記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

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The objective of the present study was to determine whether oestrous detection with the help of oestrous detection aids during the Heatsynch without timed AI protocol is equally effective with the progesterone-combined protocol in dairy heifers. A total of 148 heifers were randomly assigned to one of the two groups. A group of heifers treated with Heatsynch with heat detection aids (n = 72) received GnRH on day 0, prostaglandin F(2 alpha) (PGF(2 alpha)) on day 7 and oestradiol benzoate (EB) on day 8, while in controlled internal drug release (CIDR)-Heatsynch group (n = 76), CIDR was included during a period from GnRH to PGF(2 alpha). Heifers were checked for oestrus twice daily, i.e. from 09:00 to 10:00 hours and from 15:00 to 16:00 hours starting on day 2 for Heatsynch group and on day 8 in CIDR-Heatsynch group, and continued up to day 12. KAMAR (R) heat mount detector (KAMAR (R) Inc., Steamboat Springs, CO, USA) and ALL-WEATHER (R) PAINTSTIK (R) (LA-CO Industries Inc., Elk Grove Village, IL, USA) were used as heat detection aids. AI was conducted within 1 h after confirming oestrus in 72 heifers, while 19 animals were transferred with embryo 7 days after oestrus according to the request of the owners. Premature oestrus before PGF(2 alpha) injection occurred in 18% of Heatsynch group. Of 13 heifers which showed premature oestrus, six were inseminated and two of them conceived. Oestrus detection rate within 12 days after initiation of the protocols did not differ between the two groups (94% vs 95%). There was no difference in the conception rate after first AI (including heifers that were inseminated before PGF(2 alpha) injection) and embryo transfer between Heatsynch with heat detection aids and CIDR-Heatsynch groups (36% vs 44% and 70% vs 56%). It is concluded that the use of heat detection aids to monitor the occurrence of premature oestrus prior to PGF(2 alpha) injection in Heatsynch protocol in dairy heifers was equally effective to the inclusion of CIDR.

DOI： 10.1111/j.1439-0531.2008.01277.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

The objectives were to characterize repeat breeding in dairy cows, including reproductive performance and risk factors Data from 613 Holstein Friesian cows in nine daily herds across Japan were enrolled A repeat breeder was defined as a cow that did not become pregnant after three inseminations, despite no clinically detectable reproductive disorders In contrast, cows that became pregnant within three inseminations were considered to have normal fertility Of the 613 cows, 87.3% eventually became pregnant after repeated Al (maximum calving to conception interval was 435 d) Mean (+/- SEM) first Al conception rate, clays in milk at first Al, calving to conception interval and service per conception were 38 3%, 82 +/- 2 d, 125 +/- 3 d, and 20 +/- 0 1 times. respectively Normal fertility cows (n = 479) required only 114 3 d to conceive and 1 7 +/- 0 1 inseminations per pregnancy, whereas repeat breeders (n = 86) required significantly more days to conceive (211 +/- 10) and more inseminations per pregnancy (4 7 +/- 0.2) Based on survival analysis. it took 94 d after calving for 50% of normal fertility cows to become pregnant, compared to 155 d for repeat breeders For repeat breeders, 31 4, 50 0, and 58 1% became pregnant within 210, 300, and 435 d after calving, respectively The risk factors for repeat breeding were parity (relative risk [RR] = 0 809, P = 0 058), resumption of postpartum ovarian cycles (RR = 1 928. P = 0 009), and days in milk at first Al (RR = 0991. P = 0 039) In conclusion, repeat breeder dairy cows had very poor reproductive performance Lower parity, abnormal resumption of postpartum ovarian cycles, and shorter clays in milk at first Al were risk factors for repeat breeding. (c) 2010 Elsevier Inc All rights reserved

