Background: Sperm quality and the number of sperm introduced into the uterus during artificial insemination (AI) are pivotal factors influencing pregnancy outcomes. However, there have been no reports on the relationship between sperm concentration at AI and sperm quality in Hanwoo cattle. In this study, we examined sperm quality and pregnancy rates after AI using sperm inseminated at different concentrations. Methods: We evaluated the motility, viability, and acrosomal membrane integrity of sperm at different concentrations (10, 15, 18, and 20 million sperm/straw) in 0.5-mL straws. Subsequently, we compared the pregnancy rates after AI with different sperm concentrations. Results: After freeze-thawing, sperm at the assessed concentrations showed similar viability and acrosomal membrane integrity. After AI, cattle in the 10 million group had significantly lower pregnancy rates compared to those in the 18 and 20 million groups. Conversely, there were no statistically significant variances observed between cattle in the 10 and 15 million groups. Conclusions: Sperm at concentrations of 10, 15, 18 and 20 million per straw exhibited comparable motility, viability, and acrosomal membrane integrity. However, a concentration of at least 18 million sperm per straw is required to achieve a consistent rate of pregnancy rate in Hanwoo cattle after AI.

This study divided the area capable of producing domestic forage into grazing pasture, hay production area, and silage crop area, calculated the required area according to the forage production volume, and examined whether self-sufficiency in forage leads to cost savings. When the self-sufficiency rate of forage for dairy cows and Hanwoo is 80%, the improvement in profitability per heaf ranges from 3% to 9%, typically around 5%, which is considered a significant benefit for both corporate and individual businesses. The average profit per ranch is expected to increase about KRW 50 million per year, and the country as a whole is expected to reduce forage costs by KRW 0.9 trillion per year. Recently, efforts are being made by the government and local authorities to cultivate summer forage at the rice fields for improving self-sufficiency in forage feed to stabilize rice supply and demand. Furthermore, it is also necessary to conduct research on reducing the cost of concentrated feed and TMR (Total mixed ration).

Background: Estrus in cows can be detected through vaginal electrical resistance or conductivity. However, there are no studies measuring vaginal electrical resistance in Hanwoo cows. This study aims to measure the vaginal electrical resistance value in Hanwoo cows and compare it with estrus and ovulation. Methods: Vaginal electrical resistance values of 73 Hanwoo cows were measured before and after estrus at the Gyeongsangbuk-do Livestock Research Institute. Measurements were taken on days -6, -3, -2, -1, 0, 1, 2, 3, and 6 of artificial insemination. Large follicles and ovulation were confirmed using transvaginal ultrasonography. Results: The vaginal electrical resistance averaged 225.6 ± 6.3 Ω days before the artificial insemination date, decreasing until the day of artificial insemination. The average vaginal electrical resistance was 163.7 ± 4.6 Ω on the date of artificial insemination, and 188.8 ± 4.3 Ω one day after artificial insemination, when large follicles were observed. In addition, on the 6th day after artificial insemination, the vaginal electrical resistance averaged 231.4 ± 5.5, which was similar to the 6th day before artificial insemination (222.5 ± 6.3). Transvaginal ultrasonography showed that most of the cows ovulated one day after artificial insemination. Conclusions: The accuracy of estrus is high if the vaginal electrical resistance is measured for cows with confirmed estrus, making is a potentially useful for determining the timing of artificial insemination.

