• Korean Journal of Animal Reproduction
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• v.22 no.4
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• pp.367-373
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• 1998

A survey was carried out to investigate the effect of the herd size on the reproductive traits of Hanwoo(Korean native cows). Data on the reproductive traits of 670 Korean native cows were collected from January, 1996 to December, 1997 and analyzed by the herd size. The results obtained were summarized as follows: 1. The average ages at first breeding were 437.9, 425.5 and 452.9 days in herd size 1 (less than 20 heads), 2 (21∼50 heads) and 3 (more than 51 heads), respectively (the over all average was 443.0 days). However, there was no significant difference between herd sizes (p＞0.05). 2. The average ages at first conception were 452.8, 438.4 and 467.1 days in herd size 1, 2 and 3, respectively (the over all average was 460.0 days). However, there was no significant difference between herd sizes (p＞0.05). 3. The average ages at first calving were 741.2, 730.2 and 755.9 days in herd size 1, 2 and 3, respectively (the over all average was 746.6 days). However, there was no significant difference between herd sizes (p＞0.05). 4. The average days to first estrus after calving was 70.1 days and it was shortest in herd size 3 (64.8 days) and longest in herd size 1(82.1 days). 5. The average numbers of services per conception were 1.54, 1.61 and 1.48 in herd size 1, 2, and 3, respectively (the over all average was 1.53). However, there was no significant difference between herd sizes (p＞0.05). 6. The average days to first conception after calving were 115.6, 99.1 and 80.6 days in herd size 1, 2 and 3, respectively (the over all average was 91.2 days). There was a trend that it was shorter as the herd size increased(p＜0.05). 7. The average length of calving interval was 375.3 days and it was shortest in herd size 3 (367. 4 days) and longest in herd size 1 (389.5 days).

• Reproductive and Developmental Biology
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• v.30 no.3
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• pp.195-199
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• 2006

This study was carried out to investigate the effect intra-uterine infusion of lipopolysaccharides(LPS) on the reproductive performance of dairy cows with retained placenta, The LPS isolated from Bacteroids helcogenes and Fusobacterium varium was injected at the rate of 100 ${\mu}g$ with 30 ml of phospahte buffer saline in each cow(n=33) at day 20 postpartum. Twelve cows with retained placenta were not heated with LPS and served as a control. Conception rate after first service was 0% and 33,3% for control and LPS groups, respectively. Service period was $149.6{\pm}34.3\;and\;53.0{\pm}12.5$ days for control and LPS groups, respectively(p<0.05). Services per conception was $3.6{\pm}0.8\;and\;2.1{\pm}0.3$ for control and LPS groups, respectively(p<0.05). In conclusion, intra-uterine infusion of LPS in cows with retained placenta can reduce the service period and services per conception. Reduced service period can improve the dairy farm profitability by decreasing cost un feeding and management of cows.

• Journal of Embryo Transfer
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• v.22 no.3
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• pp.195-198
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• 2007

This study was carried out to investigate the effects of hormones treated (progesterone, and combination of progesterone and estradiol) on the reproductive performance of dairy cattle. The intravaginal CIDR was inserted in the vagina of cow on day 14 (P-7, PE-7), 16 (P-5, PE-5) and 18 (P-3, PE-3) post-insemination to stimulate progesterone secretion with (PE) and without estradiol(P). The CIDR was removed on 7 (P-7, PE-7), 5 (P-5, PE-5) and 3 (P-3, PE-3) days after. The cows for control group were not treated with CIDR or hormones. Conception rate, the duration needed for conception after AI and the number of AI services needed for conception were measured. Conception rate in control, CIDR without estradiol (P-7, P-5 and P-3) and CIDR treated (PE-7, PE-5 and PE-3) cows were 15.8%, 40.0%, 31.5%, 28.6%, 62.5%, 50.0% and 0%, respectively. The days needed for conception after AI in control, P-7, P-5, p-3, PE-7, PE-5 and PE-3 were 64.9, 63.0, 59.1, 8.0, 0.0, 18.9 and 83.3 days, respectively. The days needed for conception in cows treated with CIDR (PE-7) has shown longer than control and PE-3 (p<0.05). The number of AI services needed for conception in control, CIDR (PE-7, PE-5 and PE-3) and CIDR without estradiol treated cows (P-7, P-5 and P-3) were 27, 2.3, 1.9, 1.3, 1.0, 1.7 and 2.8 times, respectively. The number of AI services needed for conception have shown significantly lower in PE-7 compared to control and PE-3.

