Plasma levels of LH, FSH, prolactin, oestradiol-17beta and progesterone during natural and induced oestrus in the dairy goat

The patterns of LH, FSH, prolactin and oestradiol-17beta, before and during natural oestrus, and of progesterone during the following cycle were studied in four French Alpine dairy goats and compared with those obtained after synchronization of oestrus in the same animals. The highest concentration of oestradiol-17beta was measured at the beginning of oestrus and was followed 3 hours later by simultaneous rises of LH, FSH and prolactin. A second FSH peak was observed 48h after the first one. On D(3) (D(0) = day of oestrus) progesterone concentration was over 1 ng/ml. The luteal phase lasted 15 days. Peak concentrations of oestradiol-17beta and progesterone were higher in animals when oestrus was induced. This was attributed to their higher ovulation rate. The second FSH peak was lower, and the interval between oestradiol-17beta peak and gonadotrophin surge longer, than at natural oestrus.     

Development of preovulatory follicles expected to form short-lived corpora lutea in beef cows

Oestrus, expected to be followed by a short luteal phase, was induced in post-partum cows by weaning their calves at 35 days after parturition. Ovaries containing the first preovulatory follicles (Type F) formed after parturition were collected 3 h after the onset of oestrus. For comparison, preovulatory follicles (Type C) were collected 3 h after the onset of oestrus in normally cycling cows. The number of granulosa cells was determined and the concentrations of receptors for follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in granulosa cells and for LH in theca cells were measured. Concentrations of oestradiol-17 beta, testosterone, androstenedione and progesterone in follicular fluid were also measured. Type F follicles contained about twice the number of granulosa cells (based on DNA) as did Type C follicles (45.8 +/- 11.3 and 24.5 +/- 3.9 micrograms DNA/follicle, respectively; P less than 0.05) but these cells had fewer receptors for LH (0.13 +/- 0.02 vs 0.29 +/- 0.03 fmol/micrograms DNA; P less than 0.01) and FSH (0.61 +/- 0.08 vs 1.3 +/- 0.29 fmol/micrograms DNA; P less than 0.08) than did those from Type C follicles. Additionally, there were fewer receptors for LH in theca tissue from Type F than from Type C follicles (28.3 +/- 5.2 vs 51.3 +/- 6.1 fmol/follicle; P less than 0.01). Concentrations of oestradiol-17 beta (475.8 +/- 85.6 vs 112.9 +/- 40.0 ng/ml; P less than 0.01) and androstenedione (214.1 +/- 48.7 vs 24.7 +/- 7.7 ng/ml; P less than 0.01) in follicular fluid were higher in Type C than in Type F follicles.(ABSTRACT TRUNCATED AT 250 WORDS)     

Concentrations of LH, oestradiol-17 beta and progesterone in the peripheral plasma of swamp buffalo cows (Bubalus bubalis) around the time of oestrus

Peripheral plasma concentrations of LH, oestradiol-17 beta and progesterone were measured in 13 mature swamp buffalo cows at 4-h intervals from 36-40 h before until 36-40 h after the onset of oestrus. Mean LH concentrations increased sharply to a peak of 35 ng/ml and returned to basal levels of 5 ng/ml within a 12-h period beginning soon after the onset of oestrus. Mean oestradiol-17 beta concentrations were within the range 9-13 pg/ml from 36-40 h before until 12-16 h after the onset of oestrus, and within the range 7-9 pg/ml thereafter. Progesterone concentrations remained around 0.1 ng/ml throughout the sampling period. There were no significant differences in hormone concentrations or changes between cows that conceived and those that did not conceive to artificial insemination 12-24 h after onset of oestrus.     

Pituitary response of prepuberal lambs to oestradiol-17 beta.

In two experiments 48 prepuberal Merino ewe lambs were injected with oestradiol-17 beta (E2) or saline to study the effect of E2 on their plasma LH levels and on oestrus and ovulation. In the three groups which received 30 (experiment I), 50 and 30 (experiment II) microgram E2 respectively, 27 out of 28 lambs showed an LH response, the corresponding mean LH peaks being 64.3 +/0 22.5, 153.6 +/-33.4 and 91.7 +/- 16.9 ng/ml at mean intervals of 11.1, 11.2 and 10.5 h, respectively, after injection. None of the 20 lambs in the control groups had an LH level higher than 18 ng/ml 12 h after injection. In the three E2 groups, 41.7, 62.5 and 37.5% of animals showed oestrus within 26 h of injection while in the control groups only one animal showed oestrus. Of 13 animals showing oestrus in the E2 groups, 11 failed to ovulate. The mean pre-injection plasma FSH level in experiment I was 102.7 ng/ml, and in four 5--7-month-old lambs over several weeks uas 155.3 ng/ml. Despite these high pre-injection levels of FSH, it appears that the follicles were unable to respond to the LH peak which followed the E2 injection.     

