Diameter Of Preovulatory Follicle Research Articles

Ovarian functionality in Poeppig's woolly monkey (Lagothrix poeppigii)

This study examined ovarian features of 60 Poeppig's woolly monkey females in different reproductive stages, collected from wild animals hunted by rural communities in the North-eastern Peruvian Amazon, to provide knowledge on the reproductive physiology of this species. The observed mean ovulation rate was 1.73 follicles, reaching a maximum diameter of 1.0cm. After ovulation, the matured follicle luteinizes resulting in functional corpora lutea (CL). In case of oocyte fertilization, the “pregnancy” CL grow to a maximum of 2cm in diameter, and luteal volume decreases related to the advance of pregnancy. Pregnant females have waves of follicular activity until late pregnancy, but dominant follicles do not attain the maximum diameter of pre-ovulatory follicles. Some non-ovulated follicles of 1mm maximum diameter do not undergo atretic processes and transform to accessory CL by luteinization of the membrane granulosa, resulting in a contribution of up to 7% of the total luteal volume. All pregnant females delivered at term only 1.00 foetus, resulting in a rate of reproductive wastage of 33.3% of embryos.

Impact of buserelin acetate or hCG administration on day 12 post-ovulation on subsequent luteal profile and conception rate in buffalo (Bubalus bubalis)

The present study investigated the impact of gonadotropic hormone administration on day 12 post-ovulation on subsequent luteal profile and conception rate in buffaloes. All the buffaloes (n=48) were estrus synchronized by a synthetic analogue of prostaglandin F2α (PGF2α), administered 11 days apart, followed by insemination during mid to late estrus. To examine the effect of mid-luteal phase hormonal treatment, buffaloes were randomly divided into control (normal saline, n=14), d12-BA (buserelin acetate, 20μg, n=17) and d12-hCG (hCG, 3000IU, n=17) groups. Ovaries were scanned on the day of induced estrus to measure the preovulatory follicle (POF) diameter and on days 5, 12, 16 and 21 post-ovulation to examine the alterations in corpus luteum (CL) diameter. On the day of each sonography, blood samples were collected for the estimation of plasma progesterone. In treatment groups, luteal profile (CL diameter and plasma progesterone) on day 16–21 post-ovulation was better (P<0.05) as well as first service conception rate was higher (52.9% in each treatment group vs. 28.6%, P>0.05) compared to controls. All the pregnant buffaloes exhibited higher (P<0.05) plasma progesterone on various post-ovulation days than their respective non-pregnant counterparts. Treatment-induced accessory corpus luteum (ACL) formation was observed in 58.8 per cent and 70.6 per cent buffaloes of d12-BA and d12-hCG group, respectively, that also had higher (P<0.05) plasma progesterone compared to controls. Compared to the spontaneous CL, the diameter of ACL was less (P<0.05) in the treatment groups. In conclusion, buserelin acetate and hCG administration on day 12 post-ovulation leads to accessory CL formation, improves luteal profile and consequently increases conception rate in buffaloes.

Effect of Ovulatory Follicle Size on Steroidogenic Capacity and Molecular Markers of Oocyte Competence prior to GnRH-Induced Ovulation in Nonlactating Beef Cows.

Gonadotropin releasing hormone (GnRH)-induced ovulation of small dominant follicles decreased pregnancy rates and increased late embryonic/fetal mortality in beef cows. Inadequate oocyte competence, as affected by the physiological status of the dominant follicle, is a potential explanation for the reduction in pregnancy rates and late embryonic/fetal survival. Molecular markers of oocyte competence in both the oocyte (i.e. inhibin beta A [INHBA], inhibin beta B [INHBB] and their binding protein follistatin [FST]) and the surrounding cumulus cells (cathepsins B [CTSB], S [CTSS], and Z [CTSZ]) have been reported. The objective was to examine the relationship between preovulatory follicle diameter, steroidogenic capacity of the preovulatory follicle, and the following measures of oocyte competence: relative abundance of FST, INHBA, and INHBB mRNA in the oocyte, relative abundance of cathepsin (CTSB, CTSS, CTSK, and CTSZ) mRNA in cumulus cells, and the fatty acid profile (total monounsaturated fatty acids, polyunsaturated fatty acids, and saturated fatty acids) in follicular fluid. Non-lactating beef cows (n = 40) were administered GnRH on d −9, prostaglandin F2a (PG) on d −2, and ovaries harvested 48 hr after PG administration (d 0). Blood samples were collected every 8 hr from PG until ovary collection to characterize serum concentrations of estradiol, progesterone, insulin like growth factor 1 (IGF1), and luteinizing hormone (LH). None of the animals had a spontaneous LH surge by the time of ovary collection. The dominant follicle was dissected from the stroma and the cumulus-oocyte complex retrieved along with the corresponding follicular fluid. Only data from cows (n = 16) that did not express estrus and that had an estrogenic follicle at harvest (estradiol to progesterone ratio = 1 in follicular fluid) were included in the simple linear regression analysis. Dominant follicle diameter ranged from 9 to 14 mm at 48 hr after PG and the correlation between dominant follicle size and serum estradiol and follicular fluid estradiol was 0.54 (P < 0.05) and 0.50 (P < 0.04), respectively. As dominant follicle diameter increased, oocyte mRNA abundance (n = 16) of FST (P < 0.02), INHBA (P < 0.01) and INHBB (P < 0.03) decreased. However, as dominant follicle diameter increased cumulus cells (n = 12) had lower mRNA abundance of CTSB (P < 0.04), and tended to have lower abundance of CTSZ (P < 0.07). Furthermore, as follicular fluid concentrations of estradiol increased, CTSS abundance increased (P < 0.04) and CTSZ abundance tended to decrease (P < 0.06). Fatty acid profiles of total monounsaturated fatty acids, polyunsaturated fatty acids, and saturated fatty acids were not affected by dominant follicle size. In summary, relative abundance of INHBA, INHBB and FST mRNA in the oocyte were all negatively correlated with follicle diameter 48 hr after PG. Furthermore, relative abundance of CTSB mRNA in the cumulus cells from the ooctyes collected was also negatively associated with follicle diameter. As follicular diameter increased there was a correlated increase in serum and intrafollicular estradiol at ovary collection, but no effect on total fatty acids. In conclusion, there was no compelling data from the study to indicate that larger dominant follicles contained more competent oocytes. Supported by USDA NRI grant 2006-35203-17284 from USDA-CSREES.

