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Tris-egg yolk based diluents provide adequate cryoprotection for the sperm of most wild species in which they have been tested. The objective of the current study was to evaluate various Tris-based diluents containing different concentrations of egg yolk, for the fertilizing ability of epididymal spermatozoa of the Spanish ibex (Capra pyrenaica) after freezing and thawing. For this purpose, we used heterologous in vivo fertilization by intrauterine insemination of domestic goats (Capra hircus). In Experiment 1, a Tris-citric acid-glucose (TCG) diluent containing 6% (v/v) egg yolk and a TCG extender containing 20% egg yolk were compared. In Experiment 2, a TCG-6% egg yolk extender was compared with Triladyl-20% egg yolk. Diluted samples were cooled slowly to 5 °C over 1 h and equilibrated at that temperature for 2 h. At that point, aliquots of samples were loaded into 0.25 ml straws, and frozen in nitrogen vapor for 10 min. The fertility of spermatozoa frozen in TCG-6% egg yolk was higher (P < 0.05) than for those extended with TCG-20% egg yolk, and tended to be higher than for those frozen with Triladyl-20% egg yolk. >From the results of this study, the use of Tris-based extenders containing low concentrations of egg yolk (6%) is recommended for cryopreserving Spanish ibex epididymal spermatozoa. © 2006 Elsevier Inc. All rights reserved.

Ten mouflon rams were kept with their mothers in a captive regimen under natural photoperiod. Seven of the mouflon lambs received a series of subcutaneous implants containing 18 mg of melatonin (Melovine ®). The first implant was inserted at the time of birth and it was followed by implant insertion every two months to maintain plasma melatonin concentrations above basal levels. Three mouflon lambs were used as controls. Body weight, outer horn length and horn base circumference were measured weekly. Three implanted lambs maintained a poor body condition throughout the experiment and died early. In the remaining four implanted lambs, the pattern of body and horn growth was similar to controls. Horn length and base circumference were correlated (P < 0.001) with body weight in both control and melatonin-implanted mouflons. No differences between control and survivor melatonin implanted mouflons were observed in weekly body weight gain (0.86 ± 0.19 kg and 0.77 ± 0.06 kg, respectively), weekly horn length growth (0.77 ± 0.03 cm and 0.77 ± 0.02 cm, respectively) and weekly base circumference growth (0.49 ± 0.03 cm and 0.45 ± 0.03 cm, respectively).

As a consequence of increasing limitations to maintaining genetic variability in endangered wildlife species, methods of assisted reproduction widely used in domestic animals are being applied to nondomestic species. However, practical efforts have met limited success to date. The Spanish ibex (Capra pyrenaica hispanica) is a wild caprine originating exclusively in the mountains of Spain. This study was designed to evaluate the fertilizing capability of cryopreserved Spanish ibex epididymal spermatozoa recovered postmortem. For this purpose, we have previously evaluated the effect of time elapsed between death and sperm recovery on spermatic parameters, and the fertilization ability of frozen-thawed spermatozoa using heterologous in vivo fertilization by intrauterine insemination in domestic goat (Capra hircus). The time of death significantly affected most sperm quality parameters (motility, viability and intact acrosomes). The fertility obtained by heterologous artificial insemination was 18.7%, and only goats inseminated with spermatozoa recovered within 8 h after death became pregnant. Our findings showed that heterologous in vivo fertilization is a useful method to evaluate the fertilizing capacity of sperm samples in rare or wild species. Sperm samples, with verified fertilization ability in the previous trial, were used to inseminate a total of six ibex females. Inseminations resulted in one pregnancy. The study demonstrated for the first time the feasibility of applying artificial insemination in Spanish ibex. © 2005 Elsevier Inc. All rights reserved.

The methods of assisted reproduction commonly used in domestic animals are currently being applied to non-domestic species. This is because of the limitation of maintaining the genetic variability in the wild, as it occurs in wild ruminants of the Mediterranean Basin. Despite the apparent progress of the technology, success of the offspring to grow and become healthy adult individuals has remained low in wild species. Difficulties usually arise from insufficient information about basic reproductive biology, such as the seasonal changes in ovarian and testicular activity. Directional adaptive evolution involves development of specie-specific physiological reproductive patterns to cope with various environmental factors. Thus, species originating and living at the same latitude display different reproductive strategies to entrain the breeding activity at an optimal time of the year. The aim of this paper was to present current knowledge on reproductive physiology of Mediterranean wild ruminants as a basic prerequisite for the successful use of assisted reproduction methods. Special emphasis is given to seasonal endocrine changes, ovarian cycles and testicular activity of Iberian wild ruminants, together with the role of social interactions on the regulation of these events. © 2006 The Authors.