Hormonal changes around oestrus of farmed fallow deer, Dama dama

Concentrations of LH, progesterone, oestradiol-17 beta and androstenedione were measured in serum from blood samples collected from 6 fallow does every hour for 46 h during a spontaneous oestrus. Four does had similar serum hormone profiles, with a pronounced preovulatory LH surge (approximately 20 ng/ml) occurring within 4 h of the onset of oestrus, a small elevation (from 0.1 to 0.3 ng/ml) of progesterone at the onset of oestrus, a gradual but non-significant increase (up to 25 pg/ml) of oestradiol-17 beta and a marked 2-fold increase of serum androstenedione concentrations occurring immediately at the onset of oestrus. The remaining 2 does showed pronounced increases in serum progesterone concentrations at the onset of oestrus and a reduction in the initial LH surge. One of these does exhibited a second preovulatory LH surge within the sampling period.     

Plasma concentrations of testosterone,androstenedione, progesterone,oestradiol-17β, LH and FSH during the preovulatory period in the ewe

Seven mature ewes were synchronized to oestrus by two injections of 125 μg Cloprostenol given 9 days apart. Blood samples, collected for 72 h at 4-h intervals beginning 16 h after the second Cloprostenol injection, were assayed for testosterone, androstenedione, progesterone, oestradiol-17β, LH and FSH. For the testosterone measurements, two radioimmunoassays, using two different antisera, were validated and used. A typical pattern of release was observed for progesterone, oestradiol-17β, LH and FSH, with a preovulatory gonadotrophin peak recorded 16.1 ± 2.1 h after the observed oestrous behaviour. In two of the experimental animals, an extra oestradiol peak was recorded before the usual preovulatory rise. The changes in the concentrations of testosterone and androstenedione during the same period were not synchronous. The levels of the two androgens fluctuated considerably with occasional peaks of 150–250 pg/ml and even 900–1400 pg/ml. Although a tendency towards an increase in the levels of both androgens was observed during the period of oestrous behaviour, the individual variations were significant.     

Sexual behaviour and LH secretion in spayed androgenized ewes after a s?ngle injection of testosterone or oestradiol-17beta

The behavioural and endocrine responses to single injections of 50 or 500 microgram oestradiol-17beta or 5 mg testosterone were recorded in spayed (control) ewes and in spayed ewes exposed to testosterone between Days 30 and 80 or Days 50 and 100 of prenatal life, The control ewes showed oestrus after injections on 17/18 occasions. The androgenized ewes showed poorer oestrous responses to each hormone although rams showed interest in the ewes. Masculine sexual and aggressive behaviour was shown by the androgenized ewes given either steroid. Both steroids caused a reduction in the plasma LH levels of all the ewes (negative feedback), followed by a preovulatory-type surge (positive feedback). The peak LH values were significantly lower (P is less than 0.05) in the Day 50-100 androgenized ewes than in the controls. It is concluded that prenatal androgenization causes a qualitative shift in the sexual behaviour of ewes from the female type to the male type and affects the sensitivity of the brain to "positive feedback" by steroids.     

Effect of neonatal testosterone and oestradiol treatment on the development of the hypothalamo-hypophysial axis in the female rat.

The hypothalamic LH-RH content and the concentrations of pituitary and plasma LH were measured at various ages in female rats treated daily with 10 micrograms testosterone propionate or 10 micrograms oestradiol-17beta from birth to Day 15. Persistent vaginal oestrus was induced in all the treated rats. Both hormones significantly reduced the hypothalamic LH-RH content and pituitary and plasma LH concentrations. Hypothalamic LH-RH increased after cessation of treatment but pituitary LH did not return to normal levels. Plasma LH levels were significantly lower than those in control rats. It is concluded that testosterone propionate and oestradiol-17beta (1) have a direct negative feed-back influence on the hypothalamus in the neonatal female rat; (2) alter the normal pattern of plasma and pituitary LH in developing female rats; (3) prevent the cyclic secretion of plasma LH after maturity; and (4) probably cause a chronic impairment in the release of LH-RH.     

