The effect of the absence or presence of a corpus luteum on the ovarian follicular population and serum oestradiol concentrations during the estrous cycle in Sanjabi ewes

The aim of this study was to determine if the presence or absence of a corpus luteum (CL) during estrous synchronization in ewes can affect the ovarian follicular population and the serum oestradiol concentrations. The estrous cycles of 197 Sanjabi ewes were synchronized using a 12-day treatment with intravaginal progestagen sponges (Chronogest^®). Estrus was detected in 144 ewes, 27–39 h after sponge removal. Blood samples were taken daily from day 2 and continued for 19 days and analyzed for serum oestradiol concentration. Nine ewes were slaughtered on each experimental day (days 1–16 after estrus) for ovary collection. The ovaries per ewe were classified as those without, or with one or two CL's, for each slaughter day. Visible follicles on the surface of the ovaries were classified, based on their diameter, into (i) very small (<2 mm), (ii) small (2–3.4 mm), (iii) medium (3.5–5 mm) and (iv) large (>5 mm) categories, and the respective numbers recorded. Results indicated, the number of ovarian follicles to decrease (P < 0.01) from days 1 to 5 of the cycle and showed a significant increase on day 7. Numbers were high again on day 11 and decreased (P < 0.01) on day 16 of the estrous cycle. The serum oestradiol concentrations were significantly higher (P < 0.001) in the double than in the single ovulating animals (one or two CL's, respectively) on days 2–0. However serum levels were also significantly higher (P < 0.001) in single, than twin ovulating animals on days 4–5 and 12–16 of the estrous cycle. There were no significant differences in the total number of very small follicles between animals without and those with two CL's. The number of small, medium and large follicles in ewes, with or without a CL on the ovary was significantly higher (P < 0.01) than ewes with two ovulations at certain stages of the estrous cycle. The present study provides evidence of differences in the follicular ovarian population in ovaries without CL's and double ovulations. The existence of an intraovarian effect of the CL numbers on follicular population is demonstrated.     

Silent ovulation, based on walking activity and milk progesterone concentrations, in Holstein cows housed in a free-stall barn

The objectives of the current study were to determine the incidence of silent ovulation (based on walking activity and milk progesterone profiles), identify risk factors for silent ovulation, and investigate its impact on reproductive performance in high-yielding dairy cows in free-stall housing. Overall, 277 lactations in 161 Holstein Friesian cows from a commercial dairy herd in northern Japan were studied. Walking activity (measured with pedometers) >80% above the mean for the preceding 2 d was defined as estrus, whereas day of ovulation was estimated using milk progesterone concentrations. Ovulation not preceded by increased walking activity was considered silent ovulation; the incidence was 55.2%, 23.8%, 21.3%, and 10.5% at the first, second, third, and fourth ovulations postpartum, respectively. Moderate and high milk yield significantly increased the risk of silent ovulation at second (odds ratio [OR] = 2.7 and 1.2; P = 0.04) and third and/or fourth ovulations (OR = 6.7 and 12.9; P = 0.03). Based on survival analysis, silent ovulations at the first, second, third, and/or fourth ovulations were associated with 28% (hazard ratio [HR] = 0.72), 55% (HR = 0.45), and 47% (HR = 0.53) reductions in pregnancy rate, respectively, and 41% (HR = 0.59), 66% (HR = 0.34), and 65% (HR = 0.35) reductions in artificial insemination (AI) submission rate. Cows with at least one silent ovulation (with the exception of the first ovulation) had a longer interval from calving to first AI (72 vs. 54 d, P < 0.001) and to achievement of pregnancy (133 vs. 80 d, P < 0.001). In conclusion, approximately one third of the ovulations (based on milk progesterone concentrations) in Holstein cows within 90 d postpartum were silent. Silent ovulations at the second to fourth ovulations were associated with high milk yields and at all ovulations were associated with impaired reproductive performance.     

