Investigating follicle growth, uterine oedema and other factors affecting reproductive success in the Lusitano mare (original) (raw)
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A total of n=159 Lusitano mares and n=309 reproductive cycles were analysed to model follicle sizes at the time of ovulation and reproductive success in dependency of several variables. Uterine oedema was found to correlate positively with probability of successful pregnancy (p<0.05). Follicle sizes at the time of ovulation are affected by treatment with hCG (p<0.05), with lower sizes found for treated mares. Follicle size at the time of ovulation correlates negatively with the mares’ age (p<0.05) (Pearson’s r = -0.168). This has implications for the way we monitor follicular growth and intervene in breeding, specific to the Lusitano breed, to accurately time artificial insemination.
Pferdeheilkunde Equine Medicine
To achieve the desired reproduction rate of one foal per year per mare and to optimize the reproductive potential of mares that are embryo donors, foal heat should be utilized as a tool for improvement of fertility. The mare is the only domestic animal showing ovulatory estrus shortly after foaling. The uterine involution and the ovarian activity (post partum follicular dynamic) in the early puerperium go through brief periods of time. Fetal expulsion at physiological delivery occurs within a short time and the placenta is expelled few hours later. Such events in the intra-and peri-partal period may be also related to the type of histological tissue that composes the cervix in these animals. The mare's cervix (muscular type) has a fantastic speed related to uterine involution, unlike the other species in domestic animals (cervix fibro-cartilaginous type) (more resistant requesting more time to involute). Nonetheless, fertility during foal heat is reported to be by some authors better or similar or even lower than fertility during heat outside this period. There are still some controversies on this matter, so we hypothesized that non-lactating mares have a greater potential for pregnancy rate than that lactating mares in foal heat, because the uterine involution is already finalized and ovarian activity is basically normalized in non-lactating mares, opening greater possibilities to became pregnant. In Southern Brazil, the Criollo breed (an original cross between Andalusian and Berber breeds) is a well stablished and widely used breed of horse, as it adapted well to the features of the Brazilian climate under field conditions, and developed two useful abilities (too much for work, and sports). To improve the reproduction mainly in Criollo horses, this study aimed to compare the pregnancy rate (PR) and other reproductive parameters (parturition-artificial insemination interval; parturition-ovulation interval; diameter of preovulatory follicle; artificial insemination-ovulation interval) between lactating mares in early puerperium and non-lactating mares artificially inseminated (AI) ≥ 180 days postpartum. This study took place at a stud farm in Southern Brazil between September and December (breeding season). Thirty-one mares Criollo breed, multiparous with mean age 9.6 years (range 6-14) and body condition score (BCS) 3.1 (1= thin, 5 = obese) were divided into two groups: lactating mares (LMs) subjected to AI <10 days postpartum (n =16) and non-lactating mares (NLMs) AI ≥180 days postpartum (n =15). The mares were selected based on clinical criteria (absence of clinical endometritis or abnormal uterine discharge and by parturition date). Both groups had the same environment and nutritional conditions. The ovaries were examined by ultrasonography every other day; after detection of a follicle ≥ 30 mm in diameter (= the sum of the larger and smaller diameter divided by 2), the examinations with ultrasonography were conducted daily. After the detection of follicles ≥ 35 mm, uterine edema, and open cervix, both groups received 1500 IU of human chorionic gonadotrophin (hCG). After 24 hours, AI was performed (fresh semen from two fertile stallions. After 15 days, pregnancy diagnosis was performed. The models were fitted in the Statistical Analysis System software (SAS). To evaluate (in LMs and NLMs) the influence of treatment on the diameter of the preovulatory follicle and on insemination-ovulation interval, the General Linear Model procedure for analysis of variance (ANOVA) with the F-test was carried out. Additionally, the correlations among the animal's age, parturitionovulation interval, and the diameter of the preovulatory follicle were estimated to verify their possible influence on one another. The correlation was estimated by the CORR procedure in SAS. Finally, the data were presented as mean ± standard error, and the significance level was set to 5 % for all the statistical tests. The parturition-insemination interval and parturition-ovulation interval were 7.8 and 9.3 days, respectively (in LMs). All the mares ovulated and the average of every parameter analyzed can be seen on table 1. The average diameter of the preovulatory follicle was 45.0 and 44.5 mm in LMs and NLMs, respectively. The insemination-ovulation interval was 38.8 and 46.3 hours (P = 0.04), and the PR was 56.2 and 46.6 % (P>0.05) in LMs and NLMs, respectively. The hypothesis that NLMs have a greater pregnancy rate than do LMs was not confirmed. On the contrary, the LMs showed a slightly better pregnancy rate than NLM did, suggesting that foal heat can be used for breeding of Criollo mares. In conclusion, no difference in the PR was found between mares inseminated at the early postpartum period and other estruses. LMs showed a shorter insemination-ovulation interval (P < 0.05) than NLMs did. No correlation was observed among the diameter of the preovulatory follicle, age, and PR in either group. Furthermore, no correlation was found between age and the foaling-ovulation interval and between the diameter of the preovulatory follicle and foaling-ovulation interval.