This study was conducted to investigate the effect of dietary total mixed ration (TMR) supplementation and dry-aging period on the physico-chemical and sensory quality of striploin (longissimus lumborum) from multiparous Hanwoo cows. The experimental cows were divided into two treatments (n=3/treatment) according to the type of feed: in one treatment (slaughter age: 87±6 months old, parity: 5±1) the cows were fed on TMR for 7 months before slaughter, while in the other treatment (slaughter age: 83±9 months old, parity: 5±2) the cows were fed on concentrate and rice straw (CRS) for the whole rearing period. After slaughtering, the striploins were dry-aged for 20 or 40 days at 2±1℃, 85% relative humidity and 2 m/sec air flow velocity and then utilized for quality measurements. The pH value, cooking loss, and hypoxanthine content were higher (p<0.05) for the striploins dry-aged for 40 days than for those dry-aged for 20 days. Notably, the inosine 5’-monophosphate content was decreased (p<0.05) by increasing the dry-aging time. With regard to microbiological quality, the striploins dry-aged for 40 days exhibited lower (p<0.05) lactic acid bacteria counts and higher (p<0.05) coliform counts than those dry-aged for 20 days. Moreover, the tenderness and overall liking scores based on sensory evaluation were higher (p<0.05) for the dry-aged striploins of the TMR treatment and those dry-aged for 40 days than for the CRS treatment and those dry-aged 20 days, respectively. These findings suggest that dietary TMR supplementation leads to an increase in the sensory preference of dry-aged striploins from multiparous Hanwoo cows, and alteration of the CRS into the TMR may improve the quality of dry-aged Hanwoo beef.

These studies were conducted to evaluate developmental competence of follicular oocyte collected from the ovaries of Hanwoo cows with the high offspring meat quality (1++ and 1+ grade). Cumulus oocyte complexes from individual cows were matured, fertilized and cultured using protocols of in-vitro maturation (IVM), in-vitro fertilization (IVF) and in-vitro culture (IVC). The rates of blastocyst development from Hanwoo cows with the offspring meat quality grades of 1++ and 1+ were 18.6 and 21.2%, respectively. The rates of blastocyst development were 26.3, 20.7, 20.7, 17.2 and 31.2% from Hanwoo cows with the meat quality grades of 1++, 1+, 1, 2 and 3, respectively. Fiftyseven transferable embryos were recovered from 11 Hanwoo donor cows (5.2/head) with the high offspring meat quality grades of 1++ and 1+ in vivo, and the pregnancy rate after embryo transfer was 61.1%. In conclusion, these results suggest that in vitro embryo production from the ovaries of cows with the high meat quality grades using individual culture system can be used an efficient method for livestock improvement. In addition, for the successful industrialization of embryo transfer, conception rate should be improved.

본 연구는 체성숙이 완료된 15개월령 이상의 한우 암소로부터 초음파 측정 장치를 활용하여 조사된 등지방두께(UBF), 배장근단면적(UEMA), 근내지방도(UMS)의 형질들에 대한 유전능력을 추정하기 위한 통계분석방법을 도출하기 위한 연구로써 신체충실지수 및 월령에 대한 사전 보정의 효율성을 알아보고 유전평가를 위한 형질별 유전모수를 추정함으로써 유전능력 추정의 효율성을 향상하기 위한 방안을 도 출하고자 실시하였다. 분석에 이용된 자료는 2001년부터 전국의 1,004농가에서 사육중인 15개월령 이 상의 한우 암소 38,663두로부터 조사된 초음파 측정 육질관련 형질들에 대하여 조사된 자료를 이용하였다. 흉위 및 도축형질들에 대한 성장곡선함수식을 추정하기 위하여 농가-년-월(HYM) 및 신체충실지 수(BCS)에 대한 통계모형식을 통하여 사전보정을 실시하고 Von Bertalanfy함수식을 이용한 비선형 성장곡선 함수식을 추정하였다. 또한 도축형질들에 대하여 개체별로 조사된 관측치는 성장곡선 함수식에 대한 편차로 자료변환한 후에 유전모수를 추정한 결과, 각 형질별 유전력은 UBF에서 0.29, UEMA는 0.56 및 UMS에서 0.49의 추정치를 보였다.