Efficiency of estrous synchronization in tropical sheep by combining short-interval cloprostenol-based protocols and “male effect”

This study assessed the efficacy of a protocol combining short-interval cloprostenol-based protocols and “male effect” for estrous synchronization in hair sheep. In Experiment 1, 24 ewes were randomly assigned to three groups (n = 8) and treated with cloprostenol on Days 3, 5 and 7 after ovulation, respectively. Estradiol secretion during the follicular phase was similar among groups. Onset of estrus (P < 0.001) and the timing of maximum LH concentration (P < 0.01) were earlier in group D3 than in D5 and D7 groups. During the subsequent cycle, the number and size of corpora lutea were higher (P < 0.05) in ewes of the groups D3 (1.9 ± 0.3 and 115.1 ± 14.3 mm²) and D5 (1.8 ± 0.2 and 100.2 ± 11.2 mm²) than in group D7 (1.3 ± 0.2 and 75.6 ± 6.4 mm²) group. In Experiment 2, 24 ewes were treated with two cloprostenol injections (7 days apart). Twelve ewes were exposed to “male effect” previous to an isolation period (ME group), whereas the remaining ewes were controls without male exposure (CTR group). Male effect induced earlier preovulatory LH surge (P < 0.05) and ovulation (P < 0.001) than CTR group. In Experiment 3, the estrus was synchronized in 68 ewes. Nineteen of them (group FGA) were treated using intravaginal sponges impregnated with fluorogestone acetate for 12 days and inseminated at 55 h. Forty-nine females (group ME) were treated like ME group. Twenty-four (ME48 group) and 25 ewes (ME55 group) were inseminated at 48 and 55 h after treatment, respectively. The fertility rate was numerically higher in ME48 than ME55 and FGA groups (62.5, 44.0 and 47.4%, respectively). In conclusions, the combined use of short-interval cloprostenol treatment and “male effect” may be an adequate alternative for synchronizing estrus and applying artificial insemination in hair sheep throughout the entire year.     

Effect of immunization against progesterone on oestrus, cycle length, ovulation rate, luteal regression and LH secretion in the ewe

The effects of active immunization against progesterone on reproductive activity were studied in Merino ewes. Immunization against progesterone caused a shortening (P less than 0.01) of the interval between ovulations from 17-18 days (controls) to between 6 and 10 days (immunized group); this was associated with a corresponding reduction in the interval between LH surges. The immunized ewes also had higher (P less than 0.05) ovulation rates (1.72) than controls (1.25) and exhibited a reduced (P less than 0.01) incidence of oestrus (26% v. 95%). Many immunized ewes continued to ovulate despite the persistence of corpora lutea from earlier ovulations which led to an accumulation on the ovaries of many corpora lutea of different ages. The frequency of LH pulses in ewes immunized against progesterone (1.8 +/- 0.2 pulses/4 h) was significantly (P less than 0.001) higher than that of control ewes (0.3 +/- 0.1 pulses/4 h). This study highlights the importance of progesterone in the control of oestrus, ovulation, ovulation rate, luteal regression and the secretion of LH in the ewe.     

Interactions between dietary protein,ovulation rate and follicle stimulating hormone level in the ewe

Ovulation rate (OR) was studied in two experiments using mature Border Leicester × Merino ewes in which oestrous cycles were synchronized using a prostaglandin analogue. In both experiments a basal ration of 500 g of lucerne/barley pellets was provided. In the first experiment, ewes were fed individually iso-energy supplements of 500 g of either peas, lupins, soybean pellets or lucerne/barley pellets. The ovulation studied at laparoscopy occurred approximately 34 days after starting the supplementary feeding. Ewes fed lupins or soybean pellets had higher (P < 0.05) OR's than the ewes fed the other diets.In the second experiment, ewes were fed either iso-protein supplements of peas or lupins or casein supplement (170 or 100 g of protein) either formalin treated or untreated. The ovulations studied at laparoscopy occurred approximately either 17 or 34 days after the first feeding of the supplement. Follicle stimulating hormone (FSH) levels in plasma were measured over the 8 days prior to the second ovulation. There were no differences (P < 0.05) in OR's at the first ovulation. However, by the second, ewes fed peas had the highest (P < 0.05) OR while those fed lupins or protected casein had similar OR's. These tended to be higher than in the ewes fed untreated casein. FSH levels were generally higher from 8 days to 3 days prior to ovulation in ewes which were to have twin ovulations compared to those having single ovulations.The results confirm that feeding high energy or high protein will increase OR. There are independent effects of energy and protein. The results suggested that the ovulation rate may be related to FSH levels.     