Impact of norgestomet supplementation during early luteal phase on subsequent luteal profiles and conception rate in buffalo: a preliminary study

The current study was aimed to establish the impact of progesterone supplementation (norgestomet progestagen) between days 4 to 10 post-ovulation on subsequent luteal profile and conception rate in buffaloes. The 28 Murrah buffaloes of second to fourth parity, having normal reproductive organs, were estrus synchronized by double PGF(2α) protocol at 11 days apart. The buffaloes were inseminated during mid- to late estrus and thereafter repeated at 24 h interval. The buffaloes were randomly assigned into two groups: (1) control (no treatment, n = 14) and (2) treatment group (CRESTAR ear implant, n = 14). The CRESTAR ear implant (3 mg, norgestomet progestagen) was inserted subcutaneous between days 4 to 10 post-ovulation. The ovaries were scanned at estrus and thereafter on days 4, 10, 16, 21, and 40 post-ovulation to examine the preovulatory follicle (POF) and corpus luteum (CL) diameter. Each ultasonography was followed by blood sample collection for analysis of plasma progesterone concentrations following ovulation. The conception rate was similar (p > 0.05) between treated and control buffaloes. The pregnant buffalo of the control group had larger (p < 0.05) POF diameter than nonpregnant counterparts. The CL diameter was similar (p > 0.05) in both treated and untreated control as well as in their pregnant and nonpregnant buffaloes of the respective groups. The plasma progesterone concentrations were higher (p < 0.05) in the treatment group on the day 10 post-ovulation as compared to the control buffaloes. It is concluded that norgestomet supplementation had no impact on conception rate and CL diameter but enhances the plasma progesterone concentrations following treatment in buffaloes.

Genetic merit for fertility traits in Holstein cows: II. Ovarian follicular and corpus luteum dynamics, reproductive hormones, and estrus behavior

The objective of this study was to characterize the estrous cycle of cows with similar proportions of Holstein genetics, similar genetic merit for milk production traits, but with good (Fert+) or poor (Fert−) genetic merit for fertility traits. In total, 37 lactating cows were enrolled on a protocol to synchronize estrus. Nineteen Fert+ and 12 Fert− cows that successfully ovulated a dominant follicle and established a corpus luteum underwent daily transrectal ultrasonography. Blood sampling was carried out at 8-h intervals from d 0 to 6 and from d 15 to ovulation, and once daily from d 7 to 15. Blood samples were analyzed for progesterone, estradiol, follicle stimulating hormone, and luteinizing hormone. Estrus behavior was recorded using neck activity collars and mounting pads. The Fert+ cows tended to have fewer follicular waves (2.2 vs. 2.7) and had a shorter estrous cycle (21.0 vs. 25.1 d) than Fert− cows. We observed no effect of genotype on day of first-wave emergence or day of first-wave dominant follicle peak diameter, but the peak diameter of the first-wave dominant follicle tended to be larger in Fert− cows. During the first 13 d of the cycle, Fert+ cows developed a corpus luteum that was 16% larger than that in Fert− cows. Circulating progesterone concentrations were 34% greater in Fert+ than in Fert− cows (5.15 vs. 3.84ng/mL, respectively) from d 5 to 13. During the final follicular wave, the interval from preovulatory follicle emergence to ovulation and the interval from preovulatory follicle dominance to ovulation were similar in both genotypes. Maximum preovulatory follicle diameter was larger in Fert+ than Fert− cows (17.9 vs. 16.8mm, respectively); however, circulating concentrations of estradiol were not different between genotypes. A greater proportion of Fert− cows ovulated to a silent heat than Fert+ cows (22 vs. 2%, respectively). Of cows that showed behavioral estrus, Fert+ cows had 41% greater mean activity count; however, no difference was seen in mounting behavior between genotypes. These results demonstrate, for the first time, that genetic merit for fertility has pronounced effects on corpus luteum development, progesterone concentration, preovulatory follicle diameter, and behavioral estrus.

Ovarian histomorphometric changes in adult offspring of diabetic rat mothers

In pregnant mothers, maternal diabetes occurs when the pancreas cannot produce enough insulin, which leads to increase blood glucose concentration in the mother and consequently in the foetus, causing various neonatal problems. This study was conducted to evaluate the effects of maternal diabetes on foetal ovarian structure. Sixteen adult female rats were allocated in two equal groups. Diabetes was induced in one group by alloxan. Both groups became pregnant by natural matting. Ninety days after birth, the female offspring were terminated, the body weight and blood glucose of the animals measured and their ovaries removed. Various histological parameters were determined using histological techniques. Results revealed a significant increase in body weight and blood glucose in the offspring of diabetic mothers (ODM) compared to that of controls. The weight, volume and diameter of the ovary and ovarian capsule thickness were decreased in the ODM group. The number and diameter of primary, preantral, antral and preovulatory follicles and corpora lutea were decreased in ovaries in the ODM. Maternal hyperglycaemia exhibited deleterious effects on the reproductive system of their offspring

