Incidence Of Multiple Ovulations Research Articles

Negative photoperiod induces an increase in the number of ovulations in dairy cattle.

This study sought to examine the impact of negative photoperiod on the incidence of multiple ovulations and pregnancies in dairy cattle. The study population consisted of 5,373 pregnant cows in their third or greater lactation that experienced their first post-partum pregnancy after spontaneous estrus. The positive photoperiod (increasing day-length) extends from December 22 to June 21, whereas the negative photoperiod (decreasing day-length) extends from June 22 to December 21. The odds ratios (ORs) for multiple ovulations and pregnancies in cows that became pregnant during the negative photoperiod and the remaining cows that became pregnant during the positive photoperiod were 1.4 and 1.3 (P < 0.0001), respectively. The ORs for cows that became pregnant ≥ 90 days in milk and the remaining cows that became pregnant < 90 days in milk were 4.3 and 4.1 (P < 0.0001), respectively. No significant differences were detected in the monthly rates of multiple ovulations or pregnancies during positive and negative photoperiods. Thus, the present study demonstrates that the ovarian function in cows is related to changes in day-length, with decreasing day-length being associated with greater multiple ovulation and pregnancy rates. The present study also shows that positive and negative photoperiods exhibit different trends. The results of this study are consistent with a growing body of work demonstrating the effects of photoperiod patterns on the reproductive physiology of cows, with clear implications for twin pregnancy prevention.

Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle.

Simple SummaryWhile cows are usually monovular, the incidence of dizygous twin births has recently increased considerably alongside increasing milk production. Genetic progress and improvements in nutrition and management practices have led to a continuous increase in milk yield and thus also to multiple ovulations and twin pregnancies. Twin pregnancies are undesirable as they seriously compromise the welfare of the cow and herd economy. A better understanding of the processes associated with multiple ovulations should help to reduce rates of twinning. During the stages of the sexual cycle, temperature gradients are established within the ovary and throughout the genital tract. Pre-ovulatory local cooling of the reproductive system favors male and female gamete maturation and subsequent fertilization. In fact, thermal mechanisms may prevent or favor multiple ovulations and thus twinning. The purpose of this review was to update this topic.While cows are predominantly monovular, over the past 30 years the incidence of multiple ovulations and thus twinning has increased considerably alongside milk production. Multiple pregnancies are not desirable as they negatively affect the health of cows and the herd economy. Although causal mechanisms associated with multiple ovulations have been extensively revised, the process of multiple ovulations is not well understood. Recent studies on the thermal biology of the reproductive system have shown how thermal mechanisms may prevent or favor multiple ovulations. This review focuses on this relationship between thermal dynamics and multiple pregnancies. Cooling of the pre-ovulatory follicle is able to regulate ovulation. In effect, pre-ovulatory local cooling of the female reproductive system favors male and female gamete maturation and promotes fertilization. Thermal stress is proposed here as a model of stress. Periods of high ambient temperature affect the processes of pre-ovulatory follicular cooling and multiple ovulations. While the ratio between unilateral and bilateral multiple pregnancies is normally close to one, under heat stress conditions, this ratio may be 1.4 favoring unilateral multiple pregnancies. A ratio approaching unity is here proposed as an indicator of cow wellbeing.

Ovarian characteristics and timed artificial insemination pregnancy risk after presynchronization with gonadotropin-releasing hormone 7 days before PGF2α in dairy cows

