Genetic relationship of energy balance predicted from milk traits with fertility in Japanese Holsteins.

We predicted the energy balance of cows from milk traits and estimated the genetic correlations of predicted energy balance (PEB) with fertility traits for the first three lactations. Data included 9,646,606 test-day records of 576,555 Holstein cows in Japan from 2015 to 2019. Genetic parameters were estimated with a multiple-trait model in which the records among lactation stages and parities were treated as separate traits. Fertility traits were conception rate at first insemination (CR), number of inseminations (NI), and days open (DO). Heritability estimates of PEB were 0.28-0.35 (first lactation), 0.15-0.29 (second), and 0.09-0.23 (third). Estimated genetic correlations among lactation stages were 0.85-1.00 (first lactation), 0.73-1.00 (second), and 0.64-1.00 (third). Estimated genetic correlations among parities were 0.82-0.96 (between first and second), 0.97-0.99 (second and third), and 0.69-0.92 (first and third). Estimated genetic correlations of PEB in early lactation with fertility were 0.04 to 0.19 for CR, -0.03 to -0.19 for NI, and -0.01 to -0.24 for DO. Genetic improvement of PEB is possible. Lower PEB in early lactation was associated with worse fertility, suggesting that improving PEB in early lactation may improve reproductive performance.

Gene-expression profile and postpartum transition of bovine endometrial side population cells†.

The mechanism of bovine endometrial regeneration after parturition remains unclear. Here, we hypothesized that bovine endometrial stem/progenitor cells participate in the postpartum regeneration of the endometrium. Flow cytometry analysis identified the presence of side population (SP) cells among endometrial stromal cells. Endometrial SP cells were shown to differentiate into osteoblasts and adipocytes. RNA-seq data showed that the gene expression pattern was different between bovine endometrial SP cells and main population cells. Gene Set Enrichment Analysis identified the enrichment of stemness genes in SP cells. Significantly (false discovery rate < 0.01) upregulated genes in SP cells contained several stem cell marker genes. Gene ontology (GO) analysis of the upregulated genes in SP cells showed enrichment of terms related to RNA metabolic process and transcription. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of upregulated genes in SP cells revealed enrichment of signaling pathways associated with maintenance and differentiation of stem/progenitor cells. The terms involved in TCA cycles were enriched in GO and KEGG pathway analysis of downregulated genes in SP cells. These results support the assumption that bovine endometrial SP cells exhibit characteristics of somatic stem/progenitor cells. The ratio of SP cells to endometrial cells was lowest on days 9-11 after parturition, which gradually increased thereafter. SP cells were shown to differentiate into epithelial cells. Collectively, these results suggest that bovine endometrial SP cells were temporarily reduced immediately after calving possibly due to their differentiation to provide new endometrial cells.

Facilitatory and inhibitory role of central amylin administration in the regulation of the gonadotropin-releasing hormone pulse generator activity in goats.

Pulsatile gonadotropin-releasing hormone (GnRH) secretion is essential for regulating reproductive functions in mammals. GnRH pulses are governed by a neural mechanism that is termed the GnRH pulse generator. In the present study, we investigated the role of central calcitonin receptor (CTR) signaling in the regulation of the GnRH pulse generator activity in ovariectomized goats by administering amylin, an endogenous ligand for CTR, into the lateral ventricle. GnRH pulse generator activity was measured using multiple unit activity (MUA) recordings in the mediobasal hypothalamus. We analyzed changes in the interval of characteristic increases in MUA (MUA volleys). The MUA volley interval shortened immediately after amylin administration, followed by prolonged intervals. Double in situ hybridization for KISS1 (kisspeptin gene) and CALCR (CTR gene) revealed that low expression levels of CALCR were found in the arcuate kisspeptin neurons, which is suggested as the main population of neurons, involved in GnRH pulse generator activity. These results suggest that central amylin-CTR signaling has a biphasic role in the regulation of GnRH pulse generator activity by acting on cells other than the arcuate kisspeptin neurons in goats.

Establishment of immortalised cell lines derived from female Shiba goat KNDy and GnRH neurones.