Preovulatory Follicular and Subsequent Luteal Size Influence Pregnancy Success in Water Buffaloes

The diameter of the preovulatory follicle (POF) and its effects on subsequent corpus luteum (CL) size and conception were studied in 38 lactating indigenous cycling buffaloes in the Mymensingh district of Bangladesh. Body condition score (BCS) at estrus was estimated for the buffaloes. The buffaloes were synchronized with two injections of a synthetic analogue of PGF2α administered 11 days apart. Transrectal ultrasonography was carried out at estrus and on days 5, 9, 12 and 16 post ovulation to determine the POF and successive CL size. Pregnancy was confirmed by ultrasound examination on day 40-45 post ovulation. Twenty one (55.3%) buffaloes were diagnosed as pregnant. The conception rates of thin (BCS ≤2.0), good (BCS 2.5-3.5) and fat (BCS glt;3.5) buffaloes were 7.7, 88.2 and 62.5% (χ² = 19.54; P<0.05), respectively. The mean diameter of the POF at estrus was larger (P<0.01) in buffaloes that ultimately were diagnosed as pregnant compared with their nonpregnant counterparts (13.7 ± 0.3 vs. 11.2 ± 0.5 mm, respectively). The conception rates of buffaloes having small (9 to ≤ 12 mm), medium (>12 to ≤14 mm) and large (>14 to 16 mm) POFs at estrus were 9.1, 70.0 and 85.7% (χ² = 13.87, P<0.01), respectively. On day 5 post ovulation, CL size was positively correlated (CL: r=.74, P<0.01) with POF diameter. Retrospective analysis revealed that on day 5 post ovulation, the pregnant buffaloes had higher (P<0.01) post ovulation CL sizes than their nonpregnant counterparts (15.6 vs. 11.8 mm). Similarly, on day 9 post ovulation, the difference in CL size (14.3 vs. 13.6 mm) between pregnant and nonpregnant buffaloes was significant (P<0.05). In conclusion, the diameter of the POF in buffaloes has a positive impact on the size of the post ovulation CL and conception.

124 RELATIONSHIPS BETWEEN PREOVULATORY FOLLICLE AND CORPUS LUTEUM BLOOD FLOW IN MARES

Colour- and power-Doppler ultrasonography have recently been used as potential new technologies to assess the degree of vascular perfusion of the ovary and follicles for research and clinical studies of ovarian and follicle hemodynamics and to predict fertility in horses, cattle and humans. In the present study, the following hypotheses were tested: (1) preovulatory follicle (POF) diameter (≥30 mm), but not blood flow, is repeatable between cycles within the same mare; (2) POF diameter and blood flow are good indicators of follicle status; (3) double POF have similar blood flow; and (4) highly vascularized POF produce corpora lutea (CL) with greater blood flow. Non-lactating mares (n = 13; 5 to 21 years old) of mixed breeds were used from March to May in the Northern Hemisphere. Follicle diameter and vascularity of the follicle wall before the first and second ovulations of the season and vascularity of the first CL were measured daily using transrectal colour-Doppler ultrasonography. The vascularity of the follicle wall and CL was based on the display of the blood-flow signals visualised in a slow, continuous-motion evaluation. Statistical analyses were performed by the SAS MIXED procedure, ANOVA and Student's t-tests and Spearman's correlation. A total of 26 periovulatory periods were evaluated. Unexpectedly, there were 84.6% (11/13) and 61.5% (8/13) double dominant POF and 30.8% (4/13) and 46.2% (6/13) double ovulations in the first and second periovulatory periods, respectively. The POF diameters were highly correlated (r = 0.68; P &lt; 0.0001) between the first and second periovulatory periods. The diameter of the POF 5 days before the first ovulation was larger (P &lt; 0.004) than before the second ovulation of the year. However, the POF vascularity did not differ between those periods. For 4 days before ovulation (Day 0), the diameter and blood flow of the POF were greater (P &lt; 0.05) than for those follicles that underwent atresia in single- and double-ovulatory mares. The POF diameter and blood flow were positively correlated in ovulatory (r = 0.51; P &lt; 0.0001) and in atretic (r = 0.32; P &lt; 0.02) follicles. In double-ovulatory mares, POF diameter and blood flow increased (P &lt; 0.0006) for 5 days before ovulation, with no difference between the 2 follicles in the same cycle for each parameter. The POF blood flow was positively correlated (r = 0.32; P &lt; 0.0009) with CL vascularity during the first periovulatory period (Day –7 to +6) of the season. Furthermore, a positive correlation (r = 0.58; P &lt; 0.01) was observed between the maximum vascularity of the POF and its subsequent CL. In conclusion, although preliminary, our results demonstrated that (a) POF vascularity is not repeatable within individuals; (b) potential atretic POF have low blood flow; (c) double POF have similar vascularity; and (d) greater blood flow to the POF is associated with higher CL vascularity.