This study compares morphological changes, performed with real-time transrectal ultrasonography, of testis and accessory glands and seasonal endocrine changes in a wild (Mouflon) and a domesticated (Spanish Merino) breed of sheep. In Mouflons, the maximum plasma testosterone concentrations, testicular diameter and vesicular gland size occurred synchronously during autumn (P < 0.001). In Merino rams the highest circulating levels of testosterone (P < 0.05) and maximum testicular diameter (P < 0.001) occurred during summer, with no seasonal variations in vesicular and bulbourethral glands. The seasonal changes in plasma concentrations of prolactin were not correlated with annual variations in testicular and glandular size in neither wild nor domestic species. No differences were observed between both species for the seasonal pattern of prolactin secretion and mean amplitude of melatonin. Wide differences in reproductive patterns between wild and domestic types of rams do not appear to be attributed to seasonal changes in prolactin and melatonin secretion. © 2005 Elsevier Inc. All rights reserved.

Serial transrectal ultrasonographies were performed measuring different structures of mouflon (Ovis gmelini musimon) fetuses to establish their gestational age. Data were obtained from 14 mouflon ewes that became pregnant after estrous synchronization. From day 25 of gestation onward, the crown-rump length and the trunk diameter of the embryo were estimated. Later, when the fetal organs and structures could be distinguished, several measurements were done in the skull (occipito-snout length and biparietal and orbit diameters), the trunk (thoracic diameter and width of vertebrae), and the abdominal cavity (stomach and kidney longitudinal diameters); femur length was also determined. All fetal measurements were correlated with gestational age (P < 0.001), but the parameters showing the highest correlation with time (R2 up to 0.94) were the crown-rump and occipito-snout lengths and the thoracic and biparietal diameters. No significant differences were observed in pregnancies with one or two fetuses in the period studied. Copyright 2005 by American Association of Zoo Veterinarians.

Annual variations in the growth of horns, and their correlation with seasonal changes of testicular size, and prolactin (PRL) and melatonin secretion were monitored in six pubertal mouflon rams living in their original latitude (40°N). Mouflons born and maintained under captive conditions were classified in two age classes sub-adult (2 years; n = 3) and adult (≥3 years; n = 3). The rate of horn growth was greater (P < 0.001) in sub-adult than in adult mouflon rams. Horn growth was influenced by season in both adult and sub-adult mouflons (P < 0.05) with largest monthly growth occurring in spring and summer. Seasonal variations of plasma PRL concentrations were correlated with horn growth in adult, but not in sub-adult mouflon rams. The rate of horn growth was inversely correlated with testicular size (r = -0.5, P = 0.07). Seasonal changes in the amplitude of the daily melatonin rhythm in solstices and equinoxes were observed, which were not correlated with variations in the rate of horn growth. These results provide support for a possible role of PRL in the control of growth of horns in the adult mouflon. © 2004 Elsevier B.V. All rights reserved.

This review offers an overview of the basic characteristics of in vivo embryo technologies, their current status, the main findings and the advances gained in recent years, and the outstanding subjects for increasing their efficiency. The use of superovulation and embryo transfer procedures remains affected by a high variability in the ovulatory response to hormonal treatment and by a low and variable number of transferable embryos and offspring obtained. This variability has been classically identified with both extrinsic (source, purity of gonadotrophins and protocol of administration) and intrinsic factors (breed, age, nutrition and reproductive status), which are reviewed in this paper. However, emerging data indicate that the main causes of variability are related to endocrine and ovarian factors, and so the number of studies and procedures addressing a better understanding and control of these factors may be increased in the future. The accomplishment of this objective, the improvement of procedures for embryo conservation and for the selection and management of recipient females, will allow further development and application of this technology. © CSIRO 2004.