17 beta-hydroxysteroid and 20 alpha-hydroxysteroid dehydrogenase activities of human placental microsomes: kinetic evidence for two enzymes differing in substrate specificity

During storage at 4 degrees C, the 17 beta-hydroxysteroid dehydrogenase activity of human placental microsomes with estradiol-17 beta was more stable than that with testosterone. In order to evaluate the basis for this difference, kinetics with C18-, C19-, and C21- steroids as substrates and/or inhibitors was studied in conjunction with an analysis of the effects of detergents. Both 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) and 20 alpha-hydroxysteroid dehydrogenase (20 alpha-HSD) activities were detected. At pH 9.0, apparent Michaelis constants were 0.8, 1.3, and 2.3 microM for estradiol-17 beta, testosterone, and 20 alpha-dihydroprogesterone, respectively, 17 beta-HSD activity with testosterone was inhibited by estradiol-17 beta, 5 alpha-dihydrotestosterone, 5 beta-dihydrotestosterone, 20 alpha-dihydroprogesterone, and progesterone. In each case 90 to 100% inhibition was observed at 50 to 200 microM steroid. Activity with 20 alpha-dihydroprogesterone was similarly sensitive to inhibition by C19-steroids. By contrast, 25 to 45% of the activity with estradiol-17 beta was not inhibited by high concentrations of C19- or C21-steroids and differed from the 17 beta-HSD activity with testosterone and the major fraction of that with estradiol-17 beta by being insensitive to solubilization by detergent. These results are consistent with an association of two dehydrogenase activities with human placental microsomes. One recognizes C18-, C19-, and C21-steroids as substrates with comparable affinities. The second appears to be highly specific for estradiol-17 beta. The former activity may account for most if not all of the oxidation-reduction at C-17 of C19-steroids and at C-20 of C21-compounds at physiological concentrations by term placental tissue.     

Effects of age, sex and renal function on urinary insulin-like growth factor I (IGF-I) levels in adults.

Insulin-like growth factor I (IGF-I) levels in urine were measured in adults using specific RIA after extraction with acid-ammonium sulfate. Mean (+/- SD) total urine IGF-I values were 267.9 +/- 112.9 ng/day and 167.8 +/- 73.2 ng/g creatinine (Cr) in 17 normal young adults. There was a positive correlation (r = 0.785, P < 0.001) between IGF-I values in early morning urine and those of 24 h urine when they were corrected by urinary Cr. IGF-I values in early morning urine were ranged from 60 to 1,100 ng/gCr with a mean value of 309.6 ng/gCr in 178 normal adults aged 21-80 yr. There was a consistent trend towards higher urinary IGF-I values in males during aging and this trend did not reach statistical significance until the sixth and seventh decades. There was a positive correlation (r = 0.465, P < 0.005) between urinary IGF-I values and age in males but not in females. Although urinary IGF-I values were higher in females than in males of the second and third decades, no sex difference was found in older adults. Urinary IGF-I values were correlated reversely with 24 h Cr clearance (CCr) and positively with urinary beta 2-microglobulin (beta 2-MG) levels in patients with renal dysfunction. These findings indicate that urinary IGF-I levels are influenced by age, sex and renal function in adults.     

Synchronisation of oestrus of goats treated with progestagen-impregnated intravaginal sponges and PMSG,and reproductive performance following natural mating or A.I. with frozen semen

Oestrus was synchronised in 88 goats using progestagen-impregnated intravaginal sponges (60 mg Repromap; Upjohn) left in place for 17 days, followed by intramuscular injection of PMSG (300 i.u.) at sponge withdrawal. The percentages of does that came into oestrus in 0–24, 25–48, 49–72 and 73–96 h periods were 42, 30.5, 10.5 and 6.5 (cumulative 89.5%). The time of onset of oestrus ranged from 16 to 40 h. Breeding at the synchronised oestrus using intact bucks (24–96 h) or artificial insemination with frozen-thawed semen, at fixed times of 24, 48, 72 and 96 h, resulted in 71% and 81% conceptions respectively. Intrauterine deposition of semen was possible in 31.3%, 62.5%, 87.5% and 6.3% of cases at 24, 48, 72 and 96 h respectively. Twinning percentages were 54.5% and 56% for natural mating and artificial insemination. Kidding was spread over a 14-day period with mean gestation lengths of 149 days for singletons and 147 days for twins. The results indicate that use of progestagen-impregnated sponges with PMSG is an efficient method of synchronisation of oestrus and may result in increased fertility in goats and, if used with A.I. with frozen semen, may contribute to increased breeding efficiency and rate of genetic improvement of goats in Asia.     