Effects of high dietary crude protein on the characteristics of preovulatory follicles in dairy heifers

The objectives were to examine the effect of high dietary crude protein on characteristics of preovulatory follicles in dairy heifers. Eight Israeli-Holstein heifers, 4 fitted with rumen fistula and 4 intact, were assigned to 1 of 3 treatments in a replicated (n=2) 4 × 3 incomplete Latin square design with 39-d periods. Treatments were: low (6.0%; LP), moderate (13.0%; MP), and high (20.0%; HP) crude-protein diets, containing 1.27 Mcal NEL/kg dry matter. Diets were based on approximately 66% wheat straw and various proportions of ground corn grain and soybean meal. The estrous cycles of the heifers were synchronized, and 14 d after behavioral estrus, heifers received PGF2α injections. After a further 40h, at d 39 of each period, follicular fluid (FF) was aspirated from follicles of diameter >7mm. The intake of the LP diet was 9% lower than that of MP and HP diets. Rumen ammonia and plasma urea nitrogen concentrations were highest in the HP and lowest in the LP, with intermediate levels in MP diets. No differences were found between treatments in plasma and FF concentrations of glucose and nonesterified fatty acids. High-protein diets increased urea concentrations very similarly in preovulatory FF and in plasma. No differences were observed between diets, in preovulatory follicle diameters and concentrations of androstenedione. However, higher estradiol and progesterone concentrations in FF were observed under the HP than under the MP diet, with no difference between diets in estrogen to progesterone ratio. It can be concluded that high concentrations of urea in plasma, caused by high dietary crude protein, penetrated into preovulatory follicles, but did not impair preovulatory characteristics. This lack of detrimental effects might be attributed to the use in this study of nonlactating heifers, which have fewer nutritional and physiological constraints and eliminate negative effects of potential interactions with high urea on dairy cows’ reproductive systems.

Effect of exogenous insulin and fasting on growth hormone receptor and IGF-I expression in the pre-ovulatory follicle of ewes

The aim of this study was to investigate the effect of fasting and exogenous insulin administration on the expression of growth hormone receptor (GHR) and IGF-I mRNA in the pre-ovulatory follicle of ewes. Fifteen ewes received an intravaginal progesterone releasing device that was removed 6 days later (day of removal = day 0). On day −2, the ewes were divided into three groups: (i) fasting group (n = 5) that was fasted from day −2 to day 2; (ii) control group (n = 5) that received a maintenance diet; and (iii) insulin group (n = 5) that received insulin injections (0.25 IU/kg) every 12 h from day −2 to day 2 under the same diet as the control group. Follicular samples were obtained on day 2. Fasting increased plasma non-esterified fatty acids concentrations from day −1 to day 2 (P < 0.001). There was no difference (P > 0.05) in the number of follicles, although there was a tendency for an increase in the pre-ovulatory follicle diameter for the insulin group in comparison to the control group (P = 0.12). Thecal GHR mRNA expression was very low and was considered insignificant. Moreover, granulosa cells GHR mRNA expression increased (P < 0.05) in the insulin group. Expression of IGF-I mRNA was not different among groups in both tissues. In conclusion, insulin administration increases GHR mRNA but not IGF-I mRNA expression in granulosa cells of the pre-ovulatory follicle. However, fasting did not change the pattern of GHR/IGF-I mRNA expression in the pre-ovulatory follicle.

Impact of pre-ovulatory follicle diameter on plasma estradiol, subsequent luteal profiles and conception rate in buffalo (Bubalus bubalis)

The present study was designed to investigate the impact of pre-ovulatory follicle (POF) diameter on the day of estrus on plasma estradiol concentration, subsequent luteal profile (corpus luteum, CL, diameter and plasma progesterone concentration) and conception rate in buffaloes. Twenty-eight buffaloes were synchronized with synthetic analogue of prostaglandin F2α (PGF2α) administered 11 days apart. Transrectal ultrasonography and jugular vein blood sampling was carried out on the day of estrus and on days 0 (day of ovulation), 5, 12, 16 and 21 post-ovulation. Out of 28 buffaloes, 11 (39.3%) were diagnosed pregnant on day 40 post-ovulation. Retrospective analysis revealed that the buffaloes getting pregnant had larger (p<0.05) POF diameter. In fact, all the buffaloes (n=5/5) having POF diameter between >14 and 16mm conceived, whereas, conception rate in buffaloes with POF diameter between >12 and ≤14mm (n=6/17) or <12mm (n=0/6) was 35.3% and 0.0%, respectively. A positive correlation (r=0.57, p<0.05) was observed between POF diameter and plasma estradiol concentration at estrus. On day 5 post-ovulation, luteal profile was positively correlated (CL: r=0.34, p<0.05; plasma progesterone concentration: r=0.27, p>0.05) with POF diameter. Further, on the same day, plasma progesterone concentration was positively correlated (r=0.47, p<0.05) with CL diameter, however, this correlation was absent (r=0.05, p>0.05) during the subsequent luteal phase. Nevertheless, the post-ovulation luteal profile of pregnant buffaloes was higher (p<0.05) compared to non-pregnant counterparts. In conclusion, the diameter of POF in buffaloes has positive impact on plasma estradiol concentration at estrus, post-ovulation luteal profile and conception rate. The diameter of CL can be used as an indicator of luteal function at early but not at mid or late luteal phase of estrus cycle in buffaloes.

Factors affecting pre-ovulatory follicle diameter in the mare: the effect of mare age, season and presence of other ovulatory follicles (multiple ovulation)

The importance of elucidating factors affecting reproductive performance and efficiency is of paramount concern to the equine industry. Oocyte viability is known to be one of the determinants of reproductive success and evidence suggests that it may be linked to follicle size. The aims of this study were, therefore, to ascertain: i) the average diameter and range of pre-ovulatory follicles in Thoroughbred mares; ii) whether this is affected by either mare age, time within the breeding season, or the presence of multiple pre-ovulatory follicles (MO). One thousand, four hundred and ninety two Thoroughbred mares, aged 2–26 years, were examined with ultrasound to ascertain ovulation date to within 24h, and pre-ovulatory follicle(s) (F1) diameter. Mares were divided into groups according to age (7 groups, 2–4 yr, 5–7 yr, 8–10 yr, 11–13 yr, 14–16 yr, 17–19 yr, >19 yr), time within the season (16 half-month groups, from Feb 1 st to Sept 30 th), and pre-ovulatory follicles (single, {SO} or multiple {MO}). Overall average F1 diameter was 39.95 ± 4.84 mm (range 22–50 mm). Mare age had a significant (P < 0.001) negative effect on F1 diameter (largest F1 38.95 ± 5.61 mm, mares 2–4 yrs; smallest F1 33.30 ± 4.66 mm, mares >19 yrs) as did season (largest F1 44.20 ± 3.95 mm, Feb 1 st–14 th; smallest F1 33.74 ± 4.87 mm, Aug 15 th–31 st) and the presence of more than one pre-ovulatory follicle (MO F1 35.45 ± 4.53 mm; SO F1 37.44 ± 4.84 mm). In conclusion older mares, bred towards the end of the breeding season, especially if MO were present, were more likely to ovulate from smaller follicles. If, as suggested, small pre-ovulatory follicle size is associated with low oocyte viability, then this may account, at least in part, for the poor fertility rates characteristic of older MO mares, bred later in the season and so justify increased monitoring and careful reproductive management of such mares.