The objective was to determine the benefit of including GnRH and PGF2α (PG) as a part of a presynchronization option before enrolling cows in a timed artificial insemination (AI) program. Holstein cows in one herd were assigned weekly at calving from January 2012 to August 2014 to a completely randomized design consisting of two presynchronization treatments. Cows in the Presynch-11 (n = 290) control were administered two PGF2α injections (Presynch PG-1 and Presynch PG-2) 14 days apart starting at 39 ± 4 days postpartum (study Days 0 and 14). Cows receiving the experimental presynchronization treatment (Gsynch-11, n = 287) were treated with GnRH (pre-GnRH) on study Day 7 and PG (pre-PG) on study Day 14. On study Day 25, all cows were enrolled in the Ovsynch-56 timed AI program: GnRH-1 on study Day 25, PG on study Day 32, GnRH-2 on study Day 34, 56 hours after PG, and timed AI on study Day 35, 16 hours after GnRH-2. In a subsample of 255 cows, ovarian structures were monitored for size and ovulation, and blood samples were collected on study Days 7, 14, 25, 32, 34, and 41 to measure progesterone. Concentrations of progesterone were greater (P < 0.05) in Gsynch-11 than Presynch-11 cows before pre-GnRH was administered (3.3 ± 0.3 vs. 2.1 ± 0.3 ng/mL), respectively, and ovulatory response to the pre-GnRH treatment also was greater (P = 0.008) in Gsynch-11 than Presynch-11 cows (53.2 vs. 35.0%), respectively. One week later, the dominant follicle was larger (P = 0.045) in Presynch-11 than Gsynch-11 cows. Eleven days after completing the presynchronization treatments, ovulatory response to the Ovsynch GnRH-1 treatment was greater (P = 0.016) in Presynch-11 than Gsynch-11 cows (62.2% vs. 45.6%), respectively. At the time of the Ovsynch-PG treatment, more (P = 0.019) Presynch-11 than Gsynch-11 cows had at least one CL. Subsequent luteal regression (>96%), ovulation to GnRH-2 (>90%), and synchronization risk (>88%) did not differ between treatments, but incidence of multiple ovulation after GnRH-2 was larger (P = 0.036) in Presynch-11 than Gsynch-11 cows (28.4% vs. 15.9%), respectively. Pregnancy per AI at 32 days (36.4% vs. 35.1%) and 60 days (30.0% vs. 29.0%) after AI did not differ between Gsynch-11 and Presynch-11 cows, respectively, but was suppressed during summer months in both treatments to less than 70% of the pregnancy per AI of nonsummer months. Because more than 90% of the cows were ovular as treatments were applied, the GnRH treatment of Gsynch-11 could not be assessed for its benefit in anovular cows. The Gsynch-11 presynchronization treatment performed comparably with the standard Presynch-11 program and provides a viable presynchronization option for use before first AI in dairy herds.

Genetic parameters of ovarian and uterine reproductive traits in dairy cows

The objective of the study was to estimate genetic parameters of detailed reproductive traits derived from ultrasound examination of the reproductive tract as well as their genetic correlations with traditional reproductive traits. A total of 226,141 calving and insemination records as well as 74,134 ultrasound records from Irish dairy cows were used. Traditional reproductive traits included postpartum interval to first service, conception, and next calving, as well as the interval from first to last service; number of inseminations, pregnancy rate to first service, pregnant within 42 d of the herd breeding season, and submission in the first 21 d of the herd breeding season were also available. Detailed reproductive traits included resumed cyclicity at the time of ultrasound examination, incidence of multiple ovulations, incidence of early postpartum ovulation, heat detection, ovarian cystic structures, embryo loss, and uterine score; the latter was a subjectively assessed on a scale of 1 (little fluid with normal uterine tone) to 4 (large quantity of fluid with a flaccid uterine tone). Variance (and covariance) components were estimated using repeatability animal linear mixed models. Heritability for all reproductive traits were generally low (0.001–0.05), with the exception of traits related to cyclicity postpartum, regardless if defined traditionally (0.07; calving to first service) or from ultrasound examination [resumed cyclicity at the time of examination (0.07) or early postpartum ovulation (0.10)]. The genetic correlations among the detailed reproductive traits were generally favorable. The exception was the genetic correlation (0.29) between resumed cyclicity and uterine score; superior genetic merit for cyclicity postpartum was associated with inferior uterine score. Superior genetic merit for most traditional reproductive traits was associated with superior genetic merit for resumed cyclicity (genetic correlations ranged from −0.59 to −0.36 and from 0.56 to 0.70) and uterine score (genetic correlations ranged from −0.47 to 0.32 and from 0.25 to 0.52). Genetic predisposition to an increased incidence of embryo loss was associated with both an inferior uterine score (0.24) and inferior genetic merit for traditional reproductive traits (genetic correlations ranged from −0.52 to −0.42 and from 0.33 to 0.80). The results from the present study indicate that selection based on traditional reproductive traits, such as calving interval or days open, resulted in improved genetic merit of all the detailed reproductive traits evaluated in this study. Additionally, greater accuracy of selection for calving interval is expected for a relatively small progeny group size when detailed reproductive traits are included in a multitrait genetic evaluation.

