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PubMed1982

Effect of PMSG on the reproductive performance of totally confined ewes bred at synchronized estrus.

The reproductive performance (fertility, prolificacy and fecundity of totally confined sheep in a controlled breeding program at the Animal Research Centre (ARC) was analyzed to evaluate the effect of pregnant mares' serum gonadotrophin (PMSG) on ewes synchronized for estrus with fluorogestone acetate (FGA). PMSG did not significantly enhance reproductive performance. Fertility for ewes receiving 500 IU PMSG was 57% and for ewes not receiving PMSG it was 47%. Corresponding values for prolificacy were 2.4 and 2.2, and for fecundity, 144 and 103%. The reproductive performance was not affected by any of the other factors (flock, strain, lighting regime, ram age or reproductive status of the ewe) indigenous to the controlled breeding program for sheep housed in total confinement.

Journal Article↗
PubMed1996

Effect of prostaglandin F2 alpha administered before estrus synchronization with norgestomet and estradiol valerate on calving rates of beef cows.

Three experiments were conducted to evaluate the effects of prostaglandin F2 alpha treatments 5, 9, and 14 d before Syncro-Mate B on calving rates of 1,072 beef cows from inseminations at a pre-set time. The administration of prostaglandin F2 alpha 5 d before Syncro-Mate B decreased (P < .01) calving rates. This reduction was associated with lower (P < .05) calving rates in cows administered Syncro-Mate B in the first half of the estrous cycle. Calving rates were unaffected n cows administered prostaglandin F2 alpha 9 d before Syncro-Mate B. The administration of prostaglandin F2 alpha 14 d before Syncro-Mate B reduced (P < .05) calving rates in previously anestrous cows. In summary, prostaglandin F2 alpha should not be administered to postpartum cows 5 to 14 d before Syncro-Mate B synchronization.

Animals↗
PubMed1999

Effect of estrus synchronization with norgestomet on the integrity of oocytes from persistent follicles in beef cattle.

Our objective was to determine whether oocyte integrity is compromised when oocytes are recovered from progestogen-induced persistent follicles. Beef cows were presynchronized using PGF2alpha (PGF). Cows detected in estrus after PGF were assigned to either NOR (one 6-mg norgestomet implant for 10 d starting on d 16 of cycle; day 0 = estrus; n = 112) or CON (control, no implant [n = 128] and presynchronized 8 d later than NOR). All cows received 25 mg of PGF at the end of treatment (NOR, d 26; CON, d 18). Treatments produced persistent preovulatory follicles (NOR) or normal preovulatory-size follicles (CON), which were measured via ultrasonography 1 d before slaughter. Ovaries were collected from all animals (NOR, d 27; CON, d 19) along with random (RAN) ovaries from cattle slaughtered on the same days. Cumulus oocyte complexes (COC) were aspirated from the preovulatory follicles with recovery rates of 63% across treatments. Small follicles (2 to 7 mm diameter) from NOR, CON, and RAN cows were also aspirated to recover COC. Preovulatory follicles were larger (19.5+/-.9 vs. 13.6+/-.4 mm, P<.05), serum P4 was lower (.4+/-.1 vs. 3.9+/-.2 ng/mL, P<.05), and serum E2 was higher (28.7+/-1.6 vs. 7.6+/-.8 pg/mL, P<.05) in NOR than in CON cows. Cumulus oocyte complexes recovered from preovulatory follicles (62 NOR, 64 CON) were matured, fertilized, and cultured in vitro for comparison of embryonic development. A subset (24 NOR, 34 CON) of COC were assigned morphological quality grades. A separate set of recovered COC (10 NOR, 15 CON) was fixed within 1 h after recovery for assessment of the stage of meiosis. Treatments did not differ for oocyte quality grade or stage of meiosis. However, COC from NOR cows had more layers of cumulus cells (P<.05), and more of those COC had undergone cumulus expansion (29.2 vs. 5.9%, P<.05 for NOR vs. CON, respectively). Development of cleaved embryos to the morula and blastocyst stages from preovulatory follicles (22.6% NOR, 18.9% CON) or small follicles (42% NOR, 40% CON, 42% RAN) did not differ with treatment. Oocyte quality and in vitro developmental competence were not compromised for oocytes from induced persistent follicles compared with oocytes from normal preovulatory follicles. Increased expansion of cumulus cells associated with oocytes from progestogen-induced persistent follicles may be relevant to the reduction of in vivo fertility associated with such follicles.