Kisspeptin plays a critical role in governing gonadotrophin-releasing hormone (GnRH)/gonadotrophin secretion and subsequent reproductive function in mammals. The hypothalamic arcuate nucleus (ARC) kisspeptin neurones, which co-express neurokinin B (NKB) and dynorphin A (Dyn) and are referred to as KNDy neurones, are considered to be involved in GnRH generation. The present study aimed to establish cell lines derived from goat KNDy and GnRH neurones. Primary-cultured cells of female Shiba goat foetal hypothalamic ARC and preoptic area (POA) tissues were immortalised with the infection of lentivirus containing the simian virus 40 large T-antigen gene. Clones of the immortalised cells were selected by the gene expression of a neuronal marker, and then the neurone-derived cell clones were further selected by the gene expression of KNDy or GnRH neurone markers. As a result, we obtained a KNDy neurone cell line (GA28) from the ARC, as well as two GnRH neurone cell lines (GP11 and GP31) from the POA. Immunocytochemistry revealed the expression of kisspeptin, NKB and Dyn in GA28 cells, as well as GnRH in GP11 and GP31 cells. GnRH secretion from GP11 and GP31 cells into the media was confirmed by an enzyme immunoassay. Moreover, kisspeptin challenge increased intracellular Ca2+ levels in subsets of both GP11 and GP31 cells. Kisspeptin mRNA expression in GA28 cells, which expressed the oestrogen receptor alpha gene, was significantly reduced by 17ß-oestradiol treatment. Furthermore, the transcriptional core promoter and repressive regions of the goat NKB gene were detected using GA28 cells. In conclusion, we have established goat KNDy and GnRH neurone cell lines that could be used to analyse molecular and cellular mechanisms regulating KNDy and GnRH neurones in vitro, facilitating the clarification of reproductive neuroendocrine mechanisms in ruminants.

Peripheral administration of SB223412, a selective neurokinin-3 receptor antagonist, suppresses pulsatile luteinizing hormone secretion by acting on the gonadotropin-releasing hormone pulse generator in estrogen-treated ovariectomized female goats.

Accumulating evidence suggests that KNDy neurons located in the hypothalamic arcuate nucleus (ARC), which are reported to express kisspeptin, neurokinin B, and dynorphin A, are indispensable for the gonadotropin-releasing hormone (GnRH) pulse generation that results in rhythmic GnRH secretion. The aims of the present study were to investigate the effects of peripheral administration of the neurokinin 3 receptor (NK3R/TACR3, a receptor for neurokinin B) antagonist, SB223412, on GnRH pulse-generating activity and pulsatile luteinizing hormone (LH) secretion in ovariectomized Shiba goats treated with luteal phase levels of estrogen. The NK3R antagonist was infused intravenously for 4 h {0.16 or 1.6 mg/(kg body weight [BW]·4 h)} during which multiple unit activity (MUA) in the ARC was recorded, an electrophysiological technique commonly employed to monitor GnRH pulse generator activity. In a separate experiment, the NK3R antagonist (40 or 200 mg/[kg BW·day]) was administered orally for 7 days to determine whether the NK3R antagonist could modulate pulsatile LH secretion when administered via the oral route. Intravenous infusion of the NK3R antagonist significantly increased the interval of episodic bursts of MUA compared with that of the controls. Oral administration of the antagonist for 7 days also significantly prolonged the interpulse interval of LH pulses. The results of this study demonstrate that peripheral administration of an NK3R antagonist suppresses pulsatile LH secretion by acting on the GnRH pulse generator, suggesting that NK3R antagonist administration could be used to modulate reproductive functions in ruminants.

Establishment of long-term chronic recording technique of in vivo ovarian parenchymal temperature in Japanese Black cows.

The reproductive performance of cattle can be suppressed by heat stress. Reproductive organ temperature, especially ovarian temperature, may affect follicle development and ovulation. The establishment of a technique for long-term measurement of ovarian temperature could prove useful in understanding the mechanisms underlying the temperature-dependent changes in follicular development and subsequent ovulation in cows. Here we report a novel method facilitating long-term and continuous recording of ovarian parenchymal temperature in cows. The method revealed that the ovarian temperature in the luteal phase was constantly maintained lower than the vaginal temperature, and that the diurnal temperature variation in the ovary was significantly greater than that in the vagina, suggesting that the ovaries may require a lower temperature than other organs to maintain their functions. This novel method could be used for the further understanding of ovarian functions during estrous cycles in cows.