• Journal of The Korean Society of Grassland and Forage Science
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• v.4 no.3
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• pp.180-186
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• 1984

From June, 1980 to October, 1982, this study was carried out to find an optimal grazing system on the timothy and orchardgrass-dominated pasture. Five different systems consisted of set stocking, modified set stocking, rotational grazing, 'wye college' system and zero grazing have been applied. The results obtained were as follow: 1. Herbage DM yield per ha with 'wye college' system, set stocking, modified set stocking, rotational grazing and zero grazing were 6936.7 kg,6794.3 kg, 6686.9 kg 6675.7 kg and 5083.4 kg respectively. Among treatments were not different in DM yield. 2. In herbage utilization, zero grazing was the highest than other. Zero Grazing, Rotational grazing, 'Wye college' system, Modified set stocking and set stocking was 89.3%, 70.8%, 64.4% and 46.1% respectively. 3. Daily intake per head with 'wye college' system was the highest than others and zero grazing was the lowest than others. 4. Daily gain with 'wye college' system, rotational grazing, modified set stocking, set stocking and zero grazing were 0.60kg, 0.55kg, 0.50kg, 0.43kg and 0.42 respectively. Among treatment, there was no significance. 5. Total weight gain per ha with 'wye college' system, rotational grazing, modified set stocking, zero grazing and set stocking were 339.5kg, 299.1kg, 253.3kg, 226.6kg and 222.2kg respectively. 6. Grazing time among treatments was not significant. 'Wye college' system spent the shortest time, 367.3 minutes and set stocking consumed the longest time, 422.1 minutes. 7. Daily grazing time by seasonal change with June, July, August, September and October was 304.9 min., 359.4 min., 437.9 min., 483.3 min. and 395.8 min., respectively. According to passing the season, grazing time was lengthened. 8. Grazing time for Korean native cow, native cow charolais and native cow holstein were not significant. Native sow charolais consumed the longest time, 457.0 min., whereas Korean native cow consumed the shortest time, 422.4 min..

• Korean Journal of Veterinary Service
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• v.42 no.2
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• pp.117-120
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• 2019

Bovine viral diarrhea Virus (BVDV) infections cause respiratory, gastrointestinal, and reproductive problems, such as infertility, abortion, stillbirth, and sickly offspring. Many countries have reduced the economic damage through the application of different control programmes, and some have successfully eradicated BVD. Detection and elimination of cattle persistently infected (PI) with BVDV is important for BVD eradication because PI cattle are a main source of BVD transmission. In this study, the prevalence of Korean native cattle persistently infected (PI) with BVDV was investigated and determined in 49 farms with 3,050 cattle. The all samples were collected by ear notch sampling. Korean native cattle with initial positives on antigen-ELISA (Ag-ELISA) were sampled again after 3~4 weeks and cattle with second positives in both Ag-ELISA and immunohistochemistry (IHC) were identified as PI cattle. Among the 49 farms, 14 (28.6%) farms had at least more than one PI cow and 21 (0.69%) of 3,050 cattle were determined as PI cattle. As a result of this work, it is suggested that national BVD eradication program is required to reduce economic losses by BVDV infection in Korean cattle industries.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2000.05a
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• pp.64-75
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• 2000

During the last three decades considerable advances has been made in goat embryo production and transfer technology. The Korean native black goat is the most useful domestic ruminant in this country for biological investigation and application because it has a lot of merits such as relatively short generation period (1 vs 2 year for a cow), easy of handling, well adaptation, high fertility, convenient and inexpensive. This article covers the methods of superovulation, estrus synchronization, embryo collection and transfer techniques, pregnancy diagnosis and subsequent pregnancy and kidding rates for the production of transgenic Korean native black goats. More than one hundred goat kids have been produced as a result of our transgenic goat project via microinjection of foreign gene into pronuclei, in vitro culture, transfer of various stages of fresh and frozen-thawed microinjected embryos into oviducts or uteri of recipient does. We have got two transgenic goats carrying a transgene targeting the expression of recombinant human granulocyte colony stimulating factor (hG-CSF) to the mammary gland so far. Since collection and transfer of embryos in this species is usually accomplished by laparotomy, exteriorization of the reproductive tract for surgical embryo collection leads to the formation of post-operative adhesions. Nonsurgical or laparoscopic technique to reduce adhesions from repeated surgeries has great advantages in improving embryo production and transfer especially from valuable donors. We will discuss this later.