• Journal of Embryo Transfer
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• v.22 no.2
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• pp.115-119
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• 2007

This study was carried out to investigate the effects of hormones (progesterone, and combination of progesterone and estradiol) on the reproductive performance of dairy cattle. The intravaginal CIDR was inserted in the vagina of cow on day 14 post-insemination to stimulate progesterone secretion with and without estradiol. The CIDR was removed on the day of next expected estrus. The cows for control group were not treated with CIDR or hormones. Conception rate, estrus interval, estrus intensity and serum progesterone were measured. Conception rates in control, CIDR without estradiol and CIDR treated cows were 15.4, 38.9 and 60%, respectively. Estrus interval in cows treated with CIDR was 26.5 days compared with 37.1 and 48.5 days in control and CIDR without estradiol treated cows. Estrus signs were more intense in cows treated with CIDR compared with control and CIDR without estradiol treated cows. Pregnant cows treated with CIDR showed higher serum progesterone concentration than pregnant and non-pregnant cows in control group. Particularly, serum progesterone was significantly higher in CIDR treated pregnant cows compared to non-pregnant cows at days 1, 2 and 6 of gestation. It may be concluded from present results that CIDR treatment is better than CIDR without estradiol to improve conception rate in dairy cattle.

• Korean Journal of Veterinary Research
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• v.16 no.2
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• pp.115-119
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• 1976

The survey was carried out to investigate the average number of days from parturition to conception to 349 calving cases out of Holstein cows in total 154 heads observed. The results were as follows: 1. The average number of days from parturition to conception was $97.41{\pm}8.22$ and it's similar during the period from primipara to 4th calving order, and irregular during on and after 5th. 2. The average number of days from parturition to conception in calving month was observed all through the year: the prolongation among on April and July, and the brief duration among on January and March. 3. In the cases under 50 and 150 days after delivery, the distribution showed 53.56% and 83.91%, respectively, and it's about 20% between 70 and 90 days after delivery.

• Reproductive and Developmental Biology
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• v.30 no.3
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• pp.213-218
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• 2006

This study was conducted to investigate the effect of abnormal ovarian cycle postpartum on subsequent reproductive performance of Holstein cows. The cows were considered to have resumed ovarian cyclicity on the day of ovulation if followed by regular ovarian cycles. Total 58.8 percentage of the cows(l14/194) had normal resumption of ovarian cyclicity(resumption within 40 days after calving), and 41.2%(80/194) had delayed resumption(resumption did not occur until >40 days after calving). Delayed resumption Type I(one or more ovarian cycles with luteal phase >20 days, i.e. prolonged luteal phase; 17.5%) and delayed resumption Type II(first ovulation did net occur until $\geq$40 days after calving, i.e. anovulation 22.7%) were the most common types of delayed resumptions. When compared with cows with a normal ovarian cycle, the cows of delayed resumption Type I had a lower 100 days AI submission conception and pregnancy rates(84.2% vs 40.0%; p<0.01, 24.0% vs 21.4% and 20.2% vs 11.1%, respectively), and longer intervals to first AI and to conception($64.7{\pm}2.79$ days vs $105.7{\pm}7.48$ days and $105.1{\pm}7.16$ days vs $133.7{\pm}11.17$ days, respectively; p<0.01). Similarly, when compared with cows with normal ovarian cycles, the cows of delayed resumption Type II had lower 100 days conception and pregnancy rates(24.0% vs 20.0% and 20.2% vs 16.3%, respectively), and longer intervals to first AI and to conception($64.7{\pm}2.79$ days vs $72.6{\pm}4.45$ days and $105.1{\pm}7.16$ days vs $120.8{\pm}12.33$ days, respectively). In conclusion, abnormal ovarian cycles postpartum adversely affected reproductive performance, including AI submission rate, pregnancy rate, interval to first AI, and calving to conception interval in Holstein cows.

• Journal of Embryo Transfer
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• v.20 no.1
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• pp.49-53
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• 2005

This study was conducted to investigate the effects of repetition usage of various estrus synchronization and seasonal breeding in Hanwoo. Body weight(kg) at birth and weaning in calves produced by seasonal breeding are 24.0kg, 75.6kg in female, 24.9kg, 78.3kg in male, respectively. Changes of birth weight(kg) by parity in Hanwoo increased gradually. Raising rates of calves by raising experience of farmer higher than in more 10 years as $88.4\%$ and in more 6 years as $84.0\%$. Delivering rates by induced estrus methods in $PGF_{2}{\alpha}$, PRID, CIDR and $GnRH-PGF_{2}{\alpha}-GnRH$ were $87.0\%$, $87.3\%$, $91.6\%$ and $96.0\%$, respectively. Conception days of post-partum following to induced estrus methods in Control, $PGF_{2}{\alpha}$ PRID, CIDR and $GnRH-PGF_{2}{\alpha}-GnRH$ were 137.1, 147.6, 141.3, 116.6 and 118.0 days, respectively. The results show that repetition usage of various estrus synchronization were not effective on postpartum reproduction in Hanwoo.

