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Results for “Estrus Synchronization”

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PubMed1995

Embryonic loss from 30 to 60 days post breeding and the effect of palpation per rectum on pregnancy.

This study was conducted over a 12-mo period to determine the rate of bovine embryo death between 30 and 60 d of gestation. In addition, palpation per rectum as a means of pregnancy detection was evaluated as a possible cause of embryo death. Estrus was synchronized in Holstein heifers (n = 1358), weighing > or = 385 kg, with a single intramuscular injection of 25 mg prostaglandin F(2alpha). Estrus was primarily detected by the absence of paint marks on the tailhead. The heifers were artificially inseminated with semen from 5 Holstein sires. Blood was collected between 30 and 45 d after breeding, and sera were evaluated for the presence of bovine pregnancy-specific protein B (bPSPB) by RIA to determine pregnancy. Palpation for fetal membrane slip was conducted by an experienced technician in approximately one-half of the inseminated heifers. To determine embryonic survival, a second blood sample was collected at approximately 60 d from 862 heifers that were determined to be pregnant at the first blood sampling. Embryonic loss averaged 5.3% during the interval between the initial detection of pregnancy at 30 to 45 d and the subsequent detection of pregnancy at 60 d of gestation. Embryo loss in heifers that were palpated was 6.5% compared with that of 4.3% in the control heifers (X(2): P = 0.145). These findings establish that there was substantial loss of embryos between 30 and 60 d post breeding but that embryo loss was not affected by palpation per rectum.

Journal Article↗
PubMed1996

Natural and induced ovarian synchrony in golden lion tamarins (Leontopithecus rosalia).

Ovarian cycle synchrony was assessed in spontaneously cycling female golden lion tamarins by monitoring longitudinal (16 mo) urinary steroid metabolite (estrone conjugates; pregnanediol-3 alpha-glucuronide, PdG) excretion in four pairs (n = 8) of females isolated from males. The overall mean ovarian cycle duration was 18.5 +/- 0.3 days (n = 136 cycles; mean range, 15.7-21.0 days), and there was no evidence of reproductive seasonality. Laparoscopic ovarian examinations confirmed that cyclic fluctuations in urinary steroid metabolite excretion were temporally associated with the formation and demise of corpora lutea. Evaluation of ovarian synchronization tested the null hypothesis that urinary hormone cycles were expressed randomly relative to those of cagemates or other females housed in separate cages but within close proximity. Natural ovarian synchrony (expressed as the mean difference in ovarian cycle onset) between cagemates (4.1 +/- 0.4 days) and among noncagemates (4.2 +/- 0.2 days) did not differ (p > 0.05) from a random ovarian cycle distribution. Two trials also were conducted to evaluate the efficacy of the prostaglandin (PG) F2 alpha analogue, cloprostenol, for artificially synchronizing ovarian cycles. Induced ovarian synchrony was not achieved with a single 0.8-microgram i.m. injection of cloprostenol. However, doubling the cloprostenol dose (1.6 micrograms) caused a rapid decrease in mean urinary PdG (p < 0.05) within 2 days, and synchronous ovulation was demonstrated by an increase (p < 0.01) in mean urinary PdG 10 days after cloprostenol administration. In summary, females housed in pairs, in the absence of males, exhibit spontaneous, year-round ovarian cycles with no evidence of among-female ovarian synchrony. Results also suggest that this New World primate has a reduced sensitivity to cloprostenol (compared to common marmosets) but that a single, midcycle cloprostenol injection of 1.6 micrograms effectively induces luteolysis and synchronous ovulation.

Animals↗
PubMed1988

Induction of persistent ovarian follicular structures following administration of progesterone near the onset of estrus in dairy cattle.

The objective of this study was to determine if progesterone administered near the onset of estrus in dairy cows would block the preovulatory surge of LH and result in subsequent persistence of ovarian follicular structures. Following synchronization of estrus with prostaglandin F2 alpha, 20 multiparous, non-lactating Holstein cows were randomly assigned into three groups: 1 ml ethanol administered i.m. at 12-h intervals for 24 h (n = 6; group 1); 1 mg progesterone administered i.m. at 12-h intervals for 24 h (n = 7; group 2); 2.5 mg progesterone administered i.v. at the onset of standing estrus (n = 7; group 3). Ovarian structures were palpated per rectum on the day of estrus and twice weekly for 14 d. Blood was collected every 2 h from onset of standing estrus for 30 h, and concentrations of LH and progesterone were determined. Numbers of cows diagnosed with persistent follicles 10 d after estrus were 1 of 6 (group 1), 2 of 7 (group 2), and 5 of 7 (group 3). The preovulatory surge of LH did not occur during the sampling period (30 h) for 1 of 6, 7 of 7 and 5 of 7 cows, for groups 1, 2, and 3, respectively, and mean serum concentrations of LH were higher in group 1 than in groups 2 and 3. Serum concentration of progesterone (ng/ml) was higher in group 1 (1.9 +/- .4) than in groups 2 (.9 +/- .4) and 3 (.9 +/- .4) 10 d following estrus. Blocking the preovulatory surge of LH with exogenous progesterone resulted in persistence of ovarian follicles.

Animals↗
PubMed2003

Melatonin implants disrupt developmental synchrony regulated by flexible interval timers.