The aim of this study was to determine, for goats, the effects of daily doses of GnRH antagonist on ovarian endocrine and follicular function. Ten does were given 45mg FGA intravaginal sponges and then five were treated with daily injections of 0.5mg of the GnRH antagonist Teverelix for 11 days from 2 days after the day of sponge insertion, while five does acted as controls. Pituitary activity was monitored by measuring plasma FSH and LH daily from 2 days before the first GnRH injection to Day 12. Follicular activity was determined by ultrasonographic monitoring and by assessing plasma inhibin A levels during the same period. In treated does, the FSH levels decreased linearly (0.8±0.1ng/ml to 0.5±0.1ng/ml, P<0.01) and remained lower than the mean concentration in control goats (0.8±0.1ng/ml, P<0.005). LH levels were also lower during the period of antagonist treatment (0.6±0.2ng/ml versus 0.4±0.1ng/ml, P<0.0005). During GnRH antagonist treatment, there was a significant decrease in the number of large follicles (≥6mm) from Day 3 of treatment (1.2±0.6, P<0.0001), with no large follicles from Day 9. The number of medium follicles (4-5mm in size) also decrease during the period of treatment (4.2±0.7 to 1.0±0.6, P<0.0001), leading to a significant decrease in inhibin A levels when compared to the control (143.7±31.3pg/ml versus 65.2±19.1pg/ml, P<0.00005). In contrast, the number of small follicles (2-3mm) increased in treated goats from Day 4 of treatment (9.6±2.9 to 20.2±6.3, P<0.005). Such data indicate that GnRH antagonist reduced plasma levels of FSH and LH with suppression of the growth of large dominant ovarian follicles and a two-fold increase in number of smaller follicles. The results confirm that GnRH antagonist treatment can be used in goats to control gonadotrophin secretion and ovarian follicle growth in superovulatory regimes. © 2003 Elsevier Inc. All rights reserved.

The aims of this study were to examine whether mouflons exposed to constant long and short day photoperiods are able to exhibit an annual cycle of hair growth and moult, and prolactin (PRL) secretion. Mouflon ewes were assigned to three groups of treatment. Ewes were maintained, either under natural photoperiod (control, n=9), or received a series of subcutaneous melatonin implants from December to April (n=8), or were exposed to a constant long day photoperiod (16-hlight8-hdark; 16L8D) during 18 months (n=7). Blood was collected weekly to determine PRL concentrations, and hair samples were clipped weekly from the base of the neck to measure the length of predominant hair. Under constant long days and with melatonin implants, mouflons expressed an annual rhythm of PRL secretion, even though these treatments modified the times of rise or falling of PRL concentrations throughout the year. Hair growth initiation was almost coincident with the summer solstice in both control and melatonin-implanted mouflons but occurred two months earlier in long day hold mouflons (P<0.001). Long day hold mouflons had a lower hair growth rate than control and melatonin-implanted mouflons (P<0.001), and at the end of the experiment, a shorter hair length (3.4±0.24cm; P<0.01) than control (4.3±0.17cm), and melatonin-implanted mouflons (4.2±0.12cm). Our data support the conclusion that in mouflon, an endogenous circannual rhythm of PRL secretion exists, and that the seasonal cycle of hair growth and moult appears to depend, at least in part, on circulating levels of PRL. © 2004 Elsevier Inc. All rights reserved.

Seasonal changes in ovulatory activity, assessed by the measurement of plasma progesterone and plasma prolactin concentrations were monitored in 10 Spanish ibex females captured in the National Wildlife Reserve of Sierra Nevada (South Spain, 37° N). Five of the 10 female ibex showed ovulatory activity with a mean (± s.e.m.) duration of the oestrous cycle of 19.4 ± 1 days (range 17-23 days). On average, the five cyclic females weighed 28 ± 0.9 kg. Progesterone cycles occurred only in animals older than 4 years of age. Ovulatory activity extended from December to January. The duration of the breeding season was 43.2 ± 7.7 days. Ibex females younger than 4 years of age had a body weight lower (P < 0.01) than that of adults and none of them displayed ovulations. Plasma concentrations of prolactin levels were significantly affected by season (P < 0.05), following a trend that was roughly parallel to daylength. The highest values occurred in the spring (119.7 ± 21.4 ng·mL-1) and the summer (139.3 ± 19.8 ng·mL-1), the lowest values in the autumn (26 ± 7.4 ng·mL-1) and in the winter (19.7 ± 3.2 ng·mL-1). Our results showed a very restricted breeding season, despite the fact that the Spanish ibex originates from and lives in a temperate latitude, revealing a remarkably good adaptation to the harsh climatic and nutritional conditions of their mountainous habitat.