DOI： 10.1016/j.theriogenology.2010.01.016

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

The objectives of this study were to derive a useful case definition of delayed resumption of ovarian activity, based on factors associated with reduced fertility, and to assess its impact on subsequent reproductive performance in Holstein cows (Bos taunts). Milk samples were collected twice weekly from 219 cows from four commercial herds, and whole-milk progesterone concentrations were determined with an enzyme-linked immunosorbent assay. Ovulation was considered to have occurred 5 d before the first rise of milk progesterone concentration above the basal level. Survival analysis was used to derive a case definition of delayed resumption of ovarian activity postpartum based on factors that were predictive of reduced pregnancy rate. First postpartum ovulation occurring beyond 35 d postpartum was associated with a reduced pregnancy rate (hazard ratio [HR] = 0.50; P < 0.001) and was defined as delayed resumption of ovarian activity; overall, 75 (34.9%) cows were in this category. These cows were more likely not to conceive on first artificial insemination (odds ratio [OR] = 2.85; P = 0.01) and more likely not to become pregnant within 100 d (OR = 3.30; P = 0.001) and 210 d (OR = 3.20; P < 0.001) postpartum compared with cows with normal resumption of ovarian activity. Furthermore, 13(6%) cows that ovulated within 35 d postpartum had a prolonged (>= 14 d) interval between either first and second or second and third luteal phases postpartum. A prolonged interluteal interval was also associated with a reduced pregnancy rate (HR = 0.35; P = 0.02). Days open (mean +/- SEM) were greater (P = 0.0002) in cows with delayed resumption of ovarian activity (213 +/- 13 d) and in cows with prolonged interluteal interval (220 +/- 37 d) than in cows with normal resumption of ovarian activity (152 +/- 9 d). In conclusion, first ovulation occurring beyond 35 d postpartum was defined as delayed resumption of ovarian activity, and the first ovulation occurring within 35 d postpartum but the absence of luteal activity >= 14 d between two consecutive luteal phases was defined as a prolonged interluteal interval; both abnormalities adversely affected the subsequent reproductive performance of Holstein cows. (C) 2010 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.theriogenology.2009.08.011

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL PUBLISHING, INC  

Objective of this study was to show plasma progesterone concentrations in ovariectomized beef cows after treatment with new, once-used and twice-used controlled internal drug-releasing devices (CIDRs). Four ovariectomized beef cows were used for the experiment. Plasma concentrations of progesterone were quantified using a validated ELISA. The CIDR was inserted into vagina of cows by using a standard CIDR applicator and then removed 7 days after insertion. One week later, once-used CIDR was inserted and removed on day 7. Twice-used CIDR was, then inserted at an interval of 7 days. Mean plasma concentrations of progesterone 24 h after new CIDR insertion was 4.0 +/- 0.1 ng/ml, which thereafter decreased gradually to 1.4 +/- 0.1 ng/ml at day 7. In cows treated with once-used CIDR or twice-used CIDR, mean plasma progesterone concentrations at day 1 were 2.4 +/- 0.2 or 1.8 +/- 0.2 ng/ml and 1.0 +/- 0 or 0.9 +/- 0.1 ng/ml at day 7 respectively. The results suggest that once-used CIDR may be still effective to produce luteal phase progesterone concentrations in plasma in non-suckling beef cows.

DOI： 10.1111/j.1439-0531.2007.01000.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Estrous expressions in dairy cows have been shortened and weakened. Dairy heifers, on the other hand, may not have had such changes in estrous signs as observed in cows, since they have less stresses than cows. The aim of this study was to describe the duration of estrus in a herd of dairy heifers. A total of 56 Holstein Friesian heifers estrus was synchronized using two different hormonal protocols. They were checked for primary and secondary estrous signs with the help of heat detection devices for 48 h at an interval of 4 h starting at 16.00 hour, one day after PGF(2 alpha) treatment. Onset and end of standing estrus during 48 h observation period was recorded in 35 of the 44 heifers coming into estrus within 5 days after PGF(2 alpha) treatment during the observation period. The duration of standing estrus on the average (+/- SD) was 9.7 +/- 5.3 h. Percentage of heifers with standing estrus longer than 12 h was 40%, and 53% showed standing estrus only for 4-8 h. It is indicated that duration of estrus in dairy heifers has been shortened recently.

