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[Hormonal interrelations in the hypophyseal-ovarian system in heifers during prostaglandin F2-alpha-induced estrus].

Study of prostaglandin F2 alpha action, synchronizing the estrus, in experiments on heifers demonstrated that Estrumeit (made by ICI, Great Britain), rostaglandin F2 alpha drug, in a dose of 500 micrograms was an active luteolytic factor, leading to the corpus luteum regress, determined by a fall in the progesteron level in the peripheral blood. During the estrus induction there was a short-term elevation in production and excretion of testosterone, this pointing to the prostoglandins participation in the activation of the androgenic ovarian function. Prolactin hyposecretion was shown to be a necessary condition for the realization of general biological processes for the occurrence of estrus.

Animals↗
PubMed1992

Pharmacologic manipulation of fertility.

The professional application of agents to the manipulation of fertility of cows requires basic and applied knowledge of the physiologic mechanisms that are affected and of the pharmacologic agents that are used. In all areas of the pharmacologic manipulation of fertility, the achievement is less than the ideal, and further research is required to improve the efficiency of treatments. The induction of estrus in acyclic animals can involve a reduction in the depth of anestrus, pretreatment with progestagen to ensure estrous behavior and the formation of a normal corpus luteum, and then treatment with exogenous gonadotropin. Responsiveness to treatment can be variable and reflects the depth of anestrus of the animals. Improved treatment regimens require a knowledge of the basic mechanisms involved with the depth of anestrus, a means of assessing the depth of anestrus, and an understanding of the hormonal requirements of ovarian follicles for development and maturation in animals at different depths of anestrus. The optimal precision in the synchronization of estrus (and ovulation) in cyclic animals requires the synchronization of both follicular waves and the end of progestational phase. The end of progestational phase can be synchronized effectively using prostaglandin F2a (or analogs), or by treatment with progestagens with or without luteolytic agents. Procedures to synchronize follicular waves need to be established. The induction of superovulation can be achieved readily using gonadotropins prior to estrus synchronization using prostaglandin F2a. The responses to standard treatments in terms of ovulation rates and yield of transferable embryos are highly variable. The development of procedures to reduce this variability requires an understanding of the intra-ovarian mechanisms involved in recruitment of follicles for a wave of follicular growth, in the selection of dominant follicles for further development, and in the mechanisms controlling follicular atresia. Cystic ovarian disease can be treated effectively using HCG or GnRH (follicular cysts) or prostaglandin F2a (luteal cysts). The basic mechanisms resulting in failure of estrogen positive feedback on LH secretion (that results in cystic follicles) remain to be determined. Small but significant increases in pregnancy rates can be achieved treating cows with prostaglandin during the post-partum period, with prostaglandin to induce estrus for insemination, with GnRH or HCG at estrus, and with GnRH or progestagen treatment during diestrus. Beneficial effects of treatment have been shown in some trials but not in others.(ABSTRACT TRUNCATED AT 400 WORDS)

Abortion, Induced↗
PubMed1982

Estrous synchronization and fertility in gilts after 14- or 18-day feeding of altrenogest beginning at estrus or diestrus.

A synthetic progestogen (altrenogest) was used to synchronize estrus in 160 Yorkshire and Duroc x Yorkshire gilts (6 to 11 mo old) in four trials. Gilts were fed 15 mg altrenogest for 14 or 18 d beginning either at or near estrus (d -1, 0, +1 or +2) or at diestrus (d +3 to +21). Mean intervals to estrus after treatment did not differ between 14- and 18-d treatments (5.4 +/- .1 vs 5.3 +/- .1 d, respectively), but were slightly longer (P less than .01) in gilts beginning treatment at or near estrus than in diestrus (5.6 +/- .1 vs 5.2 +/- .1, respectively). Average intervals to estrus were similar between treatment groups and among stages of the cycle even though more gilts (P less than .01) beginning treatment at estrus had serum progesterone concentrations greater than 2 ng/ml at the end of progestogen treatment. Although more 18- than 14-d treated gilts (P less than .05) were in estrus on d 5 post-treatment, proportions in estrus from 3 to 10 d post-treatment were similar (greater than 98%). Neither stage of estrous cycle at onset of treatment nor duration of progestogen treatment affected percentages of gilts farrowing (greater than 73%), average gestation length (116.5 d), or total (10.3), live (9.7) and dead (.6) pigs at birth after artificial insemination at the post-treatment estrus. We concluded that 14-d feeding of altrenogest effectively synchronized fertile estrus in gilts regardless of stage of estrous cycle at the onset of progestogen treatment. Although 18-d treatment of gilts with altrenogest improved estrous synchronization precision compared to 14-d treatment, there was no advantage of the 18-d treatment for subsequent farrowing responses.