Retrospective study of factors affecting multiple ovulations, embryo recovery, quality, and diameter in a commercial equine embryo transfer program

In this study, 198 donor mares of different breeds, ages, and reproductive category were inseminated with fresh, cooled and frozen or frozen and cooled semen at the embryo transfer station or in private artificial insemination centers during 10 breeding seasons. The results of this activity were retrospectively analyzed by Pearson Chi-square test and logistic regression to evaluate factors affecting multiple ovulations, embryo recovery, embryo quality, and embryo diameter. Out of the 661 cycles, 937 ovulations were recorded (mean ovulations/cycle: 1.42 ± 0.58). Ovulation rate and incidence of multiple ovulations were significantly affected by age, breed, and reproductive category. Uterine flushings for embryo recovery were performed between 7 and 10 days after ovulation and resulted in the recovery of 338 embryos (51.1% embryos/cycle and 36.1% embryos/ovulation, respectively). At least one embryo was recovered in 298 flushings (45.1%). The factors affecting embryo recovery were age, breed, reproductive category, type of semen, number of ovulations, and location of artificial insemination. Flushing protocol and day of flushing had no effect on embryo recovery. Age, type of semen, number of ovulations, and day of flushing had a significant influence on embryo diameter (N = 215). None of the factors included in the model had an effect on embryo quality distribution.

Low progesterone concentration during the development of the first follicular wave reduces pregnancy per insemination of lactating dairy cows

Objectives were to determine the effect of progesterone (P4) concentration on fertility of lactating dairy cows induced to ovulate follicles of the first follicular wave. Lactating dairy cows (n=989) at 38±3d postpartum were balanced by parity and body condition score and randomly assigned to 3 treatments: first follicular wave (FFW), first follicular wave with exogenous P4 (FFWP), or second follicular wave (SFW). All cows had their estrous cycle presynchronized with 2 injections of prostaglandin (PG) F2α given 14d apart. Cows in the FFW and FFWP treatments started the ovulation synchronization protocol 3d after the last PGF2α of the presynchronization protocol, whereas SFW cows received a GnRH injection (100μg of gonadorelin diacetate; Cystorelin, Merial Ltd., Duluth, GA) 3d after the last PGF2α of the presynchronization protocol and started the synchronization protocol 7d later. The synchronization protocol consisted of GnRH on d −10, PGF2α on d −3, and GnRH concurrent with timed artificial insemination (AI) on d 0. Cows in the FFWP treatment received 2 controlled internal drug release inserts containing 1.38g of P4 from d −8 to −3. Progesterone concentration was determined on d −10, −8, −6, −3, and 0 from all cows and at 7, 14, and 21d after AI from a subsample of cows (n=170). Cows (n=715) had their ovaries scanned by ultrasound on d −10, −3, and 7d. Pregnancy was diagnosed at 38 and 66d after AI. Concentration of P4 from study d −8 to −3 was lowest for FFW cows (1.4±0.1ng/mL) and similar between SFW (3.7±0.2ng/mL) and FFWP (3.7±0.1ng/mL) cows. Diameter of the dominant follicle on study d −3 was greater for FFW cows (16.5±0.3mm) than for SFW cows (15.4±0.3mm), but diameter of the dominant follicle of FFWP cows was not different (15.9±0.3mm) compared with that of SFW and FFW cows. The incidence of multiple ovulation was largest for FFW cows (SFW=19.5, FFW=33.6, FFWP=19.0%), but pregnancy per AI (P/AI) at 66d was smallest for FFW cows (SFW=38.9, FFW=22.3, FFWP=32.0%). Anovular cows in the SFW (19.4 vs. 42.8%) and FFWP (22.1 vs. 37.2%) treatments had reduced P/AI compared with cyclic cows, despite having similar or greater P4 concentration from study d −8 to −3, respectively. Estrus and ovulation synchronization protocols for lactating dairy cows must result in growth of ovulatory follicle under P4 concentration >2ng/mL to ensure high P/AI.