An abattoir survey of ovine reproductive tracts in Ireland

Reproductive tracts were collected from 870 ewes slaughtered at an abattoir in County Dublin over a 9-m.o. period from September 1993 to June 1994. Ovarian activity was evident in 59.3% of the tracts examined. The mean ovulation rate was 1.26 +/- 0.045 (mean +/- SEM). The spatial relationship between corpora lutea (CL) and dominant follicles was established. Ten percent of the ewes examined were pregnant. Embryonic transuterine migration was observed in 12% of the single ovulating ewes and in all ewes pregnant with twins which had double ovulations on one ovary. Based on the observation of tracts with contemporaneous double ovulations and a single fetus, the prevalence of embryonic loss was 17.2%. Overall, 9.4% of the tracts showed evidence of pathological change, and 5.5% of the tracts had abnormalities likely to impair fertility.     

Regulation of the proliferative activity of ovarian surface epithelial cells by follicular fluid

Despite critical roles of the ovarian surface epithelium (OSE) in ovulation and post-ovulatory wound repair, little is known about the physiological mechanism regulating OSE proliferation. A role of follicles and corpora lutea in locally regulating the proliferative activity of OSE has been suggested. In this study, the effects of follicular and luteal products on proliferation of cultured OSE cells were tested using cells obtained from seasonally anoestrous ewes. Follicular fluid but not luteal extracts induced OSE cell proliferation (2.5-fold relative to untreated controls; P < 0.0001). The response of OSE cells was not affected by follicle size or previous charcoal-extraction of follicular fluid (P > 0.1). Treatment with IGF-1 (2.2-fold; P < 0.01), EGF (1.9-fold; P < 0.01) and, to a lesser extent, FSH (P < 0.05) also induced OSE cell proliferation. In contrast, oestradiol or progesterone did not induce cell proliferation or enhance the effects of FSH on proliferation (P > 0.1). It was concluded that follicular fluid can directly stimulate ovine OSE cell proliferation and that this effect is attributable to non-steroidal mitogens.     

Effect of reproductive status on twinning and on side of ovulation and embryo attachment in mares

Brood-farm records were used to test several hypotheses concerning twinning and inequalities in the side of ovulation and embryo attachment. Ovulation occurred more frequently (P<0.05) from the left ovary (61% versus 39%) in maiden mares, but with equal frequency from either ovary in lactating and barren mares. The embryo attached more often (P<0.05) to the left horn in lactating mares (60%) and to the right horn in barren (59%) and maiden (67%) mares. Double ovulations and twin embryos were diagnosed more frequently (P<0.05) in barren mares (11% and 6%, respectively) than in lactating mares (5% and 1%). Pregnancy rates for double ovulations were affected (P<0.01) by the length of the interval between the two ovulations (0 days, 83%; 2 days, 87%; 4 days, 67%; 6 days, 54%; 8 days or more, 38%). Pregnancy rates were higher (P<0.01) for double ovulations 0 or 2 days apart (84%) than for single ovulations (54%). Twins were diagnosed more frequently (P<0.05) when double ovulations were two or more days apart (9 32 ) than when the ovulations were synchronous (0 19 ). These results support the conclusion that an embryo-reduction mechanism exists in mares for the elimination of excess embryos and indicate that the mechanism loses its effectiveness when the embryos originate from asynchronous ovulations.     

Plasma progesterone concentration in relation to ovulation rate and embryo yield in Chios ewes superovulated with PMSG

The main purpose of this work was to investigate the relationship between plasma progesterone concentration and the number of ovulations and/or the number of embryos collected from Chios ewes induced to superovulate with various doses of PMSG.The oestrous cycles of the animals were synchronized by means of MAP intravaginal sponges for 14 days and PMSG was injected i.m. (1500 IU, Group 1; 1000 IU, Group 2; 750 IU, Group 3; 500 IU, Group 4; 0 IU, Group 5) at the time of sponge withdrawal. Seven days after sponge removal and 5 days after mating, mid-ventral laparotomy was performed and the uterine horns and/or oviducts were flushed. The number and diameter of corpora lutea (CL), the number of large (diameter > 0.5 cm) anovulated follicles and the total ovarian response (TOR = CL + large anovulated follicles) were recorded. The embryos were examined under a dissecting microscope and evaluated according to morphological criteria. Blood samples were collected once daily for 4 days starting on the day of sponge withdrawal. One more sample was taken on the day of embryo collection. Progesterone concentration was determined using a conventional ELISA.A significant positive correlation was found between plasma progesterone concentration and number of corpora lutea (r = 0.61, P < 0.001), total diameter of corpora lutea (r = 0.63, P < 0.001), total ovarian response (r = 0.63, P < 0.001), number of eggs (r = 0.51, P < 0.001), number of embryos (r = 0.43, P < 0.001) and number of transferable embryos (r = 0.36, P < 0.01) collected per ewe treated. A negative relation between progesterone concentration (≥ 2 ng ml⁻¹) at the beginning of oestrus and number of corpora lutea (CL) was observed. The investigation of the relationship between ovulation rate and plasma progesterone concentration on the day of embryo collection resulted in the calculation of a formula for the prediction of the response of Chios sheep after superovulation with the specific hormonal regimen.     

