본 연구는 2019년부터 2021년 9월까지 수집된 홀스타인 젖소 19,930두의 자료를 수집하였으며, 3 SD (Standard Deviation, SD) 범위에서 벗어나는 이상치를 제외한, 8,675두를 분석에 이용하였다. 자료분석은 Statistical Analysis System (SAS) 9.4 software를 사용하였고, 뒷유방높이, 뒷유방너비, 유방깊이, 유두길이 및 유두둘레의 실측치를 사용하였다. 그리고 뒷유방높이, 뒷유방너비, 유방깊이, 유두길이 및 유두둘레의 실측치와 산차, 305일 유량, 비유단계 및 착유속도의 환경요인의 효과를 추정하였다. 산차와 유량이 증가함에 따라 뒷유방너비, 유두길이 및 유두둘레의 실측치는 유의적으로 증가하는 것으로 나타났으며(p < 0.0001), 비유단계에 따라서 뒷유방너비 및 유방깊이의 실측치는 비유단계가 증가할수록 유의적으로 감소하는 것으로 나타났다(p < 0.0001). 각 환경효과에 따른 유방형질 실측치의 표현형 상관의 결과에서는 뒷유방너비와 유방깊이 실측치가 산차 및 유량수준에 대해 높은 상관을 나타냈으며, 특히, 유방형질 중 유방깊이 실측치와 산차에 대해 -0.40 ~ -0.67로 높은 음(-)의 상관을 보였다. 본 연구 결과로 미루어 볼 때, 유방형질이 유생산에 밀접한 관련이 있는 만큼 중요한 형질로 취급되어야 하며, 이들의 기초연구와 함께 유전적 특성을 구명하는 등 더 많은 연구가 수행되어야 할 것으로 사료된다.

This study attempted to determine the characteristic features of postpartum dairy cows during their return to estrus. Moreover, it investigated the effects of abnormal ovarian cycles (AOC) on subsequent reproductive performance and the relationship between normal ovarian cycles (NOC) and the blood urea nitrogen (BUN) level postpartum. Incidentally, 56.3% of the Holstein cows and 66.7% of the Jersey cows had NOC, whereas the 43.7% and 33.3% of the Holstein and Jersey, respectively, had AOC. Within 100 days of calving, the cows with AOC had significantly lower rates of artificial insemination (AI) submission as well as pregnancy and a significantly longer interval to first AI, as compared to that in the cows with NOC. Additionally, the cows with NOC had a significantly higher first AI conception rate than that in the cows with AOC. In this study, of the 32 Holstein cows, 8 resumed their ovarian cycle within 20 days of calving, 10 resumed the cycle with 21-40 days of calving, 8 within 41-60 days of calving, while the remaining 6 did not resume their ovarian cycles until 60 days postpartum. Furthermore, the likelihood ratios of incidence of NOC are 0.93, 1.94, and 0.38, respectively, in the groups with BUN levels ＜ 15, 15-19.9, and ≥ 20 mg/ dl. In conclusion, AOC postpartum adversely affects reproductive performance such as AI submission rate, pregnancy rate, interval to first AI and first AI conception rate; moreover, an increase or decrease in the BUN levels beyond 15-19.9 mg/dL leads to the AOC postpartum.

In this study the effect of vitamin C administration on pregnancy rates during summer heat stress in dairy cows was examined. A total of 80 Holstein-Friesian cows were divided into control and treatment groups (n = 40 each). Control group animals were given 10 mL isotonic normal saline, and treatment group, Vitamin C (4 mg/kg) on artificial insemination day (day 0) and 4th, 8th and 12th day post insemination. Pregnancy diagnosis was performed on 30th day post insemination by ultrasonography. Blood samples were randomly taken from 11 animals from each group. Serum P4, GSH, MDA and plasma 8-OHdG levels were determined by using ELISA method. Results showed that 8-OHdG levels were lower in treatment group on day 4, 8 and 12 (p < 0.05) compared with the control group. Similarly, pregnancy rate was higher in treatment group (32.5%) than control (22.5%), respectively. However, MDA, P4 and GSH levels were similar in both groups at 4th, 8th and 12th day. A gradual increase in P4, and MDA levels, and a strong positive correlation between 0, 4th (r = 0.54), 4, 8th (r = 0.59) and 8, 12th (r = 0.51) day was found. Similarly, GSH levels also showed positive correlation at days 0, 4th (r = 0.47) and 4, 8th (r = 0.56). However, a strong negative correlation (r = -0.56) between MDA day 0, and GSH day 8 was found. In conclusion, vitamin C application during insemination period in postpartum cows increases pregnancy rate, and reduces oxidative stress metabolite 8-OHdG levels.