Factors affecting preovulatory follicle diameter and ovulation rate after gonadotropin-releasing hormone in postpartum beef cows. Part II: Anestrous cows1

There is large variation in dominant follicle diameter at the time of GnRH-induced ovulation in the CO-Synch protocol [a first GnRH injection on d -9 (GnRH1), followed by PGF(2alpha) on d -2, and a second GnRH injection (GnRH2) with timed AI on d 0], and the reason for the presence of small dominant follicles at GnRH2 is not known. Our hypothesis was that ovulatory response to GnRH1 and progesterone exposure [controlled intravaginal drug-releasing insert (CIDR; EAZI-Breed, Pfizer Animal Health, New York, NY)] would affect ovulatory follicle size at GnRH2 in anestrous cows. This study used a 2 x 2 factorial arrangement of treatments in which anestrous suckled beef cows (n = 55) either ovulated (Ov1+) or failed to ovulate (Ov1-) after GnRH1 and either received (CIDR+) or did not receive (CIDR-) a 7-d CIDR treatment (from GnRH1 to PGF(2alpha)), resulting in the following treatment groups: Ov1+CIDR+, Ov1-CIDR+, Ov1+CIDR-, and Ov1-CIDR- (n = 9, 17, 11, and 18, respectively). The Ov1+ cows had larger follicles at GnRH2 (12.3 vs. 11.0 mm; P = 0.04), a decreased proportion of small follicles within cows that ovulated to GnRH2 (2/16 vs. 14/23; P = 0.003), and a similar growth rate of the ovulatory follicle from d -5 to 0 (d 0 = GnRH2; 1.1 +/- 0.06 vs. 1.1 +/- 0.07 mm/d; P = 0.99) compared with Ov1- cows. Administration of a CIDR had no effect on follicle diameter at GnRH2 (11.8 vs. 11.2 mm; P = 0.3), proportion of small ovulatory follicles at GnRH2 (7/19 vs. 9/20; P = 0.6), and follicular growth rate from d -5 to 0 (d 0 = GnRH2; 1.2 +/- 0.07 vs. 1.1 +/- 0.07 mm/d; P = 0.76). Administration of a CIDR, but not ovulation to GnRH1, increased follicle growth from d -2 to 0 (d 0 = GnRH2; P = 0.03 and 0.9, respectively). Large follicles (>11 mm) had a similar growth rate from d -5 to 0 (d 0 = GnRH2; P = 0.44) compared with small follicles (1.1 +/- 0.07 vs. 1.2 +/- 0.07 mm/d), but the large ovulatory follicles were larger at d -5 compared with small ovulatory follicles (P < 0.001). Follicle diameter was positively correlated with serum concentrations of estradiol at GnRH2 (r = 0.622; P < 0.0001). In summary, ovulation to GnRH1, but not CIDR administration, resulted in increased dominant follicle diameter at GnRH2 in anestrous suckled beef cows. Large follicles were already larger 5 d before GnRH2 but grew at a rate similar to small follicles; follicle size was positively correlated with serum concentrations of estradiol at the time of GnRH-induced ovulation.

Factors affecting preovulatory follicle diameter and ovulation rate after gonadotropin-releasing hormone in postpartum beef cows. Part I: Cycling cows1

Cows induced to ovulate small dominant follicles were reported to have reduced pregnancy rates compared with cows that ovulated large follicles. The reason for the presence of small dominant follicles at the time of GnRH-induced ovulation in timed AI protocols is unknown. The objectives of this experiment were to examine the role of day of the estrous cycle at initiation of treatment on ovulation after the first GnRH injection (GnRH1) and associated effects on growth rate and final size of the ovulatory follicle at the second GnRH injection (GnRH2), serum concentrations of estradiol at GnRH2, and subsequent luteal concentrations of progesterone in suckled beef cows. Estrous cycles of cows were manipulated to be at 1 of 5 specific days of the cycle (d 2, 5, 9, 13, and 18, d 0 = estrus; n = 12 per treatment group) at the beginning of the CO-Synch protocol (GnRH1 on d -9, PGF(2alpha) on d -2, and GnRH2 on d 0). Day of the estrous cycle at GnRH1 did not affect the size of the preovulatory follicle or the proportion of cows ovulating at GnRH2 (P = 0.65 and 0.21, respectively). When all cows were included in the analysis, cows that ovulated after GnRH1 had similar follicle size at GnRH2 compared with cows that did not ovulate after GnRH1 (11.4 and 10.4 mm, respectively; P = 0.23). When only cows that could ovulate after GnRH1 (excluding cows treated on d 2) were included in the analysis, cows that ovulated to GnRH1 had a larger follicle at GnRH2 than cows that did not ovulate after GnRH1 (11.4 and 9.5 mm, respectively; P = 0.04). Follicle growth from d -5 to 0 was similar between cows that ovulated after GnRH1 and cows that did not (1.01 vs. 0.89 mm/d, respectively; P = 0.75). There was a tendency for faster follicle growth rate in cows that ovulated a large follicle (>11 mm) compared with cows that ovulated a small follicle (< or = 11 mm; 1.01 vs. 0.86 mm/d, respectively; P = 0.07). Serum concentrations of estradiol at GnRH2 and progesterone after ovulation were reduced in cows that ovulated small follicles compared with cows that ovulated large follicles (P = 0.006 and 0.005, respectively). In summary, day of the estrous cycle at initiation of synchronization did not affect ovulatory follicle size, but follicle growth rates affected the size of the follicle at GnRH2. Cows that ovulated a small follicle had reduced serum concentrations of estradiol at GnRH2 and progesterone after ovulation.