Administration, Oral↗
PubMed1990

Comparison of methods for the synchronization of estrous cycles in dairy cows. 1. Effects on plasma progesterone and manifestation of estrus.

Dairy cows (n = 571) were treated with 1) one or two injections of prostaglandin F2 alpha given 11 or 14 d apart, 2) two injections given 14 d apart and a progesterone coil inserted 8 d after the first injection for a 7-d period; or 3) a coil inserted for 7 d and prostaglandin injected 1 d before its removal. Cows given two prostaglandin injections that conceived had higher progesterone concentrations during the luteal phase preceding AI than did cows that did not conceive. Cows with progesterone coils that conceived did not have higher progesterone concentrations than did cows that did not conceive. Older cows had lower progesterone concentrations than younger ones, and they appeared in estrus earlier after treatment. In four daily observations, 75% of cows were seen in estrus within 7 d after treatment. Cows mounting two or more times had a conception rate (62%) similar to that of cows that stood to mount. Fewer cows (56%) treated with prostaglandin that had low concentrations of progesterone appeared in estrus than did cows with high progesterone (84%). Cows treated with prostaglandin differ from cows treated with progesterone coils in respect to manifestation of estrus and to the relationship between plasma progesterone and conception.

Administration, Intravaginal↗
PubMed2002

Effect of alternating bulls as a management tool to improve the reproductive performance of suckled Zebu cows in the humid tropics of Costa Rica.

A study was undertaken to evaluate the effect of alternating bulls between a single and a multiple sire mating (MSM) program on the reproductive performance of suckled Zebu cows raised under range conditions in the humid tropics of Costa Rica. Multiparous Zebu cows (n=94) suckling calves were distributed between two experimental trials (A and B) consisting of 47 animals each. A single sire mating (SSM) system was alternated weekly with a MSM system with three bulls. This period lasted for 8 weeks. To facilitate estrous expression, four cows were strategically synchronized (estrus-stimulated) in alternate weeks. Courtship predominated over mounting under non-stimulated estrus, for each mounting performed an average of 6.0 and 6.3 courtship activities were recorded in the SSM and MSM, respectively. Under the influence of strategic synchronization corresponding values were 3.9 and 4.2 in the SSM and MSM, respectively (P>0.05). Blood samples for progesterone evaluation were taken twice weekly. All cows in trial A were in anestrus at the start of the study. By second week, 5 out of the 47 cows had initiated estrous cycles and by the third week six were pregnant. In contrast in trial B, 9 out of 47 had initiated estrous cycles before interacting with the bulls and on week 3, only two females had become pregnant and three had initiated estrous cycles. Significant differences were found in the cumulative percentage of cows pregnant between trials A and B (P<0.05). Even though these results occurred, the rotation of the bulls (one or three), or the type of cows (estrus-stimulated or not) did not influence the results in this study.

Anestrus↗
PubMed2000

Effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats.