Progesterone, oestradiol-17 beta and LH during the oestrous cycle of muskoxen (Ovibos moschatus)

Progesterone, oestradiol-17 beta and LH were measured in plasma from 6 non-pregnant, captive, female muskoxen during the 1984 and 1985 breeding seasons. Jugular blood samples were taken on an alternating 3/4-day schedule in 1984 and daily or at 4-h intervals over oestrus, via indwelling jugular cannulae, for 6 weeks in 1985. Oestrous cycle length was 19.6 +/- 0.96 (s.d.) days (n = 19) and did not vary between the first and subsequent cycles of the season. Progesterone was lowest at oestrus (less than or equal to 0.1 ng/ml), began to rise on Days 4-5, peaked on Days 10-12 (mean = 2.6 ng/ml) and returned to baseline 2-5 days before the next oestrus. A small rise in progesterone before the first cycle of the breeding season was observed on 7 of 12 occasions. Oestradiol-17 beta was significantly higher (P less than 0.001) 1-4 days before, or coincident with, oestrus. The average duration of the LH peak was 24.6 h (n = 7) and coincided with observations of behavioural oestrus. In one animal behavioural oestrus and an LH peak preceded a small progesterone rise at the beginning of the breeding season. The temporal relationship of these three hormones during the muskox oestrous cycle is very similar to that seen in domestic ruminants.     

Fertility, ovulation and maturation of eggs in mares injected with HCG

Pony mares were observed from January to August for incidence of oestrus, duration of oestrus, length of the oestrous cycle and for ovulation and fertility after injection of HCG. From January to 15 May most mares showed oestrus but the duration of oestrus was quite variable and few mares ovulated in response to HCG. From 15 May to 17 August oestrous cycles were more regular and ovulation was induced within 40-50 h by an intramuscular injection of 1500-5000 i.u. HCG. Pregnancy was established by one mating at a fixed time after HCG in 20 of 69 mares. Degenerate eggs were recovered from the oviducts of anoestrous recently ovulated, mated, unmated and pregnant mares. The first polar body was formed before ovulation in 2 eggs and had not formed in 2 recently ovulated eggs flushed from the oviduct. The second polar body formed after sperm penetration 10-12 h after ovulation. After formation of pronuclei, the first cleavage division occurred at 20 h and the second at 32 h after ovulation. Oestrus was inhibited by progesterone administered by vaginal devices but occurred within 1-3 days in 12 of the 20 mares after withdrawal of the devices.     

Influence of gonadotropin treatment interval on follicular maturation, in vitro fertilization, circulating steroid concentrations, and subsequent luteal function in the domestic cat.

The impact of the eCG-hCG interval on in vitro fertilization (IVF), endogenous hormonal patterns, and luteal integrity was studied in the domestic cat. Adult cats with inactive ovaries were given eCG (i.m.) and then hCG (i.m.) 80, 84, 88, 92, or 96 h later. Oocytes were aspirated 25-27 h after hCG and co-cultured with swim-up-processed cat spermatozoa. Blood samples were collected daily from 2 days before eCG treatment (Day -2) through Day 14, and sera were analyzed for estradiol-17 beta and progesterone. The mean number of oocytes recovered from the 80-92-h groups (range, 17.2 +/- 2.1 to 21.1 +/- 3.0) did not differ (p greater than 0.05); however, oocyte number was reduced (p less than 0.05) in the 96-h group (10.3 +/- 2.1). The proportion of all oocytes classified as mature was greater (p less than 0.05) when hCG was given 80, 84, or 88 h compared to 92 or 96 h after eCG. Delaying hCG treatment until 96 h caused more than 25% of all oocytes to degenerate, which was a greater rate (p less than 0.05) than in all other groups. The IVF rate at 80 (57.1%), 84 (56.5%), 88 (65.0%), and 92 (52.5%) h was greater (p less than 0.05) than that observed at 96 h (33.6%). Circulating estradiol-17 beta concentrations began to rise above nadir within 24 h of eCG injection in all interval groups. On the basis of areas under the curve, cats in the 80- and 84-h treatments produced more (p less than 0.05) estradiol-17 beta than other groups.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of removal in late pregnancy of the corpus luteum, graafian follicle or ovaries on plasma progesterone, oestradiol, LH, parturition and post-partum oestrus in the tammar wallaby, Macropus eugenii

