• Korean Journal of Animal Reproduction
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• v.5 no.1
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• pp.26-30
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• 1981

The purpose of this study was to measure the serum content of progesterone, estradiol 17${\beta}$ and cortisol. Blood samples collected from day 20 prepartum to day 20 postpartum in 8 sows. Progesterone and estradiol-17${\beta}$ were assayed by radioimmunoassay methods and cortisol was determined by competitive protein-binding methods. Progesterone levels began to decline on day -4, reached 1.9ng/ml by day +2 and remained quite constant thereafter. Progesterone levels remained fairly constant(18.4 to 20.0 ng/ml) from 20 to 6 days before parturition. Estrdiol-17${\beta}$ increased from 205 pg/ml at day 6 prepartum to 425 pg/ml at the time of parturition. Cortisol reached a peak level of 86.5 ng/ml at day 0.

• Korean Journal of Animal Reproduction
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• v.12 no.1
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• pp.20-23
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• 1988

The 3211 Korean native cows raised in Muan, Milyang were investigated for the purpose of finding reproductive rate of cows that retained fetal membrane for two years from April, 1981 to March, 1983. The results obtained were summarized as follows ; 1. The incidence of retained fetal membrane was found in 64 cows(1.98%). 2. The day to first estrus was similar to normal postpartum period unless concurrent genital infection occured. 3. Conception rate of cows that retained fetal membrane was 32.7%, 10.9%, 5.2% and 3.6% at the first, second, third and forth service, respectively and non pregnant cow was 47.6%. 4. Reproductive disorder of non pregnant cows was the highest in repeat breeder and the effect of treatment was very low.

• Asian-Australasian Journal of Animal Sciences
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• v.16 no.8
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• pp.1093-1101
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• 2003

Reproductive data, such as numbers of days to the first estrus and A.I. service postpartum, number of days to conception, number of A.I. services required for conception, interval between the first estrus and first A.I. service and the average interval of A.I. service in Thai native-Friesian crossbred and pure Friesian dairy cows, were compiled in the National Dairy Training and Applied Research Institute in Chiang Mai, Thailand. The data were analyzed statistically and the effect of milk production on these reproductive traits was investigated. The reproductive efficiency of purebred cows was obviously inferior when compared with crossbred animals, in spite of special care being given to the purebred only in order to alleviate the effect of a tropical climate and provide better feeding. However, the regression analysis between reproductive and lactational parameters revealed a definite antagonistic effect of lactation on reproduction, especially in the purebred cows, which had a larger amount of milk production and longer lactation period. If these effects of lactation were eliminated, there would be no evident difference in reproductive efficiency between purebred and crossbred cows in the conditions of this study. Among the reproductive parameters examined, the number of days to the first estrus and interval between the first estrus and first A.I. service were less affected by breed difference and the magnitude of lactation than other reasons.

• Korean Journal of Animal Reproduction
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• v.22 no.1
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• pp.29-34
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• 1998

Jugular plasma concentrations of luteinizing hormone, prolactin, estradiol-17\ulcorner and 13, 14-dihydro-15-keto-prostaglandin-F2봬(PGFM) were meausred prepartum during the last 12 days of pregnancy, at parturition, then 1 day after parturition in 16 goats. Plasma samples were analyzed for luteinizing hormone(LH), estradiol-17\ulcorner(E2), prolactin(PRL) and prostagladin F2봬(PGF2봬) concentrations by radioimmunoassay. 1. The concentrations of plasma luteinizing hormone in Korean native goats remained fairly constant(0.20 0.02\ulcorner0.38 0.04 mlu/ml) from 12 days prepartum to 1 postpartum but the concentrations of plasma prolactin rose slightly from 1 day prepartum. 2. The estradiol-17\ulcorner concentrations increased rapidly after day 1 before partum, reaching a peak at parturition(74.8 77.5 pg/ml), and falling to 63.8 2.8 pg/ml at day 1 postpartum. 3. Starting at 323.2 69.6 twelve days before parturition, the concentrations of plasma prostaglandin F2봬 rose during the 1 day preceeding parturition(650.7봬57.8 pg/ml) and peaked at 1081.4 164.9 on the day of parturition. At day 1 postpartum, the concentrations of PGF2봬 decreased to 425.3 60.4 pg/ml. Finally, these results show that changes in prostaglandin F2봬 concentrations before parturition were closely related to changes in estradiol-17\ulcorner concnetrations, but after parturition they remained elevated whereas estradiol-17\ulcorner concentrations fell abruptly.

