Given the recent increases in feed cost, the demand for rice straw has been increasing on dairy farms because it is cheaper than expensive imported forages. Therefore, it is necessary to study the effect of rice straw feeding on the growth and productivity of dairy heifers. This study compared how feeding tall fescue and rice straw affects the growth, age at first calving, and feed cost of heifers. we compared the growth, age at first calving, and feed cost for each group during the breeding period. Body height was higher in the tall fescue-fed group than in the rice straw-fed group (p<0.05). The length of the growing stage was significantly shorter in the tall fescue group than in the rice straw group (p<0.001) and the age at calving also showed a significant reduction in the tall fescue group compared to the rice straw group (p<0.001). However, the feed cost was lower in the rice straw group because of the difference in the unit price of forage (p<0.001). Based on these results, during the growing period, the rice straw group had delays in growth and the age at first calving compared to the tall fescue group, but also had reduced feed costs in the short term.

This study evaluated genetic parameters of direct and maternal effects for calving ease in Hanwoo. A total of 2,102 records for calving ease were collected from 2018 to 2020 from the Hanwoo Genetic Improvement Center in Korea. The calving ease score was rated from 1 to 4 (1=unassisted delivery, 2=assisted easy calving, 3=assisted difficult calving, 4=mechanical or caesarean section) as categorical data, and the data were converted using a truncated normal distribution for linear model analysis. To evaluate the genetic parameters, the birth year-season of calving, the sex of the calf, parity, and the age of the dam at calving were considered as fixed effects, and genetic and maternal effects were considered random effects. The genetic parameters were evaluated using the program BLUPF90. The calving ease scores for male calves, first parity cows, and currently calving cows were much higher than for females, later parities, and past calving cows. The direct genetic variance (0.0164) was higher than the maternal genetic variance (0.0018), and the estimated heritabilities of the direct and maternal effects were 0.055 and 0.006, respectively. The parameters determined here should help with the genetic evaluation of calving ease in Hanwoo.

A diverse of recommendation has been made for the structure and management of dairy cows, despite demanding research, the relationship between lactation number and various factors is yet to be established. The present study was aimed to investigate the covariance among lactation number, growth performance, calving interval, and milk production was considered to increase an efficiency of selection schemes and to manage more efficiently Holstein dairy cows that have been raised on small-scale family farms in Republic of Korea. For that purpose, the data were observed from 850 Holstein dairy cows, which a total of 3929 milking, since April 2016 - January 2017. We measured the body weight, height, age, calving interval, and milk production of the each dairy cow. Also, information about the date of lactation, calving interval, and milk production was recorded using an automatic milking system(AMS) with identification numbers. Milk production was calculated per udder quarter in the AMS. Our study results showed the increased average body weight(p>0.05) in 1, 2, 3, and 4th lactating dairy cows and afterwards, we noticed the tendency on the average body weight(p<0.05) per lactation progressed. There was no significant difference noticed on height measurement of dairy cows. From the processing data of 850 Holstein dairy cows, the lactation number 1 and 7 had a greater calving interval with significantly lowered milk production, and the lactation number 2, 3, 4, 5, and 6 had significantly lowered the calving interval(p<0.05) with a greater milk production. From our study results, we evidenced that there is a significant relationship between the lactation number, growth performance, calving interval, and milk yield, and the maximum production of milk occurring in the 3rd and 4th lactation dairy cows. The achieved results from this study can be used by the small-scale farmers to encourage the structure and management of growth performance, calving interval, and milk yield in Holstein dairy cows in Korea.

본 연구의 목적은 분만간격에 따른 추가 착유일수를 계산하여 불완전 Gamma모형으로 추정된 비유곡 선모수값을 통하여 추가 착유일 만큼의 산유량을 계산하고, 추가 착유에 따른 경제성을 분석하기 위함 이다. 경제성 분석을 위하여 농협중앙회 젖소개량사업소에서 진행하고 있는 유우군 능력검정사업에 참 여하고 있는 홀스타인 젖소로부터 조사한 착유기록 2,072개를 분석하였는데, 분석에 이용된 착유기록은 2010년 1월부터 2012년 12월 사이에 분만한 초산우 및 경산우로부터 자료이다. 비유곡선 모수는 Wood 모형을 적용하여, SAS 9.2 NLIN Procedure를 이용해 추정하였다. Wood 모형으로 추정한 비유곡선 함수는 초산우 및 경산우에 대해 각각 yt = 18.00t0.189e-0.00231t 및 yt = 24.73t0.181e-0.00315t로 추정되었다. 초산 우의 경우 산유량이 8,000kg 이하인 우군의 적정 분만간격은 400일 이하로 유지하는 것이 바람직하며, 8,000kg 이상인 우군은 분만간격을 400일에서 500일 사이로 유지하는 것이 바람직하다. 경산우의 경 우 산유량이 9,000kg 우군은 적정 분만간격을 400일 이하로 유지하고, 9,000kg 이상인 우군의 분만간 격은 400일에서 500일 사이로 유지하는 것이 바람직하겠으며, 11,000kg 이상의 고능력 경산우 우군의 경우 분만간격이 길어질수록 순수이익은 증가하나, 차기 임신 및 분만을 위해서는 분만간격을 450일에 서 500일 사이로 유지하는 것이 바람직하다고 할 수 있겠다.