The effect of sterile service on estrus duration, fertility and prolificacy in artificially inseminated dairy goats during breeding season was studied. Nubian does (n=126) were divided into 2 equal groups: service and control. Estrus was synchronized with intravaginal sponges containing either fluorgestone acetate (FGA; 40 mg) or medroxiprogesterone acetate (MAP; 60 mg) for 12 or 14 d, respectively. Two vasectomized teaser bucks were used to detect estrus at 6-h intervals for 5 d after sponge removal (0600, 1200, 1800 and 2400 h). The teasers were fitted with aprons and permitted to mount all does in both groups, but to penetrate only the service does within the first 12 h of estrus. Does in both groups were inseminated twice at 12 and 24 h after estrus was first detected, using 1 straw per insemination containing 200 million of cooled spermatozoa from 1 buck. The semen was placed in mid-cervix. Estrus duration for the service and control does was (mean +/- SD) 29.4 +/- 6.5 and 41.8 +/- 9.6 h, respectively. Fertility for the service does was 73.7% (46/63); for control does it was 58.7% (37/63). Prolificacy was 2.1 (96/46) and 2.0 (74/37) for service and control does, respectively. Estrus duration (P<0.001) and fertility (P<0.05) differed between the service and control group, but prolificacy was similar (P>0.05). It is concluded that sterile service reduces the duration of estrus and increases fertility in artificially inseminated dairy goats.

Animals↗
PubMed2001

Improved synchrony of estrus and ovulation with the addition of GnRH to a melengestrol acetate-prostaglandin F2alpha synchronization treatment in beef heifers.

The objective of this experiment was to determine the effect of a GnRH injection within a melengestrol acetate (MGA)-PGF2alpha (PGF) estrus synchronization protocol on follicular dynamics and synchronization of estrus. Pubertal crossbred beef heifers (n = 34) were randomly assigned to one of two treatments. Both treatment groups were fed MGA (0.5 mg x hd(-1) x d(-1)) for 14 d and injected (i.m.) with PGF (25 mg of Lutalyse) 19 d after MGA withdrawal. Melengestrol acetate was delivered in a feed supplement of 1.8 kg x hd(-1) x d(-1). Seventeen heifers received an injection of GnRH (100 microg Cystorelin) 12 d after MGA withdrawal and 7 d before PGF. The control group (n = 17) received only MGA-PGF. Estrus was detected four times/d for 7 d beginning on the day PGF was injected. Transrectal ultrasonography was performed daily on eight heifers from each treatment to monitor ovarian activity and characterize changes in follicular dynamics after MGA withdrawal and until ovulation after PGF. Each of the GnRH-treated heifers either ovulated or had a luteinized dominant follicle following GnRH and subsequently initiated a new follicular wave (8/8, 100%). All GnRH-treated heifers (17/17, 100%) and 94% of controls (16/17) exhibited estrus after PGF. Estrus was exhibited over a 132-h period (12 to 144 h) for control heifers compared with 60 h (48 to 108 h) for GnRH-treated heifers. The peak synchronized period for both treatments was between 48 and 72 h after PGF, during which time 76% (13/17) of the GnRH-treated heifers exhibited estrus compared with 63% (10/16) for controls. Seventy-one percent (12/17) of the GnRH-treated heifers exhibited estrus from 48 to 60 h after PGF, compared with 38% (6/16) for controls (P < 0.05). In summary, injection of GnRH within a 14- to 19-d MGA-PGF protocol increased the synchrony of estrus during the synchronized period and concentrated the period of detected estrus. This protocol may offer potential for the fixed-time insemination of replacement beef heifers.

Animal Husbandry↗
PubMed1992

Active and passive immunoneutralization of inhibin increases follicle-stimulating hormone levels and ovulation rate in ewes.