Siberian hamsters born into short daylengths near the end of the breeding season are reproductively inhibited from birth and delay gonadal maturation until the following spring. This vernal transition to a reproductive phenotype coincides with an abrupt increase in body weight, and both processes are triggered by an interval timing mechanism that becomes insensitive, or refractory, to short-day inhibition. It was previously demonstrated that hamsters born into simulated natural photoperiods in early August became photorefractory at later ages than hamsters born into September photoperiods. As a consequence of flexibility in the duration programmed by the interval timer, development of seasonal birth cohorts was synchronous with respect to the calendar date simulated by laboratory photoperiod. In the present study, hamsters were born into simulated August or September photoperiods. Hamsters from each cohort were given removable constant release melatonin implants to reversibly obscure the neuroendocrine representation of daylength between 3 and 9 weeks or 9-15 weeks of age. When control hamsters were given beeswax capsules throughout, August-born males were approximately 6 weeks older than September males at the onset of photorefractoriness as assessed by accelerated increases in body weight and testicular size. Females exhibited the same pattern in body weight. These measures were synchronized with respect to calendar date. Synchronization of cohorts was disrupted by melatonin capsules from 3-9 weeks of age but not by later implants. Melatonin implants altered synchronization by influencing the developmental trajectory of September-born hamsters without influencing the August cohort. These results demonstrate that the function of the interval timer underlying photorefractoriness is influenced by photoperiod and by melatonin. The endogenous pattern of melatonin signals adjusts the duration measured by the interval timer to insure that developmental milestones of seasonal cohorts are synchronized with environmental conditions.

Animals↗
PubMed2005

Timing of emergence of ovulatory follicles in polyovulatory goats.

The current study characterized the timing of emergence of ovulatory follicles during the follicular phase of the estrous cycle in polyovulatory does and assessed whether selection may influence ovulation rate through differences in ovarian follicular dynamics, by characterizing preovulatory follicular emergence and growth in two ecotypes of Neuquen-Criollo Argentinean goats (Short-Hair, n=11 and Long-Hair, n=9). During the breeding season, the time of estrus was synchronized in all does with two doses of a prostaglandin analogue. Ovarian laparoscopies were performed on days 17 and 19 after the induced estrus (day 0) and 7-15 h after the beginning of the subsequent estrus. Results indicate that both ecotypes of goats have common features in the ovarian follicular population and in the patterns of preovulatory follicular enlargement. In all the goats, most of the preovulatory follicles arose from the pool of follicles present in the ovary between days 17 and 19 of the estrous cycle. These follicles were all larger than 2mm at emergence, being the largest growing follicle present in the ovaries on days 17 and 19 in 56.5 and 78.6% of the does, respectively. The appearance of new follicles remained unaffected, while the mean number of small growing follicles decreased (P<0.05) during the follicular phase, indicating that preovulatory follicles do not suppress the emergence of new follicles but inhibit the growth of small follicles. A separate analysis of single and double ovulating does showed that 75% of the second ovulatory follicles in polyovulatory goats was present on the ovarian surface between days 17 and 19 of the estrous cycle, but appeared later in the other 25% of the estrous cycles. These findings support the hypothesis that follicular dominance effects are exerted during the preovulatory period, when the growth of follicles other than the ovulatory is inhibited, and that increases in ovulation rate in small ruminants are related to a reduced incidence of follicular atresia and an extended period of ovulatory follicle recruitment.

Animals↗
PubMed1985

A seven-day synchronization method for ewes using medroxyprogesterone acetate (MAP) and prostaglandin F2 alpha.

Estrous cycles of adult (n = 27), farm-flock, Suffolk ewes and Polypay range ewes (n = 224) were controlled with medroxyprogesterone acetate (MAP)-impregnated vaginal pessaries inserted (d 0) for 7 d in combination with prostaglandin F2 alpha (PGF2 alpha) injected on d 6. Descriptive criteria of the effects of this treatment regimen on endocrine characteristics of the estrous cycle were evaluated in the experiment with farm-flock ewes. The efficacy of this synchronization regimen on reproductive performance of range-bred ewes was tested in a second trial. Suffolk ewes bred at the second observed estrus after treatment to provide comparisons of cycle length between treated and control ewes. Polypay ewes were exposed to fertile rams at the controlled estrus. Eighty-nine percent of Suffolk ewes were in estrus within 3 d after pessary removal. All nonsynchronized Suffolk ewes (n = 24) were in estrus over a 21-d period. Estrous cycle lengths of treated ewes averaged 16.8 +/- .2 d. Plasma progesterone concentrations were similar for treated and control ewes during the luteal phase of the estrous cycle. Ninety-one percent of the range-bred, controlled ewes lambed. Sixty-two percent of these ewes lambed within 150 d after exposure to fertile rams compared with only 17% of nonsynchronized ewes (P less than .05). Lambing percentage was similar by 167 d for treated (87%) or control (88%) ewes. Lambs per ewe exposed averaged 1.68 and 1.80 for treated and nonsynchronized groups, respectively. These data indicate the effectiveness of this 7-d treatment method for control of the estrous cycle of ewes during the normal breeding season. Results further show that this treatment scheme has practical application for range breeding of ewes.

Animals↗