The Effect of Cloprostenol on the Incidence of Multiple Ovulation and Anovulatory Hemorrhagic Follicles in Two Mares: A Case Report

Reproductive records of the entire lives of two mares with abnormally high incidence of multiple ovulation and hemorrhagic anovulatory follicles were analyzed retrospectively. Chi-square analysis was used to test statistically the effect of cloprostenol, a prostaglandin F2 analog, on the incidence of multiple ovulations, hemorrhagic anovulatory follicles, and its ultrasonographic appearance. A total of 319 estrous cycles during a 17-year period were analyzed. Cycles induced with cloprostenol were more likely ( P < .000) to develop hemorrhagic anovulatory follicles than spontaneous cycles. The incidence of multiple ovulation was higher in induced cycles than in spontaneous cycles in one of the two mares.

Use of a Low Dose of Equine Purified FSH to Induce Multiple Ovulations in Mares

The effects of a low dose of equine purified FSH (eFSH) on incidence of multiple ovulations and embryo recovery rate in mares were studied. During the physiological breeding season in Brazil (19 degrees 45'45'S), 14 Mangalarga Marchador donor mares were used in a crossover study and another 25 mares of the same breed, between 3 years and 12 years of age were used as recipients for the embryo transfers. Donors were monitored during two consecutive oestrus cycles, an untreated control cycle followed by a treated cycle, when eFSH was administered. In both cycles, after an embryo collection attempt on day 8 post-ovulation all mares received 7.5 mg dinoprost and had their two largest follicles tracked daily by ultrasonography until the period of ovulation. Mares were inseminated every 48 h with extended fresh semen from a single stallion after the identification of a 35-mm follicle until the period of ovulation. Ovulations were induced by intravenous administration of 2.500 IU of human chorionic gonadotropin, upon detection of a 35- to 40-mm follicle. In the treated cycle, 5 mg eFSH was given intramuscularly once a day, from day 8 post previous ovulation until at least one follicle reached 35 mm in diameter. Embryo flushes were performed on day 8 of dioestrus (day 0 = ovulation). Treatment with eFSH resulted in higher (p < 0.05) ovulation rate and incidence of multiple ovulations compared to the control (1.6 vs 1.0 and 50% vs 0%, respectively--one mare had triple ovulation). However, embryo recovery rates in the control and treated cycles were similar (0.8 and 1.0, respectively; p > 0.05). Pregnancy rates in the recipient mares following embryo transfer were similar for the control and eFSH cycles (11/11 and 10/14, respectively). Additional studies are necessary in order to develop a low-dose protocol for the use of eFSH that brings a more consistent contribution to the efficiency of commercial equine embryo transfer programs.

Does hCG administration increase the incidence of double and multiple ovulations in Campolina mares with co-dominant follicles?

The human chorionic gonadotrophin (hCG) has been routinely used in the equine species to induce ovulations for more thanfour decades. The incidence of multiple ovulations in horses is variable, being double ovulations a common occurrence insome Brazilian breeds, such as Brasileiro de Hipismo and Campolina. The aim of this work was to evaluate the role of hCGadministration to increase, in Campolina mares, the incidence of double and multiple ovulations, which are desirable inembryo transfer programs. One hundred and four (104) mares had their estrous cycles recorded through rectal palpation andultrasonographic evaluation during the breeding season of 2003 - 2004, in a total of two hundred and eight (208) cycles (twocycles per mare). Animals were allocated in two groups, with fifty two (52) horses each. In Group I mares, once one or more= 35 mm follicles and grade 2 uterine edema were present, 2.500 IU of hCG were intravenously administered. The untreatedmares in Group II served as control. The Chi-Square test was used to analyze obtained results. The incidence of doubleovulations in groups I and II was, respectively, of 32.7% (34/104) versus 30.8% (32/104). The incidence of triple ovulations waslow in both groups, of 1.9% (2/104). Only once in the control group (1.0% - 1/104) was a quadruple ovulation detected. Therewas no difference in the incidence of double and multiple ovulations between both groups (p > 0.05). Possibly, hCG administrationdid not influence ovulation patterns in this work due to the fact that Campolina breed mares physiologically show a considerableincidence of double and multiple ovulations.