Effects of presynchronization and eCG on pregnancy rates to GnRH-based, fixed-time artificial insemination in beef heifers

Three experiments were conducted to determine the effects of presynchronization and treatment with equine chorionic gonadotropin (eCG) on corpus luteum (CL) and ovarian follicular development, plasma progesterone concentrations, and pregnancy rates in beef heifers subjected to a gonadotropin releasing hormone (GnRH)-based, fixed-timed AI (TAI) protocol. All heifers were given GnRH on day 0, prostaglandin F2α (PGF) on day 7, and a second GnRH on day 9 concurrent with TAI (54 h after PGF). In exp. 1 (N = 148), presynchronization with PGF (days -22 and -11) decreased the percentage of heifers with non-luteal plasma progesterone concentrations on day 0 (5.4 vs 29.7%) and day 7 (0 vs 11.6%; P &lt; 0.05), but not on day 9 (74.3 vs. 66.2%; P &gt; 0.20), and reduced the number of heifers in estrus and bred before TAI (P &lt; 0.05). Although presynchronization reduced preovulatory follicle diameter (12.9 ± 0.3 vs. 14.9 ± 0.3 mm; mean ± SEM; P &lt; 0.01), it did not affect TAI pregnancy rates (36.5 vs. 29.7%; P &gt; 0.20). In exp. 2, heifers (N = 128) were presynchronized with melengestrol acetate (MGA) (days -27 to -12), and received a controlled internal drug release (CIDR) on day 0; on day 7, half were given 300 IU of eCG at CIDR removal. Treatment with eCG tended to increase preovulatory follicle diameter in heifers that did not ovulate to GnRH on day 0 (P = 0.06), but did not affect the percentage of heifers with non-luteal plasma progesterone concentrations on day 9 (57.8 vs. 57.8%) or TAI pregnancy rates (48.4 vs. 53.1%; P &gt; 0.20). Experiment 3 was a 2 × 2 factorial arrangement of presynchronization (PGF concurrent with a CIDR on day -7) and eCG treatments (on day 7) applied to heifers in three herds (A, N = 150, B, N = 260 and C, N = 40). All heifers had a once-used CIDR from days 0 to 7. Presynchronization increased the percentage of heifers (Herd A) with low-luteal plasma progesterone concentrations on day 0 (70.7 vs. 22.7%) and day 7 (90.7 vs. 53.3%; P &lt; 0.01), but did not affect the percentage of heifers with non-luteal concentrations of progesterone on day 9 (97.3 vs. 93.3%; P &gt; 0.20). Combined for all herds, presynchronization reduced the prevalence of a CL on day 0 (23.5 vs. 73.7%; P &lt; 0.01), and increased the prevalence of follicles ≥ 10 mm on day 7 (96.8 vs. 86.7%; P &lt; 0.01); however, TAI pregnancy rates (195/439 = 44.4%) were not improved by either presynchronization or eCG treatment (P &gt; 0.20).Key words: Presynchronization, equine chorionic gonadotropin, GnRH, fixed-time artificial insemination, progesterone

219 FOLLICLE AND HORMONE DYNAMICS IN SINGLE- v. DOUBLE-OVULATING HEIFERS

The present experiment used the Day 4 ablation model for increasing the incidence of double ovulations in heifers. The objective was to compare follicle growth and plasma hormone concentrations associated with single v. double ovulations. Follicles ≥5 mm were ablated at 4 days post-ovulation to induce a prominent FSH surge and a new follicular wave, and 2 injections of PGF2 (12 h apart) were given 2 days later (Day 6) to favor ovulation. Beginning on Day 5, the 3 largest follicles of the induced wave were scanned twice a day until 36 h after the next ovulation. Blood samples were taken at 6-h intervals starting when the largest follicle reached ≥8.0 mm (expected deviation at 8.5 mm; Ginther et al. 1996) and continued until 36 h after the next ovulation. Concentrations of LH and FSH were measured by validated RIA for cattle (LH measured by Ginther et al. 1999; FSH measured by Adams et al. 1992) and concentrations of oestradiol measured by a commercially available RIA kit (Siddiqui et al. 2009). From a total of 31 heifers, 16 (52%) or 15 (48%) developed a single or more than 1 dominant (≥ 10 mm) follicle in the follicular wave after ablation, respectively. For heifers with 2 dominant follicles, the second-largest follicle ovulated in 9 (60%) heifers and the overall double ovulation rate was 29% (9/31). Follicle diameters and plasma hormone concentrations were compared between single ovulators (n = 12) and double ovulators (n = 8). Diameter of the preovulatory follicles did not increase between the LH peak and ovulation in either the single or double ovulations. In double ovulators, the interval from follicle deviation to the peak of the preovulatory LH surge was shorter (1.9 ± 0.2 days v. 2.5 ± 0.2 days; P &lt; 0.02) and the diameter of the largest preovulatory follicle was smaller (12.2 ± 0.5 mm v. 13.3 ± 0.3 mm; P &lt; 0.02) than in single ovulators, respectively. The LH concentrations of the preovulatory surge did not differ between single and double ovulators for 24 h on each side of the peak (main effect of hour only; P &lt; 0.0001). When data were normalized to the LH peak, the peak of the preovulatory FSH and estradiol surges occurred in synchrony with the peak of LH surge for both groups. A group effect (P &lt; 0.0001) for FSH resulted from a lower concentration averaged over hours in double ovulators. Estradiol showed a group by hour interaction (P &lt; 0.008), reflecting greater concentrations in the double ovulators before and at peak. In conclusion, an increased Supported by the Eutheria Foundation, Cross Plains, WI, USA. Submission supported by FAPEMIG.