• Korean Journal of Animal Reproduction
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• v.16 no.2
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• pp.149-155
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• 1992

The present study was conducted to find out the changes of progesterone and 20$\alpha$-dihydroprogesterone(20$\alpha$-OHP) levels before and after parturition, 4 pluriparous goats were offered for this experiment. Blood samples were taken from jugular vein on Days, 5, 3, 2 and 1 before parturition, the day of parturition, 1, 3, 5, 7 and 9 after parturition. The blood samples were centraifuged and stored at -2$0^{\circ}C$ until hormone assay. The serum levels of progesterone and 20$\alpha$-OHP were measrued by radioimmunoassay. The changes of serum progesterone level during peripartum period were characterized as a remarkable decrease. The progesterone level was 4.05$\pm$0.52ng/ml on 56 days before parturition and decreased to 2.24$\pm$0.38ng/ml on 1 day before parturition and 0.79$\pm$0.09ng/ml on the day of parturition and the basal level was maintained through 9 days of postpartum period. The serum level of 20$\alpha$-OHP during the peripartum period was 1.25$\pm$0.21ng/ml on 5 days before paturition and increased to 1.32$\pm$0.25 on 3 days and 1.59$\pm$0.24ng/ml on 1 day before parturition, and reached a peak level of 1.78$\pm$0.25ng/ml just prior to parturition and then decreased greatly to 0.31$\pm$0.03ng/ml on 1 day postpartum and the basal level was remained until 9 days postpartum. The high serum level of 20$\alpha$-OHP, which was peak just prior to parturition, was maintained for 2 days following the onset of remarkable decrease in the serum level of progesterone. From the above results, it was concluded that the enzyme 20$\alpha$-hydroxysteroid dehydrogenase (20$\alpha$-HSD) catalyzing the conversion of progesterone to a biologically inactive steroid, 20$\alpha$-OHP was active properly in the luteal cells in Korean native goats.

• Korean Journal of Animal Reproduction
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• v.26 no.2
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• pp.183-192
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• 2002

The present studies were carried out to examine the effects of exogenous oxytocin(OT) on plasma, uterine and placenta of estradiol-17$\beta$, progesterone, prostaglandin F$_2$$_{\alpha}$ (PGF$_2$$_{\alpha}$), Prostaglandin E$_2$(PGE$_2$) and OT receptor concentrations in pregnant rats. Pregnant rats received an injection of exogenous OT on days 14, 16, 18, 20, 22 of pregnancy and day 1 of postpartum. Concentrations of plasma estradiol-17 $\beta$ after OT injection started to increase after day 18 and peaked on day 22 of pregnancy but decreased on day 1 of postpartum. Plasma progesterone concentrations declined gradually from day 18 of pregnancy and decreased more rapidly until postpartum 1 day. Concentrations of estradiol-17$\beta$in uterine tissues after OT injection were sharply increased from day 20 to 22 of pregnancy and progestrone concentrations were peaked on day 16 and decreased rapidly from day 16 to 20 and maintained the same level until day 1 of postpartum. Uterine concentrations of PGF$_2$$_{\alpha}$ and PGE$_2$increased gradually until day 20 and peaked on day 22 of pregnancy but showed a marked decrease on day 1 of postpartum. Concentrations of PGF$_2$$_{\alpha}$ in placental tissues increased rapidly from day 14 of pregnancy and decreased sharply on day 1 of postpartum. Concentrations of PGE$_2$increased gradually after day 14 and peaked on day 20 of pregnancy. The concentration of OT receptor in uterus was significantly elevated from day 20 and rose to maximum on day 22 of pregnancy. These findings show that OT suppress the concentration of progestrone and stimulate productions of estradiol-17 $\beta$, PGF$_2$$_{\alpha}$, PGE$_2$ and oxytocin receptor concentrations in pregnant rats.

• Reproductive and Developmental Biology
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• v.41 no.2
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• pp.25-31
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• 2017

Effective estrus detection and artificial insemination (AI) are necessary for profitable management of dairy herd. In current study, 45 crossbred lactating cows have been selected with the complaint of unobserved oestrus for more than sixty days postpartum. All cows had functional corpus luteum as examined by transrectal ultrasonography. Cows were treated with $PGF_2{\alpha}$ analogue and AI was performed with observed oestrus and then single dose of GnRH was administered. Similar synchronization protocol has been repeated after 14 days in cows that did not repose to first treatment. Remaining cows received additional $PGF_2{\alpha}$ after 14 days of second treatment and timed AI was performed following GnRH administration. Among 45 cows, 28.89% showed estrus after first treatment and 78.79% responded to second hormonal intervention. A higher conception rate (88.89% vs 26.66 and 72.72%) was observed in cows after triple administration of $PGF_2{\alpha}$ and timed AI. We noticed a significant differences in body condition score (BCS, 1~5 scale), postpartum period, and daily milk production between cows that either responded of non-responded following first and second hormonal treatment. In addition, there was a significant positive correlation between daily milk production and BCS, age and postpartum days, milk production and estrus/BCS, and milk production/BCS/estrus and conception rate. Depending upon the findings we conclude that hormonal intervention with $PGF_2{\alpha}$ and GnRH enhances postpartum ovarian cyclicity and help decreasing the days open of dairy herd. Therefore, this finding might provide an excellent guideline for target breeding system for profitable dairy herd management.