Objectives of this study were to characterize patterns of follicular development in sheep superovulated with purified follicle stimulating hormone (FSH) (OVAGEN™, ICP, Auckland, New Zealand) and to determine its influence on preovulatory events (onset of the oestrus behaviour and timing of the preovulatory luteinizing hormone surge) and ovarian response (ovulation rate and embryo yield). Number and size of all ≥ 23 mm follicles from the first FSH injection to withdrawal of progestagen sponges was determined by transrectal ultrasonography just prior to every FSH injection in nine Manchega ewes superovulated with eight decreasing doses (ml) (1.5 × 3, 1.25 × 2 and 1 × 3) of OVAGEN injected twice daily from 60 h before to 24 h after the withdrawal of 40 mg fluorogestone acetate sponges. Oestrous detection and jugular blood sampling for LH radioimmunoassay were performed every 3 h from 14 to 53 h after sponge removal and ovulation rate and number of embryos were determined 4 days after progestagen withdrawal. Administration of OVAGEN induced a significant rise (p < 0.0005) in the number of follicles ≥ 4 mm in size because of an increased growth in size of follicles from the first FSH injection to sponge removal, an increase in the number of newly detected follicles from 12 to 36 h of the first FSH dose (p < 0.005) and a decrease in regression rate from 24 h (p < 0.001). The number of follicles 2-3 mm in size at first FSH dose (10.4 ± 1.5) was positively correlated with the number of ≥ 4 mm follicles at 0 h (19.0 ± 2.7, p < 0.01). A higher number of ≥ 4 mm follicles at 0 h was related with an earlier appearance of oestrus (31.5 ± 1.5 h, p = 0.08) and LH surge (45.0 ± 2.3 h, p < 0.005), and a higher ovulation rate (18.2 ± 3.8, p < 0.005). On the other hand, the rate of embryo recovery was decreased in ewes with earlier preovulatory LH peaks (p < 0.005), with a shorter interval between oestrus and LH peak (p < 0.05).

Daily transrectal ultrasonographies were conducted to study development of all follicles with antral diameters ≥2 mm during the follicular phase of oestrous cycle in Mouflon, a strictly monovular wild-sheep. A total of 14 follicular phases was studied after oestrus synchronization with two cloprostenol doses, 9 days apart, in five cyclic Mouflon ewes. In 13 cycles (92.8%), the ovulatory follicle arose from those antral follicles present in both ovaries when luteolysis was induced, being the largest one with a mean size of 4.4±0.3 mm at that moment in 10 cycles (76.9%). The remaining cycles had a larger follicle, but it was decreasing in size. Appearance of new follicles ≥2 mm in size remained unaffected during the follicular phase (3.7±0.2), but there was found a linear decrease in the number of those growing to ≥3 mm (2.5±0.4 to 1.1±0.2, P < 0.05) and ≥4 mm (0.6 ±0.2 to 0.1±0.1, P < 0.005), detection of new follicles growing to ≥5 mm was negligible. Then, number of medium (4-5 mm) growing follicles present in both ovaries decreased from 1.5 ± 0.3 at 0 h to 0.3 ± 0.1 at 72 h (P < 0.005). In conclusion, the single ovulatory follicle is the largest growing follicle present in both ovaries at the moment of luteolysis. This follicle is selected to grow and ovulate while development of other follicles is inhibited. © 2001 Elsevier Science B.V.

The timing of the onset of puberty, duration of seasonal ovulatory activity, and length of postpartum anestrus were studied by means of blood plasma progesterone concentrations in a flock of European female mouflons (Ovis gmelini musimon) maintained in captivity under natural photoperiod (40°25′N). Concentrations of progesterone in the peripheral blood were determined by radioimmunoassay in samples collected from the jugular vein twice a week. First ovulations in the breeding season were highly synchronized and occurred in mid-October. In contrast, the cessation of ovulatory cycles showed significant variation among females and extended from February to May, depending on age, with 2-yr-old animals exhibiting the longest anovulatory period (P < 0.01). When lambing occurred within the breeding season (February-April), 12 out of 26 animals had their first ovulation 25 ± 1.8 days after parturition. The 14 late-lambing females had the first postpartum ovulation delayed until the next breeding season. March/April-born mouflon lambs that reached a minimum threshold body weight (23.8 ± 0.6 kg) in their first breeding season reached puberty at 8 mo of age. In those with slower growth rates, however, the prepubertal period was extended throughout the first breeding and nonbreeding seasons, reaching puberty during the breeding season of the following year at 19 mo of age and 27 ± 0.3 kg body weight. Further, attainment of puberty in ewe lambs born in June/July was also delayed until the breeding season of the following year, when animals had reached a threshold body weight at 17 mo of age.