Concentrations of oestradiol-17 beta, progesterone, and luteinizing hormone (LH) were measured in plasma collected at 6- to 12-h intervals from tammars around the time of parturition and post-partum oestrus. Parturition occurred on Day 26 or 27 after reactivation of lactation-delayed pregnancy and coincided with a precipitous decline in progesterone levels. A sharp rise in oestradiol, from basal concentrations of less than 10 pg/ml to a peak of 13 to 32 pg/ml, as well as oestrus, followed the drop in progesterone by 8.3 and 9.8 h, respectively. The LH surge was dependent on the oestradiol rise and followed it by 7 h. Ovulation followed mating by about 30 h and the LH surge by 24 h. Removal of the ovary with the large Graafian follicle prevented the oestradiol rise, oestrus and the LH surge, but not parturition. Peripartum changes in peripheral oestradiol do not appear to be involved in initiation of parturition but the oestradiol rise and associated change in the oestradiol:progesterone ratio are important signals for post-partum oestrus and the LH surge.     

Oestrogen and progesterone concentrations in plasma and oviductal tissue of ewes exhibiting a natural or induced oestrus

Synchronisation of oestrus in Karagouniki ewes by administration of the standard dose of progesterone results in lower fertility than observed when these ewes ovulate naturally. This suggests that the optimum dose of progesterone may be breed dependent. The exogenous progesterone may perturb the concentrations of oestradiol-17beta and progesterone in blood plasma and the oviductal wall. This possibility was investigated using Karagouniki ewes allocated at random to three treatments (n=4 per treatment). Ewes were allowed to exhibit natural oestrus (N) or oestrus was synchronised by administration of 250 mg (LP) or 375 mg (HP) progesterone (subcutaneous implants) followed by PMSG at 8 mg/kg live weight i.m. 14 days later. Oestrus was observed using teaser rams. Blood samples were collected for plasma oestradiol-17beta and progesterone assay from the onset to the end of oestrus at 2 h intervals. The uterus of each ewe was recovered at the end of oestrus and samples of the oviductal wall were taken from both oviducts and prepared, separately, for progesterone and oestradiol-17beta assay. Statistical analysis was performed using univariate analysis of variance. Plasma oestradiol-17beta concentrations from the onset to the end of oestrus were highest for N ewes and lowest for HP ewes with the values for LP ewes occupying an intermediate position. The differences were significant (P<0.05) between HP and the other two treatments from 4 to 12 h after the onset of oestrus and then between all treatments until the end of oestrus. Plasma progesterone levels were similar and fairly constant from the onset to the end of oestrus for N and LP. The plasma progesterone levels for HP were significantly (P<0.05) higher than for the other two treatments throughout oestrus. In oviductal wall samples, the oestradiol-17beta concentration was significantly (P<0.05) higher for N ewes than for synchronised ewes and the levels were similar for LP and HP ewes. The concentration of oestradiol-17beta differed (P<0.05) between right and left oviducts for N ewes but not for ewes of either of the synchronised oestrus treatments. Progesterone concentrations in oviductal wall samples were highest (P<0.05) for HP ewes and the values for N and LP ewes were similar. The concentration of progesterone did not differ between right and left oviductal wall samples within treatments. It was concluded that the higher dose of exogenous progesterone perturbed the levels of oestradiol-17beta and progesterone in blood plasma and the oviductal wall, and this could explain the lower levels of fertility (relative to naturally occurring oestrus) observed when this protocol is used for Karagouniki ewes in practice.     

