Keisuke Koyama

Although circulating and follicular insulin-like peptide 3 (INSL3) levels in female cattle have recently been characterized, its effect on oocyte maturation remains unclear. The objectives of the present study were to examine the expression of the INSL3 receptor, relaxin family peptide receptor 2 (RXFP2), in bovine oocytes and early embryos, and to assess the effects of INSL3 on oocyte nuclear and cytoplasmic maturation. Bovine cumulus-oocyte complexes (COCs), aspirated from 2 to 8 mm follicles of slaughterhouse ovaries, were matured in four maturation media (HPM199, IVMD 101 including TGFα, IVMD 101 without TGFα, and IVMD 101 including TGFα and FSH), each supplemented with 0, 10, or 100 ng/mL INSL3. Nuclear maturation was assessed by the first polar body extrusion rate, and cytoplasmic maturation by BMP15 and GDF9 mRNA expression, mtDNA copy number, and ATP content. Immunofluorescence showed RXFP2 protein in mature oocytes and early embryos, peaking in mature oocytes (P < 0.05), declining through the 8-cell stage, then rising at the morula and blastocyst stages (P < 0.05). In IVMD 101 medium, 10 ng/mL INSL3 increased the first polar body extrusion rate (P < 0.05) and mtDNA copy number (P < 0.001), while 100 ng/mL increased BMP15 mRNA expression (P < 0.05); ATP content was unchanged. In conclusion, consistent with the high RXFP2 expression in mature oocytes, INSL3 supplementation promoted nuclear and cytoplasmic maturation in a TGFα-dependent manner. The novel re-emergence of RXFP2 at the morula and blastocyst stages suggests a role for INSL3 signaling in late preimplantation development, warranting further study of continuous INSL3 supplementation on developmental competence.

The influence of post‐ovulatory corpus luteum (CL) and first‐wave dominant follicle (1DF) location on pregnancy establishment in cattle remains controversial. This study aimed to reveal the relationship between CL and 1DF positioning, pregnancy outcomes, and blood steroid hormone levels following artificial insemination (AI) in Holstein cattle. Data from heifers (n = 163) and cows (n = 69) with optimally timed AI, defined as ovulation within 24 h post‐AI, were analyzed to determine associations between CL (left/right ovary) and 1DF (ipsilateral/contralateral to CL) locations and conception rates. Plasma progesterone (P₄) and estradiol‐17β (E₂) concentrations were measured five days post‐insemination. In heifers, neither CL (p = 0.24) nor 1DF location (p = 0.44) affected conception rates. Cows with left‐sided CL tended to have higher conception rates than those with right‐sided CL (p = 0.08). Relative 1DF location did not affect conception in cows. The location of CL and 1DF did not affect plasma P₄ and E₂ concentrations or the ratio of plasma E₂ to P₄ in heifers or cows. These findings suggest a trend towards improved conception rates in cows with CL located on the left ovary post‐AI, regardless of 1DF location. The mechanism should not be associated with systemic ovarian hormones.

The aim of this study was to investigate the relationship between parity and the optimal insemination–ovulation interval (IOI) in lactating dairy cows, as well as the relationship between the optimal timing of artificial insemination (AI) based on the onset of oestrus and parity. A total of 183 postpartum lactating Holstein cows participated in the study and underwent 522 AI procedures using unsorted frozen semen between 2011 and 2018. Transrectal ultrasound was used to detect ovulation times in 326 AI procedures, and a pedometer was used to detect oestrus onset times in 470 AI procedures. An analysis was also performed on data from 265 AI procedures in which all the times of oestrus onset, oestrus end and ovulation were detected. The results showed that ovulation occurring 6–12 h after AI was associated with the numerical highest conception rate in multiparous cows. Moreover, the conception rate was higher when ovulation occurred between 6 and 12 h after AI than when it occurred between 0 and 6 h or 18 and 24 h after AI. In contrast, the effect of IOI on the conception rate in primiparous cows was insignificant. There was no effect of AI timing based on the oestrus onset on the conception rate in either primiparous or multiparous cows. Furthermore, the interval from oestrus onset to ovulation was similar in primiparous and multiparous cows. The difference in optimal IOI between primiparous and multiparous cows may be due to the larger uterus size in multiparous cows. These findings suggest that the optimal timing for AI in multiparous cows is more restricted than in primiparous cows. Therefore, it is essential to carefully determine the timing of AI when it is performed in multiparous cows.