Ovarian and endocrine responses in tropical sheep treated with reduced doses of cloprostenol

The present study aimed to assess the efficacy of reduced doses of cloprostenol for synchronizing estrus and ovulation in hair sheep. With the aim to evaluate the luteolytic activity of reduced cloprostenol doses, a first experiment was performed using a relatively large (group H: 126 μg; n = 8), medium (group M: 68.25 μg; n = 6) and small (group L: 38.5 μg; n = 6) cloprostenol dose. Luteolysis was assessed at Days 3 and 6 after injection (Day 0) by progesterone concentrations (P₄) and transrectal ultrasonography (US). In Experiment 2, sheep were randomly assigned to the same three doses to evaluate a protocol for estrous synchronization using two injections administered 9 days apart. A third trial was performed with ewes treated (9 days apart) with the large dose (H = 126 μg; n = 12) and with a small dose adjusted for facilitating volume management (LA = 43.75 μg; n = 12). Presence of estrous cycling was determined in all the ewes by US and P₄ assay, at Days −9, −6, −2, 0 (Day of second cloprostenol injection), 8 and 11. Bleeding and US were done every 4 h from 16 h of the beginning of the estrus during the third trial to assess the preovulatory LH surge and timing of ovulation. Additionally, blood samples were drawn at Days 0, 1, 2 and 3 to assess estradiol (Experiments 2 and 3) and P₄ (Experiment 2) concentrations during the ovarian follicular phase. In all experiments, percentage of animals showing luteolysis, preovulatory follicular dynamics and function and percentage of ewes showing behavioral estrus in response to treatment was similar among groups. Timing of estrus for group H was earlier than group L (28.6 ± 1.8 h compared with 37.1 ± 2.4 h; P < 0.05). In the third trial, the preovulatory LH peak was higher in the LA group than group H, in terms of maximum mean concentration during the surge (27.7 ± 1.8 ng/mL compared with 21.3 ± 2.2 ng/mL; P < 0.05) and area under the curve (AUC; 183.4 ± 12.7 ng/mL compared with 127.7 ± 10.9 ng/mL; P < 0.01). However, timing of ovulation was similar for H and LA groups. Thereafter, ovulation rate and luteal function at Day 11 were similar. Current results demonstrate that reduced doses of cloprostenol may be applied in a practical manner for reproductive management of sheep, with the additional advantage of reducing treatment costs.     

Effects of low versus physiologic plasma progesterone concentrations on ovarian follicular development and fertility in beef cattle