Animals↗
PubMed2006

Comparison of two estrus-synchronization protocols and timed artificial insemination in dairy cattle.

The objective of this study was to evaluate the effect of the Ovsynch protocol with and without exogenous progesterone on pregnancy rate (PR) in cows in which estrous cycles were previously synchronized with 2 doses of PGF(2alpha) and that were not detected in estrus during the presynchronization period. The study was conducted in Chihuahua, Mexico (8,650 Holstein milking cows; 305-d mature equivalent milk yield = 13,790 kg). On d 47 postpartum, estrous cycles in cows were synchronized by using 2 doses of PGF(2alpha) 14 d apart. Any cow detected in estrus during this presynchronization period was inseminated. Cows not detected in estrus were selected at random and assigned to receive progesterone supplementation or to serve as controls. Controls (n = 594) were subjected to the Ovsynch protocol and cows in the progesterone supplemented treatment (n = 594) were subjected to the Ovsynch protocol plus an intravaginal insert containing 1.9 g of progesterone inserted at the time of the first GnRH injection and removed 7 d later. Progesterone-supplemented cows had a greater PR (31.2%) compared with controls (22.7%). Plasma progesterone concentrations at artificial insemination (AI) were <1 ng/mL and did not differ between treatments. At 14 d post-AI, however, more cows that received progesterone supplementation had concentrations of progesterone >1 ng/mL compared with controls. It was concluded that after a presynchronization period, cows subjected to the Ovsynch program and supplemented with exogenous progesterone had a greater PR and greater concentrations of progesterone after AI than those subjected to the Ovsynch protocol and not supplemented with progesterone.

Animals↗
PubMed1998

Measures of estrus detection and pregnancy in dairy cows after administration of gonadotropin-releasing hormone within an estrus synchronization program based on prostaglandin F2 alpha.

The objective of this study was to assess the use of GnRH in a controlled breeding program (7 d prior to the second of two injections of PGF2 alpha, 14 d apart) as a means to improve the expression and detection of estrus, first service conception rate, and overall pregnancy rate of lactating dairy cows. On 17 farms, 348 cows were assigned randomly to either of two breeding programs prior to first insemination. Cows in both programs received PGF2 alpha approximately 2 wk prior to the end of a herd-specific voluntary waiting period for breeding. One group received GnRH 1 wk later, 7 d prior to the second of two injections of PGF2 alpha. Control cows received saline and a second injection of PGF2 alpha at corresponding times. Cows were observed for 7 d and were bred by artificial insemination following detection of estrus. There were no differences between programs in estrus detection rate, observed signs of estrus, conception rate, days to first service, or interval from calving to conception. The means and standard deviations of the interval from PGF2 alpha to estrus were not different between programs. Administration of GnRH 1 wk prior to PGF2 alpha did not alter the expression of estrus or fertility in lactating dairy cows. In this study population, no advantage was found for the addition of GnRH to a controlled breeding program that was based on two administrations of PGF2 alpha at a 14-d interval.

Animals↗
PubMed2003

Endocrine events during the periestrous period and the subsequent estrous cycle in ewes after estrus synchronization.