본 연구는 우리나라 일반 농가에서 사육중인 한우 암소 348두의 도체중, 등심단면적, 등지방두께 및 근내지방도에 대하여 EBV(Estimated Breeding Value) 및 GEBV(Genomic Estimated Breeding Value)의 정확도를 비교하였다. EBV 분석은 한우 암소 348두의 혈통정보와 농협경제지주 한우개량사 업소의 당대검정우 및 후대검정우의 혈통정보 및 표현형정보를 이용하여 혈연계수행렬(Numeric Relation Matrix, NRM)을 구축하여 BLUP(Best Linear Unbiased Prediction) 방법으로 분석하였다. GEBV 분석은 표현형정보와 유전체정보가 있는 후대검정우 3,820두를 참조집단으로 이용하여 한우 암소 348두의 SNP 50K 정보와 유전체 혈연 행렬(Genetic Relationship Matrix, GRM)을 구축하여 GBLUP(Genomic Best Linear Unbiased Prediction) 방법으로 분석하였다. 그 결과, 한우 암소 348두 에 대한 EBV 및 GEBV의 정확도 차이는 도체중, 등심단면적, 등지방두께 및 근내지방도에서 GEBV의 정확도가 각각 22.90%, 11.14%, 12.28% 및 8.69% 증가됨을 보였다. 이러한 결과는 유전체 선발 시 육종가 추정의 정확도 증가를 볼 수 있을 것으로 기대되며, 이는 유전체선발을 위한 기초자료로써 활용될 수 있을 것으로 판단된다.

본 연구는 부모의 혈통정보를 모두 아는 혈통 및 고등등록우로 등록된 한우 암소 25,516두의 선형 및 외모심사형질에 대해 유전모수를 추정하였다. 각 심사형질에 영향을 주는 것으로 판단되는 주요인을 선 정하여 다형질 개체모형에 적용하여 EM-REML 알고리즘 분석방법을 통해 각 형질에 대한 유전력과 유 전상관과 표현형상관을 추정하였다. 한우 암소의 17개 선형심사형질 및 10개 외모심사형질(종합점수 포 함)의 유전력 추정치의 범위는 0.03(유두배열)에서 0.42(체장)까지로 추정되었다. 체고, 체장, 강건성, 체심, 윤곽성, 정강이두께, 피모의 색, 엉덩이기울기, 고장, 좌골폭, 넓적다리의 두께, 유방용적, 유두길 이, 유두배열, 발굽기울기, 뒷다리 비절기울기, 뒤에서 본 뒷다리자세, 체적․균형, 자질․품위, 머리․목, 전구, 중구, 엉덩이, 넓적다리, 유기, 지제보양 및 종합점수의 유전력은 각각 0.4, 0.42, 0.27, 0.25, 0.06, 0.14, 0.22, 0.31, 0.19, 0.17, 0.29, 0.04, 0.07, 0.02, 0.11, 0.03, 0.16, 0.27, 0.08, 0.15, 0.14, 0.14, 0.19, 0.16, 0.05, 0.08 및 0.3으로 추정되었다. 한편, 다형질개체모형에 의해 추정된 17개 선형심사형질과 종합점수에 대한 유전상관추정 결과는 다음과 같다. 고장과 좌골폭간에 0.96의 가장 강 한 양(+)의 유전적 관계를 나타내었다. 반면 발굽기울기와 뒷다리 비절기울기간에는 -0.57의 가장 큰 음(-)의 유전상관을 보였다. 전체외모 형질인 체고, 체장, 간겅성 및 체심은 각 형질간에, 그리고 기타 형 질들과 강한 양(+)의 유전상관관계를 나타내었다. 특히 체고 및 체심과 고장 및 좌골폭간에 높은 양(+)의 상관관계를 나타내었으며, 체고와 엉덩이기울기간에는 0.32의 양(+)의 상관을 나타내었다.

Commercial applications of OPU/IVP were to produce embryos and calves from high genetic cows.The aim of this present study was to compare the number of recovered oocytes and cultured in vitro produced embryos from Ovum Pick-up (OPU). OPU derived embryo production was carried out of oocytes by ultrasonographic guided follicular aspiration and then produced in vitro produced blastocysts by IVP culture system. In result, the rate of recovered oocytes was obtained 612 (57.2%) and 451(73.7) G1+G2 grade oocytes. No difference of recovered rate (51.1~62.1%) was seen in six donor. The rate of cleavage and blastocyst development were obtained 320 (70.9%) and 78 (24.4%) that was 3.3±0.4 cleaved embryo and 0.9±0.2 blastocysts per session. Cleavage rate of OPU oocytes in No. 6 donor was 90.6%, significantly (P<0.05) higher than that in the other donors, However, blastocysts was similar (25.8~30.0%). In conclusion, limited numbers of OPU oocytes had competent development when cultured in SOF culture medium