• Proceedings of the Korean Society of Embryo Transfer Conference
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• 2000.06a
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• pp.64-75
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• 2000

During the last three decades considerable advances has been made in goat embryo production and transfer technology. The Korean native black goat is the most useful domestic ruminant in this country for biological investigation and application because it has a lot of merits such as relatively short generation period(1 vs 2 year for a cow), easy of handling, well adaptation, high fertility, convenient and inexpensive. This article covers the methods of superovulation, estrus synchronization, embryo collection and transfer techniques, pregnancy diagnosis and subsequent pregnancy and kidding rates for the production of transgenic Korean native black goats. More than one hundred goat kids have been produced as a result of our transgenic goat project via microinjection of foreign gene into pronuclei, in vitro culture, transfer of various stages of fresh and frozen-thawed microinjected embryos into oviducts or uteri of recipient does. We have got two transgenic goats carrying a transgene targeting the expression of recombinant human granulocyte colony stimulating factor(hG-CSF) to the mammary gland so far. Since collection and transfer of embryos in this species is usually accomplished by laparotomy, exteriorization of the reproductive tract for surgical embryo collection leads to the formation of post-operative adhesions. Nonsurgical or laparoscopic technique to reduce adhesions from repeated surgeries has great advantages in improving embryo production and transfer especially from valuable donors. We will discuss this later.

• Korean Journal of Veterinary Research
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• v.30 no.2
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• pp.243-247
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• 1990

A study was conducted to improve the reproductive performance of Korean native cows. Plasma progesterone concentrations were determined by radioimmunoassay during the estrous cycle and early pregnancy. Plasma progesterone concentrations during the estrous cycle in the 15 cows were the lowest (0.30ng/ml) at estrus, gradually increased after 6 days, remained high from 8 to 17 days (3.87~5.59ng/ml) and drastically decreased thereafter to reach minimal concentrations at the next estrus. Plasma progesterone concentrations of the 10 pregnant cows at 20 days after insemination were $5.82{\pm}1.33ng/ml$ (mean${\pm}$SD) and those of 10 non-pregnant cows were $0.30{\pm}0.21ng/ml$, respectively. Therefore, plasma progesterone concentrations in the pregnant cows at 20 days after insemination were significantly higher than in non-pregnant cows (p<0.001).

• Journal of Embryo Transfer
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• v.12 no.2
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• pp.203-209
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• 1997

This study was carried out to compare the actual size(length and height) of ovaries, follicles and corpora lutea of Korean native cow with those on sonograms. We used 3 different probes(3.5 MHz abdominal probe, 6.5 MHz transvaginal probe and 5.0 MHz transrectal probe) and a calipher for measurements of ovaries, follicles and corpora lutea on sonograms and actual size. Under water immersion, 157 ovaries were scanned with 3 probes and measured in actual size and compared each other. The average height and width of ovaries of Korean native cows were 17.40$\pm$3.99 and 34.23$\pm$6.02mm, respectively. In comparison of height, length of ovaries and preovulation follicles, we found that image with a transvaginal probe was nearly the same as the actual size(p<0.01), but with an abdominal probe the image was appeared larger than the actual size. In measurement(diameter) of preovulation follicles the transvaginal probe was proven to be more accurate to the actual size than other probes and in corpus luteum measurement all probes were accurate. In the comparison of number of follicles by different size ranges, there was no statistical difference in the count of follicles over 10 mm in diameter between the transvaginal probe and naked eyes.

