Social Stress during the Estrus or Luteal Phase in Sheep.

In mammals, progesterone and estrogens affect the stress response. The study aimed to compare the physiological and behavioral responses to the social isolation of ewes during the estrus or luteal phase. Estrous and diestrous ewes (n = 10 and 8 respectively) were individually isolated in a novel place for 10 min. Ewes' behavior was recorded during the test. Cortisol, blood proteins and glucose concentrations, and the skin surface temperature were determined before and after the test. Cortisol increased immediately after the test ended (P = 0.02). Serum total protein (P = 0.02), globulin (P < 0.0001), and plasma glucose (P = 0.006) concentrations were greater in estrus than in the luteal phase. The abdominal skin surface temperature was greater during estrus than during the luteal phase (P = 0.02). Ewes in estrus spent more time standing up immobile than ewes in the luteal phase (P = 0.05). In conclusion, the physiological and behavioral responses changed according to the phase of the estrous cycle. These results highlight the need for future studies focusing on how reproductive status influences the stress response to different management practices in sheep.

Reproductive response of postpartum spring-lambing ewes: effects of weaning on follicular growth and postpartum interval on response to ram placement with ewes ("ram effect").

The aim of the first experiment was to determine if follicular growth rate in ewes increases spontaneously or after gonadotropin administration after lamb weaning during the period of seasonal anestrus. To conduct this experiment, there were postpartum lactating ewes from which lambs were or were not weaned when 68 to 72 days old (Day 0). The ovaries were assessed using ultrasonography from Day 0 to 9, followed by the administration of 200 IU of eCG on Day 7 to all ewes to determine capacity of follicles to respond to gonadotropin stimulation. There were no differences in duration of follicular wave dynamics, or maximum dominant follicle diameter during the first follicular wave after lamb weaning or after administration of eCG. Because weaning did not have positive effects on follicular development, the aim of the second study was to compare responses to placement of rams with lactating ewes (47 or 68 days postpartum; PP47 and PP68, respectively) and seasonal anestrous ewes that lambed during the previous year (Control). There were no differences in the proportion of ewes of the three groups that developed a corpus luteum after placement with rams, but more ewes of the Control than PP47 and PP68 groups expressed behavioral estrus and lambed as a result of placement of ewes with rams (P < 0.0001). In extensive grazing management systems, weaning of lambs did not modify spontaneous or induced follicular growth in Corriedale ewes that lambed in the spring. The placement of rams with ewes resulted in induction of ovulations, estrus and pregnancies even when ewes have lambs suckling.

Maternal and fetal ultrasonographic characteristics, vulvar temperature, and vaginal mucous impedance as variables associated with the onset of parturition in term and induced pre-term ewes.

The aim of this study was to assess and compare ultrasonographic characteristics of maternal and fetal structures, vulvar temperatures, and vaginal mucous impedance in pregnant ewes in the term parturition group (TPG, n = 15) and induced pre-term parturition group (IPPG; n = 15). All the measurements were taken every 12 h throughout the last gestational week. Maternal and fetal structures and the fetal heart rate (HR) were assessed using ultrasonography. The vulvar temperature and vaginal mucous impedance were determined using a non-contact infrared thermometer, and an electronic estrous detector, respectively. The vulvar temperature was less in the TPG and greater in the IPPG; the end-diastolic velocities (EDVs) of the arteries of the placentome and uterus gradually increased before parturition in the IPPG (P = 0.02, P = 0.02 and P = 0.009, respectively). The placentome shear wave velocity (SWV) was greater in the ewes of the IPPG than TPG 48, 36, and 0 h before parturition (P = 0.001). The following variables were associated with the onset of parturition within the next 12 h in the ewes of the IPPG: resistance index (< 0.54) and EDV (> 0.34 cm/s) of the uterine artery; and vulvar temperature (> 37.3 °C). A fetal kidney SWV of < 1.31 m/s was associated with the onset of parturition in the next 12 h in all the ewes. Results indicate vulvar temperature and certain maternal and fetal factors detected using ultrasonograpy may aid in determining fetal maturity and/or the time of parturition in ewes.

Early luteal development in Santa Inês ewes superovulated with reduced doses of porcine follicle-stimulating hormone.

The aim was to compare the early luteal development in ewes superovulated with different doses of pFSH. Twenty-nine Santa Inês ewes received a progesterone device (CIDR®) for 8 days. Gonadotrophic treatment started on Day 6: G200 (control, n = 9, 200 mg); G133 (n = 10, 133 mg); and G100 (n = 10, 100 mg of pFSH). On Day 6, all females received eCG (300 IU). B-mode and spectral Doppler ultrasonography were performed daily during the early luteal phase (Days 11-15) to monitor the development of corpora lutea (CLs; dimensions) and ovarian arteries indices. CLs were also classified as normal or prematurely regressed (PRCL) on Day 15 by videolaparoscopy. Ewes from G100 and G133 showed gradual increase in luteal diameter during the early luteal phase (p < 0.001), whereas G200 animals presented increase from Day 11 to Day 13, and then decrease on Days 14 and 15 (p < 0.001). The G200 females showed greater percentage of PRCL (45.20%) than those of the other groups (p < 0.001). The normal CLs number was greater in G100 than in G133 (p = 0.04), while the PRCL number was greater in G200 than in the other groups (p = 0.03). Resistive index (RI) was greater in G200 than in G100 (p = 0.02). RI was lower in Day 12 than Day 15 (p = 0.02). Pulsatility index (PI) was greater on Days 14 and 15 (p < 0.01). In conclusion, the lowest dose of pFSH (100 mg) can be considered sufficient for an efficient superovulatory response in sheep, producing better CLs development dynamic in early luteal phase and ovarian blood perfusion and smaller number of PRCL than the traditional (200 mg) pFSH dose.

B-mode ultrasonography and ecobiometric parameters for assessment of embryonic and fetal development in sheep.

The aim in this study was to evaluate the maternal-fetal development during physiological gestation in sheep by means of ultrasonography and to predict the gestational age by mathematical formulae. Thirty Santa Inês sheep were included. Evaluations were performed weekly from the 3rd to 21st gestational week. The Shapiro test was used to determine normality of the data, and Spearman test was used for determining correlations of real or transformed measurements as gestation advanced. If there was a significant difference detected, variable adjustments and gestational weeks were tested using regression models. Significance level was set at 5% and the results presented as mean ± SD. Principal components analysis (PCA) was used for data clustering and graphic analysis. The gestational vesicle, abdominal, thoracic, biparietal, ocular orbit, and placentome diameters; and the lengths of crown-to-rump, nuchal to snout, scapula, humerus, radius, metacarpus, femur, tibia, metatarsal, heart length, heart width and kidneys were measured. Using pulsed Doppler ultrasonography, heart rate (HR) was obtained. The greatest coefficients of determination (r²) were obtained for the biparietal diameter (BPD; 96.5%) and metacarpus length (MCAR; 93%), followed by the abdominal diameter (AD; 91.7%) and heart width (HTW; 90.2%). The PCA analysis indicated graphically that at week 8 to 9, there was no significant change related to technique, whereas, at weeks 19, 20, and 21 a decrease in growth was observed, with the greatest data variability at week 19. Ultrasonographic assessments indicated there were significant correlations between developmental stages of all maternal-fetal structures and the gestational age, which can be used as reference values for gestational age assessments and detection of development abnormalities.