Environmental effects and repeatability of the follicular diameter in mares
Revista Brasileira de Zootecnia, 2019
The objective of this study was to evaluate the effect of environment on follicular diameter and repeatability of the size of preovulatory follicles of mares. Temperature, rainfall, and photoperiod were measured, and their effects were evaluated on follicular dynamics. Data were studied by analysis of variance of follicular size and environment traits. During the five years, 7% double ovulations and 159 anovulatory follicles were recorded. Mean preovulatory follicle diameters of left and right ovaries were 39.3±3.8 and 39.2±3.5 mm respectively. There was no effect of evaluation year on follicular diameter. Reproduction season affected the right preovulatory follicle diameter. There was no effect of temperature and rainfall on follicular diameter. Repeatability values of the preovulatory follicular diameter were low. In the subtropical climate studied, temperature and rainfall caused no effect on follicular dynamics, and photoperiod had only a small effect on dominant preovulatory follicular diameter. Repeatability of follicular diameter was low, so this characteristic should be evaluated daily to predict ovulation and the optimal time to inseminate mares.
Prediction of the day of ovulation in mares through physiologicalparameters measured during estrous
Revista Cientifica, 2004
Behavioural, echographic and exploratory characteristics of the estrous period were studied daily for 120 preovulatory periods in 80 mares. The ovulation across preovulatory days of estrous behaviour, follicular size, follicular texture, echographic follicular appearance, uterine tone and echographic uterine appearance were analyzed. Follicular size increased between fourth and second day before ovulation. Follicular texture showed a progressive softening before ovulation. Echographic follicular appearance evidenced a triangularization of follicle near ovulation. The variability of the rest of studied parameters showed tendencies but did not reach statistical significance. In the other hand, the stepwise procedure selected ovarian texture and follicular size, in this order, as the variables that influence significantly the probability of ovulation in the next days. A logit link function with three intercept estimates, -4.35, -3.06 and -1.59 (1,2 and 3 days to ovulation), and the slopes, 0.495 for follicular size and 1.05 for follicular texture, calculate the cumulative probabilities of ovulation in the following days. With a combination of a very soft follicle and a follicle larger than 45 mm in diameter we have 79% of probabilities that the mare ovule in 24h. But several combinations of follicular size and follicular texture offer probabilities higher than 80% that mare ovule in 48h.