• Journal of Embryo Transfer
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• v.32 no.3
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• pp.171-176
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• 2017

This study was conducted to investigate the breeding status of farms to improve the production efficiency of Hanwoo calf. The study was conducted on 45 farms divided into two groups. This study was conducted to investigate the breeding size and breeding area of Hanwoo cows. The average age at first delivery of Hanwoo was 28.7 months. The number of artificial insemination per pregnancy was $1.45{\pm}0.32$, and the number of artificial insemination days after birth was 119.8 days. Conception rates were $75.2{\pm}16.93%$ for small farms and $70.6{\pm}17.46%$ for medium sized farms and $71.4{\pm}11.03%$ for large farms. When we looked at farming methods, 'the farmers using estrus observation aids' had 10.42% higher calf production rate than the 'unused farmers'. The farms vaccinated with IBR and BVDV for breeding cattle showed a 4.41% decrease in abortion, stillbirth and mortality. According to farming conditions, conception rate and delivery rate improved by 3.47% and 18.29%, respectively, when grazing and exercising were performed. Observation, immunization and grazing were found to be important indicators for improving calf production efficiency in Hanwoo farm. This study can be used as a research data to improve the reproductive rate of farmhouse sites through the survey on the breeding status of Hanwoo farmers.

• Journal of Animal Science and Technology
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• v.46 no.1
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• pp.31-38
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• 2004

Data from five Hanwoo breeding farms were collected to analyze the effects of parity, season, nutrition and reproduction on body conditions of heifers and cows and to analyze the relationships of body conditions with reproductive performances and body growth. Analytic models included farms and parity which were run through SAS to estimate least squares means and correlation coeflicients between traits body condition scores(BCS) of I(very emaciated) through 9(very obese) scale at service and at calving. calving interval, days to rebreeding, gestation length. number of services per conception. Overall averages were 4.55 for BCS at service, 5.42 for BCS at calving. 406.7days of calving interval, 287.7days of gestation length, 66.2days from calving 10 first service and 1.78 times of services per conception. Number of services per conception was 1.50${\sim}$1.74 times for the cows of BCS 5 or under and 2.00${\sim}$3.00 for those of BCS 6 or higher. Body weight of calves from cows observed averaged 23.3kg at birth and 70.7kg at weaning. 57 percent of cows showed BCS 4${\sim}$5 at service while 46 percent of those showed 5${\sim}$6 at calving. Estimated phenotypic correlation coefficients of BCS at service with BCS at calving, calving interval, gestation length, number of services per conception were low but positive: 0.16, 0.26. 0.08 and 0.06. respectively. Phenotypic correlations of BCS at calving with calving interval, gestation length and number of services per conception were estimated to be also low and positive: 0.10, 0.13 and 0.10. respectively. However, phenotypic correlations between calving interval and gestation length, and between gestation length and number of services per conception were negative but low as - 0.11 and- 0.13 each.

• Journal of Practical Agriculture & Fisheries Research
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• v.4 no.1
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• pp.110-118
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• 2002

This study was conducted to investigate the physiology of optimal reproductive age in Hanwoo for protection to decrease of reproductivity and improvement of production of offspring. Thirty two cows were devided into 4 groups of treatments : T1(12 months of age and 0.5kg daily gain), T2(12 months of age and 0.8kg daily gain), T3(15 months of age and 0.5kg daily gain) and T4(18 months of age and 0.5kg daily gain). The days of the first heat of treated cows were 263.3±6.4 days and average weight was 181.1±11.3kg. The conception rates of first insemination were 25%(T1) and 75%(T4), and the number of insemination of T3 and T4(both 1.5) was lower than those of T1 and T2(2.3 and 2.4), respectively. With regard to estrus return after the first parturition, T1, T2, T3 and T4 showed 66.2,76.7, 62.4 and 68.5 days, respectively, indicating the average days of estrus return was 65.7. Plasma progesterone(P4) concentration was nearly the same during the observation periods of treated cows and P4 began to be detected after 12months. Only 5(15.6%) out of 32cows showed normal estrus cycle and ovulation before 12 months. During the peri-parturition period, P4 concentration was rapidly decreased and there was no detection of P4 from parturition to 40 days after milking. P4 would be released again on 45 day after parturition. The results imply that the optimal reproductive age of Hanwoo heifers would be around at the 14 months of age, 110cm height and 265kg weight.