Two experiments were conducted to determine effects of active and passive immunoneutralization of inhibin on FSH secretion and ovulation rate. A synthetic peptide (alpha-IF) matching the N-terminus of the alpha-subunit of ovine inhibin was coupled to human alpha-globulin (h alpha-G) and used as an immunogen. In experiment 1, estrus was synchronized in 10 sheep that had been actively immunized against alpha-IF-h alpha-G or h alpha-G. Plasma FSH levels were similar in the two groups of ewes at -52 and -48 h (0 h = onset of estrus). In alpha-IF-h alpha-G-immunized ewes, FSH increased from -48 to -44 h (18.8-22.1 ng/ml), and then fell to 16.2 ng/ml by 0 h. In h alpha-G-immunized ewes, FSH decreased from -48 to 0 h (17.6-7.2 ng/ml). Ovulation rate was higher in alpha-IF-h alpha-G- than h alpha-G-immunized ewes (9.4 vs. 2.4). In experiment 2, antibodies (Ab) were extracted from sera obtained from experiment 1 ewes and then were injected i.v. into 12 other ewes. Estrus was synchronized twice during the breeding season using progesterone-releasing pessaries (CIDR-G). One day before CIDR-G withdrawal, alpha-IF-h alpha-G and h alpha-G Ab were administered in a crossover design. After injection of Ab against alpha-IF-h alpha-G, plasma FSH increased from 0 to 24 h post-injection (10.9-21.5 ng/ml), after which levels fell to 14.2 ng/ml by onset of the preovulatory LH surge.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Fertilization and embryo recovery rates in superovulated chios ewes after laparoscopic intrauterine insemination.

Forty superovulated dairy ewes of the Greek Chios breed were used in an experiment to evaluate the efficiency of laparoscopic intrauterine insemination on fertilization and embryo recovery rates as well as embryo quality. Estrus was synchronized by intravaginal progestagen impregnated sponges and superovulation was induced by administration of 8.8 mg o-FSH i.m. following a standard 8 dose protocol. A small volume (0.3 mL) of diluted fresh ram semen was deposited in each uterine horn 24 to 28 h after onset of the estrus by a laparoscopic technique. The animals were allocated randomly into two groups (Group A and B) of 20 animals each. In Group A, embryos were recovered 18 to 24 h after the intrauterine insemination and in Group B on Day 6. The average number of corpora lutea was 12.8 +/- 1.2 and 11.5 +/- 1.1 (+/- SEM); the overall embryo recovery was 66.4% and 57% and the percentage of recovered fertilized ova was 81% and 82.8% in Groups A and B, respectively. More fertilized ova were collected per ewe from Group A (P < or = 0.1). Results indicated that in Chios breed, superovulation using homologous FSH combined with laparoscopic AI leads to good ovarian response with satisfactory results in fertilization, embryo recovery and quality of embryos. This could lead to improved and more efficient methods for obtaining large numbers of high quality oocytes and embryos for embryo transfer programs which could contribute to genetic improvement and increase of the population size.

Animals↗
PubMed1986

[Superovulation induction in donor cows using the embryo transfer method].

A total of 108 cows were gynecologically investigated. Twenty-four of them were found to be suitable as donors. These were within the range of the 40th to the 60th day following calving, were not inseminated, and had no complications at calving and over the puerperal period. Estrus was synchronized via implants (3 mg norgestomet Synchromate B, Intervet in s/c application); 8 days later the donors were injected with 3000 IU PMSG each in order to induce superovulation. On the 10th day the implants were removed, and each animal was injected with 22 mg prostaglandin F3 alpha. At the 24th hour following the onset of estrus half of the donors were injected with anti-PMSG (i/v). It was found that the capacity of cows to respond with superovulation after hormonal treatment was quite individual. The application of antigonadotropic sera on the first day of estrus limited superovulation and raised the number of fertilized ova, resp., of embryos able to be transplanted. It was demonstrated also that to shorten the period from washing the uterus up to the impregnation of the donor animals it is necessary to apply hormonal therapy and preventive measures in dependence on the functional and morphologic state of the ovaries and the sexual apparatus.

Animals↗
PubMed2004

The influence of the corpus luteum on ovarian follicular dynamics during estrous synchronization in goats.