Attainment of puberty in female pigs: Clinical appearance and patterns of progesterone,oestradiol-17β and LH

The object of the study was to investigate the clinical and endocrine patterns of progesterone, oestradiol-17β and LH during the peripubertal period in female pigs. Crossbred gilts were penned in groups at an age of 10–12 weeks and boars were kept in adjacent pens during the entire experimental period. Daily oestrous checks started at 4.5 months of age and the gilts were slaughtered after their third heat. At the age of 4.5–5 months a permanent catheter was inserted in the cephalic vein and blood samples were collected from the gilts once daily until either the first or second oestrus. In three gilts hourly blood samples were taken during their first and second oestrus, beginning at early pro-oestrus.The gilts showed their first oestrus at the average age of 183 days. No corpora lutea from earlier ovulations were observed in gilts laparoscoped after their first detected oestrus. During the 30-day period before first oestrus the mean daily progesterone levels varied between 32 and 329 pmol/l. The average levels of oestradiol-17β varied between 15.6 and 30.8 pmol/l. There was no tendency for the oestradiol-17β level to rise before onset of first pro-oestrus. The average levels of LH varied between 0.15 and 0.94 μg/l. The statistical analyses revealed no significant relationship between the level of the hormones studied and onset of first oestrus. The mean progesterone levels during the first and second oestrous cycles were almost identical, however. Oestradiol-17β increased gradually during pro-oestrus, reaching maximum levels before onset of oestrus and thereafter decreasing sharply to values around 30 pmol/l. The oestradiol-17β levels were higher at the second than at the first pro-oestrous period. The concentrations of plasma LH rose sharply with declining plasma levels of oestradiol-17β. The duration of elevated plasma LH levels (> 1 μg/l) was, on average, 26 h and the LH levels were higher during the first oestrus than during the second oestrus. The first rise in progesterone was observed 11–29 h after the LH levels had decreased to concentrations below 1 μg/l.     

Radioimmunoassay of androstenedione and testosterone in cow plasma at the time of luteolysis and oestrus

Androsteredione and testosterone were measured by radioimmunoassay after chromatography on micro-columns of Lipidex-5000 in jugular plasma samples taken every 2-3 h at the time of luteolysis and oestrus in 3 dairy cows. The concentrations of androstenedione and testosterone varied between 5 and 60 pg/ml and 5 and 80 pg/ml respectively and no consistent pattern in the fluctuations of either steroid was observed.     

Changes in oestrogen-synthesizing ability of preovulatory bovine follicles relative to the peak of LH

Preovulatory bovine follicles (n = 28) were collected at different times after the onset of standing oestrus until shortly before ovulation. In-vitro conversion of tritiated androstenedione in the presence of NADPH by homogenates of the follicular wall was compared in phases relative to the LH peak. During phase 0 (before the LH surge) conversion into oestradiol-17 beta was high and production of oestrone was about 8-fold lower. During phases 1 (0-6 h after the LH peak) and 2A (6-14 h after the LH peak) the production of oestradiol and oestrone remained constant; the percentage of remaining androstenedione increased. In phase 2B (14-20 h after the LH peak) conversion into oestradiol and oestrone had decreased to about one third correlating with a higher percentage of remaining androstenedione. In phase 3 (20 h after the LH peak until ovulation) conversion into oestradiol and oestrone remained constant. The ratio between the production of oestrone and oestradiol remained constant throughout the phases of preovulatory development (0.13), indicating a concurrent inhibition of aromatase and 17 beta-hydroxysteroid dehydrogenase activities. Conversion into 19-hydroxyandrostenedione showed a pattern similar to that of oestradiol, and testosterone was produced in minute quantities. The results indicate that in preovulatory bovine follicles eventual inhibition of aromatization takes place at about 14 h after the preovulatory LH peak.     

Comparison of embryo recovery, embryo quality, oestradiol-17 beta and progesterone profiles in domestic cats (Felis catus) at natural or induced oestrus

Domestic cats experiencing a natural or FSH-induced oestrus were studied. Mated cats produced fewer (P less than 0.01) unfertilized oocytes and more (P less than 0.01) morulato blastocyst-stage embryos of better quality after a natural oestrus than after FSH treatment. Serum oestradiol-17 beta concentrations were lower (P less than 0.05) and progesterone levels rose earlier (P less than 0.05) in the induced oestrus compared to the natural oestrus group. Morula/blastocyst-stage embryos from both groups transferred to 15FSH/hCG-treated recipients produced 3 pregnancies and 2 live-born litters (1 from a natural oestrus donor and 1 from an FSH-treated donor). These results indicate that fertilization rates and embryo quality in domestic cats appear to be compromised by the FSH treatment, probably because of altered oestradiol-17 beta and progesterone concentrations.