• Korean Journal of Veterinary Research
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• v.33 no.3
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• pp.525-530
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• 1993

Studies were conducted in 13 Korean native heifers to determine the puberty based on plasma progesterone profiles and estrus observations. Blood samples for determination of progesterone profiles were collected from jugular vein twice a week from 8 to 24 months of age, and all heifers werce observed for estrous behaviours twice a day. Heifers attained puberty at 11.3 months of age and 188.5kg body weight as determined by progesterone profiles, whereas the first estrous behaviours were observed at 14.2 months of age and 215.4kg body weight. This result indicates that determination of plasma progesterone profiles could be utilized for monitoring the puberty in Korean native heifers, and one or more ovulations occurred before pubertal heifers showed overt estrous behaviours.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.381-386
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• 2016

The objective of this research was to evaluate the effects of two different feeding systems on blood metabolites in Holstein heifers and analyze the economic impacts of the feeding systems. The following two experiments were conducted to investigate the effects of feeding system on blood metabolite changes in Holstein heifers and analyze the economic impacts of the two systems. In experiment 1, the effects of two different feeding systems on cortisol, progesterone, and estradiol in Holstein heifers were examined. In experiment 2, the effects of two different feeding systems on the body weights of Holstein heifers and profitability of the two feeding systems were studied. Results showed that the pasture-raised heifers showed significantly decrease in the levels of blood cortisol (p<0.05) and increases in the levels of progesterone and estradiol (p>0.05) when compared with heifers raised in indoor feeding system. The average daily gain was significantly higher (p<0.05) in indoor-raised heifers (0.73 kg/day) as compared to pasture-raised heifers (0.58 kg/day). Also, 25.2% more profits were obtained from the pasture feeding system as compared to the indoor feeding system. These results together would be useful in the investigation of feeding system and growth performance in dairy cattle.

• Asian-Australasian Journal of Animal Sciences
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• v.15 no.12
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• pp.1714-1718
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• 2002

Twelve prepubertal Karan Fries heifers (15 months, $167.7{\pm}13.5kg$) were divided into two equal groups. Group 1 was fed as per NRC requirements and group 2 was fed 20% more protein than group 1 heifers. The experimental feeding was continued until the onset of puberty in both the groups. Blood samples were collected at fortnightly intervals and analyzed for amino acids using HPLC. Group 1 and 2 heifers required $178.6{\pm}33.8$ and $152.8{\pm}33.2$ days of experimental feeding to exhibit first estrus resulting in total age at puberty as $639.4{\pm}27.3$ and $618.6{\pm}24.6$ days in the two groups respectively. The concentration of total amino acids averaged 4.40 and 4.89 mmol/l and those of non-essential amino acids (NEAA) was 2.32 and 2.49 mmol/l in groups 1 and 2, respectively. The concentration of plasma essential amino acids i.e. histidine, threonine, valine, methionine, isoleucine, leucine and phenylalanine were higher (p<0.01) in group 2 than group 1. Plasma concentration of large neutral amino acids (LNAA) was significantly higher in group 2 (1.28 mmol/l) than in group 1 (1.12 mmol/l). Increased levels of leucine, isoleucine and valine are implicated in increased follicular growth and development in prepubertal heifers and resulted in a 26 day earlier attainment of puberty by 26 days in an experimental period of six months in group 2 heifers. Increased concentrations of aspartate and tyrosine in group 2 heifers might be associated with the release of GnRH from the hypothalamus influencing LH release from anterior pituitary in such animals. It is therefore evident that increased availability of certain amino acids in heifers fed high protein diet might have led to early onset of puberty.

• Asian-Australasian Journal of Animal Sciences
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• v.33 no.8
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• pp.1360-1368
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• 2020

Objective: The aim of our study was to determine the associations of heifer reproductive performance with survival up to the first calving, first-lactation milk yield, and the probability of being culled within 50 days after first calving. Methods: Data from 33 large Holstein-Friesian commercial dairy herds were gathered from the official milk recording database in Hungary. The data of heifers first inseminated between January 1, 2011 and December 31, 2014 were analyzed retrospectively, using Cox proportional hazards models, competing risks models, multivariate linear and logistic mixed-effects models. Results: Heifers (n = 35,128) with younger age at conception were more likely to remain in the herd until calving, and each additional month in age at conception increased culling risk by 5.1%. Season of birth was related to first-lactation milk yield (MY1; n = 19,931), with cows born in autumn having the highest milk production (p<0.001). The highest MY1 was achieved by heifers that first calved between 22.00 and 25.99 months of age. Heifers that calved in autumn had the highest MY1, whereas calving in summer was related to the lowest milk production (p<0.001). The risk of culling within 50 days in milk in first lactation (n = 21,225) increased along with first calving age, e.g. heifers that first calved after 30 months of age were 5.52-times more likely to be culled compared to heifers that calved before 22 months of age (p<0.001). Calving difficulty was related to higher culling risk in early lactation (p<0.001). Heifers that required caesarean section were 24.01-times more likely to leave the herd within 50 days after first calving compared to heifers that needed no assistance (p<0.001). Conclusion: Reproductive performance of replacement heifers is closely linked to longevity and milk production in dairy herds.