Ovarian follicular dynamics and fertility are unaffected by the presence or absence of a corpus luteum during synchronization of estrus with progestins in goats. On day 5 of the estrous cycle (estrus= day 0), a gestagen-containing sponge was inserted in the vagina for 11 days. To remove corpora lutea, one group of goats (CL-, n=41) received 7.5 mg of luprostiol on days 7 and 8 of the estrous cycle. The second group of goats retained the CL (CL+, n=38). Growth and development of follicles > or =4 mm in diameter were measured daily from onset of estrus to 2 days after subsequent ovulation in seven goats from each group, using rectal ultrasonography. Estrus was detected by the use of a reproductively sterilized buck and estrous does were subsequently mated. The number of waves of follicular development (CL- =3.57+/-0.2 versus CL+ =3.14+/-0.14; P>0.05) did not differ between groups. The second wave of follicular development was present at the time of progesterone decline in the CL- group and neither its duration (CL- =4.8+/-0.4 versus CL+=5.6+/-0.7 days; P>0.05) nor the day of commencement of the third wave of follicular development (CL -=11.6+/-0.7 versus CL+=11.8+/-0.6; P>0.05) were altered by the concentration of endogenous progesterone. The pregnancy rate was similar between the two groups. (CL-=68.29% versus CL+=65.79%; P>0.05). Thus, in goats, ovarian follicular dynamics and fertility were not altered by the presence or absence of a corpus luteum during estrous synchronization.

Animals↗
PubMed2001

Ultrasonic study of follicular dynamics following superovulation in German Merino ewes.

Ewes are commonly superovulated with a single dose of eCG or multiple doses of pFSH. It would be convenient and less expensive to use a single dose of FSH, but results of various trials have been controversial. We wished to investigate ovarian dynamics using ultrasonography after superovulation with a single dose of pFSH and hMG as compared with a single dose of eCG. Estrus was synchronized during the breeding season with fluorogestone acetate-containing intravaginal sponges in adult German Merino ewes (n = 38). They were superovulated with single doses of pFSH (17 mg; n = 10), hMG (600 IU FSH and 600 IU LH; n = 9) or eCG (1250 IU; n = 10) given at the time of sponge removal, or pFSH (17 mg; n = 9) given 36h before sponge removal. Follicular and luteal development were observed by ultrasonic scanning every 8 h from the gonadotrophin injection until the end of estrus, and then once daily until Day 6 after estrus. Jugular venous blood was collected starting immediately before and 1 h after superovulation treatment, then twice daily until the end of estrus and once daily for the following 7 days. Concentrations of estradiol-17beta (E2) and progesterone (P4) were measured in plasma. Differences in the follicular dynamics of the 4 superovulation groups were obvious. The functional duration of the pFSH action was estimated to last approximately 48 h, whereas eCG and hMG were active for up to 72 h. The diameter of the ovulatory follicles proved to be smaller than it was described for unstimulated ewes. Single applications of pFSH or hMG can induce a superovulatory response, although the post-estrus progesterone profile revealed a high premature luteal regression rate in the different superovulation groups. Premature corpus luteum regression could not be seen by ultrasonography at this early stage of the luteal phase, indicating that the technique may fail to detect these corpora lutea in an embryo transfer program. However, ultrasonography represents a suitable method to observe follicular dynamics following different superovulation regimens in sheep.

Administration, Intravaginal↗
PubMed1995

Detection of fetal twins in sheep using a radioimmunoassay for pregnancy-specific protein B.