Theriogenology, 2017
Follicular development and deviation processes during the postpartum period are not completely known in horses. Thus, we aimed to study the characteristics of follicular dynamics and ovarian vascular perfusion during the postpartum period in mares that demonstrated estrous behavior and had early (<10 days) or late (!10 days) postpartum ovulation. Ten mares were scanned daily by transrectal ultrasonography from the first day postpartum (d1) to the sixteenth day after the first postpartum ovulation (D0 ¼ ovulation). The animals were split in the early (n ¼ 3) and late (n ¼ 7) ovulation groups (average interval between parturition and ovulation: 8.0 ± 0.0 and 14.7 ± 1.2 days, respectively). For the follicular growth, no difference (P > 0.1) was detected between the groups when the data were normalized for the days preceding the first postpartum ovulation (from DÀ7 to DÀ1). However, when the data were normalized to days postpartum, the dominant follicle was larger (P < 0.05) in the early-ovulated group in all days during this period (d1 to d7). The number of follicles >25 mm diameter was greater (P < 0.05) in the early-ovulated group during the first 3 days postpartum, and the late-ovulated mares showed greater number of follicles with 20e25 mm during d4 to d7. For blood flow characteristics, no difference (P > 0.1) was detected between groups in vascular perfusion of the dominant follicle or in the ovarian pedicle ipsilateral to the largest follicle. Similarly, no difference (P > 0.1) was detected in progesterone concentrations, corpus luteum (CL) area and vascular perfusion of the CL. Pregnancy rate did not differ (P > 0.1) between the early (3/3; 100%) and late (5/7; 71.4%) groups. Therefore, the characteristics of the follicle growth on the preceding days of ovulation were similar between the early-and late-ovulated mares and were consistent with the follicular dynamics expected in non-pregnant and non-lactating mares. However, when the data were analyzed for the days relative to parturition, greater follicle development was present in mares that ovulate earlier during the postpartum period (<10 days). The results suggest that important events may occur before parturition, resulting in early follicle development, mainly in those mares that show estrus and ovulate within 10 days postpartum.
Experimental Assumption of Dominance by a Smaller Follicle and Associated Hormonal Changes in Mares
Biology of Reproduction, 1999
A two-follicle model was used to study the nature of selection of the dominant follicle in mares by ablating neither or one of the two follicles on the day the larger follicle reached Ն 20 mm (Day 0). The larger follicle became the dominant follicle in all mares in which both follicles (n ؍ 8) or only the larger follicle (n ؍ 10) was retained. When only the smaller follicle (n ؍ 9) was retained, it became dominant and ovulated in six mares and became atretic in three mares; the difference in diameter between the two follicles on Day 0 was less (p Ͻ 0.01) in mares in which the retained smaller follicle grew and ovulated (2.2 ؎ 0.6 mm) than in the mares in which the follicle became atretic (5.9 ؎ 1.2 mm). A decline (p Ͻ 0.0001) in FSH concentrations occurred over Days Ϫ4 (8.4 ؎ 0.7 ng/ml) to 0 (5.9 ؎ 0.3 ng/ml), averaged over all groups, and the decline continued for several more days in the groups with both follicles or with only the larger follicle retained. In the group with only the smaller follicle retained, compared to the group with both follicles retained, FSH concentrations and diameter of the smaller follicle increased between Days 0 and 1 (significant interaction for each end point). After Day 1, FSH concentrations continued to increase when the smaller retained follicle became atretic; concentrations decreased when the smaller retained follicle became dominant. An increase (p Ͻ 0.0001) in LH concentrations occurred over Days Ϫ4 (12.2 ؎ 1.1 pg/ml) to 0 (21.1 ؎ 2.0 pg/ml), averaged over the three groups. In 23 of 27 mares, a transient peak in LH concentrations occurred within 2 days of Day 0. In the groups with both follicles or with only the larger follicle retained, an increase (p Ͻ 0.0001) in systemic estradiol concentrations occurred between Day 0 (5.3 ؎ 0.6 pg/ml) and Day 2 (7.5 ؎ 0.4 pg/ml). When only the smaller follicle was retained, estradiol did not begin to increase until Day 2, and it increased only when the retained follicle grew and became dominant. The beginning of an increase in estradiol and continued decrease in FSH at the expected beginning of deviation were attributable to the future dominant follicle; there was no indication that the smaller follicle was involved.