18 RELATIONSHIP BETWEEN MULTIPLE OVULATIONS AND CONCEPTION IN LACTATING DAIRY COWS

The relationship between multiple ovulations and various factors involved in conception in lactating Holstein cows was investigated in this study. A total of 53 AI cows housed in a free-stall barn were assigned to this study. They were offered a balanced TMR ad libitum during the experimental period. Cows were milked at 0830 and 1900 h. Milk yields were recorded at each milking. Estrus was detected by radiotelemetric pedometers (Yoshioka et al. 2007 Reprod. Fertil. Dev. 19, 129). The body condition score (BCS) of cows was recorded at estrus. Artificial insemination was performed according to the pedometry data. Pregnancy was diagnosed 42 days post-AI by transrectal ultrasonography. Ovulation was assessed by transrectal ultrasonography of the ovary every 3 h from the end of estrus. Ovulation time was measured from the onset of estrus to ovulation. Milk production of each cow was determined from 14 days before the day of estrus. Blood samples for estradiol-17β (E2) were collected at the peak of estrus, and for progesterone (P4), samples were collected on Days 0, 3, 6, 9, and 12 (estrus = Day 0). The E2 and P4 concentrations were measured by enzyme immunoassay. Preovulatory follicles at estrus and CL on Day 0, 3, 6, 9, and 12 were monitored by transrectal ultrasonography. The overall incidence of multiple ovulations was 28.3% (15/53). There was no difference in duration of estrus between cows with multiple ovulations and cows with single ovulations (10.2 h, n = 15 v. 9.8 h, n = 38). Ovulation time was longer for cows with multiple ovulations than that for cows with single ovulations (30.4 h, n = 10 v. 28.7 h, n = 26; P = 0.0545). In all cases of multiple ovulations, 2 follicles ovulated simultaneously. The milk production of cows with multiple ovulations was higher than that of cows with single ovulations (40.1, n = 15 v. 36.2 kg d–1, n = 38; P = 0.0515); however, BCS showed the opposite results (2.86, n = 15 v. 3.13, n = 38; P &lt; 0.05). There was a significant inverse correlation between milk production and BCS in cows with multiple ovulations (r = –0.768; P &lt; 0.01). The E2 concentrations showed no difference between cows with multiple and single ovulations (9.6 pg mL–1, n = 8 v. 8.2 pg mL–1, n = 23). The diameters of preovulatory dominant follicles and secondary follicles at estrus in cows with multiple ovulations were significantly smaller than those in cows with single ovulations (18.2 and 14.2 mm, n = 14 v. 19.9 mm, n = 38, respectively; P &lt; 0.05). Cows with multiple ovulations showed a significantly higher P4 concentration and a larger CL than those with single ovulations from Day 3 to 12. The conception rate for AI was significantly higher for cows with multiple ovulations than for cows with single ovulations (73.3%, n = 15 v. 36.2%, n = 38; P &lt; 0.05). Our results showed that high conception rates, high levels of milk production, and low BCS were associated with multiple ovulations.

Factors Influencing Upfront Single- and Multiple-Ovulation Incidence, Progesterone, and Luteolysis Before a Timed Insemination Resynchronization Protocol

Our objectives were to determine relationships among factors influencing responses to the first GnRH injection in a timed artificial insemination (TAI) protocol and subsequent fertility after altering timing of the second GnRH injection and AI relative to PGF2α injection. Replacement heifers (n = 86) and 613 lactating cows previously inseminated were diagnosed not pregnant to form 77 breeding clusters spanning 36 mo. At not-pregnant diagnosis (d 0), females received 100μg of GnRH, and then 7 d later, they received 25mg of PGF2α. Females in 2 treatments received GnRH 48h (G48) after PGF2α injection and TAI at the time of the second GnRH injection (G48 + TAI48) or 24h later (G48 + TAI72). Females in the third treatment received GnRH 72h after PGF2α when inseminated (G72 + TAI72). Neither timing of GnRH nor time of AI altered TAI pregnancy rates (average of 20.4%). Ovaries of females in 65 clusters were scanned on d 0 (first GnRH injection) and 7 d later (PGF2α injection). Ovarian structures were mapped and ovulation in response to the first GnRH injection was evaluated on d 7. When estrus was detected before scheduled TAI, females were inseminated; otherwise, TAI conception of remaining females was based on timing of GnRH and AI in 3 treatments. On d 7, 1 or more new corpora lutea (CL) were detected in 43% of females and their pregnancy rate was subsequently greater (28 vs. 18%) than those not ovulating. Follicle diameters on d 0 did not differ between females that did (11.9±0.3mm) and did not (11.8±0.4mm) subsequently ovulate in response to GnRH. Follicle diameter and number of follicles ≥5mm increased with increasing lactation number, but decreased with increasing number of CL. Diameter of follicles in which more than 1 follicle ovulated decreased linearly from that in which only 1 follicle ovulated. Incidence of ovulation increased with increasing lactation number and total number of follicles ≥5mm, but decreased with increasing number of CL. Incidence of multiple ovulations (15%) was greater in females having more follicles ≥5mm and in those in early diestrus. Multiple ovulation did not occur in heifers, but was decreased in cows having more than 1 CL. In cows having more than 1 CL, luteal regression was reduced by 5.6 percentage units compared with those having 1 CL. In a TAI protocol, pregnancy rate was greater for females in early diestrus compared with females in other stages of the cycle, in those that ovulated after the first GnRH injection, in those having luteolysis, and in those inseminated during nonsummer months.