In this study, we developed a calving prediction model based on continuous measurements of ventral tail base skin temperature (ST) with supervised machine learning and evaluated the predictive ability of the model in 2 dairy farms with distinct cattle management practices. The ST data were collected at 2- or 10-min intervals from 105 and 33 pregnant cattle (mean ± standard deviation: 2.2 ± 1.8 parities) reared in farms A (freestall barn, in a temperate climate) and B (tiestall barn, in a subarctic climate), respectively. After extracting maximum hourly ST, the change in values was expressed as residual ST (rST = actual hourly ST - mean ST for the same hour on the previous 3 d) and analyzed. In both farms, rST decreased in a biphasic manner before calving. Briefly, an ambient temperature-independent gradual decrease occurred from around 36 to 16 h before calving, and an ambient temperature-dependent sharp decrease occurred from around 6 h before until calving. To make a universal calving prediction model, training data were prepared from pregnant cattle under different ambient temperatures (10 data sets were randomly selected from each of the 3 ambient temperature groups: <15°C, ≥15°C to <25°C, and ≥25°C in farm A). An hourly calving prediction model was then constructed with the training data by support vector machine based on 15 features extracted from sensing data (indicative of pre-calving rST changes) and 1 feature from non-sensor-based data (days to expected calving date). When the prediction model was applied to the data that were not part of the training process, calving within the next 24 h was predicted with sensitivities and precisions of 85.3% and 71.9% in farm A (n = 75), and 81.8% and 67.5% in farm B (n = 33), respectively. No differences were observed in means and variances of intervals from the calving alerts to actual calving between farms (12.7 ± 5.8 and 13.0 ± 5.6 h in farms A and B, respectively). Above all, a calving prediction model based on continuous measurement of ST with supervised machine learning has the potential to achieve effective calving prediction, irrespective of the rearing condition in dairy cattle.

Modern genetic improvement in dairy cattle is directed towards improvement of fertility; however, reproduction traits generally exhibit a genetic antagonism with milk yield. Herein, we aimed to clarify the effects of sire predicted transmitting ability (PTA) for daughter pregnancy rate (DPR) on the reproductive performance and milk yield of daughters in Japanese dairy herds. We conducted a retrospective cohort study on four dairy herds in eastern Hokkaido, Japan, using 1,612 records from 1,018 cows with first, second, or third calvings between March 2015 and September 2018. First, we classified sires into three groups based on the tertile value of their DPR estimate: ≤ −2.2 (low), −2.1 to −0.4 (intermediate), and ≥ −0.3 (high). Subsequently, we compared the sire PTA estimates, reproductive performance, and milk production among DPR groups for each parity of the daughters. In the first and second parity, the hazard of pregnancy by 200 days postpartum was highest in cows from the high-DPR group (P < 0.05); in the third parity, it was unaffected by DPR group. Although sire PTA for milk production in cows from the low-DPR group was highest, actual milk production was unaffected by DPR group regardless of parity. Our findings demonstrate that using sires with PTA for high fertility can enable farmers to improve reproductive performance without decreasing milk yield in Japanese dairy herds. However, it should be noted that sires with PTA for high fertility are at risk for reducing the genetic merit for milk production.

In bovine placentomes, the inflammatory response is considered important for the detachment of the fetal membrane from the caruncle after parturition. Glucocorticoids, a trigger of the onset of parturition, facilitate functional maturation of placentomes via prostaglandin (PG) and estrogen production in cattle. This study investigated how exogeneous glucocorticoids, which exert immunosuppressive effects, affect placental inflammation at parturition. Placentomes were collected immediately after spontaneous or induced parturition. Parturition was conventionally induced using PGF2α or dexamethasone or with a combination of triamcinolone acetonide and high-dose betamethasone (TABET treatment). PCR array analysis indicated that 9/13 C–C motif chemokine ligands (CCLs) were upregulated > two-fold in spontaneous parturition, with CCL2 and CCL8 being highly expressed. The expressions of CCL2, CCL8, C–C motif chemokine receptor 1 (CCR1), and CCR5 in caruncles were significantly higher in spontaneous parturition than in induced parturition. Although the clinical dose of dexamethasone did not influence the expression of these CCLs and CCRs, TABET treatment increased CCR1 expression. CCL8, CCR1, CCR2, and CCR5 were localized in the caruncular epithelial cells. CCR2 was also localized in the epithelial cells of the cotyledonary villi. This study is the first report to reveal the disruption in CCL and CCR expression in bovine placentomes at induced parturition. Enhanced glucocorticoid exposure for the induction of parturition may upregulate CCR1 expression in placentomes, but the treatment does not adequately promote CCL expression. Additionally, immunohistochemistry suggested that the CCL–CCR system is involved in the functional regulation of maternal and fetal epithelial cells in placentomes at parturition.

Ghost cell odontogenic carcinoma (GCOC), a malignant counterpart of calcifying odontogenic cyst (COC) and dentinogenic ghost cell tumor (DGCT), is extremely rare. We report the case of a large GCOC arising in the mandible. A 50-year-old woman was referred to our hospital because of swelling of the left side of the mandible. Biopsy yielded a diagnosis of odontogenic carcinoma. Imaging findings revealed an extensive radiolucent lesion causing bony destruction of the mandible. In December 2014, we performed bilateral neck dissections and a segmental mandibulectomy with metal plate reconstruction using a fibula osteoseptocutaneous flap. Histopathologically, the lesion was diagnosed as GCOC because it consisted of malignant epithelial tumor and benign features of COC or DGCT. After operation, there has been no sign of recurrence or metastasis for 2 years 6 months.