Embryos from five anesthetized mouflons (Ovis gmelini musimon), superovulated with FSH-o (Ovagen™) were transferred into preselected Spanish Merino sheep (Ovis aries). Myorelaxation was complete in four of five donor mouflons. The status of the uterus of potential recipients was evaluated by transrectal ultrasonography, and those ewes with fluid in the uterine horn were rejected. The corpus luteum in each ewe was assessed ultrasonographically the day before surgery. Plasma progesterone levels and the quality of the corpora lutea were the criteria for selection of recipients. Ten embryos were transferred to the five selected Spanish Merino recipients, resulting in four pregnancies and seven live-born lambs, including three sets of twins. This study shows that determination of plasma progesterone levels combined with ultrasonographic assessment of the corpus luteum provides information useful for screening of potential recipients.

The onset of puberty was assessed from plasma progesterone profiles for Mouflon (n = 8) and Manchega (n = 7) female lambs born in April. Four Mouflons exhibited their first ovulation at a mean date of 27 November ± 1.4 days, the mean age being 248.5 ± 3.9 days and the mean body weight 23.8 ± 0.6 kg. The remaining four Mouflons, which had a slower growth rate, attained puberty during the autumn of the following year. Five of seven Manchega lambs attained puberty in their first year at a mean date of 5 Oct ± 3.3, the mean age being 185.6 ± 2.6 days and the mean body weight 41.8 ± 2.0 kg. The mean live-weight at the onset of puberty was 65.1 and 82% (p < 0.05) of adult body weights for Manchega and Mouflons, respectively. Overall, the results indicate that there is a threshold of body-weight necessary for the attainment of puberty in the first breeding season for spring-born lambs, which is very different between both Mouflon and Manchega. When body weight was below 23.8 ± 0.6 and 41.8 ± 2.0 kg for Mouflon and Manchega lambs, respectively, first ovulation did not occur until the beginning of the next breeding season. The onset of puberty during the second year of life occurred within the specific reproductive seasons for Mouflon (October-April) and Manchega (July-March) ewes, despite minimal further growth.

Ultrasonographic observations of the corpus luteum (CL) and collection of blood samples for progesterone radioimmunoassay were performed daily during 15 oestrous cycles in Spanish Merino ewes, a consistently monovular breed. Ultrasonographic image of the CL changed during the oestrous cycle, increasing its echogenic pattern from ovulation to luteolysis. The size of the CL and mean progesterone levels were significantly affected by day of cycle (p < 0.05 and p < 0.001, respectively). Both increased their values from day 1 to day 12 (from 49.6 ± 7.4 to 154.6 ± 11.8 mm2 and from 0.2 ± 0.0 to 2.8 ± 0.5 ng/ml, respectively) and then declined sharply until day 0 (28.2 ± 5.3 mm2 and 0.1 ± 0.0 ng/ml, respectively). There was a significant correlation between CL area and plasma progesterone concentrations during the entire oestrous cycle, taking the developing and regressing phases of the CL separately (p < 0.05). A central cavity was observed in 33.3% of the CL studied. The presence of this cavity had no effect in total luteal-tissue area of the CL nor on oestrous cycle length or on progesterone concentrations. Likewise, the cavity did not affect the correlations observed between CL size and progesterone levels, CL size and day of cycle and progesterone levels and day of cycle. It is concluded that ultrasonographic assessment of CL area is a reliable method for estimating peripheral plasma progesterone levels, regardless to the presence or absence of a cavity in the CL.

Seasonal changes in ovulatory activity, plasma prolactin and melatonin concentrations were monitored in a wild (Mouflon) and a domesticated (Manchega) breed of sheep, both originating and living under similar latitudes (40°N). Mouflons express ovarian cycles significantly later than Manchega ewes (October vs. July, P < 0.001); however, they ended cycling one month later than Manchegas (April vs. March, P < 0.05). While prolactin concentrations were high when Manchega ewes started to cycle, they were at their lowest concentrations when Mouflons started cycling. Overall, mean prolactin concentrations were higher (P < 0.001) in Mouflons than Manchegas throughout most of the year. Within the limits of sampling frequency, the duration of melatonin secretion was similar in both groups during the solstice and equinox periods; however, the amplitude was lower (P < 0.01) in Mouflons than Manchegas during the solstice periods. The significant breed differences in the seasonal hormonal changes may be attributed to a genetic influence in the endocrine responses to the same photoperiodic cues.