The objective of this study was to determine the effects of low versus physiologic plasma progesterone concentrations during the ovulatory wave on fertility in cattle. Suckled beef cows (Bos taurus; n = 129) and pubertal heifers (Bos taurus; n = 150) at random stages of the estrous cycle were given a luteolytic dose of prostaglandin F_2α (500 μg cloprostenol; PGF) twice, 11 d apart. Ten days after the second PGF treatment, cattle were given estradiol benzoate im (1.5 and 1.0 mg for cows and heifers, respectively) and a progesterone-releasing intravaginal device (Cue-Mate) with a single pod containing 0.78 g progesterone (Day 0). Cattle in the low-progesterone group (n = 148) received a luteolytic dose of PGF on Day 0, whereas those in the high-progesterone (i.e., physiologic plasma concentrations) group (n = 131) were allowed to retain their corpora lutea. On Day 8, the Cue-Mate was removed, and PGF was given to both groups. Fifty-four hours to 56 h later, cattle received 12.5 mg of porcine LH (pLH) im and were concurrently artificially inseminated. The dominant follicle in the low-progesterone group was larger (P < 0.001) than that in the high-progesterone group on the day of insemination (14.9 ± 0.3 mm vs. 12.7 ± 0.3 mm, mean ± SEM). At 7 d after ovulation, the low-progesterone group had a larger corpus luteum (24.5 ± 0.54 mm vs. 21.9 ± 0.64 mm, P < 0.01) and higher plasma progesterone concentration (4.0 ± 0.3 vs. 3.1 ± 0.2, P < 0.01) than that of the high-progesterone group. However, pregnancy rates did not differ (79 of 148, 53.4%, and 70 of 131, 53.4%) for low- and high-progesterone groups, respectively). In summary, low circulating progesterone concentrations during the growing phase of the ovulatory follicle resulted in a larger dominant follicle and a larger CL that produced more progesterone, with no significant effect on pregnancy rate.     

Interruption of the canine estrous cycle with a low and a high dose of the GnRH antagonist, acyline

To test the efficacy and clinical safety of a low and high dose of the GnRH antagonist, acyline, on estrous cycle interruption and anovulation in female dogs, 20 proestrous (<3 d) bitches were randomly assigned to one of the following pharmacological protocols (given sc): acyline 110 μg/kg (ACY-L; n = 6); acyline 330 μg/kg (ACY-H; n = 8); or placebo (PLACE, n = 6). The animals were monitored (clinical and vaginal cytology examinations) daily for 60 d. Blood samples for serum progesterone serum concentrations were collected 14 d after treatment to determine if ovulation had occurred. Appearance of side effects and days to the onset of the first spontaneous estrous cycle after treatment were also recorded. In both ACY groups, but not the PLACE group, estrous cycles were interrupted after treatment (P < 0.05). The interval from treatment to estrus interruption in ACY-L and ACY-H groups was 3.0 ± 0.6 and 3.2 ± 0.2 d, respectively (LSM ± SEM; P > 0.05). In the PLACE bitches, physical, behavioral and cytological proestrus slowly progressed to estrus and diestrus. Ovulation was absent in all ACY, but not in PLACE bitches (P < 0.05). None of the females manifested side effects related to the treatments (P > 0.05). Spontaneous return to a normal estrous cycle during the study period occurred in all ACY (ACY-L 19.5 ± 2.7 d vs ACY-H 24.8 ± 2.0 d; P > 0.05), but in none of the PLACE bitches (P < 0.05). In conclusion, acyline efficiently, safely and reversibly interrupted an early phase of the estrous cycle in bitches by preventing ovulation.     

Corpus luteum size and function following single and double ovulations in non-lactating dairy cows

Data was collated from a number of studies on various aspects of luteal function in non-lactating dairy cows to allow comparisons to be made between single and double ovulating animals. In these studies, estrous cycles had been synchronized and animals slaughtered on day 5 or 8. The overall incidence of double ovulations was 28.3%. Double ovulation was associated with smaller individual corpora lutea but no difference in total weight of luteal tissue or any aspect of luteal tissue function or plasma concentrations of progesterone. Furthermore, in a sub set of animals, there was no difference in preovulatory follicle characteristics or plasma concentrations of estradiol around ovulation. These results demonstrated a high incidence of double ovulation in non-lactating cows that had no influence on circulating progesterone concentrations.     

Effects of treatment with a prostaglandin analogue on developmental dynamics and functionality of induced corpora lutea in goats