• Asian-Australasian Journal of Animal Sciences
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• v.7 no.2
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• pp.255-260
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• 1994

Calving records of 107 heifers from two breed groups were used to identify the major factors contributing to calving difficulty (dystocia) and compare the influence of pelvic diameters, weight and height of heifers measured after breeding and before calving on dystocia. The horizontal and vertical pelvic diameters, hip height and weight of heifers were measured two months after breeding and again two months before calving. Snell transformed calving difficulty scores (0 = normal to 100 = surgical intervention) were used in analyzing the data by analysis of covariance. Body condition score of the heifer, sire birth weight of the calf, birth weight of the calf, and ratio of calf birth weight to pelvic area all had significant effects on dystocia. Calf birth weight, ratio of calf birth weight to pelvic area, and heifer's condition score were especially important. However, sex of calf did not have a significant influence on dystocia. Generally, the variables measured before calving accounted for a higher proportion of variation in dystocia than those measured after breeding. Thus, based on the relative importance of the major factors affecting dystocia, it is suggested that selection of bulls with low birth weight for breeding on normal size heifers with optimum body condition score, and well developed pelvic opening, would be effective in reducing the incidence and severity of dystocia in beef heifers.

• Journal of Embryo Transfer
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• v.27 no.4
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• pp.223-228
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• 2012

This study was designed to adopt two estrus synchronization protocols in zebu and crossbred heifers and their effects on pregnancy rate after timed artificial insemination (TAI). A number of 120 cyclic heifers were allotted for two different treatment groups and one control group. Heifers under protocol A were injected with GnRH at first day followed by a single dose of $PGF_{2{\alpha}}$ at Day 11 and injection of GnRH at the day of AI; and heifers belonged to protocol B were treated with GnRH, two $PGF_{2{\alpha}}$ injections at 11 days apart and injection of GnRH at AI. AI was done at fixed time (within 72~96 hours after $PGF_{2{\alpha}}$ injection) in both protocols and pregnancy was confirmed by rectal palpation on 80~120 days of post AI. In control group; local heifers were conceived higher (30%) proportion than that of crossbred heifers (25%; p<0.05). In protocol A, the local breed were conceived higher (38.9%) proportion compared with crossbred (25%; p<0.05). In protocol B, local breed heifers were conceived higher (38.9%) proportion compared with crossbred heifers (33.3%; p<0.05). The overall pregnancy rate in protocol A and protocol B was 33.3% and 36.6%, respectively. The proportion of pregnancy rate of local heifers (38.9%; Protocol A) was significant (p<0.05) in comparison with local heifers (30%) in control group (p<0.05). The overall pregnancy rate between pooled control group (28.3%) and treatment group (35%) was significantly (p<0.05) differ from each other's. Results of present study concluded that estrus synchronization followed by fixed time AI could be applied for higher pregnancy rate in zebu and crossbred heifers.

• Reproductive and Developmental Biology
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• v.34 no.3
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• pp.247-252
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• 2010

This study was carried out between 2008 and 2009 in four dairy farms to investigate the effect of feeding of whole crop barley silage on the reproductive performance of Holstein heifers. Two diets, mixed hay or whole crop barley silage separately from concentrate were fed 6-month old Holstein heifers (=37). In control group (=CON), heifers (n=16) were fed 6 kg (/head) mixed hay and 4 kg (/head) commercial diet. In whole crop barley silage group (=WBS), heifers (n=21) were fed 10 kg (/head) whole crop barley silage, 4 kg (/head) mixed hay and 2 kg (/head) commercial diet. To manage body weight gain, the body condition score of heifers were measured every month. The results obtained were as follows: 1. Body weight in CON and WBS heifers at 13-, 14-, 15- and 17-month old were $340{\pm}17.9$ and $342{\pm}13.6\;kg$, $356{\pm}15.7$ and $366{\pm}14.7\;kg$, $382{\pm}13.1$ and $387{\pm}14.4\;kg$, and $429{\pm}15.0$ and $417{\pm}10.3\;kg$, respectively. 2. Body condition score in CON and WBS heifers at 9-, 12-, 15- and 17-month old were $2.88{\pm}0.04$ and $2.80{\pm}0.04$, $2.88{\pm}0.04$ and $2.80{\pm}0.04$, $2.89{\pm}0.08$ and $3.00{\pm}0.07$, and $2.89{\pm}0.08$ and $3.00{\pm}0.07$, respectively. 3. Average age of sexual maturity in CON and WBS heifers were $437.3{\pm}9.9$days and $939.6{\pm}12.5$days, WBS group heifers were significantly shorter (p<0.05) than CON group heifers. 4. First-service conception rates in CON or WBS group were 81.3% (13/16) and 66.7% (14121), respectively, and cumulative conception rate to 2nd artificial insemination were 87.5% for CON and 85.7% for WBS group. Conception rate was not different between treatments.