Ovarian follicular development was characterized in 24 Spanish Merino ewes to study effects of the follicular status and the FSH commercial product used on follicular growth and subsequent superovulatory response. Estrus was synchronized using 40 mg fluorogestone acetate sponges. The superovulatory treatment consisted in 2 daily im injections of FSH from 48 h before to 12 h after sponge removal. Sheep were assigned randomly to 2 groups treated with 6 decreasing doses (4, 4, 3, 3, 2, 2 mg) of FSH-P(TM) or with 6 doses of 1.25 mL of OVAGE(TM) Growth and regression of all follicles ≥2 mm were observed by transrectal ultrasonography, and recorded daily from Day 6 before sponge insertion to the first FSH injection, and then twice daily until estrus was detected with vasectomized rams. Differences were detected in follicular development from the first FSH injection to detection of estrus (-48 to 36 h from sponge removal) between groups. Administration of FSH-P increased the appearance of new follicles with respect to OVAGEN (6.3 ± 0.7 vs 4.8 ± 0.4; P < 0.05), and the mean number of medium (4 to 5 mm) follicles (8.9 ± 1.2 vs 6.6 ± 0.9; P < 0.05). However, the mean number of follicles that regressed in size after sponge removal (5.9 ± 0.4 vs 3.3 ± 0.4) and the number of preovulatory sized follicles that did not ovulate (60 vs 42.4%) were also higher in FSH-P treated ewes (P < 0.05). So, finally, there were no differences in ovulation rate, as determined by laparoscopy on Day 7 after sponge removal, between ewes treated with FSH-P or OVAGEN (6.3 ± 1.9 vs 7.0 ± 1.7 CL). In all the ewes, the ovulatory response was related (P < 0.05) both to the number of small follicles (2 to 3 mm in diameter) present in the ovaries at the start of treatment with exogenous FSH and to the number of follicles that reached ≥4 mm in size at estrus, despite differences in the pattern of follicular development when using different commercial products. (C) 2000 by Elsevier Science Inc.

The objective of this study was to compare ovulatory activity of Mouflon and Manchega ewes lambing at different times of the year. A total of 38 adult European Mouflon and 26 Manchega ewes were divided into two groups according to whether lambing occurred in late winter/early spring or summer. Plasma progesterone concentrations were monitored to assess the interval to first ovulation after parturition. Both season and type of sheep affected the postpartum interval. When parturition occurred towards the end of the breeding season for Mouflon (February-March), 12 of 26 animals had a mean (±s.e.) interval to first ovulation of 25 ± 1.8 days and exhibited between 1 and 6 short or normal cycles before the onset of anoestrus. The remaining 14 animals did not resume ovulatory activity until the following breeding season which started in October. Similarly, female Mouflon (n = 12) giving birth in June reinitiated their breeding activity only at the start of the following season in October. Manchega ewes that lambed in April (n = 11) and June (n = 15) had postpartum intervals to first ovulation of 111.5 ± 4.1 and 31.5 ± 1.9 days, respectively. Both groups of Manchegas reinitiated ovulatory activity at the start of the expected breeding season for the breed (July). It can be concluded that the time of year is a major factor controlling the duration of ovarian inactivity following parturition in both Mouflon and Manchega ewes. (C) 2000 Elsevier Science B.V.