Folia Veterinaria, 2021
This current study is an effort to understand the hormonal and follicular growth in the Barb and Arabian mares during the oestrous cycle; as mares are unique creatures. A total of 53 mares with 97 oestrous cycles were studied. The mares with a mean age of 10.38 ± 4.55 were examined by ultrasonography every day during their breeding season (2017). Two blood samples from each mare (n = 24) were obtained for progesterone (P4), oestrogen (oestradiol-17 beta) and follicle-stimulating hormone (FSH) determinations. The data revealed that the duration of the oestrous cycle was between 19 to 22 days. The pre-ovulatory follicle grew (3.02 ± 1.04) millimetre per day. The rate of cycles exploited in the mare (Arabian versus Barb) for conception was significantly different (P < 0.001). The maximal diameter of the follicle was 50.00 millimetre. The serum progesterone levels (P < 0.01) in mares were significantly higher in the luteal phase than those recorded during the time of oestrous. How...
Determination of Ovulation Time in Gayo Mares Based on Image of Preovulatory Follicle Growth
Jurnal Kedokteran Hewan - Indonesian Journal of Veterinary Sciences
This study aimed to obtain the ultrasound image of preovulatory follicle growth in gayo mares to predict the ovulation time. This study used three Gayo mares and one gayo stallion for teaser aged 5-10 years and weighed 200-250 kg. Preovulatory follicle growth was observed using transrectal ultrasonography which was performed when the dominant follicle size was ≥ 3.5 cm. Observations were made for 3 consecutive estrous periods on gayo mares at relatively the same time. The absence of previous follicular appearance and the presence of hypoechoic area in the same ovary indicate that ovulation has occurred. The result revealed that the diameter of preovulatory follicle of gayo mares was 4.02±0.32 to 5.05±0.04 cm. There was no significant follicle growth in the last 48 hours before ovulation and the preovulatory follicle shape altered from spherical to pearshape. Many small follicles (2 cm in diameter) were observed in peripheral area of the ovary indicated the recruitment of follicles w...
Follicle Deviation and Intrafollicular and Systemic Estradiol Concentrations in Mares
Biology of Reproduction, 1999
By definition, follicle deviation begins on the day the two largest follicles of a wave begin to differ in growth rates. The relationships between follicle deviation and intrafollicular and systemic estradiol concentrations were studied in ponies, using a two-follicle model in which all but the two largest follicles were ablated. A 20-l sample of follicular fluid was obtained from each of the two follicles by transvaginal ultrasonography. In experiment 1, the two follicles were sampled when the larger follicle reached 15 mm. No differences (p Ͼ 0.05) in post-sampling follicle characteristics were found between control (n ؍ 6) and sampled (n ؍ 8) groups except that the growth rate was slower (p Ͻ 0.01) in the larger follicle between the day of sampling and the next day (0.7 ؎ 0.7 mm per day) than in the controls (3.3 ؎ 0.3 mm per day). The growth rates between 2 and 5 days after sampling were not different between groups. Follicular fluid estradiol-17 concentrations were higher (p Ͻ 0.007) in the larger follicle (460 ؎ 67 ng/ml; diameter, 16.4 ؎ 0.4 mm) than in the smaller follicle (322 ؎ 50 ng/ml; diameter, 14.6 ؎ 0.6 mm). In experiment 2, the pair of follicles was sampled when the larger follicle reached 15 mm, 20 mm, or 25 mm (n ؍ 5 per group). There were no significant differences among the three groups for day of deviation and diameters of larger and smaller follicles at deviation. The difference in diameter between the larger and smaller follicles was similar for the 15-mm (2.2 ؎ 0.9 mm) and 20-mm (3.1 ؎ 1.0 mm) groups, but the difference between follicles for the 25-mm group (7.9 ؎ 1.2 mm) was greater (p Ͻ 0.004) than for the other two groups. In contrast, the differences in estradiol concentrations between the larger and smaller follicles increased (p Ͻ 0.0001) progressively for the 15-mm (13.0 ؎ 86.8 ng/ml), 20-mm (722.0 ؎ 173.8 ng/ ml), and 25-mm (1873.5 ؎ 310.3 ng/ml) groups. The first significant (p Ͻ 0.007) increase in systemic estradiol occurred between the day before and the day of the beginning of deviation. Detection of an increased difference in estradiol concentrations between the two follicles before the detection of a change in differences in diameter suggests, on a temporal basis, that estradiol is a candidate for involvement in the mechanism that leads to follicle-diameter deviation in mares.