The aim of the present study was to investigate the endocrinology of the periestrus period and that of the subsequent estrous cycle in ewes synchronized during the breeding season. Animals were treated for 14 days with either MAP intravaginal sponges or subcutaneous progesterone implants, followed by administration of 500 IU PMSG at the time of withdrawal. The time to estrus occurrence following progestagen withdrawal differed significantly between groups (45.3+/-2.7h for the MAP and 21.5+/-1.2h for the implant group, P<0.001). Estradiol levels around estrus did not differ between groups, but a significant difference was detected for the interval from peak estradiol to estrus, with a shorter interval for the implant group (26.7+/-0.7 and 2.7+/-0.9h, P<0.001). Progesterone implants shortened the interval from removal to LH surge, compared to the MAP group (31.2+/-4.4 and 56.5+/-3.6h, respectively, P<0.05). An earlier response was also observed for the interval from estradiol peak to LH peak in the implant group (12.1+/-3.3 and 37+/-2h, respectively, P<0.005), but no difference was observed for the interval from estrus to LH surge. Progesterone levels, particularly during the Days 6 to 10 of the subsequent estrous cycle were significantly higher (P<0.05) in the implant group. It is concluded that the kind of progesterone treatment may affect the time of estrus and the LH peak as well as the progesterone levels of the subsequent cycle.

Administration, Intravaginal↗
PubMed1996

Use of melengestrol acetate-based treatments to induce and synchronize estrus in seasonally anestrous ewes.

Ten experiments utilizing 1,659 ewes were conducted to determine the potential of melengestrol acetate (MGA)-based treatments in inducing and synchronizing estrous activity in ewes during the nonbreeding season. In May or June, ewes were given .25 mg of MGA.ewe-1.d-1 or control diet and(or) a subsequent i.m. injection of zeranol, estradiol-17 beta, or oil vehicle. Fertile rams were introduced, and estrous and(or) lambing responses were determined. In Exp. 1, more (P < .01) ewes given MGA for 14 d followed by 5 mg of zeranol (i.m.) were in estrus than controls. Melengestrol acetate and zeranol independently induced estrus in Exp. 2, with MGA-treated ewes exhibiting the greatest lambing response (P < .05). The optimum duration of feeding MGA was 8 d vs 11 or 14 d (Exp. 3). In Exp. 4, as the dose of zeranol increased, synchrony of estrus increased but lambing response decreased. A dose of 1.25 mg of zeranol represented a compromise in estrous and lambing response and was determined to be optimally effective when given 54 h after the last feeding of MGA (Exp. 5). Shortcomings in lambing responses were treated in Exp. 6 by supplementing ewes with MGA after breeding, which proved unsuccessful, and in Exp. 7 by substituting estradiol-17 beta for zeranol, which proved effective when given 54 h after the last feeding of MGA (Exp. 8). In Exp. 9, use of MGA + estradiol increased (P < .05) the estrous and subsequent lambing response of 30-d postpartum ewes temporarily weaned of their lambs. In contrast, lambing response of 90-d postpartum ewes treated with MGA + estradiol was not increased by temporary removal of lambs (Exp. 10). These data collectively support the hypothesis that treatment of ewes with MGA + estradiol is an effective and practical approach for inducing and synchronizing a fertile estrus in ewes during the non-breeding season.

Anestrus↗
PubMed2001

Ovulation of aged follicles does not affect embryo quality or fertility after a 14-day progestagen estrus synchronization protocol in ewes.

The aim was to examine the effect of ovulation of aged follicles on embryo quality and fertility in ewes. In Experiment 1, ewes (n = 39) received a prostaglandin analogue on Day 6 of the cycle and then received either a progestagen sponge from Day 6 to 20 after estrus (Single sponge) or a progestagen sponge on Day 6 that was replaced on Day 11 and 16 and removed on Day 20 (Multiple sponges). In a subgroup of ewes, the growth of ovarian follicles was characterised using ultrasonography. Fertile rams were introduced 48 hours after sponge withdrawal; we slaughtered the ewes on Day 5 of pregnancy and recovered the embryos. The mean age of the ovulatory follicles was greater in ewes that received a single sponge compared with multiple sponges (8.7+/-0.8 days, range 4 to 14, versus 4.5+/-0.7 days, range 3 to 6; P<0.05). However, the groups did not differ (P>0.05) in ovulation rate (2.4+/-0.3 corporal lutea per ewe) or the proportion of good quality embryos recovered (71 to 82%; developed to the early morula stage or further). In Experiment 2, ewes (570 in total) received treatments similar to those in Experiment 1 but were kept until lambing. Ewes that received a single sponge came into heat earlier (P<0.05) than those that received multiple sponges, but > or = 97% of ewes in all groups (P>0.05) were bred by 48 to 72 hours after ram introduction. There was no difference (P>0.05) between groups for the proportion of ewes that lambed to first service (80 to 86%) or the number of lambs per ewe (1.94+/-0.08 lambs). We conclude that when luteolysis occurs at the beginning of progestagen synchronisation, ewes will ovulate aged follicles, but that compared to shorter duration follicles, these follicles produce oocytes that are equally competent to be fertilised and develop into good quality embryos and full-term lambs.