Development of all follicles with antral diameter ≥2 mm during the oestrous cycle was characterized in goats of the Murciana-Granadina dairy breed by daily transrectal ultrasonography. Of nine does initially synchronized in oestrus, six returned to oestrus and three did not. In the first six does, mean cycle length was 21·2 (s.e. 2·3) days. There were mean total numbers of 6·2 (s.e. 0·6) small (2 to 3 mm), 1·9 (s.e. 0·3) medium (4 to 5 mm), and 1·0 (s.e. 0·2) large follicles (≥6 mm) each day but only numbers of large follicles differed with day of cycle CP < 0·01). The diameters of the largest follicle (LF1), the second largest (Lf2) and the remaining follicles (RF) varied with day of cycle (P < 0·01). The LF1 and LF2 varied with day in similar patterns but the difference in diameter between them (P < 0·05) was greatest on days 7 and 9 (2·3 mm) and days 19 to 23 (2·2 to 3·8 mm), and least on days 2, 15, 16 and 18 (0·5 to 0·8 mm). The relationship between the LF1 and LF2 to the RF differed only early or late in the cycle when concentrations of progesterone were low (P < 0·05). There was some evidence to support follicular growth in waves. Although the number of apparently new follicles detected (4·8 (s.e. 0·4) per day) did not vary with day of cycle, follicles emerging at 3 mm over a 48-h period that grew to a diameter of ≥6 mm were distributed non-randomly in three of six cyclic does. The three cystic does that did not return to oestrus by day 25 had large follicles (16 to 28 mm), fewer new follicles (3·3 (s.e. 1·1) per day; P < 0·01) than cyclic does (4·8 (s.e. 0·4) per day) and fewer follicles that became largest (4·0 v. 8·8 in cyclic does; P < 0·01).

Serial transrectal ultrasonographies were performed during the first three months of gestation measuring different structures of ovine fetuses to establish their gestational age. Data were obtained from 23 Manchega ewes that became pregnant after oestrous synchronization. Embryonic vesicle diameter, from day 12 to 29 of pregnancy, showed high correlation with gestational age (p < 0.01). From day 19 of gestation onwards, the crown-rump length and the trunk diameter of the embryo were estimated. Later, when the foetal organs and structures could be distinguished, several measurements were done in the skull (occipito-snout length and biparietal and orbit diameters), the trunk (thoracic diameter, width of three vertebrae and width of three ribs), and the abdominal cavity (stomach and kidney longitudinal diameters); femur length was determined too. All measurements were correlated with gestational age (p < 0.005), but the parameters showing the highest correlation coefficients with time (up to 0.92) were the crown-rump and occipito-snout lengths, and the thoracic, biparietal and orbit diameters. No significant differences were observed in pregnancies with one or two fetuses in the period studied. © 1998 Elsevier Science B.V.

A clinical and ultrasonographic study has been completed with analysis of plasma progesterone concentrations by radioimmunoassay in three pseudopregnant goats and one pseudopregnant ewe. Persistence of luteal function (> 0.5 ng/ml of plasmatic progesterone) and accumulation of aseptic fluid within the uterus (hydrometra) are characteristics of pseudopregnancy in goats and ewes. Cloprostenol treatment effectively reduced the plasma progesterone concentration to levels < 0.5 ng/ml in all animals and induced a re-establishment on ovulatory activity. The ultrasonic morphology of corpora lutea was not different of corpora lutea during the oestrus cycle.

Growth and regression of ovarian follicles with antral diameters ≤2 mm were characterized during 15 estrous cycles by daily transrectal ultrasonography (7.5 MHz probe) in 9 ewes of Merino del Pais, a consistently monovular Spanish breed. Mean interovulatory interval was 17.5±0.5 days and ovulation rate was 1 in all ewes; of 60 to 116 follicles, ≤2 mm observed during the entire estrous cycle, 13.0 ± 1.2 reached a maximum diameter ≤4 mm and 7.9 ± 0.6 different follicles became the largest follicle in the animal at some point during the cycle. An average of 4.5 new follicles per ewe were detected each day, with no significant effect of day of cycle. Appearance of new follicles that grew to ≤ 4 mm tended to differ during the first 8 days of the cycle, being highest on day 3 and lowest on day 6 (P < 0.10), but did not vary significantly during the last 6 days. Growth of new follicles from the day of detection to the next day differed between, but not within, periods, averaging 1.4±0.3 mm of the first 8 days of the cycle and 1.8±0.5 mm from day -6 through - 1 (P < 0.05). Total number of follicles ≤2 mm per ovary on days 1 through 8 varied with the interaction of ovary by day, being more variable in the non-CL ovary. During the last 7 days, a linear decline in total follicles was coupled with a linear increase in number of large follicles (P < 0.05). Differences in the size between the largest and second largest follicles were greater on days 5 through 8 than on days 1 through 4, did not differ with day of cycle on days -6 through -1, then increased on the last day from 1.5 mm to 2.9 mm (P < 0.001). In conclusion, the monovular Merino del Pais ewe showed a more rapid growth and turnover of ovarian follicles than other breeds studied, but identified 3-mm follicles did not emerge in other than a random distribution. There was little evidence of dominance until the ovulatory follicle had been identified.