본 시험은 성 성숙기의 한우 암송아지 18두(14개월령, 평균체중 251kg)를 이용하여 저 수준의 농후사 료 급여에 따른 성장과 번식능력에 미치는 영향을 규명하기 위하여 실시하였다. 공시축은 시판 한우 번 식우용 배합사료를 체중의 0.8%(T1) 및 1.2%(T2)씩 총 30개월(사양시험 20개월, 번식능력시험 10개월) 동안 섭취하였으며, 처리구당 9두를 2우리에 완전임의 배치를 하였다. 본 시험의 사양시험 결과를 한국 가축사양표준의 영양소 요구량과 비교해 볼 때, T1구에서 성장이 제대로 되지 못한 이유는 에너지 보다 는 단백질 섭취부족 때문인 것으로 나타났다. 공시축의 체형변화에서 저 영양수준으로 인하여 영향을 가장 많이 받는 부위는 흉폭과 체장이었으며 특히, 흉폭은 시험시작시보다도 종료시 측정치가 오히려 3.7% 작았다. 난소의 크기는 T1구가 T2구의 약 63%수준밖에 되지 않았으며, 수태율(33.3% : 77.8%)과 송아지의 생시체중(22.5kg : 29.5kg)도 T1구에서 심각하게 저하되었다. 따라서 한우번식우 사양에 있 어서 성성숙기 이후에도 에너지보다는 단백질 공급수준에 의해 사양성적 및 번식능력에 많은 영향을 끼 치는 것으로 나타났다.

The aim of this study was to compare ultrasonic measured traits (Eye muscle area : EMA, backfat thickness : BF and marbling score : MS) of Hanwoo cows by months of age and periods around 1st calving. The data used in this study were taken 2,636 cows which were measured from 20 months old to 28 months old and within 5 months around 1st calving. According to comparison of cows' month of age, ultrasonic measured EMA, BF and MS were not significantly different between 21 months old and 26 months old, 21 months old and 25 months old and 23 months old and 27 months old, respectively. According to comparison of periods around 1st calving, ultrasonic measured EMA, BF and MS were not significantly different between -45 days and 30 days, -15 days and 75 days, -105 days and 90 days around 1st calving, respectively. The selection of cows could be possible based on the phenotypic ultrasonic measurement performance if the traits are measured between 23-month old and 25-month old and between - 15 days and 30 days around 1st calving.

The major limiting factor of the reproductive performance on many farms is the failure to detect estrus in a timely and accurate manner. The estrus detection for Hanwoo cows (Bos taurus coreanea) is generally performed by the visual observation which is estimated at about 40% detection rate only. This recurring problem among farmers has motivated the development of various estrus detection aids. The mounting event duration threshold, standing heat event frequency threshold, estrus detection algorithm and so on, are necessarily needed in order to detect the estrus of Hanwoo cows accurately when using some automatic devices. However, they are not yet investigated for Hanwoo cows. Therefore, the objective of this study was to establish a mounting event duration threshold and standing heat event frequency threshold more specifically for Hanwoo breed by discriminating the duration of standing heat mounting from shorter duration spurious mountings which routinely occur in cattle herds. One hundred and fifty Hanwoo cows with an age between 2 to 5 years were used in this study. Cows that were expected to come into estrus within 3days were randomly assigned to each compartment for the estrus group (EG). The heated cows were video recorded for about 24 hours until after post estrus. The results showed that Hanwoo cows can be considered on estrus when it stand immobile during mounted by any other cow in more than or equal to 3.15s and 3.22s in chest-tail head mount (CTM) and head-above back mount (HBM) and that occurs consecutively at least three times within 876.4s interval. The algorithm was also developed using the thresholds of the mount duration, mount interval and consecutive occurrence number.