• Korean Journal of Animal Reproduction
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• v.13 no.1
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• pp.1-6
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• 1989

A field survey was conducted to obtain the data on reproductive performation of Korean native cattle. The data for this study were taken from 6,461 breeding records of cows raising at general farms in 8 Hanwoo(native cattle) pure breeding areas from June, 1984 through November, 1985. The recycling rate within 30 days, 31 to 60 days, and 61 to 90 days postpartum was 7.5%, 40.0%, and 32.8%, and it amounted to 80.3%, while the non-recyling rate up to 120days postcalving was 8.4%. Conception rate according to insemination(AI) frequencies was 65.7% at 1st AI, 21.3% at 2nd AI, and 8.4% at 3rd AI, respectively. It amounted to 95.4% up to 3rd AI. Clving rate during the spring time was the highest, 39.6%, and tended to be reduced according to summer(31.6%), autumn (16.3%), and winter (12.5%). Spring and summer were the highest seasons for pregnancy and their gestation rates are 33.7% in spring and 39.2% in winter, respectively. The days from calving to estrus and conception, and calving interval of the cows, which calved two or three times, tended to be reduced. However, the more parities, the more they are extended. According to parities, gestation length and services per conception showed irregular tendencies.

• Asian-Australasian Journal of Animal Sciences
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• v.12 no.7
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• pp.1025-1030
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• 1999

Fifth one Nili-Ravi dairy buffaloes in their last two months of gestation, were selected in NWFP Pakistan. Rectal palpation was carried out fortnightly, until the occurrence of first estrus. Ovulation was confirmed per rectum and milk progesterone levels (MPL). Body condition score (BCS)was recorded weekly. Milk samples were collected weekly for MPL and blood samples fortnightly for metabolites analysis. Milk yield was recorded and samples were collected for milk fat. The buffaloes calving during the normal breeding season (NBS, August to January)had short (p<0.01) postpartum estrus interval of $55.95{\pm}4.90$ days versus $91.15{\pm}11.61 $ days in the buffaloes calving during the low breeding season (LBS, February to July). MPL in the LBS calvers remained lower than NBS calves (p<0.01). The incidence of silent ovulation was higher during LBS as compared to NBS (70.6% versus 29.4%). MPL showed a pattern opposite to atmospheric temperature. In NBS calvers serum glucose levels were higher (p<0.01) and magnesium levels were lower (p<0.01) than LBS calvers. Higher serum urea was found in summer and spring than that autumn and winter (p<0.05). The reproductive performance in buffaloes calving in the LBS coincided with a low BCS (p<0.01). Fat corrected milk production (FCM) was higher in NBS than LBS (p<0.01) calvers.

• Korean Journal of Animal Reproduction
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• v.17 no.1
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• pp.27-34
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• 1993

The present study was conducted to examine the reproductive performance of dairy cow at alpine area. 1,515 dairy cows were managemented at above 800m of sea level around the Dea-Gwan Ryeong in Kangweon-Do. The results at this study were as follows ; 1. The average first estrus was 105.0 days after pastruation. 2. The highest percentage ofpregnancy(26.4%) and parturation(27.6%) were obtained at September to November and June to August, respectively. 3. The rate of pregnancy was 61.0%. Pregnancy rates according to insemination times of 1, 2 and 3 were 60.8, 23.5 and 9.8%, respectively and insemination time per pregnancy was 1.64. 4. Ages of first inseminatin, pregnancy and parturition of heifer were 17.9, 18.6 and 27.7 months, respectively. 5. Time of postpartum pregnancy was 133.0 days after parturition, and pregnancy period and calving interval were 279.6 and 410.3 days, respectively. 6. Six ratio of offspring was 52.1% of female versus 47.9% of male, and the proportion of twins was 0.65%. 7. The proportions of normal parturition, stillbirth and abortion were 91.9, 2.2 and 5.9%, respectively.