본 연구는 분만간격과 비유곡선 모수들 간의 상관관계를 규명하기 위하여 농협중앙회 젖소개량사업 소에서 진행하고 있는 유우군 능력검정사업에 참여하고 있는 홀스타인 젖소로부터 조사한 착유기록 36,505개를 분석하였는데, 분석에 이용된 착유기록은 모두 2011년부터 2013년 사이에 분만한 경산우 로부터 조사하였다. 비유곡선 모수는 Wood 모형을 적용하여, SAS 9.2 NLIN Procedure를 이용해 추 정하였다. 분만년도-계절(봄, 여름, 가을, 겨울)효과와 산차(2, 3, 4산차)의 효과를 고정효과로 한 다 형질 일반선형모형으로 SAS(GLM procedure)를 이용하였다. 분만간격, 305일 유량, 비유곡선모수(A, b, c), 비유지속성, Peak 일시 및 Peak기 유량에 대해 분만년도-계절과 산차의 효과는 모두 유의적 으로 나타났다(p<0.05). Wood 모형으로 추정한 비유곡선 함수는 2, 3 및 4산차에 대해 각각 yt = 24.66t0-175e-0.00302t, yt = 24.69t0-192e-0.00334t 및 yt = 24.22t0.200e-0.00341t으로 추정되었다. 분만간격과 305일 유량, 모수값 A, b, c, 비유지속성, Peak 일시 및 Peak기 유량과의 표현형상관(잔차상관)은 각 각 0.093, -0.014, 0.028, -0.046, 0.099, 0.085 및 0.052으로 나타났다. 분만간격이 길어지면 비유 곡선의 상향경사도, 비유지속성, Peak 일시, Peak기 유량은 증가하고, 비유곡선의 하향경사도는 감소 하여, 305일 유량은 증가할 것으로 판단된다.

The Korean native cattle, Hanwoo, is the most popular breed of beef cattle in Korea. However, the reproductive performance data are limited although reproduction is one of the most economically and biologically important in beef production. Therefore, this study was undertaken to investigate reproductive performance parameters including calving interval, parity for life time production. Data collected from 206,827 calvings were analyzed. There were no significant differences in calving interval and gestation days as parity increased from 2nd and 13rd parity cow, from spring to winter. However, we found a dramatic increase in calving interval after year 2000. About 1 month were increased per year ( y = 30.578x + 344.45 R² = 0.9157). Interestingly, we observed that parities for life time can be affected by birth weight. Calves with 23 kg at birth showed highest parities, 3.4±2.0 times. In summary, this study provides valuable data on reproductive performance of Hanwoo and the data presented here can be used as a standard target for optimising and enhancing reproductive performance.

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.

Growth rate during rearing, which varies depending on provided nutrition, has been related with age at 1st calving (AFC). This study investigated the effect of upgrowth parameters during the rearing period on the reproduction of nulliparous Holstein heifers. The study comprised 77 successively born heifers from the same herd. Growth rate and fertility traits were measured during rearing and fertility parameters were recorded in lactations 1. Growth parameters (body weight, height, heart girth and body length) were measured at the approximate birth time, 270 and 450 d of age. Reproduction data collected included age at 1st breeding, number of services per conception (S/C), pregnancy rate to 1st artificial insemination, AFC. Animals were subsequently divided into 4 AFC groups for analysis: <23 mo, 23∼ 25 mo, 26∼30 mo and >30 mo. The AFC reflected both upgrowth rate and heifer reproduction, with later calving heifers smaller. Increased skeletal growth (at 270 and 450 d) was related with a reduced AFC (p<0.05). Early calving animals (<23 mo) had the best reproduction as nulliparous heifers, with most conceiving at first service (87.5%). Fertility in the first lactation was the worst in the oldest AFC group (>30 mo). In the 1st lactation period, a number of services per conception (3.1±0.3) increased with increasing AFC (>30 mo). Sub-optimal upgrowth related with an increased AFC could be mitigated by improved monitoring of replacement heifers during the rearing period.