DOI： 10.1111/j.1740-0929.2009.00694.x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：WILEY-BLACKWELL  

Estrous expressions in dairy cows have been shortened and weakened. Dairy heifers, on the other hand, may not have had such changes in estrous signs as observed in cows, since they have less stresses than cows. The aim of this study was to describe the duration of estrus in a herd of dairy heifers. A total of 56 Holstein Friesian heifers estrus was synchronized using two different hormonal protocols. They were checked for primary and secondary estrous signs with the help of heat detection devices for 48 h at an interval of 4 h starting at 16.00 hour, one day after PGF(2 alpha) treatment. Onset and end of standing estrus during 48 h observation period was recorded in 35 of the 44 heifers coming into estrus within 5 days after PGF(2 alpha) treatment during the observation period. The duration of standing estrus on the average (+/- SD) was 9.7 +/- 5.3 h. Percentage of heifers with standing estrus longer than 12 h was 40%, and 53% showed standing estrus only for 4-8 h. It is indicated that duration of estrus in dairy heifers has been shortened recently.

DOI： 10.1111/j.1740-0929.2009.00694.x

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOCIETY REPRODUCTION & DEVELOPMENT-SRD  

The objective of this study was to describe the responses of the plasma progesterone and cortisol concentrations in ovariectomized lactating cows to low doses of adrenocorticotropic hormone (ACTH). The estrous cycles in 3 lactating cows were synchronized, and the cows were ovariectomized in the luteal phase. ACTH challenge tests were conducted at doses of 3, 6, 12 and 25 IU. Blood samples were collected at 30 min intervals, and the plasma progesterone and cortisol concentrations were analyzed by EIA. A concomitant rise in plasma progesterone and plasma cortisol was observed in cows treated with 12 IU or higher doses of ACTH. Significant increments in the plasma cortisol concentrations were observed at all doses of ACTH. The means ( SE) of the peak plasma progesterone concentrations after the 3, 6, 12 and 25 IU ACTH challenge tests were 0.6 +/- 0.1, 1.3 +/- 0.4, 1.5 +/- 0.3 and 2.4 +/- 0.3 ng/ml, respectively. The means of the peak plasma cortisol concentrations in the 3 cows after the ACTH challenge were 14.0 +/- 1.5, 17.0 +/- 2.5, 23.3 +/- 3.0, and 33.3 +/- 7.0 ng/ml, respectively. The effects of the doses, time after treatment, and their interaction on the plasma progesterone concentrations after the ACTH challenge were significant (P < 0.01). Likewise, the effects of the doses, time after treatment, and their interaction on the plasma cortisol concentrations after the ACTH challenge were significant (P < 0.01). The mean AUC values for the plasma progesterone and cortisol concentrations after the ACTH treatments were also significantly affected by the dose of ACTH (P < 0.01 and P < 0.05, respectively). A significantly positive correlation was obtained between the peak plasma progesterone and cortisol concentrations after different doses of ACTH (r=0.7, P < 0.05). The results suggest that lactating dairy cows are capable of secreting a significant amount of adrenal progesterone, reaching up to the minimal concentration necessary to cause suppression of estrus in response to 12 IU ACTH (P < 0.01). The concomitant plasma cortisol concentration was 23.3 ng/ml.