Ovine pregnancy-specific protein B (oPSPB) was isolated from sheep placentas. Antiserum to oPSPB was developed in rabbits. A quantitative RIA was developed and used to assay the serum concentrations of oPSPB during and after pregnancy in ewes bearing single or twin fetuses. Suffolk and Panama ewes, kept with rams equipped with a marking harness, were checked daily for breeding marks as an indication of estrus and bled daily between 10 and 30 d after marking. Ovine PSPB became detectable at 19.7 +/- .14 (mean +/- SE) d after breeding and increased steadily to d 30. Panama oPSPB concentration increased at a greater rate than that of Suffolks (breed x day interaction, P < .01). Ten ewes were bled twice weekly 3 wk before their expected date of lambing and weekly for 7 wk postpartum. Serum concentrations differed considerably between prepartum ewes, but concentrations remained stable within the period of 20 d prepartum. Following parturition, oPSPB concentrations dropped rapidly. In nine ewes, oPSPB was last detectable at 12.78 +/- 2.26 (mean +/- SE) d postpartum. In the 10th ewe, oPSPB was .65 ng/mL at the last sample on d 46 postpartum. To determine the effect of fetal number on oPSPB concentrations, ewes in which estrus was synchronized were bled at d 18, 25, 38, 60, 90, and 120 after breeding. Ewes were killed at d 60, 90, 120, and 148 and fetal number determined. There was a significant (P < .01) difference in the log of oPSPB concentrations according to number of fetuses, day postbreeding, and the day x fetal number interaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

The gestation length of wapiti (Cervus elaphus) revisited.

As an ancillary activity to an artificial insemination program in farmed wapiti, the length of gestation of 28 wapiti hinds that delivered single calves of established parentage was calculated. Estrus was synchronized in 47 wapiti using progesterone impregnated devices (controlled internal drug release, CIDR) and an injection of PMSG. All hinds were artificially inseminated between 60 and 63h after CIDR removal. Pregnancy was determined between 45 and 65 days by ultrasound. A verifiable figure for gestation length was obtained based both upon timed-artificial insemination, date of parturition, and confirmation of sire identity through microsatellite DNA technology. The calculated gestational length of 247 +/- 5 days was significantly (P < 0.0001) shorter than the generally quoted figure of 255 +/- 7 days.

Animals↗
PubMed2003

Luteal activity at the onset of a timed insemination protocol affects reproductive outcome in early postpartum dairy cows.

This study was designed to compare two timed insemination protocols, in which progesterone, GnRH and PGF2alpha were combined, with the Ovsynch protocol in presynchronized, early postpartum dairy cows. Reproductive performance was also evaluated according to whether cows showed high or low plasma progesterone concentration, at the onset of treatment. One hundred and six early postpartum dairy cows were presynchronized with two cloprostenol treatments given 14 days apart, and then assigned to one of the three treatment groups. Treatments for the synchronization of estrus in all three groups started 7 days after the second cloprostenol injection, which was considered Day 0 of the actual treatment regime. Cows in the control group (Ovsynch, n=30) were treated with GnRH on Day 0, PGF2alpha on Day 7, and were given a second dose of GnRH 32 h later. Cows in group PRID (n=45) were fitted with a progesterone releasing intravaginal device (PRID) for 9 days, and were given GnRH at the time of PRID insertion and PGF2alpha on Day 7. In group PRID/GnRH (n=31), cows received the same treatment as in the PRID group, but were given an additional GnRH injection 36 h after PRID removal. Cows were inseminated 16-20 h after the administration of the second GnRH dose in the Ovsynch group, and 56 h after PRID removal in the PRID and PRID/GnRH groups. Ovulation rate was determined on Day 11 postinsemination by detecting the presence of a corpus luteum in the ovaries. Lactation number, milk production, body condition at the onset of treatment and treatment regime were included as potential factors influencing ovulation and pregnancy after synchronization. Logistic regression analysis for cows with high and low progesterone concentration on treatment Day 0 revealed that none of the factors included in the models, except the interaction between progesterone and treatment regime, influenced the risk of ovulation and pregnancy significantly. In cows with high progesterone concentration at treatment onset, Ovsynch treatment resulted in a significantly improved pregnancy rate over values obtained following PRID or PRID/GnRH treatment. In cows with low progesterone concentration, PRID or PRID/GnRH treatment led to markedly increased ovulation and pregnancy rates with respect to Ovsynch treatment. These findings suggest the importance of establishing ovarian status in early postpartum dairy cows before starting a timed AI protocol, in terms of luteal activity assessed by blood progesterone.

Administration, Intravaginal↗