본 연구는 다양한 사료들을 유지수준에서 섭취한 한우 암소 경산우의 에너지 대사 시험의 결과로 부터 섭취에너지 균형과 메탄배출계수를 구하였다. 오차드그라스(orchard grass) 위주의 혼합목건초 섭취 7두, 혼합목건초의 30~50% 를 볏짚으로 대체한 12두, 혼합목건초와 볏짚에 밀기울 (wheat bran) 1 kg 추가급여한 6두, 총 25 개체의 대사실험 성적을 분석하였다. 실험축은 10일간 대사틀에서 개체별로 각각의 실험사료 적응 및 7일간 분 뇨 시료채취 후, indirect respiratory chamber 1대에 교대로 수용되어 1일간 호흡대사 실험이 이루어졌다. 혼합목건초 단독 급여구와 비교하여 나머지 두 처리구의 평균 건물섭취량은 약 11%, 15% 높았으나 통계적인 유의성은 없었고, gross energy (GE) 섭취량도 차이가 없었다. 총 섭취에너지 중 메탄으로 손실된 에너지 비율인 메탄전변율(methane conversion rate, Ym)과 메탄배출계수(emission factor, kg/head/year)도 각각 0.055~0.062 (평균 0.058)와 33.6~38.6(평균 35.2) 범위로 처리간 유의성이 없었다. 본 실험에서는 혼합목건초를 볏짚으로 대체하거나 또는 밀기울 추가급여에 의한 메탄발생량 차이가 없었으나, 메탄발생량을 줄일 수 있는 것으로 알려진 양질 조사료 급여효과 연구는 축산현장의 온실가스 감축 사업 참여가 가능한 분야이기 때문에 추가 연구들을 통해 시급히 증명되어져야 된다고 판단된다.

본 연구에서 한우를 공란우로 사용하여 OPU 방법으로 가장 더운 계절의 hot season과 선선한 cool season의 두 계절의 차이에 따른 생성된 난포의 수, 난자 회수율, 난자 등급율, 수정율 및 배반포 발달 능력을 분석하여, 두 계절이 공란우의 번식 능력에 미치는 영향에 관하여 조사하였다. 1. 계절의 영향이 OPU 공란우의 난포 생성 수에 미치는 결과는 난포 생성 개수는 1154개(18.32±2.26), 971개(15.41±3.34)로 hot season 그룹이 유의적으로 높은 것을 알 수 있었다(p＜0.05). 2. 계절에 따른 난자 수 및 난자 회수율은 hot season 그룹의 475개(7.54±3.14), 41.16%로 cool season 그룹 448개(7.11±3.42), 46.14%와 비교하여 유의적인 차이가 없었다(p＜0.05). 3. OPU를 통하여 회수된 두 계절별 난자 등급은 Grade A는 Hot season 그룹 110개(1.75±1.86), Cool season 그룹 63개(1.00±1.46)로 hot season 그룹이 cool season 그룹과 비교하여 유의적으로 높았다(p＜0.05). 하지만 다른 등급인 Grade B는 87개(1.38±1.60) vs. 97개(1.54±1.39), Grade C는 166개(2.63±2.43) vs. 170개(2.70±2.04), Grade D는 112개(1.78±2.65) vs. 118개(1.87±1.86)로 hot season과 cool season 간의 유의적인 차이를 보이지 않았다(p＜0.05). 4. 계절에 따른 체외 수정 후의 수정률은 hot season과 cool season 각각 242(66.67%)와 209(63.3%), 배반포 발달율 214(58.95%) vs. 188(56.97%)로 수정률과 배반포 발달율은 유의적인 차이가 없었다(p＜0.05). 본 연구의 결과로 계절에 따른 영향에 의해 공란우의 난포생성수와 A등급의 난자 출현율에서 유의적인 차이를 보였다. 하지만 나머지 등급의 난자 출현율, 수정률 및 배반포 발달율은 차이가 없는 것으로 보아, 계절의 차이로 인한 한우 공란우의 번식 능력에 미치는 영향은 미비하다고 판단된다.