The aim of this study was to compare morphological and functional features of spontaneous and induced corpora lutea (CLs) in goats. Fourteen adult and cycling Anglo Nubian goats (Argentina) were randomly allocated to two groups: Group N (n = 7) included goats with natural spontaneous oestrus and Group PG (n = 7) included does in which oestrus was synchronized by the administration of two i.m. cloprostenol doses, 10 days apart. In both groups, oestrous behaviour was checked twice daily (Day of oestrus = Day 0) and daily transrectal ultrasonographies were performed for evaluating CLs and follicles dynamics through the complete subsequent oestrous cycle; the luteal activity was determined directly, in terms of progesterone (P4) secretion, and indirectly, by assessing effects of CL on follicular dynamics. All goats exhibited oestrous behaviour and ovulation without differences in ovulation rate (N: 1.67 ± 0.2, PG: 2.0 ± 0.1). The total luteal tissue area showed linear growth from Day 4 to Day 15 of oestrous cycle in all goats, but the developmental dynamics differed between groups, treated goats had larger area (P < 0.01). Plasma P4 concentrations also increased from Day 0 to Day 15 in all the does; however, from Day 5 to Day 15, treated does had a lower concentrations than the untreated group (P < 0.001). There were differences in the development of follicular waves between groups; assessment of size-distribution showed that treated group had a higher number of small and larger follicles (P < 0.05). The largest follicles recorded in treated goats had a higher maximum diameter both at the first (PG: 7.6 ± 0.8 mm; N: 4.9 ± 0.7 mm, P < 0.05) and second follicular waves (PG: 6.3 ± 1.4 mm; N: 5.0 ± 0.4 mm, P < 0.05) and a longer growth phase during the second wave (PG: 6.5 ± 1.7 days; N: 4.6 ± 0.7 days, P < 0.05), coincident with the period of maximal luteal secretion. In conclusion, synchronization of oestrus and ovulation by the administration of a prostaglandin analogue causes differences in developmental dynamics and functionality of induced corpora lutea when compared to natural spontaneous ovulation.     

Ovarian response in ewes following horse anterior pituitary extract and progestagen treatment

Sixty adult ewes were treated intravaginally for 12 days with one of three progestagen treatments: (1) 500 mg progesterone pessary, (2) 30 mg flurogestone acetate pessary, (3) 12% (w/w) progesterone in a Controlled Internal Drug Release (CIDR) device. On days 10, 11 and 12 of progestagen treatment ewes received either 60, 45 and 30 mg; 45, 45 and 45 mg or 30, 45 and 60 mg of horse anterior pituitary extract (HAP), respectively. Progestagen treatment was terminated on day 12 at the time of the last HAP treatment. Ewes were bred by artificial insemination at 8- and 16-h intervals during oestrus, which was checked by using vasectomized rams. Ovarian response and fertility were determined at laparotomy 8 days after progestagen withdrawal. Progestagen treatment significantly increased (P<0.05) ovulation rate, with a mean of 9.1, 12.0 and 6.6 ovulations from treatments (1), (2) and (3), respectively. The method of HAP administration had no significant effect on ovulation rate, with a mean of 9.8, 10.0 and 7.8 after either decreasing, constant or increasing levels during treatment. There was no difference in the fertilization rate following flurogestone acetate (45.7%) or CIDR (47.0%), but a lower rate resulted after the progesterone pessary (30.0%) (P<0.025). More eggs were recovered following local than following general anaesthesia (P<0.05). Results indicate that cervical insemination does not give a satisfactory yield of fertilized eggs following hormonal inductions of superovulation.     

Calm Merino ewes have a higher ovulation rate and more multiple pregnancies than nervous ewes

In 1990, two selection lines of Merino sheep were established for low and high behavioural reactivity (calm and nervous temperament) at the University of Western Australia. Breeding records consistently showed that calm ewes weaned 10% to 19% more lambs than the nervous ewes. We hypothesise that calm ewes could have a higher ovulation rate than nervous ewes and/or calm ewes could have a lower rate of embryo mortality than nervous ewes. We tested these hypotheses by comparing the ovulation rate and the rate of embryo mortality between the calm and nervous lines before and after synchronisation and artificial insemination. Merino ewes from the temperament selection lines (calm, n=100; nervous, n=100) were synchronised (early breeding season) for artificial insemination (day 0) (intravaginal sponges containing fluogestone acetate and eCG immediately after sponge withdrawal). On day-17 and 11 ovarian cyclicity and corpora lutea, and on days 30 and 74 pregnancies and embryos/foetuses were determined by ultrasound. Progesterone, insulin and leptin concentrations were determined in blood plasma samples from days 5, 12 and 17. Ovarian cyclicity before and after oestrus synchronisation did not differ between the lines, but ovulation rate did (day-17: calm 1.63; nervous 1.26; P<0.01; day 11: calm 1.83; nervous 1.57; P<0.05). Ovulation rate on day 11 in nervous ewes was higher than on day-17. Loss of embryos by day 30 was high (calm: 71/150; nervous: 68/130); but nervous ewes had a lower proportion (15/47) of multiple pregnancies compared with calm ewes (30/46; P<0.01). Reproductive loss between days 30 and 74 represented 7.3% of the overall loss. Temperament did not affect concentrations of progesterone, but nervous ewes had higher insulin (32.0 pmol/l±1.17 SEM; P=0.013) and lower leptin (1.18 μg/l±0.04 SEM; P=0.002) concentrations than calm ewes (insulin: 27.8 pmol/l±1.17 SEM; leptin: 1.35 μg/l±0.04 SEM). The differences in reproductive outcomes between the calm and nervous ewes were mainly due to a higher ovulation rate in calm ewes. We suggest that reproduction in nervous ewes is compromised by factors leading up to ovulation and conception, or the uterine environment during early pregnancy, that reflect differences in energy utilisation.     

