe.0.0990329
Asa CS, Robinson JA, Ginther OJ.Daily blood samples from four mares were assayed for cortisol through a total of eight ovulatory cycles. Mean cortisol concentrations on days -14, -13, -10, -9 and -8 before ovulation (dioestrus) were greater than on days -5 to -1 (oestrus). The highest mean (+/- S.E.M) value of cortisol occurred on day -10 (260 +/-28 nmol/l) and the lowest on day -2 (142 +/- 14 nmol/l). A single episode on a day in late dioestrus characterized the maximum cortisol value per cycle for five of eight cycles. Extraction of plasma samples with petroleum ether or chromatography before assay, to eliminate interferen... Steroids present in the follicular fluid of the mare.
The Journal of endocrinology
April 1, 1960
Volume 20 147-156 doi: 10.1677/joe.0.0200147
SHORT RV.No abstract available Horse plasma corticotrophin-releasing hormone (CRH): characterisation and lack of a late gestational rise or a plasma CRH-binding protein.
The Journal of endocrinology
December 1, 1994
Volume 143, Issue 3 455-460 doi: 10.1677/joe.0.1430455
Ellis MJ, Livesey JH, Donald RA.Immunoreactive corticotrophin-releasing hormone (irCRH) was present in methanolic extracts of equine peripheral blood and showed no elevation in maternal peripheral serum in late gestation (0.54 +/- 0.25 pmol/l; mean +/- S.D.) compared with control horses (0.41 +/- 0.15 pmol/l). The irCRH of methanolic extracts of pituitary venous plasma had a similar elution position following reverse-phase HPLC to synthetic human CRH(1-41) and to irCRH released from horse stalk-median eminence tissue incubated in vitro. Gel chromatographic studies showed no evidence for a plasma CRH-binding protein (CRHBP) a... Adrenocortical function in the horse.
The Journal of endocrinology
November 1, 1970
Volume 48, Issue 3 319-335 doi: 10.1677/joe.0.0480319
James VH, Horner MW, Moss MS, Rippon AE.No abstract available Pregnant mare serum gonadotrophin: ratio of follicle-stimulating hormone and luteinizing hormone activities measured by radioreceptor assay.
The Journal of endocrinology
December 1, 1976
Volume 71, Issue 3 471-482 doi: 10.1677/joe.0.0710371
Stewart F, Allen WR, Moor RM.Specific radioreceptor assays for FSH and LH, which employ tissue receptors from rat testis and highly purified human FSH (LER 1575-C) and LH (Hartree IRC-2, 24/6/69) as standards, have been developed to determine the FSH-like and LH-like activities in pregnant mare serum gonadotropin (PMSG). Measurements of FSH and LH concentrations in the serum of six pregnant Pony mares showed that the ratio of these two activities did not vary significantly between mares and remained constant between days 40 and 80 of gestation with a value of 1-45 +/- 0-04 (S.E.M.). The FSH:LH ratio of PMSG produced by cu... Maturation of pancreatic beta-cell function in the fetal horse during late gestation.
The Journal of endocrinology
September 2, 2005
Volume 186, Issue 3 467-473 doi: 10.1677/joe.1.06176
Fowden AL, Gardner DS, Ousey JC, Giussani DA, Forhead AJ.At birth, the endocrine pancreas becomes more directly involved in the control of glycaemia than in utero. However, compared with other tissues, relatively little is known about the maturational changes that occur in the fetal endocrine pancreas in preparation for extrauterine life. This study examined the pancreatic beta-cell response to exogenous administration of glucose and arginine in fetal horses with respect to their gestational age and concentration of cortisol, the hormone responsible for prepartum maturation of other fetal tissues. Glucose administration had no effect on fetal insuli... Secretion rates and short-term patterns of gonadotrophin-releasing hormone, FSH and LH throughout the periovulatory period in the mare.
The Journal of endocrinology
September 1, 1987
Volume 114, Issue 3 351-362 doi: 10.1677/joe.0.1140351
Alexander SL, Irvine CH.We have developed a non-surgical technique for long-term collection of pituitary venous blood which consists of slightly diluted hypophysial portal blood into which pituitary hormones have been secreted. In these experiments jugular and pituitary venous blood samples were collected from five unmedicated, ambulatory mares at 5-min intervals for 2-6 h on 11 occasions during the 6 days surrounding the ovulatory LH peak. Jugular blood only was collected from another five periovulatory mares without pituitary cannulae. The duration of oestrus was similar in mares with and without pituitary cannulae...