Treatment of Cycling and Noncycling Lactating Dairy Cows with Progesterone During Ovsynch

Our objective was to determine whether progesterone (P4) supplementation during an Ovsynch protocol would enhance fertility in lactating dairy cows. Lactating dairy cows (n = 634) at 6 locations were assigned randomly within lactation number and stage of lactation to receive the Ovsynch protocol [OVS; synchronization of ovulation by injecting GnRH 7 d before and 48h after PGF2α, followed by one fixed-time AI (TAI) 16 to 20h after the second GnRH injection] or Ovsynch plus a controlled internal drug release (CIDR) P4-releasing insert for 7 d, beginning at the first GnRH injection (OVS + CIDR). Blood was sampled to quantify P4 10 d before the first GnRH injection, immediately before the first GnRH injection, at the time of CIDR removal, before the PGF2α injection (1 to 2h after CIDR insert removal), and 48h after the PGF2α injection to determine cyclicity status before initiation of treatment, luteal status at the PGF2α injection, and incidence of luteal regression. Overall, conception rates at 28 (40 vs. 50%) and 56 d (33 vs. 38%) after TAI differed between OVS and OVS + CIDR, respectively; but a treatment×location interaction was detected. Compared with OVS, pregnancy outcomes were more positive for OVS + CIDR cows at 4 of 6 locations 28 d after TAI and at 3 of 6 locations 56 d after TAI. An interaction of luteal status (high vs. low) before CIDR insert removal and PGF2α injection with pretreatment cycling status indicated that cows having low P4 at PGF2α injection benefited most from P4 supplementation (OVS + CIDR = 36% vs. OVS = 18%), regardless of pretreatment cycling status. Pregnancy loss between 28 and 56 d after TAI was greater for noncycling cows (31%) compared with cycling cows (16%). Pregnancy loss for cows receiving P4 (21%) did not differ from that for cows not receiving P4 (21%). Supplementation of P4, pretreatment cycling status, and luteal status before PGF2α injection altered follicular diameters at the time of the second GnRH injection, but were unrelated to pregnancy outcomes. Incidence of multiple ovulation was greater in noncycling than in cycling cows. Further, cows having multiple ovulations had improved pregnancy outcomes at 28 and 56 d after TAI. In summary, a CIDR insert during the Ovsynch protocol increased fertility in lactating cows having low serum P4 before PGF2α injection. Improved pregnancy outcomes were observed at some, but not all locations.

Relationship Between Level of Milk Production and Multiple Ovulations in Lactating Dairy Cows