본 연구는 한우암소검정사업을 통하여 수집된 자료를 이용하여 한우 집단의 근교계수 및 혈통구조를 분석함으로써 한우 집단의 유전적 다양성 정도를 알아보고자 실시하였다. 한우 암소 데이터는 9개 도에서 2000년부터 2012년에 출생한 228,177두에 대한 정보 및 이들과 혈연관계가 있는 440,429두에 대한 혈통정보를 이용하여 분석하였다. 각 지역별 평균 근교계수는 강원도 0.63%, 경기도 0.46%, 경상남도 0.49%, 경상북도 0.48%, 전라남도 0.71%, 전라북도 0.51%, 충청남도 0.40%, 충청북도 0.61%, 제주도 0.55%로 나타났으며, 선조 3세대까지의 조상을 알고 있는 개체의 비율은 동일한 지역에서 각각 80.0%, 79.3%, 75.5%, 76.8%, 77.3%, 71.6%, 75.4%, 79.3% 및 73.3%였다. 또한 아비에서 딸소까지 평균 세대간격은 7.63년으로 나타났으며, 어미에서 딸소까지 평균세대간격은 4.11년으로 나타났다. 근교계수 및 세대간격의 정보를 이용하여 유효집단의 크기를 추정한 결과 2000년생부터 2005년생까지가 215두, 2006년생부터 2010년생까지가 140두, 2011년생부터 2012년생까지가 77두로 추정되어 시간이 지남에 따라 유효집단의 크기가 감소는 것으로 추정되었다. 따라서 한우 집단의 근교율을 감소시키면서 유전적 개량량을 극대화 할 수 있는 한우 암소 맞춤형 교배 전략 및 모니터링 시스템이 필요할 것으로 사료된다.

The objectives of this study were to estimate genetic parameters for 10 linear conformation traits and final score in Hanwoo cows. A total of 53,277 records for type traits of Hanwoo cows were collected from 2008 to 2012 from Korea Animal Improvement Association. Ten linear traits studied were stature, body length, chest depth, body rump angle, rump length, pin bone width, udder volume, foot angle, rear legs side view, and rear legs rear view. The model included the fixed effects of herd-year-classifier, age at measurement and age after calving, the random animal additive genetic effect and residual effect. Heritability estimates for linear type traits were ranged from 0.003 for rear legs side view to 0.213 for final score. Genetic correlations among linear type traits were ranged from -0.068 (for rear legs side view and rear legs rear view) to 0.982 (for body length and rump length). The final score was found to be in a strongest genetic correlation with rear legs rear view (0.947), followed by pin bone width (0.918), body length (0.887), rump length (0.883), chest depth (0.883), udder volume (0.811), stature (0.802), rump angle (0.637), foot angle (0.519) and rear legs side view (0.176). Corresponding phenotypic correlations for pairs of linear type traits were mostly similar in direction, but smaller than the genetic correlations.

s study was carried out between November 2008 and October 2009 in the experimental farm of Chunnam National University to investigate the effect of feeding of Sudangrass silage on the reproductive performance of Hanwoo cows. Two diets, rice straw or Sudangrass silage separately from concentrate were fed 19 Hanwoo cows. In control group (=CON), cows (n=9) were fed 5 kg (/head) rice straw and 3 kg (/head) commercial diet. In Sudangrass silage group (=SGS), cows (n=10) were fed 12.5 kg (/head) Sudangrass silage and 1 kg (/head) commercial diet. 1. Days to post-partum insemination were 78.8±25.3 days for CON and 84.7±24.6 days for SGS group and days to post-partum conception in CON or SGS were 90.1±24.1 and 87.7±26.8 days, respectively. 2. Post-partum conception rates for first service in CON or SGS was 66.7% and 90.0%, respectively, and caving interval was 375.1±46.7 days for CON and 370.2±34.4 days for SGS group. 3. Body Condition Scores of Hanwoo cows at artificial insemination was 5.36 for CON group and 4.93 for SGS group.