A pregnancy diagnosis is an important standard for control of livestock’s reproduction in paricular dairy cattle. High reproductive performance in dairy animals is a essential condition to realize of high life-time production. Pregnancy diagnosis is crucial to shortening the calving interval by enabling the farmer to identify open animals so as to treat or re-breed them at the earliest opportunity. MicroRNAs are short RNA molecules which are critically involved in regulating gene expression during both health and disease. This study is sought to establish the feasible of circulating miRNAs as biomarkers of early pregnancy in cattle. We applied Illumina small-RNA sequencing to profile miRNAs in plasma samples collected from 12 non-pregnant cows (“open” cows: samples were collected before insemination (non-pregnant state) and after pregnancy check at the indicated time points) on weeks 0, 4, 8, 12 and 16. Using small RNA sequencing we identified a total of 115 miRNAs that were differentially expressed weeks 16 relative to non-pregnancy (“open” cows). Weeks 8, 12 and 16 of pregnancy commonly showed a distinct increase in circulating levels of miR-221 and miR-320a. Through genome-wide analyses we have successfully profiled plasma miRNA populations associated with pregnancy in cattle. Their application in the field of reproductive biology has opened up opportunities for research communities to look for pregnancy biomarker molecules in dairy cattle.

The milk fever and mastitis that occur during the colostrum period in dairy cattle cause great damage in the dairy industry by causing a rapid decline in the cattle’s health and decreasing milk production. In order to prevent this, gradual milking (GM), calcium injection with gradual milking (CG), and calcium injection with complete milking (CC) methods are used. However, differences in effectiveness between these methods have not been established. Therefore, this study was conducted to determine the effects of each preventive method on milk fever and mastitis. The results of this study showed that while there was a significant negative correlation of GM with milk fever and mastitis (r = –0.657, p < 0.05), there was no correlation of CG and CC with milk fever and mastitis. The incidence of milk fever was significantly lower in CG and CC than in GM (p < 0.05) but no differences in the incidence of mastitis were observed between the three groups. No significant differences in the rate of recovery from milk fever and mastitis were observed between the three groups. The recurrence rate of milk fever was significantly higher in CG and CC than in GM (p < 0.05), though no differences in the recurrence rate of mastitis were observed. This study showed an inverse relationship between the incidence rates of milk fever and mastitis when calcium injection was not used during the colostrum period. When calcium injections were used, the incidence of milk fever was reduced without affecting the incidence of mastitis regardless of the milking method, but the recurrence rate of milk fever was increased. The results of this study would be useful for controlling blood calcium concentrations and establishing efficient milking strategy in order to effectively prevent milk fever and mastitis in dairy cattle during the colostrum period.

Milk fever is a metabolic disease with manifestation of clinical signs due to hypocalcemia, which usually occurs within 48-72 h after delivery. However, even after a successful treatment of milk fever, recurrence of milk fever may occur, and studies on recurrent milk fever are still lacking. Accordingly, the present study was conducted for the purpose of identifying the characteristics of recurrent milk fever according to farm, season, parity, and dystocia that can cause physiological changes in the mother during peri- and postpartum periods. The analysis results showed that the incidence rate of initial and recurrent milk fever according to breeding farm was 5.7%-14.1% and 3.1%-7.2%, respectively, demonstrating a positive correlation between the initial and recurrent milk fever (r = 0.613, p < 0.01). With respect to season, the incidence rate of initial and recurrent milk fever during summer was 12.3% and 7.5%, respectively, which were significantly higher than that of other seasons (p < 0.05). In addition, the recurrence rate, the ratio of recurrence relative to initial milk fever, was highest during summer with 62.7%. Regarding parity, the incidence rate of initial and recurrent milk fever in 3rd parity was 11.1% and 5.8%, respectively, which was significantly higher than in 1st and 2nd parity (p < 0.05). Furthermore, the recurrence rate in 4th parity was 64.1%, showing a pattern of increase in incidence rate with increase in parity. Finally, there were no differences in the incidence rate of initial and recurrent milk fever according to eutocia and dystocia. The findings indicated that the incidence rate of initial milk fever should be reduced to effectively prevent the recurrent milk fever, while animals with 3rd parity or higher should be expected to occur high rate of recurrent milk fever, especially during summer, and the necessary preparations should be made for intensive treatment of such individuals.