Our objective was to evaluate factors associated with spontaneous multiple ovulations in lactating dairy cows. Ovaries of cows [n=267; >50 days in milk (DIM)] were evaluated weekly using ultrasound to determine spontaneous (i.e., no hormonal treatment) ovulation rate starting at 50 DIM and continuing until pregnancy diagnosis. Cows were fitted with a transmitter to record standing activity during estrus, and serum progesterone concentration was assessed weekly starting at wk 1 postpartum for all cows. Overall, 76 (28.5%) cows were anovular and 191 (71.5%) were ovular by 71 DIM. Incidence of anovulation was not associated with level of milk production but was associated with lower body condition. For anovular cows (n=41) that spontaneously recovered, the multiple ovulation rate at first ovulation was 46.3%. For second and subsequent ovulations (n=463), the level of milk production for 14 d preceding estrus was associated with increased ovulation rate. To illustrate, incidence of multiple ovulations was 1.6% (2/128), 16.9% (32/189), and 47.9% (70/146) for ovulations when cows were producing <35, 35 to <45, and ≥45 kg/d, respectively. Among cows for which estrous behavior was recorded, those with multiple ovulations (n=48) had shorter duration of estrus (4.3±0.7 vs. 9.9±0.5h) and higher production (47.2±0.9 vs. 38.1±0.5 kg/d) than cows with single ovulations (n=237). Circulating concentrations of estradiol were lower (5.5±0.3; n=15 vs. 7.8±0.4 pg/mL; n=71) during periods of estrus with multiple ovulations despite a greater preovulatory follicular volume (4136±123 vs. 3085±110mm3). Similarly, serum progesterone concentration 7 d after estrus was lower for cows with multiple than single ovulations (2.5±0.3 vs. 3.2±0.1 ng/mL) despite a greater luteal volume (8291±516 vs. 6405±158mm3). In summary, the first spontaneous ovulation in anovular cows and a higher level of milk production for 14 d preceding estrus were associated with increased multiple ovulation rate. Additionally, cows with multiple ovulations had lower estradiol at estrus, a shorter duration of estrus, and lower progesterone at 7 d after estrus than cows with single ovulations.

Effect of inhibin immunisation using different synthetic peptide fragments of the bovine αc-subunit on plasma anti-inhibin titres, plasma FSH concentrations and the incidence of multiple ovulation in heifers

In an effort to improve the effectiveness of inhibin immunisation in promoting multiple ovulation in cattle and to clarify the mechanism(s) involved, heifers (n = 5 per group) were immunised against ovalbumin conjugates of different synthetic peptide sequences of the αc-subunit of bovine inhibin (bIα) selected using antigenic prediction methods. Plasma inhibin antibody titre (percentage binding of 125I-labelled Mr 32 000 native bovine inhibin), plasma follicle-stimulating hormone (FSH) concentration and ovulatory response (number of corpora lutea observed by transrectal ovarian ultrasonography) were recorded over a 16 week period. Heifers immunised against the bIα1–29 and 63–72 peptides (alone or in combination), had relatively high anti-inhibin titres (over 7.5% binding) and showed a significantly (P < 0.05) increased incidence of multiple ovulations (18–65%) compared with ovalbumin-immunised controls. However, immunisation against the 1–16 and 108–123 peptides was relatively ineffective in generating antibodies reactive with native inhibin (less than 7.5% binding) and gave little or no increase in incidence of multiple ovulations (0–10%). Analysis of results for all 33 heifers revealed a significant linear relationship between mean inhibin antibody titre and mean plasma FSH concentration (r = 0.42; P < 0.02) and between mean inhibin antibody titre and incidence of multiple ovulation (r = 0.89; P < 0.0001). A significant quadratic relationship existed between mean inhibin antibody titre and the mean number of ovulations per cycle (r = 0.88; P < 0.0001). However, partial correlation analysis showed a highly significant association between anti-inhibin titre and ovulatory response which was independent of changes in mean plasma FSH concentrations. These results extend previous studies involving inhibin peptide-immunised cattle by showing that the magnitude of the ovulatory response is directly related to the prevailing titre of antibodies reactive with native inhibin. However, they do not support the hypothesis that the ovulatory response is mediated solely by a rise in FSH secretion.

Incidence of multiple ovulation and multiple pregnancy in mares

Incidence of multiple ovulation and multiple pregnancy in mares

The effects of low level of feeding on response to synchronization of estrus, ovulation rate and embryo loss in goats

Mature nonlactating British Saanen and Toggenburg does with a body score 2 were fed 25% (n=24) and 100% (n=16) maintenance rations from about 19 days before mating until slaughter at approximately 60 days after mating. Estrus was synchronized using PGF 2α, and the ovulation rate was determined by laparoscopic examination of the ovaries once between Days 6 and 10 after mating. Pregnancy rate, potential kidding rate and embryo loss were determined by counts of viable fetuses at slaughter. The proportion of does in estrus within 96 hours of PGF 2α administration was not different (P<0.5) between the feed-restricted and the maintenance groups (71.0% and 87.5%, respectively); however, the time of onset of estrus after PGF 2α tended to be longer (P=0.12) in the feed-restricted group. Ovulation rate, incidence of multiple ovulations and proportion of does pregnant at 60 days were significantly lower (P=0.0004, P=0.025, P=0.05, respectively) in the restricted group. More embryos from single than multiple ovulations were lost in the restricted group (P=0.01). There was no difference in the overall ovulatory activity between right and left ovaries in the 2 groups. Transuterine migrations were observed in all does that had unilateral multiple ovulations. No migration was observed in does which had single ovulations. These data indicate that restricted feed intake in goats tended to delay the onset of estrus and lowered the ovulation rate, incidence of multiple ovulations, and pregnancy rate.