In this study, genotyping was executed by using 11 microsatellite markers (BM1824, BM2113, ETH10, ETH225, ETH3, INRA23, SPS115, TGLA122, TGLA227, TGLA53, and TGLA126) for diversity of 214 Hanwoo cows in Hoengseong area. Each marker's size and number of allele, observed heterozygosity, expected total heterozygosity, and polymorphism information content were analyzed by 11 Microsatellite marker. The average of size range was detected from 150.9 to 174.9 in Hanwoo cows of Hoengseong. The number of average allele was 10.0 that is similar to the average of Kangwon Hanwoo, which is known as 10.5 in the previous report. The average were 0.751 for observed heterozygosity, 0.760 for expected total heterozygosity, 0.725 for polymorphism information content, respectively. These results were similar to previous studies in Kangwon Hanwoo, National Hanwoo and Korean Proven Bulls. This study is expected to contribute for genetic improvement of Hanwoo cows in Hoengseong as a popular brand.

This study was carried out between November 2007 and October 2008 in the experimental farm of Chunnam National University to investigate the effect of feeding of whole crop barley silage on the reproductive performance of Hanwoo heifers and cows. Two diets, rice straw or whole crop barley silage separately from concentrate were fed 11 Hanwoo heifers and 26 Hanwoo cows. In control group (=CON), heifers (n=6) and cows (n=13) were fed 7 kg (/head) rice straw and 4 kg (/head) commercial diet. In whole crop barley silage group (=WBG), heifers (n=5) and cows (n=13) were fed 8 kg (/head) whole crop barley silage and 1 kg (/head) commercial diet. 1. Conception rates for first service in CON or WBG heifers were 66.7% (4/6) and 60.0% (3/5), respectively, and the services per conception cows were 1.5±0.2 for CON and 1.4±0.2 for WBG group. 2. Days to post-partum insemination were 106.6±26.3 days for CON and 85.6±12.6 days for WBG group, and days to post-partum conception in CON or WBG were 128.4±27.1 and 96.8±16.8 days, respectively. 3. Post-partum conception rates for first service in CON or WBG were 76.9% (10/13) and 84.6% (11/13), respectively, and caving interval was 418.1±50.7 days for CON and 392.8±20.7 days for WBG group.

This study was performed to investigate the result that in-vivo or in-vitro embryos of Hanwoo cows were transferred to Holstein cows. Seventeen Hanwoo cows were used as donors for production of in-vivo embryos and fresh hanwoo in-vivo embryos were transferred to 1,150 Holsteins. And 2 embryos were transferred to 188 Holstein recipients to produce twin calves. Diagnosis on pregnancy was performed by rectal palpation at days after transfer. The pregnancy rate of Holstein recipients was 55.8% after transfer with Hanwoo in-vivo embryos and 38.2% after transfer with Hanwoo in-vitro embryos. The delivery rate of pregnant Holstein recipients was 88.4% after transfer with Hanwoo in-vivo embryos and 75.6% after transfer with Hanwoo in-vitro embryos. The rate of delivery of Holstein recipients transferred with two Hanwoo embryos was 36.2% and the rate of twin production was 25.9%. The rate of twin production by embryo transfer with in-vivo embryos was 30.4%, whereas the fate with in-vitro embryos was 15.6%. The pregnancy rate according to the grade of corpus luteum of Holstein recipients transferred with Hanwoo in-vitro embryos was 41.5 and 36.0% for A and B grade, respectively. The pregnancy rate according to the transfer in site in the uterine lumen of recipients was 40.9 and 32.7% for anterior and middle site, respectively. The pregnancy rate according to day of embryo transfer after estrus of recipients was 45.5, 38.8 and 39.7% for day 6, day 7 and day 8, respectively. There was difference of pregnancy rate according embryo transfer technician () individual dairy farm (). These results are supposed to indicate that the rate of pregnancy after transfer with Hanwoo embryos to Holstein recipients was similar to that within the same breed, and consequently that this method would be beneficial to enhance the productivity in Hanwoo reproduction.