Administration, Intravaginal↗
PubMed1997

Gonadotropin-releasing hormone enhances the calving rate of beef females administered norgestomet and alfaprostol for estrus synchronization.

One hundred fifty beef heifers and 403 beef cows suckling calves were administered norgestomet implants (8 d) and alfaprostol, a PGF2 alpha analogue, approximately 28 h before implant removal. Thirty hours after implant removal, females were administered either GnRH via injection, GnRH via implantation, or no GnRH. The dosage of GnRH was 250 micrograms, and implants prolong the induced LH surge. Ovulation response, incidence of short cycles, and calving rate were analyzed as a 2 x 2 x 3 completely randomized factorial design with female (heifers and cows), estrous cycles (with or without), and GnRH as the main effects. There were no interactions (P > .10), and because heifers and cows had responses that did not differ (P > .25), they were summarized together. Females with estrous cycles had a higher (P < .05) ovulation response, fewer (P < .01) short luteal phases, and a higher (P < .01) calving rate than females without estrous cycles. Gonadotropin-releasing hormone treatment increased the ovulation response (P < .01) and the calving rate (P < .05), and these responses were not affected (P > .10) by the method of GnRH administration. Based on these data, the increased ovulation response to GnRH may account for 29% of the increase in calving rate observed in the GnRH-treated females. In summary, in norgestomet- and alfaprostol-synchronized females, GnRH enhanced calving rate regardless of how it was administered. This increase was due to more than an increased ovulation rate.

Animals↗
PubMed1975

[Estrus synchronization in cattle using chlormadinone acetate ("Bovisynchron" Jenapharm) in the tropics. 1. On the effect of blocking the cycle using chlormadinone acetate and on the introduction of this biotechnical method in the Republic of Mali].

The oestrus synchronization in cattle is being tested as a biotechnical method supporting the implementation of the crossing programme in the Republic of Mali Using the latest results of sexual physiology, the effect is described of Bovisynchron Jenapharm (chlormadinonacetate). Bovisynchron is characterised by a high certainty of synchronization and a good toleration. It leads to a highly fertile oestrus of all animals and to a high rate of conception. An analysis of the situation in the Republic of Mali is used to discuss the advantages of this method.

Animals↗
PubMed1981

FSH or FSH plus LH superovulation in ewes following estrus synchronization with medoxyprogesterone acetate pessaries.

The estrous cycles of 28 ewes 9 to 10 months of age were synchronized with Medoxyprogesterone (MAP) pessaries. Superovulation was attempted by injecting either (follicle stimulating hormone) FSH or FSH plus Luteinizing Hormone (LH). MAP pessaries were in place for 12 days. FSH was administered (IM) to all ewes at 12-hr intervals over a 3-day period, 5 mg injected twice on day 11 after pessary insertion, followed by 4 and 3 mg twice daily on days 12 and 13, respectively. LH (25 mg injected IV) was given to 14 ewes within 8 hr after the onset of behavioral estrus. All ewes were hand mated with several rams at 12-hr intervals from the onset to the end of behavioral estrus. Ovulation, embryo recovery and fertilization rates were recorded for each ewe. Of 14 ewes injected with only FSH, 13 ovulated, with a mean ovulation rate of 8.2 +/- 5.6; embryo recovery rate averaged 62%, and fertilization rate was 97%. All 14 ewes given both FSH + LH ovulated, with an ovulation rate of 8.9 +/- 5.8 per ewe; embryo recovery averaged 70%, and 91% of all embryos recovered were fertilized. No statistical differences in ovulation, embryo recovery or fertilization rates were found between the FSH and FSH + LH superovulation treatment groups. In addition, no difference in the number of ewes showing estrus or duration of behavioral estrus was noted between FSH and FSH + LH treatments.