Ovulation rate of Lincoln ewes at Bahia Blanca, Argentina

ABSTRACTAn experiment was carried out at Bahia Blanca (38°44' S, 62°10' W) to estimate the seasonal variation in ovulation rate and its components shown by Lincoln ewes of constant live weight.Twenty-three 5-year-old ewes were subjected to nine 17-day observation periods which were evenly spaced within 405 days.Percentage of ewes showing oestrus and ovulation, incidence of multiple ovulations and ovulation rate were estimated for each period by using vasectomized rams and performing iaparoscopies.Traits showed a similar seasonality which was presumably induced by the natural light regime to which the ewes became exposed before and during each observation period.A significant and periodic relationship was found between each trait and the number of days elapsed from the longest day.The predicted maximum values for each parameter were reached about 40 days before the shortest day. Prior to and after this date both the percentage of ewes showing oestrus and ovulation and the incidence of multiple ovulations declined so that the expected ovulation rate values became zero for a period of about 3 months before the longest day.

Seasonal variation in ovarian activity of fat-tailed sheep in the subtropics

The ovaries of 1217 fat-tailed ewes slaughtered in a Cairo abattoir over a period of one year were examined. Cyclic activity, indicated by the presence of current corpora lutes, was significantly higher ( P < 0.01) between August and January (85.1–96.5%) than between February and July (64.3–79.4%), coinciding with periods of decreasing and increasing hours of daylight, respectively. Ovulation rate and incidence of multiple ovulations were also significantly higher ( P < 0.01) between September and December (1.7–1.8 and 54.9–65.3%) than during the other months (1.3–1.5 and 30.2–43.2%). Anoestrum associated with strictly follicular activity and lack of corpora lutea was more frequent ( P < 0.01) between February and July (19.1–25.2%) than between August and January (1.2–10.7%). Static ovaries with no visible follicles contribute very little to the frequency of anoestrum except during February (6.7%) and March (10.4%).

The effect of frequency of feeding a lupin grain supplement at mating on the reproductive performance of maiden and mature Merino ewes

Two groups of South Australian strong-wool Merino ewes, each consisting of maiden and mature ewes, were supplemented with lupin grain either once or three times weekly. Both groups received 1.75 kg of supplement per head per week from two weeks before joining to three weeks after joining. A third group of ewes received no supplement. All groups grazed a cereal stubble. Mature and maiden ewes supplemented once weekly and maiden ewes supplemented three times weekly did not respond in ovulation rate, fertility or fecundity. However, the mature ewes supplemented three times weekly had a 16 per cent higher incidence of multiple ovulations (0.05 &lt; P &lt; 0.1), an 11 per cent higher ovulation rate (ns.) and a 21 per cent higher fecundity (P &lt; 0.05) than unsupplemented mature ewes. Under the conditions of this experiment we conclude that the supplement needs to be offered more frequently than once weekly to stimulate reproductive activity.

Anatomical features of cystic ovaries in cattle found during an abattoir survey.

During an abattoir survey, 8071 bovine genitalia were examined. Cysts of 2-5 cm or larger were found on one or both ovaries in 307, an incidence of 38 per cent. The cysts were arbitrarily classified anatomically into eight groups according to the number present and their texture, whether thin or thick walled, and to the presence or absence of a corpus luteum. The weight and dimensions of the cysts were recorded and any abnormalities of the genital tracts were noted. Ninety-six specimens (30-67 per cent) were associated with a corpus luteum and 217 (69-33 per cent) had no corpus luteum. One hundred and sixty eight tracts (53-67 per cent) had single cysts and in 145 (46-33 per cent) they were multiple. The incidence of multiple ovulations was higher in the cystic ovaries which had corpora lutea than in the non-cystic population. The incidence of ovaro-bursal adhesions in the cystic population was three times higher than in that found in the genitalia which had no cysts and it is possible that this resulted from trauma during rectal palpation.