A. López Sebastián

Estimation of fetal development in Manchega dairy ewes by transrectal ultrasonographic measurements

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.

Effect of season on plasma concentrations of prolactin and cortisol in pregnant, non-pregnant and lactating ewes

Abstract The objective of this study was to examine the effect of season and the interaction between season and reproductive status on secretion of prolactin and cortisol. Plasma concentrations of these hormones were determined in non-pregnant ewes (n = 3), pregnant ewes mated in January (Group A; n = 5) or June (Group B; n = 5) and in lactating ewes after lambing in June (Group J; n = 5) or November (Group N; n = 5). In non-pregnant ewes, concentrations of prolactin in plasma were significantly higher during spring and summer than during autumn and winter. During the first 2 months of gestation, concentrations of prolactin did not differ between pregnant ewe groups, but from Day 61 until 2 days before parturition, mean values were higher in Group A than in Group B. An abrupt rise in concentration of prolactin the day before parturition, followed by a decrease on the day of lambing, was noted in both groups. The discharge of prolactin before parturition tended to be larger in Group B than in A; mean values did not differ between groups. In lactating animals, suckling increased the secretion of prolactin: the magnitude of the response was greater in ewes lambed in November (Group N) than in those lambing in June (Group J), owing to seasonal differences in pre-suckling baseline levels, but no differences between groups were detected in the maximum concentration after suckling. Except for the increased levels observed in non-pregnant animals in September and October, mean concentrations of prolactin did not differ between pregnant and non-pregnant ewes. Higher values were recorded in lactating ewes as compared with non-pregnant and pregnant females. No significant relationship was found between season and circulating levels of cortisol in non-pregnant, pregnant and lactating ewes, but a tendency for greater values during the spring was apparent in non-pregnant ewes. During pregnancy, concentrations of cortisol were similar in Groups A and B; the highest concentrations occurred during the first 60 days and then declined until the day of parturition, when there was a significant but transient increase. The secretion of cortisol rose after suckling in lactating females, but there was no difference in the magnitude of the response between the two groups. Mean values did not differ between ewes lambing in June (Group J) or November (Group N).

Effects of follicular status at treatment on follicular development and ovulation in response to fsh in spanish merino ewes

Cyclic Spanish Merino ewes were treated on Day 13 of the estrous cycle with 12 mg, i.m., FSH-P in saline (n = 9) or propylene glycol (n = 24), currently with 100 micrograms, i.m., Cloprostenol (Day 0). From Day-6 to Day 0, the ewes were observed daily by transrectal ultrasonography, after Day 0, ultrasonography was performed every 12 h for 72 h. Sizes and locations of > or = 2 mm follicles were recorded at each observation. The ovulation rate was determined by laparoscopy on Day 7 after estrus. The number of ovulations ranged from 0 to 6 in ewes treated with FSH-P in saline and from 0 to 16 in ewes receiving FSH-P in propylene glycol (P < 0.05). In the latter group, the response was bimodally distributed; about half of the females had 1 ovulation, whereas the remainder had > 4 with a mean of 7 ovulations. The ovulation rate was associated with 2 characteristics of the largest follicle present at treatment (Day 0). First, if the largest follicle on Day 0 had not changed in diameter from Day-1 to Day 0, then 7 of 9 ewes had > 3 ovulations; if the largest follicle had either increased or decreased, only 8 of 24 ewes had > 3 ovulations (P < 0.05). Second, there was a linear trend (P < 0.07) for ovulation rate to decrease as the persistence of the largest follicle at treatment increased; no ewe in which the largest follicle on Day 0 remained present for more than 36 h ovulated more than 6 follicles. As with the ovulation rate, the numbers of large follicles on Days 1.5, 2 and 2.5 varied with the interaction of change in diameter of the largest follicle on Day 0 from Day-1 to Day 0 and with vehicle. In summary, the superovulatory response was affected by the change in diameter from Day-1 to Day 0 of the largest follicle on Day 0 and the period required for that follicle to regress after treatment with FSH-P and cloprostenol.

Ultrasonographic assessment of the ovarian response in eCG-treated goats

A study was conducted to evaluate the accuracy of ultrasonographic evaluation of ovulation rate during the early luteal phase of does and to estimate the reliability of ultrasonic scanning to differentiate between the corpus luteum and luteinized follicles. Both ultrasonographic and laparoscopic observations of ovarian structures and radioimmunoassays of progesterone in plasma were performed in 47 goats on day 7 after estrus synchronization using intravaginal FGA sponges and eCG. Ultrasonographic scanning allowed the determination of the presence or absence of ovulation. Total efficiency in detecting the occurrence of multiple ovulations was 87.5%. However, accuracy to establish the number of corpora lutea decreased to 23.5% in goats with three or more ovulations, due to an increasing underestimation as the number of corpora lutea in the ovary increased (p<0.001). Ultrasonographic assessment of ovulation rate can be used to determine if a goat has ovulated or if multiple ovulations have occurred, but not to establish the precise number of corpora lutea. Evaluation of the ratio between cavity diameter and total luteal-tissue diameter is useful in distinguishing between corpora lutea and luteinized follicles, since the diameter differed between the two (0.36±0.21 vs. 0.64±0.16, respectively; p<0.005).