224 THE EFFECT OF TREATMENT WITH VARIOUS DOSES OF A SYNTHETIC GONADOTROPIN-RELEASING HORMONE ON INDUCTION OF OVULATION IN LLAMAS

Llamas require a copulation stimulus to elicit an LH surge that subsequently leads to induced ovulation. Gonadotropin-releasing hormone has been used to induce ovulation in llamas; however, results have been variable because of the different analogues and doses in previous studies (Bravo PW et al. 1992 Biol. Reprod. 47, 884-888; Ratto M et al. 2006 Anim. Reprod. Sci. 91, 299-306). Additionally, the effect of different doses and types of GnRH analogues on CL formation and function has not been described in detail. The purpose of the present study was to conduct a dose response trial to examine the effect of a synthetic analogue of GnRH, gonadorelin acetate (Ovalyse®, Pfizer, Santiago, Chile) on ovulation and CL formation in llamas. Nonpregnant and nonlactating adult llamas (range 4-8 years) weighing 90 to 130 kg were examined once daily by transrectal ultrasonography using a B mode scanner with a 7.5-MHz linear-array transducer (Aloka® SSD 500, International Clinics, Santiago, Chile). Llamas with a follicle ≥8 mm in diameter that had grown for 3 consecutive days were assigned randomly to be given an i.m. administration of gonadorelin at a dose of 1) 50 μg (n = 5); 2) 25 μg (n = 8); 3) 12.5 μg (n = 9); 4) 6.25 μg (n = 8), or 5) i.m. administration of 0.5 mL of PBS as a negative control group (n = 5). Llamas were examined by ultrasonography every 12 h from treatment (Day 0) to ovulation and thereafter on Day 8 to determine CL formation. Ovulation was defined as the sudden disappearance of a large follicle ≥8 mm that was detected during the previous examination and was confirmed by subsequent CL formation on Day 8. Ovulation rate was analyzed by chi-square analysis. Follicle diameter (at the time of treatment), interval from treatment to ovulation, and CL diameter on Day 8 were analyzed using one-way ANOVA. Mean ± SD diameter of preovulatory follicle did not differ (P = 0.4) among groups (11 ± 1.6, 10.6 ± 1.5, 11.5 ± 1.9, 11.7 ± 1.9, and 9.8 ± 2.9 mm for 50, 25, 12.5, and 6.25 μg of gonadorelin and 0.5 mL PBS, respectively). The proportions of ovulated llamas did not differ (P = 0.1) among GnRH-treated groups (100, 62.5, 77.7, and 62.5% for 50, 25, 12.5, and 6.25 μg of gonadorelin, respectively) but they did differ (P &lt; 0.01) from the control group (0%). Also, the interval from treatment to ovulation in those ovulated females ranged from 36 to 48 h and it did not differ (P = 0.6) among groups. Corpus luteum diameter on Day 8 (12.2 ± 1.8, 10.2 ± 1.1, 11.7 ± 2.2, and 11.3 ± 1.8 for 50, 25, 12.5, and 6.25 μg of gonadorelin, respectively) did not differ (P = 0.3) among groups. In conclusion, the minimal dose of gonadorelin used in this study (1/8 dose) was as equally effective as the highest dose to induce ovulation in llamas without compromising CL formation. The study was supported by Proyecto FONDECYT 11080141, Convenio de Desempeño en Investigacion (2007 DGI-CDA-04), Universidad Catolica de Temuco, and College of Graduate Studies, Faculty of Veterinary Sciences, Universidad Austral de Chile.