• Journal of Veterinary Clinics
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• v.21 no.3
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• pp.280-285
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• 2004

Pathological and bacteriological studies were made of a total of 111 udders from slaughtered Korean native cows originating from various locations in Chonnam province. Incidence of supernumerary teats was 8.1%. Gross lesions were found in 21.4% of mucous membranes of total teat cisterns; these lesions comprised epithelial hyperplasia (12.6%), congestion (4.1%), slight fibrosis (3.8%) and severe fibrosis with congestion (0.9%). Gross lesions in the glandular tissues were found in 35.1% of cows; these lesions comprised slight fibrosis (27.9%), moderate fibrosis (6.3%) and severe fibrosis with pus (0.9%). Mastitis was found only in one cow. One hundred and twenty-five strains of microorganisms were isolated from mammary gland fragments of the cows. Pathogens most commonly isolated were Staphylococcus spp.; most of them were minor mammary pathogens. Major mammary pathogens were Streptococcus spp. (9.6%) and E. coli (2.4%). Most of the isolates were susceptible to many of 13 antimicrobial agents used, but Streptococcus spp. and Gram-negative rods showed resistance to 7 and 8 agents, respectively. 97.5% of the isolates showed susceptibility to amoxicillin, but only 55.8% to erythromycin.

• Journal of Animal Science and Technology
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• v.65 no.4
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• pp.748-758
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• 2023

This study was conducted to investigate the change in activity and mounting behavior in Hanwoo (Korean Native Cattle) during the peri-estrus period and its application to estrus detection. A total of 20 Hanwoo cows were fitted with a neck-collar accelerometer device, which measured the location and acceleration of cow movements and recorded the number of instances of mounting behavior by the altitude data. The data were analyzed in three periods (24-, 6-, and 2-h periods). Blood samples were collected for 5 days after the prostaglandin F2α (PGF2α) injection, and the concentrations of estradiol, progesterone, follicle-stimulating hormone, and luteinizing hormone were determined by enzyme-linked immunosorbent assays. Activity and mounting behavior recorded over 2-h periods significantly increased as estrus approached and were more efficient at detecting estrus than over 24- and 6-h periods (p < 0.05). Endocrine patterns did not differ with the variation of individual cows during the peri-estrus period (p > 0.05). Activity was selected as the best predictor through stepwise discriminant analysis. However, activity alone is not enough to detect estrus. We suggest that a combination of activity and mounting behavior may improve estrus detection efficiency in Hanwoo. Further research is necessary to validate the findings on a larger sample size.

• Reproductive and Developmental Biology
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• v.29 no.1
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• pp.37-41
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• 2005

The aim of this study was to improve efficiency and quality of the production of Korean Native Cow embryos. We examined effects of ovarian morphology and maturation vessel on the development and cell number of blastocysts. The development rates to the 2-cell embryos from oocytes collected from the ovaries of different morphological statues were similar ranging between 70.3 and 84.1%. The development rate to the 8 cell- and blastocyst-stage embryos was the highest in the group without both corpus luteum (CL) and follicle. The inner cell mass (ICM), trophectoderm (TE) and total cell number (TCN) were significantly higher in the groups of follicular cyst and regressive CL than other treatment groups, and the same pattern was observed in the ICM/TCN ratio. The development rate to the 2-cell stage was significantly higher in 0.5-㎖ straw group than 0.25-㎖ straw group. However, the development rates to the blastocyst stage were similar between the dish and the straw group. There were no differences in the number of ICM and TE cells, TCN and ICM/TCN ratio of blastocysts from oocytes matured in the different vessels.

• Journal of Embryo Transfer
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• v.20 no.1
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• pp.17-24
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• 2005

This study was conducted to investigate the effects of various factors of recipients such as recipient parity, body condition score(BCS), estrus type, corpus luteum, uterine size and uterine horn, on pregnancy and abortion after transfer of in vitro produced Korean Native Cow embryos. The pregnancy rate of nulliparous $(43.5\%)$was significantly higher than that of multiparous $(33.6\%)$, but there were no difference in the abortion rates $(122.6\;vs.\;7.5\%)$. There were no difference in pregnancy among the groups of BCS treatment, but the abortion rate was significantly higher in the group of below BCS $2.0\~3.0\;(55.6\%)$ than the group of BCS $3.0\~3.9\;(10.8\%)$. The pregnancy and abortion rates from the estrus type, corpus luteum, uterine size and uterine hem were not differ among treatment groups.