Reproductive response and LH secretion in ewes treated with melatonin implants and induced to ovulate with the ram effect

Abstract Two experiments were conducted to examine the effects of treating seasonally anoestrous ewes with melatonin before ram introduction on reproductive response, and on LH secretion in anoestrous ewes induced to ovulate by rams. In Experiment 1, a total of 667 ewes from three flocks involving Merino (Flock 1, N = 149), Merino entrefino (Flock 2, N = 325) and Rasa Aragonesa (Flock 3, N = 203) breeds were used. Within each flock, ewes isolated from rams since the previous lambing were assigned at random to receive melatonin implants of Regulin (75, 175 and 105 in Merino, Merino entrefino and Rasa Aragonesa flocks, respectively) or to serve as untreated controls (74 in Merino, 150 in Merino entrefino and 98 in Rasa Aragonesa flocks). Fertile rams were introduced into all flocks 5 weeks after implantation in March (Flocks 1 and 2) or April (Flock 3), and remained with the ewes for a 50 day mating period. Percentage of ewes with luteal activity at ram introduction did not differ between melatonin treated and control ewes in any flock. There were no significant differences in either the mean interval from ram introduction to lambing or the distribution of lambing. Implantation with melatonin resulted in an improvement of prolificacy in all three flocks, although this only reached statistical significance in the Merino flock (1.15 vs. 1.03 in treated and control ewes, respectively, P In Experiment 2, two trials were undertaken utilizing a total of 63 ewes. Trial 1 involved 24 mature Manchega ewes and Trial 2 involved 39 Merino ewe lambs. Half of the animals in each trial received a Regulin implant on 28 February (Trial 1) or 12 March (Trial 2) and the remaining half acted as controls. Rams were introduced 5 weeks after implantation and remained with the ewes for a 25 day period. In both trials, anoestrous ewes at ram introduction were bled at 20 min intervals for 3 h before and 5 h after ram introduction and then at 3 h intervals over the next 24 h for assessment of plasma concentrations of LH. Secretion of LH before or following introduction of rams was not affected by melatonin. Both treated and control anoestrous ewes in each trial responded to introduction of rams with an increase in the frequency of the LH pulses (P Results from this study show that: (1) melatonin implants administered during early seasonal anoestrus have the potential to improve reproductive performance in Spanish breeds of sheep, but the response is conditioned by breed, management system and environmental factors; (2) melatonin did not modify the secretion of LH in anoestrous ewes induced to ovulate by the ram effect under our experimental conditions.

Nocturnal variation of prolactin secretion in the Mouflon (Ovis gmelini musimon) and domestic sheep (Ovis aries): seasonal changes.

Seasonal changes in nocturnal prolactin secretion and their relationship with melatonin secretion were monitored in wild (Mouflon, Ovis gmelini musimon) and domesticated sheep (breed Manchega, Ovis aries). Two groups of eleven adult females each, were maintained outdoors under natural photoperiod. Plasma concentrations of prolactin and melatonin were determined during the summer and winter solstices and the autumn and spring equinoxes. Blood samples were collected every 3h during the night hours, and 1h before and after the onset of darkness and sunrise. Maximum mean plasma concentrations of prolactin during the dark-phase in Mouflons were observed in the summer solstice, (P<0.001) and in the summer solstice and spring equinox in Manchega ewes (P<0.001). Mean plasma concentrations of prolactin were higher in the wild species (P<0.001) during the summer solstice. In contrast, during the spring equinox, mean levels of prolactin were higher in Manchega ewes than in Mouflons (P<0.05). Plasma prolactin concentrations showed a nocturnal rhythm in both breeds, with seasonal variations (P<0.001). The increase in plasma melatonin levels during the first hour after sunset was accompanied to increasing concentrations of PRL 1h after the onset of darkness, only in the autumn and spring equinox for the Mouflon, and in the summer solstice and spring equinox for the Manchega ewes. In Mouflons, the fall of plasma PRL concentrations about the middle dark-phase in all the periods studied, coincided with high levels of melatonin. A similar relation was observed in Manchega ewes only in the winter solstice and spring equinox. The current study shows that the nocturnal rhythm of prolactin secretion exhibits seasonal variation; differences in the patterns of prolactin secretion between Mouflon and Manchega sheep are taken to represent the effects of genotype.

Effects of progesterone pretreatment and duration of ram exposure on synchronization of estrus, conception and pregnancy by prostaglandin during seasonal anestrus

Abstract Four experiments were conducted to compare effectiveness of three intervals from introduction of rams to synchronization of estrus and the effect of treatment with progesterone at ram introduction on the optimum interval in Rasa Aragonesa ewes. In Experiment 1, data from 292 ewes revealed that treatment with prostaglandin at 12, 14 or 16 days after ram introduction improved pregnancy rate after two service periods compared to introduction of rams alone (64 vs. 45%; P