Although some factors, including season, age, type of estrus (natural estrus vs. induced estrus) and semen type (conventional vs. sexed), affect the conception rate following artificial insemination (AI) in dairy cattle, there is little information about the influence of ovarian characteristics, such as preovulatory follicle (PF) location at estrus, on fertility in dairy cattle. In most breeds of cattle the right ovary appears to function more actively than the left and about sixty percent of pregnancies in dairy cattle occur in the right horn of uterus (Reece and Tuner, 1938). Our study aimed to compare conception rates in dairy cattle between PFs that developed in the left ovary and those that developed in the right ovary at estrus. In this study, we examined the locational effect (left or right ovary) of the preovulatory follicle (PF) on fertility in dairy cattle. In total, 955 artificial inseminations (AI) were analyzed. At AI, PF locations were examined using rectal palpation, and dairy cattle were divided into two groups on their PF locations: (i) the PF located in the left ovary (L-PF); and (ii) the PF located in the right ovary (R-PF). Pregnancy was diagnosed by rectal palpation or ultrasonographic examination 60 days after AI. The conception rate was 38.1% in all dairy cattle. Conception rate was higher in the R-PF (40.8%) than in the L-PF (33.2%). In summary, PF development in the right ovary was associated with increased conception rates in dairy cattle.

The objective of this study was to evaluate the effect of treating dairy cattle with exogenous human chorionic gonadotrophin (hCG), five (5) days post artificial insemination (AI) on serum progesterone (P4) concentration and pregnancy rate. In this experiment, five days after AI, cows were assigned randomly to two groups namely: a) treated group (67) which were administrered with 1500 IU hCG (Chorulon) and b) control group (61), which received no treatment. On day 5, 10, 15 and 20 after the artificial insemination, blood samples from a total of 8 cows (4 from each group) were collected and were analyzed for serum P4 concentration. Cows were detected for estrus according to standing heat by visual observation. Cows that were detected still in estrus after days 18-24 were re-inseminated and recorded as not pregnant (open). Pregnancy diagnosis was conducted by ultrasonographic examination and transrectal palpation of the uterus on approximately 60 days in cows that observed to be not in estrus. The conception rate in hCG treated and control groups were 52.5 and 36.1%, respectively. The results proved that there were no significant differences in conception rate between two groups (p=0.0568). However, pregnancy rates were reduced by hCG treatment. Average serum P4 concentrations did not differ between Hcg-treated and control groups on day 5 (0.377 versus 0.375 ng/ml). On day 20 serum P4 concentrations were greater in the treated group compared with the control group (3.085 versus 2.010 ng/ml). The treatment with hCG seemed to increase P4 level compared with the control. In conclusion, the results of this study showed that 1500 IU of hCG administered on 5 day post AI increased conception rate in dairy cows. This was supported by the results on serum P4 concentration which was greater in hCG treated group.

본 연구는 홀스타인 젖소 201,327두의 1산에서 5산까지의 검정기록 총 388,747개를 이용하여 유생산 형질에 대한 유전모수를 추정하고자 수행되었다. 1산차의 검정기록이 전체자료의 51.8%를 차지하였으며, 산차가 증가할수록 검정기록의 수는 현저히 감소하였다. 1산차의 유량, 유지방량과 유단백량에 대한 유전력은 각각 0.28, 0.26과 0.23으로 추정되었으며, 산차가 증가할수록 유전력은 일괄적으로 감소 하였다. 유량, 유지방량, 유단백량에서 산차간 유전상관계수의 범위는 0.83~1.00, 표현형상관계수의 범위는 0.21~0.51로 유전상관계수보다 항상 낮게 추정되었다. 연간 표현형 개량량은 유량, 유지방량과 유단백량에서 각각 121.50kg, 4.45kg과 4.65kg, 연간 유전적 개량량은 각각 13.70kg, 0.33kg과 0.36kg이었다.

Ensuring timely ovulation concerning the service is valuable. A satisfactory conception rate can be achieved by making sure that ovulation occurs within 7-18 hours after artificial insemination (AI). Delayed ovulation is one of the disturbances commonly encountered in repeat breeding animals. Although demanding research, many studies have not been conducted. Therefore, we aimed to examine the relation between ovulation confirmation and conception rate in dairy cattle. The research findings showed that the signs of true estrus were bred 12 hours after the onset of estrus by AI in cattle. Also, the performance of AI on ovulation was confirmed by the presence of fluctuant Graafian follicles through rectal palpation. From the results, we confirmed that cow encountered delayed ovulation were bred again. The Conception rate in cows with confirmed ovulation was 51.9%, while for those without confirmed ovulation were 33.3%. In conclusion, the results indicate that ovulation confirmation will likely increase conception rate.