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

Raising replacement heifers is important aspect of dairy farm management that can be characterized as a long-term performance and high-cost production period. This study was investigated the effect of month of age at the first pregnancy on calving difficulty of Holstein heifers. Heifers was inseminated with semen of easy-calving sire and the reproductive performance was compared for the effect of first pregnancy at 12-14 months of age (12 month old), 15-16 months of age (15 month old), 17-19 months of age (17 month old) and > 20 months of age (20 month old) in Holstein heifers. Holstein heifers showed different easy calving score (ECS) depending on their ages; frequency of ECS 1 was 55.2%, 64.9%, 59.4% and 52.0% at 12, 15, 17 and 20 month of age, respectively. Frequency of ECS 4 was 5.2%, 1.8%, 6.3% and 4.8% at 12, 15, 17 and 20 month of age, respectively. The rates of retained placenta postparturition in first pregnancy age category was 12.3% at 12 months of age, 5.3% at 15 months of age, 9.4% at 17 months of age and 19.0% at 20 months of age. When It was evaluated by present results, the reproductive performance like easy calving score (ECS), retained placenta rates, and abortion and stillbirth rates of heifers which was inseminated at 14 months old or less and at 17 months old or more was reduced. Therefore, the first pregnancy age for optimum reproductive performance was 15-16 months.

본 연구는 젖소의 분만계절에 비유곡선 모수를 추정하고, 추정된 비유곡선 모수를 이용하여 우리나라 젖소의 비유특성에 대한 기초자료를 제공하고자 실시하였다. 자료는 2009년부터 2011년까지 분만한 1산차 14,189두의 농협중앙회 검정자료를 이용하였으며, 비유곡선 모수는 Wood 모형을 적용하여, SAS 9.2 NLIN Procedure를 이용해 추정하였다. Wood 모형으로 추정 된 비유곡선 함수는 봄, 여름, 가을 및 겨울 분만에 대해 각각 yt=17.1726t0.2074e-0.00243t, yt=17.4108t0.1868e-0.00206t, yt=16.1367t0.2171e-0.00224t 및 yt=15.7759t0.2378e-0.00258t이었다. 봄, 여름, 가을 및 겨울의 분만에 대한 추정최고유량과 최고유량도달시기는 각각 32.55 kg, 84.70일, 31.53 kg, 90.99일, 32.21 kg, 96.51일 및 32.95 kg, 90.20일 이었다. 겨울의 분만이 여름의 분만보다 추정최고유량이 높았다. 또한 봄의 분만이 다른 계절보다 최고유량도달시기가 더 빨랐다.

A study on estrus synchronized dairy cows using progesterone intravaginal device was done to classify each cow's reproductive status from calving to synchronization and to evaluate the reproductive performance according to ovarian and uterine status, and calving season. From calving to estrus synchronization, silent heat or error of estrus detection among ovarian status and endometritis among uterine disorders were exposed in the most distribution (75.4% and 48.3%, respectively). The pregnancy rate of cows with inactive ovaries was lower than those in the follicular and luteal phase. And according to the uterine status before estrus synchronization, the pregnancy rate was similar in three groups; normal, endometritis, and pyometra (70.9, 69.1 and 100%, respectively). The interval from calving to conception was shorter (p<0.05) in cows calved during autumn than in cows calved during spring and winter.

The purpose of this study was to determine the effect of cows parity and calving seasons on the subsequent reproductive performance of the herd of Korean native cows raised under the same condition. With the parity of the cows ranged 1 to 4 (mean: 1.9), significant associations were found between parity and calving interval (p<0.05). Calving interval of the primiparous cows group was 395.0 16.5 days, which was the longest calving interval among the four groups. On the other hand, calving interval of the second parity group was 333.7 3.6 days. The primiparous cows had tendencies that long interval from calving to conception and small number of service per conception relatively when compared with the multiparous cows. In the case of calving season, the interval from calving to first service was short in summer and winter relatively. The interval from calving to conception in summer was the shortest in four seasons. The number of service per conception was larger in spring and winter and smaller in summer and autumn. Calving in spring showed delayed reproductive performance and calving in summer showed desirable reproductive performance.