DOI： 10.1262/jrd.17051

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOCIETY REPRODUCTION & DEVELOPMENT-SRD  

The objective of this study was to describe the responses of the plasma progesterone and cortisol concentrations in ovariectomized lactating cows to low doses of adrenocorticotropic hormone (ACTH). The estrous cycles in 3 lactating cows were synchronized, and the cows were ovariectomized in the luteal phase. ACTH challenge tests were conducted at doses of 3, 6, 12 and 25 IU. Blood samples were collected at 30 min intervals, and the plasma progesterone and cortisol concentrations were analyzed by EIA. A concomitant rise in plasma progesterone and plasma cortisol was observed in cows treated with 12 IU or higher doses of ACTH. Significant increments in the plasma cortisol concentrations were observed at all doses of ACTH. The means ( SE) of the peak plasma progesterone concentrations after the 3, 6, 12 and 25 IU ACTH challenge tests were 0.6 +/- 0.1, 1.3 +/- 0.4, 1.5 +/- 0.3 and 2.4 +/- 0.3 ng/ml, respectively. The means of the peak plasma cortisol concentrations in the 3 cows after the ACTH challenge were 14.0 +/- 1.5, 17.0 +/- 2.5, 23.3 +/- 3.0, and 33.3 +/- 7.0 ng/ml, respectively. The effects of the doses, time after treatment, and their interaction on the plasma progesterone concentrations after the ACTH challenge were significant (P < 0.01). Likewise, the effects of the doses, time after treatment, and their interaction on the plasma cortisol concentrations after the ACTH challenge were significant (P < 0.01). The mean AUC values for the plasma progesterone and cortisol concentrations after the ACTH treatments were also significantly affected by the dose of ACTH (P < 0.01 and P < 0.05, respectively). A significantly positive correlation was obtained between the peak plasma progesterone and cortisol concentrations after different doses of ACTH (r=0.7, P < 0.05). The results suggest that lactating dairy cows are capable of secreting a significant amount of adrenal progesterone, reaching up to the minimal concentration necessary to cause suppression of estrus in response to 12 IU ACTH (P < 0.01). The concomitant plasma cortisol concentration was 23.3 ng/ml.

DOI： 10.1262/jrd.17051

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.14882/jrds.99.0.12.0

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.14882/jrds.98.0.90.0

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：BLACKWELL VERLAG GMBH  

Shortened and weakened oestrous signs in dairy cows may cause a failure of oestrus detection and artificial insemination timing error leading to poor reproductive performance. The aims of this study were to investigate the duration of standing oestrus in high-producing dairy cows under a free stall system, to determine the duration of expression of secondary oestrous signs before and after standing oestrus (Expt 1) and to compare the duration and intensity of oestrus between cows and heifers (Expt 2). Cattle were checked for primary and secondary oestrous signs at an interval of 4 h. Heat detection aids were also used. In Expt 1, of 56 cows which were detected in oestrus, 36 cows (64.3%) showed standing oestrus and other 20 cows (36.6%) showed secondary oestrous signs only. Duration of the standing oestrus was 6.6 +/- 6.3 h on average (+/- SD), ranging between 2 and 32 h. The cows in standing oestrus showed secondary oestrous signs during a period from 9.6 +/- 8.1 h before onset of standing to 18.4 +/- 18.8 h after the end of standing oestrus. In the cows that did not show standing oestrus, expression of secondary oestrous signs were observed for 25.7 +/- 20.5 h, which was 7.5 It shorter than the average duration of oestrus in cows showing standing oestrus. In Expt 2, nine (82%) of the 11 lactating cows in oestrus showed standing, while all the 10 heifers exhibited standing oestrus. Average duration of standing oestrus was 6.4 +/- 4.3 h in cows and 6.2 +/- 3.9 It in heifers, respectively. It may be concluded that the duration of standing oestrus is substantially shortened in lactating dairy cows, and more than one-third of cows did not show standing oestrus. In cows showing standing oestrus, duration of expression of secondary oestrous signs before and after standing is not shortened. Duration of standing oestrus in heifers was as short as that in cows.