Lambing rates and litter size following carazolol administration prior to insemination in Kivircik ewes

The effect of carazolol on the ease of penetrating the cervix during artificial insemination, lambing rate and litter size was studied using 1.5–4.0-year old Kivircik ewes in an incomplete 3 × 2 × 2 experimental design. All of the ewes in this study were synchronized for oestrus by insertion of a progesterone impregnated vaginal sponge for 12 days and administration of 400 IU PMSG at sponge withdrawal. Three methods of service were compared: natural service, artificial insemination (AI) with fresh semen, or AI with frozen semen. Two times of insemination (fixed time AI versus AI at observed oestrus) were compared on the fresh and frozen AI treatments. The absence (control) or use of carazolol (carazolol; 0.5 mg/ewe i.m. 30 min before mating) was the third factor in the design and penetration of the cervix by the insemination pipette was assessed as shallow (<10 mm), middle (10–20 mm) or deep (>20 mm). Natural service ewes were only mated at observed oestrus. Consequently, the factorial design was incomplete and there were a total of 10 treatments each represented by 30 ewes. Natural service resulted in a significantly (P < 0.05) higher lambing rate and litter size (86%; 2.0 ± 0.05 lambs/ewe) than AI using fresh (65%; 1.6 ± 0.1 lambs/ewe) or frozen (40%; 1.4 ± 0.14 lambs/ewe) semen. For AI animals the lambing rate and litter size were not significantly different when service was at a fixed time (50%; 1.5 ± 0.12 lambs/ewe) or at observed oestrus (56%; 1.5 ± 0.12 lambs/ewe). Carazolol did not permit complete cervical penetration in any ewe. Deep penetration of the cervix at AI was achieved in 33% of untreated (control) and 48% of carazolol treated ewes (P < 0.05). However, the proportion of ewes in which penetration of the cervix and semen deposition was greater than shallow was similar for control (82%) and carazolol (85%), and lambing rate and litter size were similar for both treatments. Over the three service methods, the lambing rate was 56% for control and 63% for carazolol (NS) and litter size was similar for both treatments. It was concluded that the carazolol treatment used prior to natural mating or AI in this experiment did not improve lambing rate or litter size in Kivircik ewes.     

Ovarian and endocrine responses to prostaglandin F2alpha (PGF2alpha) given at the expected time of the endogenous FSH peak at mid-cycle in ewes