본 조사연구는 충남 예산지역에 위치하고 있는 젖소 사 육농가 중 10개 전업 검정농가를 대상으로 2015년 1월부터 2015년 12월까지 농협중앙회 젖소개량사업소의 검정성적 을 통하여 유량 및 유조성분을 조사·분석하여 젖소농가의 경영지표 설정과 농가의 경영기술 개선을 위한 기초적 자 료를 얻고자 실시한 결과를 요약하면 다음과 같다. 평균 산유량은 33.62kg로 나타났다. 산차별로는 유의한 차이 (p<0.05)를 보였으며 1산차는 29.60kg로 가장 낮은 산유량 을 나타났으나, 2산차 이상부터 높은 산유량을 보였다. 산 유량별로도 유의한 차이를 보였으며(p<0.05), 계절별 평균 산유량은 봄에 34.51kg으로 다른 계절보다 높은 유량을 보 였다(p<0.05). 산차별의 유지율은 유의성 없이 1산에서 6산 차까지 비슷한 결과를 보였다. 산유량별 간에 유지율은 유 의한 차이(p<0.05)가 있었고, 계절별 간에는 유의한 차이 (p<0.05)를 보였는데, 겨울에 유지율 4.15%로 가장 높은 성 적을 보였으나, 여름에 3.61%로 가장 낮은 함량을 보였다. 산차별 간의 단백율은 유의한 차이 없이 평균치와 비슷한 수준을 보였다. 산유량별 간의 유단백율은 유의한 차이 (p<0.05)로 1일 30kg미만 군에서는 3.51% 높은 유단백율을 보였고, 40kg이상 군은 3.14%로 가장 낮은 함량으로 나타났다. 계절별 간의 유단백율은 가을과 겨울은 각각 3.40% 와 3.41%으로 높았으나, 봄과 여름은 각각 3.28%와 3.27% 로 낮은 수준를 보였다(p<0.05). 총고형분은 산차별 간에 1 산차가 8.92%로 가장 높은 함량를 보였으나(p<0.05), 산차 가 커질수록 감소현상을 보였다. 산유량별에 따른 총고형 분율은 1일 30 kg미만 군에서 8.92%로 높았으나, 40kg이상 군은 8.62%로 낮은 총고형분율을 나타났다(p<0.05). 계절 별 간의 총고형분율은 가을과 겨울에 각각 8.87%와 8.84% 으로 높은 함량이 었으나, 봄과 여름에는 각각 8.77%와 8.75%로 낮았다(p<0.05). 산차별간의 체세포수는 1산차가 100.75천개/ml로 가장 낮은 수를 나타냈으나, 산차가 커질 수록 체세포수는 증가현상을 보였다(p<0.05). 산유량별로 는 1일 30kg미만 군은 157.00천개/ml의 높은 체세포수로 유의한 차이를 보였으나(p<0.05), 40kg이상 군의 123.64천 개/ml로 낮은 수로 나타났다. 산유량은 유지율, 유단백율 및 총고형분율과 각각 -0.378, -0.534 및 –0.370으로 음(-)의 상관계수를 나타냈다. 유지율은 유단백율 및 총고형분율과 의 상관계수는 각각 0.600과 0.493으로 매우 높은 양(+)의 관계를 보였다. 유단백율과 총고형분율 간에는 0.833으로 양(+)의 매우 높은 상관관계를 보였다. 산유량과 유지율의 단순회귀모형은 y=-0.0297x+4.907(R2=0.1426), 유지율과 유 단백율은 y=0.2824x+2.2482(R2=0.3606), 유단백율과 총고형 분율은 y=0.8564x+5.9404(R2=0.6942)를 나타냈다. 따라서 젖소의 산유량과 유성분은 계절적 요인, 그리고 체세포수 는 산차와 산유능력에 영향을 받는 것으로 나타나 적절한 젖소의 산유량과 유질개선에 각별한 관리가 요구된다.