• Asian-Australasian Journal of Animal Sciences
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• v.19 no.9
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• pp.1262-1265
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• 2006

The present study was undertaken to analyze the status of erythrocytic malonyl dialdehyde (MDA) as an index of lipid peroxidation in normal cycling and ${\alpha}$-tocopherol supplemented anestrus buffalo heifers. Before supplementation, the blood samples were collected at weekly interval in anestrus and normal cycling buffalo heifers and data from four samples was pooled to establish pre-supplementation base line. Thereafter, the blood samples from anestrus and ${\alpha}$-tocopherol supplemented anestrus buffalo heifers were taken at fortnightly interval for 12 weeks during supplementation and for four weeks during the post-supplementation period. The pre-supplementation endogenous erythrocytic MDA, 0.3% $H_2O_2$ induced-erythrocytic MDA and 1.5% $H_2O_2$ induced-erythrocytic MDA levels (nmol/g Hb) increased significantly (p<0.05) in anestrus heifers ($372.3{\pm}5.0$, $564.4{\pm}5.7$, $862.4{\pm}8.5$) when compared to normal cycling animals ($289.6{\pm}3.0$, $508.2{\pm}6.0$, $777.7{\pm}4.9$). Oral supplementation of 3,000 mg of ${\alpha}$-tocopherol per week per animal in anestrus heifers resulted in a progressive and significant (p<0.01) decline in erythrocytic MDA levels. These observations implied that supplementation of ${\alpha}$-tocopherol to anestrus buffalo heifers ameliorated their antioxidant status by alleviating the effects of oxidative stress.

• Asian-Australasian Journal of Animal Sciences
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• v.23 no.8
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• pp.1007-1012
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• 2010

The aim of the present study was to describe whether abnormal cervical mucus discharge (A-CMD) or pathogens in cervical mucus discharge (CMD) have effects on reproductive performance of cows and heifers in estrus. Animals having clear discharges (68 cows, 38 heifers) with normal viscosity and without bad odor were grouped as normal cervical mucous discharge (N-CMD) group. The other animals (84 cows, 32 heifers) were grouped as A-CMD group. Microorganisms isolated from samples were divided into three groups as uterine pathogens (UP), potential uterine pathogens (PUP) or opportunistic uterine pathogens (OUP). Presence of PUP was associated with A-CMD for both cows (p<0.01) and heifers (p<0.02). First service conception rates (FS-CR) were lower in cows positive for PUP (p<0.01). Moreover, presence of PUP and OUP affected FS-CR in heifers (p<0.01). Although A-CMD significantly affected FS-CR in cows (p<0.04), it did not affect FS-CR in heifers. Differences in average open day for cows (p<0.02) and first service age for heifers (p<0.01) were significant between N-CMD and A-CMD groups, respectively. The current study suggested that CMD should be evaluated more carefully when there are infertility problems. In addition to the known microorganism that causes sterility and infertility in the UP group, pathogens in the PUP group should be considered for their potential to cause infertility.

• Korean Journal of Animal Reproduction
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• v.18 no.1
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• pp.1-6
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• 1994

The effects of exogenous estrogen on growth, mammary development, and the age at which the first estrous symptoms are detected were investigated for the first time in Korean native heifers at 6 months of age. At 90 days after treatment, weight gains of heifers implanted with 10 mg of estradiol were not different from those of the control heifers. However, weight gams of heifers implanted with 20 mg of estradiol were significantly increased at 90 days by 18%, relative to control values. At 180 days, cumulative weight gains of heifers implanted with either 10 mg or 20 mg of estradiol averaged 6.7% or 17.8%, respectively, greater than controls. But these values were not statistically significant. Regardless of dosage, teat diameter gains in the treatment groups were significantly increased at 90 days about 159%, relative to controls. Cumulative teat diameter gains in the heifers implanted with either 10 mg or 20 mg of estradiol were also significantly increased at 180 days by 100% or 128%, respectively, compared to controls. Teat length gains in the heifers implanted with either 10 mg or 20 mg of estradiol were significantly increased at 90 days by 200% and 295%, respectively, compared to controls. Cumulative teat length gains in the heifers implanted with either 10 mg or 20 mg of estradiol were significantly 265% and 325%, respectively, higher than controls. The heifers implanted with either 10 mg or 20 mg of estradiol showed a significant increase in teat volume gains at 90 days of 282% or 246%, respectively, over those of the control heifers. Cumulative teat volume gains in the heifers implanted with either 10 mg or 20 mg of estradiol were significantly increased at 180 days by 251% and 244%, respectively, compared to control values. However, there were no significant differences m gams of teat diameter, length and volume between heifers implanted with 10 mg and 20 mg of estradiol regardless of 90 days or 180 days. Heifers implanted with 10 mg or 20 mg of estradiol showed the first estrus 20 or 124 days, respectively, faster than controls. Overall, These data strongly suggest that estradiol implantation into heifers stimulates growth and mammary development and hasten the age at which the first estrus in Korean native heifers is observed.