Animals↗
PubMed1994

[Levels of sodium and potassium and their relation to ovarian hormones during estrus synchronization and pregnancy in ewes].

The active transport of mineral substances by cell membranes plays an important role in the neurohumoral regulation of reproductive processes in farm animals. A great importance is attributed to lipoproteins as sources of the primary precursor of steroid synthesis in the placenta and ovaries (Knopp et al., 1986; Grummer et al., 1988). The effects of hormones on K metabolism in the blood serum of ewes were studied by Hawk et al. (1961). Krajnicáková et al. (1993) observed the dynamic changes of electrolytes in the course of the reproductive cycle in ewes. Na and K levels and their relation to ovarian hormones were determined in the systemic blood stream of ewes during oestrus synchronization and pregnancy. Ten Slovak Merino ewes aged 3-5 years and weighing 40-50 kg were included in the experiment. The animals were reared conventionally. A feed ration consisted of silage, hay, feeding beet-pulp, straw and in the last two months of pregnancy it was supplemented with roughage. Water and salt were given ad libitum. Blood samples were obtained from the jugular vein prior to synchronization (day 0) and on days 3, 7 and 14 of synchronization with Agelin vaginal implants. After removing the implants the animals received 500 I.U. PMSG (Pregnant Mare Serum Gonadotropin). The animal in oestrus cycle were inseminated with fresh diluted semen. Reinsemination was not performed in this experiment. Sampling was continued on the day of insemination and on days 7, 14 and in month 2, 3, 4 and 5 of pregnancy. Na and K levels were measured by atomic absorbtion spectrophotometry using the Atom Spek device (RANG-HIGLER). Progesterone (P4) and 17 beta-oestradiol (E2) levels were assayed radioimmunologically using the respective kits (RIA-test-PROG and RIA-test-ESTRA) manufactured by URVJ Kosice. During the observation period Na levels fluctuated within 131.50 +/- 1.71 and 153.55 +/- 4.77 nmol/l of serum (Tab. I) and significantly decreased between day 14 of synchronization and the end of the investigation (P < 0.05; P < 0.01; P < 0.001). Potassium levels were observed to significantly decrease from the day of insemination on, throughout the first days of pregnancy and the above-mentioned months of gravidity, the values ranging between 4.57 +/- 0.52 and 3.93 +/- 0.36 nmol/l.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Influence of an agonist of gonadotropin-releasing hormone (buserelin) on estrus synchronization and fertility in beef cows.

The objective of this experiment was to determine the effect of sequential treatment with buserelin (a GnRH agonist) and cloprostenol (a prostaglandin F2 alpha analog) on estrous response and fertility in beef cattle with different ovarian conditions. On d 0 (1st d of treatment), the control group (n = 52, 10 heifers and 42 cows) and the GnRH group (n = 48, 10 heifers and 38 cows) received 2 mL of saline or 2 mL of Receptal (8 micrograms of buserelin), respectively. On d 6, all cows that had not exhibited spontaneous estrus were given i.m. 500 micrograms of cloprostenol (PGF). Ultrasonography on d 0 and assays of progesterone in blood on d -11, 0, and 6 were used to identify follicular and luteal status of animals. Cattle were observed for estrus from d 0 to 10. Cows showing estrus were bred artificially 12 h after onset of estrus. Over the 10-d period, the number of cows detected in estrus and pregnancy and conception rates were identical for the two groups. However, between d 0 and 6, the proportion of cows exhibiting estrus was lower (P less than .01) in the GnRH group than in the control group. Between d 6 and 10, the synchronization rate and precision of estrus were greater (P less than .01) in the buserelin-treated group than in the control group. Conception rate and interval from PGF injection to onset of estrus were not different between the two treatment groups. Presence of a large (greater than 10 mm) follicle on d 0 enhanced synchronization rate and precision of estrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