DOI： 10.1111/j.1439-0531.2005.00572.x

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOCIETY REPRODUCTION & DEVELOPMENT-SRD  

Shortened and weakened estrous expressions could be one of the causes of poor heat detection rate. Non-specific acute stresses are assumed to depress expression of estrus by an increase of plasma progesterone which may originate from the adrenal cortex. The objective of the present study was to examine whether the adrenal cortex can secrete significant amounts of progesterone in response to exogenous adrenocorticotropic hormone (ACTH) in lactating cows. Four cows had estrus synchronized and were ovariectomized in the luteal phase. The cows were given 25 IU ACTH through an indwelling catheter 5 h after catheterization. Blood samples were collected at an interval of 30 min. In 3 of the 4 cows, plasma progesterone concentrations increased significantly 0.5-1.5 h after the first ACTH challenge with a mean peak value of 4.2 +/- 0.4 (S.D.) ng/ml. A similar response was also observed after the second ACTH challenge. Peak plasma progesterone concentrations in the 3 cows after first ACTH challenge were comparable with the progesterone values in the luteal phase of each cow. The results suggest that lactating cows have the capability to secrete a significant amount of progesterone from the adrenal cortex.

DOI： 10.1262/jrd.51.99

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

A female Japanese Black calf was born on 25 March 2003 at Hiroshima University Farm as a co-twin to a male Japanese Black calf. The male calf showed no external urogenital abnormalities. The absence of anal opening and external features of freemartinism were observed in the female. A small opening to the vulva (about 1.5 cm in length) with fused lips and a prominent clitoris were seen. The hair around the vulva was 3.5 cm in length and was heavy and dense. The distance from the vulva to the atretic anus was 9.0 cm. There were no other detectable abnormalities on physical examination. The PCR-based DNA test showed male-specific sequences confirming the calf to be freemartin. At autopsy I day after the calf birth, the gonads were found to be small and hard and the left uterine horn showed segmental aplasia near its proximal end. Two seminal glands (remnants of mesonephric duct) were located on both sides of the uterine body. A cervix was absent. The vagina was underdeveloped and looked like a tubual structure. The rectal end was closed, while the distance from the end of the atretic rectum to the absent anal opening was about 4.0 cm. On histological examination, the gonads exhibited extensive morphologic alteration; there was no cortex with the absence of ovarian structures. The seminal glands consisted of hypoplastic glandular tissue surrounded by extensive fibrous connective tissue. In conclusion, this is a case report of a freemartin with atresia recti and ani. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.anireprosci.2004.04.044

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE BV  

A female Japanese Black calf was born on 25 March 2003 at Hiroshima University Farm as a co-twin to a male Japanese Black calf. The male calf showed no external urogenital abnormalities. The absence of anal opening and external features of freemartinism were observed in the female. A small opening to the vulva (about 1.5 cm in length) with fused lips and a prominent clitoris were seen. The hair around the vulva was 3.5 cm in length and was heavy and dense. The distance from the vulva to the atretic anus was 9.0 cm. There were no other detectable abnormalities on physical examination. The PCR-based DNA test showed male-specific sequences confirming the calf to be freemartin. At autopsy I day after the calf birth, the gonads were found to be small and hard and the left uterine horn showed segmental aplasia near its proximal end. Two seminal glands (remnants of mesonephric duct) were located on both sides of the uterine body. A cervix was absent. The vagina was underdeveloped and looked like a tubual structure. The rectal end was closed, while the distance from the end of the atretic rectum to the absent anal opening was about 4.0 cm. On histological examination, the gonads exhibited extensive morphologic alteration; there was no cortex with the absence of ovarian structures. The seminal glands consisted of hypoplastic glandular tissue surrounded by extensive fibrous connective tissue. In conclusion, this is a case report of a freemartin with atresia recti and ani. (C) 2004 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.anireprosci.2004.04.044

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：SOCIETY REPRODUCTION & DEVELOPMENT-SRD  