High reproductive efficiency is a prerequisite for dairy animals in order to optimize dairy production. An accurate and early pregnancy diagnosis is a crucial aspect for better reproductive management in livestock. The indigenous, visual and clinical methods have various limitations including accuracy, sensitivity, specificity, later stages of applicability and requires highly skilled manpower. This hurdles the researchers to ensue further research on developing novel early pregnancy diagnostics for dairy animals. However, the advantage of molecular techniques like proteomics has given a new hope to look for pregnancy biomarkers in animal research. In this study, we assayed the pregnancy-associated glycoprotein (PAG) levels using anti-bPAG antibody. Serum plasma samples were collected 30, 60, 90 and 120 days after insemination. Cattle diagnosed pregnant with singleton are used for this experiment in which blood samples were collected. The plasma PAG level is gradually increased after insemination to until 60 days and drastically decreased after that. The PAG level was approximately 2-fold greater during 30 days compared with 60 days. These results concluded to validate our other pregnancy diagnosis methods including circulating microRNA and cell free DNA concentration (data not shown). Despite this proteomic approach, validating all other molecular technique results may give the exact time for early pregnancy diagnosis.

The objective of this study was to identify the phenotypic relationships among calving difficulty, calf birth weight and gestation length of Holstein dairy cattle under the environment of Korea. A total of 1,834 calving records collected by Dairy Science Division of National Institute of Animal Science, RDA from 2000 to 2014 was analyzed. General linear multivariate models for calving difficulty scores (CD: 1=no assistance, 2=minor assistance, 3=two to three persons assisted, 4=more than three persons assisted, 5=cesarean section), calf body weight at birth (BW), and gestation length (GL) included fixed effects of year and season (spring, summer, autumn, winter) of births (YS), sex of calves, and parity. For GL and BW, all three fixed effects (YS, sex of calves, parity) were significant (p<0.05). For CD, the effects of YS and sex of calves were significant (p<0.05). Bull calves were born with heavier BW by 3.18 kg, with greater CD by 0.18 point and with longer GL by 0.6 days than heifer calves. The least squares mean of BW was the heaviest at the third parity (44.1 kg) compared to those at the first, the second and the fourth parities or later (41.3-41.9 kg). The least squares mean CD at the first parity was 1.74 point, which was higher than CD at the second and later parities (about 1.68 points). Phenotypic correlation (partial residual correlation) between GL and BW was 0.36. But those between GL and CD and between BW and CD were -0.03 and 0.04, almost zeros. To conclude, we observed higher incidence of calving difficulty in the first calving than in the later ones. Further investigation on the relationships between calf’s birth weight and calving difficulty is needed

genetic selection has resulted in modern dairy cow with very high milk yields but reduced fertility, due mainly to an increase in reproductive disorders. The study was conducted to estimate the proportion of reproductive disorders among dairy cattle. The factors analyzed were; milk yield, cow parity, periparturient disorders, and reproductive status. The result of this study showed the incidence of reproductive disorders in high yielding dairy cows was prevalent. Repeat breeding was the major postpartum reproductive problem comprising (42.3%) of the samples. Higher reproductive disorders were also associated with lower parity. These disorders subsequently reduced reproductive performance by prolonged intervals from calving to first artificial insemination and from calving to pregnancy. Abnormalities in the reproductive system such as repeat breeder, silent heat, anestrous and ovarian cysts, as well as lower fertility have been recorded during the summer months (June to August). In conclusion, the study revealed that incidence of repeat breeder is mostly prevalent in dairy cows. Moreover, the incidence of reproductive disorders was higher in summer season and hence appropriate preventive and or therapeutic measures as per the type of abnormalities need to be undertaken.

The occurrence of mastitis in diary cattle has been caused by genetic, physiological, managemental and environment factors accounted for the highest percentage of worldwide disease in dairy cattle. The purpose of this study was to analyze the occurrences and causative bacteria of subclinical mastitis in milking cows and also examine the distribution of bacteria in milk by isolating and identifying bacteria both in whole milk and quarter milk. 31.4% of the milking cows suffered subclinical mastitis, and 9.5% had it in terms of quarter milk. According to the results of analyzing bacteria in quarter milk of which somatic cell count (SCC) was over 500 thousand, 15 kinds of bacteria were isolated, and among them, Pantoea spp. formed the biggest part as 15.8%. From whole milk, 37 kinds of bacteria were identified, and among them, Klebsiella oxytoca showed the highest identification rate as 30.1%. According to the results of bacteria analyzed from the quarter milk of entire milking cows, 52 kinds of bacteria were identified. Among them, 17 kinds of Staphylococci were isolated, and CNS (Coagulase-Negative Staphylococci) formed a large part as 44.9%. The findings of this study showed that various kinds of bacteria were isolated from cows having subclinical mastitis; therefore, when managing specifications about milking or such, dairy farm will have to take proper action like performing sanitary control or counting somatic cells regularly in order to do their best for reducing mastitis.