In the ewe, a rise in circulating concentrations of FSH preceding follicular wave emergence begins in the presence of growing follicles from a previous wave. We hypothesized that prostaglandin F(2alpha) (PGF(2alpha)) given at the time of an endogenous FSH peak in cyclic ewes would result in synchronous ovulation of follicles from two consecutive waves, increasing ovulation rate. Twelve Western White Face (WWF) ewes received a single i.m. injection of PGF(2alpha) (15 mg/ewe) at the expected time of a peak in FSH secretion, from Days 9 to 12 after ovulation. The mean ovulation rate after PGF(2alpha) treatment (2.3+/-0.3) did not differ (P>0.05) from the pre-treatment ovulation rate (1.7+/-0.1). Five ewes ovulated follicles from follicular waves emerging before and after PGF(2alpha) injection (3.0+/-0.6 ovulations/ewe) and seven ewes ovulated follicles only from a wave(s) emerging before PGF(2alpha) treatment (2.0+/-0.3 ovulations/ewe; P>0.05). The mean interval from PGF(2alpha) to emergence of the next follicular wave (1.0+/-0.4 and 4.0+/-0.0 d, respectively; P<0.001) and the interval from PGF(2alpha) treatment to the next FSH peak (0 and 3.5+/-0.4d, respectively; P<0.05) differed between the two groups. Six ewes ovulated after the onset of behavioral estrus, with a mean ovulation rate of 1.7+/-0.2, and six ewes ovulated both before and after the onset of estrus (3.0+/-0.5 ovulations/ewe; P<0.05). None of the ovulations that occurred before estrus resulted in corpora lutea (CL) with a full life span. At 24h before ovulation, follicles ovulating before or after the onset of estrus differed in size (4.1+/-0.3 or 5.5+/-0.4mm, respectively; P<0.05) and had distinctive echotextural characteristics. In conclusion, the administration of PGF(2alpha) at the expected time of an FSH peak at mid-cycle in ewes may alter the endogenous rhythm of FSH secretion and was not consistently followed by ovulation of follicles from two follicular waves. In non-prolific WWF ewes, PGF(2alpha)-induced luteolysis disrupted the normal distribution of the source of ovulatory follicles and may be associated with untimely follicular rupture and luteal inadequacy.     

Plasma FSH,LH, prolactin and progesterone profiles of Cheviot ewes with different levels of intake before and after mating,and associated effects on reproductive performance

Patterns of secretion of FSH, LH and prolactin were investigated in the luteal and follicular phases of the cycle prior to mating in Cheviot ewes on high and low intakes (approximately 3.0 and 0.8 kg DM per head per day) during the weeks before mating. Ewes on the high intake had a higher mean ovulation rate (1.95 vs 1.40; P < 0.01) and higher mean potential litter size (1.75 vs 1.00; P < 0.001) as determined at slaughter 3 weeks after mating.No significant differences associated with intake were observed in the endocrine profiles during the luteal phase of the cycle before mating, indicating that differences in reproductive performance were not mediated by changes in endocrine profiles in this period. However, during periods of the subsequent follicular phase, ewes on a high intake had a higher LH pulse frequency, higher mean prolactin levels and non-significantly higher FSH levels. The preovulatory peaks of these hormones were not altered by the level of intake but the mean peak values for prolactin and LH were significantly higher in ewes with multiple ovulations than in those with single ovulations. Differences in endocrine status prior to mating were not associated with differences in luteal function after mating, as measured by circulating progesterone levels. However, mean progesterone levels were higher in ewes on a low intake after mating compared with those on a high intake.     

Accuracy of in vivo and ex vivo ultrasonographic evaluation of ovarian follicles and corpora lutea in sows

Current study determined, in sows, the accuracy of ultrasonography for in vivo (n = 8) and ex vivo (n = 7) evaluation of corpora lutea (CLs) and follicles ≥1.5 mm in size, by comparison with macroscopic findings in sliced ovaries. The accuracy for ex vivo detection of follicles increased with follicle size (P < 0.05), being low for 1.5-1.9 mm follicles (65.9%) and higher for ≥6 mm follicles (93.3%); differences between ultrasonographic and macroscopic observations were significant only for follicles smaller than 3.9 mm (P < 0.05), due to underestimation. Ex vivo observation succeeded to detect presence or absence of CLs in all the ovaries; the efficiency for determining the exact number of CLs being 94.4%. The accuracy for in vivo detection of follicles also increased with follicle size (P < 0.05), dropping to values lower than 40% for 1.5-1.9 mm follicles; therefore, there were significant differences between ultrasonographic and macroscopic observations (P < 0.05). On the other hand, accuracy remained around 92% for ≥6 mm follicles. Ultrasonography was useful again for detecting presence of CLs in all the ovaries; the efficiency for determining CLs number reached 86.7%, due to underestimation in ovaries with higher number of CLs (P < 0.05). Overall, there were no significant differences when comparing the accuracy of ex vivo and in vivo scannings for determination neither of the number of follicles in each size-category larger than 1.9 mm nor of the presence of ovulations or of the CLs number in each ovary. In conclusion, the use of ultrasonography allows an accurate detection of the presence and number of CLs and follicles ≥2 mm of diameter in sows, without significant differences between in vivo and ex vivo observations.