Shortened and weakened estrous expressions could be one of the causes of poor heat detection rate. Non-specific acute stresses are assumed to depress expression of estrus by an increase of plasma progesterone which may originate from the adrenal cortex. The objective of the present study was to examine whether the adrenal cortex can secrete significant amounts of progesterone in response to exogenous adrenocorticotropic hormone (ACTH) in lactating cows. Four cows had estrus synchronized and were ovariectomized in the luteal phase. The cows were given 25 IU ACTH through an indwelling catheter 5 h after catheterization. Blood samples were collected at an interval of 30 min. In 3 of the 4 cows, plasma progesterone concentrations increased significantly 0.5-1.5 h after the first ACTH challenge with a mean peak value of 4.2 +/- 0.4 (S.D.) ng/ml. A similar response was also observed after the second ACTH challenge. Peak plasma progesterone concentrations in the 3 cows after first ACTH challenge were comparable with the progesterone values in the luteal phase of each cow. The results suggest that lactating cows have the capability to secrete a significant amount of progesterone from the adrenal cortex.

DOI： 10.1262/jrd.51.99

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：ELSEVIER SCIENCE INC  

Atresia ani, a common genetic defect in animals, is often accompanied by urogenital defects in calves. This paper reports a case of atresia ani with diphallus and separate scrota in a calf. The calf was born with atresia ani; surgery (to open the anus) was performed 3 days after birth. No urogenital abnormalities were noticed until 4 months after birth. At that time, two separate scrota (each containing a testis) and a sac-like structure in the middle of two scrota, were visible. The gait was abnormal, with abduction of the hind limbs while walking. Additionally, the hind legs appeared wider than usual at the hip joints. Two weeks later, two peni (diphallia) was observed, each in a separate preputial sheath. The calf had a normal karyotype on cytogenetic examination. Plasma concentrations of testosterone at 5.5, 6, and 7 months of age were 3.5, 1.9, and 1.7 ng/ml, respectively. At necropsy (7 months of age), the prepuce was thick and the glans of the right penis was adhered to the prepuce. The left penis did not have a urethra or retractor penis muscles. The sac-like structure in the middle of the two scrota contained the urinary bladder and a loop of small intestine. The pubic bone had failed to fuse at the pelvic symphysis. In conclusion, this is the first reported case of atresia ani with diphallus, separate scrota, and pubic bone separation in a calf. (C) 2003 Elsevier Inc. All rights reserved.

DOI： 10.1016/j.theriogenology.2003.04.002

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：M H SCHAPER GMBH CO KG  

The present study was undertaken to show the incidence of silent ovulation in high producing dairy cows, by monitoring ovarian cyclicity based on practical milk progesterone assay which was established in this study. The direct milk progesterone enzyme linked immunosorbent assay (ELISA) was developed using anti-progesterone-3(E)-carboxymethyloxime-BSA antibody for the antibody and horse radish peroxidase labeled progesterone for tracer. High sensitivity (26 mug/mL, 0.65 pg/well), high recovery rates (83-97 %), high reproducibility (CV of intra-assay 4.8-11.5 %; CV of inter-assay 14.3-19.1 %) and high correlation between milk progesterone concentrations measured by the direct ELISA and the values obtained by the ELISA after extraction proved the reliability of the assay. In second experiment the incidence of silent ovulation was investigated based on the milk progesterone concentrations in 32 dairy cows within 70 days postpartum. The incidences of silent ovulation at the first, second, third and fourth ovulation postpartum were 83, 46, 13 and 0 %, respectively. Most commonly observed patterns of sequential occurrence of silent ovulation in cows ovulating 2, 3 or 4 times within 70 days postpartum were silent-estrus (50 %), silent-silent-estrus (60 %) and silent-silent-estrus-estrus (67 %), respectively. These results suggest that the present ELISA is a reliable and practically applicable method for determination of progesterone in milk and that high producing dairy cows show a high incidence of silent ovulation at the first postpartum ovulation as well as the second ovulation, which then decreased with the increased frequency of ovulation.

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記述言語：日本語   掲載種別：研究論文（学術雑誌）  

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：日本語   掲載種別：研究論文（その他学術会議資料等）  

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記述言語：英語   掲載種別：研究論文（その他学術会議資料等）  

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