215 DELETERIOUS EFFECTS OF PROGESTAGEN TREATMENT ON FUNCTIONALITY OF PREOVULATORY FOLLICLES IN SHEEP

The use of progestagen for 14 days in protocols for estrus synchronization has been reported to affect conception rate in sheep. We evaluated the effects of progestagen treatment on the growth pattern and follicular function of preovulatory follicles (PF) and their implication for subordinated follicles (SF). Adult female sheep were randomly assigned to the following estrus synchronization groups: 1) FGA (n = 7), which received an intravaginal device of fluorogestone acetate sponges (Chronogest®, Intervet International, Boxmeer, the Netherlands) for 14 days, or 2) PGF (n = 7), which received 3 i.m. administrations of 125 μg of cloprostenol (Estrumate®, Mallinckrodt Vet GmbH, Friesoythe, Germany) 10 days apart. The third cloprostenol administration in the PGF group was given at the same time of sponge withdrawal in the FGA group (Day 0 = day of sponge withdrawal). Ultrasonographic examinations of the ovaries for assessment of follicular development were carried out daily from Days 0 to 2 by using a scanner (Aloka SSD500) equipped with a 7.5-MHz transducer adapted for transrectal examinations. Follicular function was evaluated in terms of estradiol secretion, and blood samples were taken every 12 h to determine plasma estradiol concentration from Days 0 to 2. Ovaries from all females in both groups were recovered by ovariectomy on Day 2 to determine apoptosis by immunohistochemistry for active caspase-3 in granulosa cells from SF of 3 to 5 mm in diameter. Additionally, SF were histologically classified as healthy, early, or advanced atretic. Data were analyzed by Student t-test and Pearson correlation. The total number of PF observed on Day 2 was 15 and 12 for the PGF and FGA groups, respectively. The 90.9 and 93.3% of PF recorded in the PGF and FGA groups, respectively, on Day 2 was retrospectively identified on Day 0. The 33.6 and 46.6% of those follicles from the PGF and FGA groups, respectively, corresponded to follicles &gt;5 mm in diameter. Although mean diameter of PF was higher in the FGA group than in the PGF group (5.4 ± 0.4 mm v. 4.5 ± 0.4 mm, respectively; P &lt; 0.01) on Day 0, PF diameter was similar between groups on Day 2. Plasma estradiol concentration was significantly higher (P &lt; 0.05) in the PGF group on Day 1 (3.1 ± 0.2 pg/mL v. 1.7 ± 0.2 pg/mL in the FGA group) but did not differ between groups on Day 2. The growing pattern of the PF in the PGF group significantly (P &lt; 0.05) affected the total number of SF, and there was a tendency (P = 0.08) for an increase of the total number of healthy follicles in the same group. In addition, advanced atretic follicles from the FGA group were significantly higher than those observed in the PGF group (P &lt; 0.001). Additionally, caspase-3 immunoreactivity was higher in the FGA group than in the PGF group (P &lt; 0.05) and it was associated with the largest SF in both groups. All of these finding are indicative of the presence of aged follicles with an extended permanence in the ovary. We concluded that the use of progestagen for 14 days in protocols for estrus synchronization in sheep affects the growth pattern and functionality of the preovulatory follicle during the follicular phase and may have a deleterious consequence on oocyte competence. CYCITAGL2005-02669 and DID-D-2007-03 UACh.

Follicle and hormone dynamics in single versus double ovulating heifers

Follicles > or = 5 mm were ablated at 4 day post-ovulation in heifers to induce a follicular wave, and prostaglandin F(2alpha) was given at day 6 to increase the incidence of double ovulations. Follicle diameters and plasma hormone concentrations were compared between single ovulators (n=12) and double ovulators (n=8). In double ovulators, the interval from follicle deviation to the peak of the pre-ovulatory LH surge was shorter (1.9+/-0.2 vs 2.5+/-0.2 days; P<0.02) and diameter of the largest pre-ovulatory follicle was smaller (12.2+/-0.5 vs 13.3+/-0.3 mm; P<0.02). The LH concentrations of the pre-ovulatory surge did not differ between single and double ovulators for 24 h on each side of the peak. When data were normalised to LH peak, the peak of the pre-ovulatory FSH and oestradiol (E(2)) surges occurred in synchrony with the peak of LH surge for both groups. Concentration of FSH for 24 h on each side of the peak showed a group effect (P<0.0001) from lower concentration in the double ovulators. A group-by-hour interaction (P<0.008) for E(2) reflected greater concentration in the double ovulators before and at the peak. Results indicated that two pre-ovulatory follicles resulted in an earlier and greater E(2) increase, leading to lower FSH concentration, an earlier LH surge, and ovulation at a smaller diameter. In conclusion, the difference in hormone concentrations during the pre-ovulatory period was an effect rather than a cause of double ovulations.

Pregnancy rates to timed artificial insemination in dairy cows treated with gonadotropin-releasing hormone or porcine luteinizing hormone

We compared the effects of porcine luteinizing hormone (pLH) versus gonadotropin-releasing hormone (GnRH) on ovulatory response and pregnancy rate after timed artificial insemination (TAI) in 605 lactating dairy cows. Cows (mean ± SEM: 2.4 ± 0.08 lactations, 109.0 ± 2.5 d in milk, and 2.8 ± 0.02 body condition score) at three locations were assigned to receive, in a 2 × 2 factorial design, either 100 μg GnRH or 25 mg pLH im on Day 0, 500 μg cloprostenol (PGF) on Day 7, and GnRH or pLH on Day 9, with TAI 14 to 18 h later. Ultrasonographic examinations were performed in a subset of cows on Days 0, 7, 10, and 11 to determine ovulations, presence of corpus luteum, and follicle diameter and in all cows 32 d after TAI for pregnancy determination. In 35 cows, plasma progesterone concentrations were determined 0, 3, 4, 5, 6, 7, and 12 d after ovulation. The proportion of noncyclic cows and cows with ovarian cysts on Day 0 were 12% and 6%, respectively. Ovulatory response to first treatment was 62% versus 44% for pLH and GnRH and 78% versus 50% for noncyclic and cyclic cows ( P < 0.01). Location, ovulatory response to first pLH or GnRH, cyclic status, presence of an ovarian cyst, and preovulatory follicle size did not affect pregnancy rate. Plasma progesterone concentrations after TAI did not differ among treatments. Pregnancy rate to TAI was greater ( P < 0.01) in the GnRH/PGF/pLH group (42%) than in the other three groups (28%, 30%, and 26% for GnRH/PGF/GnRH, pLH/PGF/GnRH, and pLH/PGF/pLH, respectively). Although only 3% of cows given pLH in lieu of GnRH on Day 9 lost their embryo versus 7% in those subjected to a conventional TAI using two GnRH treatments, the difference was not statistically significant. In summary, pLH treatment on Day 0 increased ovulatory response but not pregnancy rate. Cows treated with GnRH/PGF/pLH had the highest pregnancy rate to TAI, but progesterone concentrations after TAI were not increased. In addition, preovulatory follicle diameter did not affect pregnancy rate.