Rich, Jerica J J

Abstract Increased numbers of antral follicles are associated with greater fertility and a uterine environment that is more supportive of early embryonic development in beef heifers. Glucose is a primary energy source for embryos and glucose concentrations are elevated in uterine luminal fluid (ULF) of pregnant heifers. We hypothesized that ULF glucose concentrations and endometrial transcript abundance for glucose transporters at d16 after insemination would be greater in heifers with increased numbers of antral follicles. Heifers classified with either increased (32 ± 1.1) or diminished (14.7 ± 1.1) antral follicle counts were selected and artificially inseminated following the Select Synch protocol (d0). At d16 after insemination, heifers were sent to the abattoir and reproductive tracts were collected to retrieve conceptuses to determine pregnancy. Uterine luminal fluid was collected, the endometrium was biopsied, total RNA was extracted and glucose transporter transcript abundance was determined. Data were analyzed using the MIXED procedure of SAS with antral follicle group, pregnancy status, and the interaction as fixed effects. Glucose concentrations in ULF were greater (P < 0.05) in heifers with increased antral follicle numbers compared to heifers with diminished numbers (122.65 ± 11.91 vs 84.12 ± 12.42 mg/dL). Glucose ULF concentrations were increased (P < 0.05) in pregnant vs. non-pregnant heifers (124.84 ± 12.81 vs 81.93 ± 11.50 mg/dL). Endometrial glucose transporter 1 (GLUT1) transcript abundance was increased in pregnant heifers (P < 0.01) but was not different due to antral follicle number or the interaction. Therefore, differences in glucose concentrations associated with antral follicle number may be due to differences in GLUT1 transcription before d16 or due to differences in protein abundance or functionality. Taken together, heifers with increased number of antral follicles may have increased energy availability in the uterus for trophoblast proliferation and function. USDA is an equal opportunity provider and employer.

Abstract Transcript abundance of two forms of GnRH and its receptor have been characterized in bovine ovaries. The objective was to investigate the relationship of GnRH-1, GnRH-2, GnRH-R, intrafollicular estradiol (E2) and progesterone (P4) during follicular development. Ovaries were collected from beef cows at specific stages of follicular development [pre-selection (PRE, n = 9), post-selection (POST, n = 9), and post-selection 24h after luteal regression (PG, n = 9)]. The largest follicle per stage was aspirated to obtain granulosa cells (GC) and follicular fluid (FF). Total cellular RNA was extracted from GC and RT-PCR was performed for GnRH-1, GnRH-2, GnRH-R and GAPDH. Radioimmunoassays were performed to determine FF concentrations of E2 and P4. Data were analyzed using the MIXED and REG procedures in SAS. There was no difference (P ≥ 0.23) in mRNA abundance of GnRH-2, GnRH-R or FF concentrations of P4 across follicular stages. There was an effect of stage on FF E2 (PRE: 17,925±20,273, POST: 28,458±21,503, and PG: 252,616±21,503 pg/mL; P < 0.01). Stage affected GnRH-1 mRNA abundance (PRE: 2.28±0.55, POST: 0.92±0.55, and PG: 0.11±0.55; P = 0.03). There was no relationship of GnRH-1 and GnRH-2 mRNA abundance or effect of FF P4 on GnRH-R mRNA abundance (P ≥ 0.23). There was no effect of FF P4 on GnRH-1 mRNA abundance (P = 0.68). There was no effect of FF E2 on GnRH-2 mRNA abundance (P = 0.66). As FF E2 increased GnRH-R mRNA abundance tended to increase (P = 0.10;r2=0.13). As FF P4 concentrations increased GnRH-2 mRNA abundance tended to decrease (P = 0.09;r2=0.12). As FF E2 increased GnRH-1 mRNA abundance decreased (P = 0.02;r2=0.20). In conclusion, there were differences in peptide and receptor mRNA abundance of GnRH in relation to FF E2 and P4 at specific stages of follicular development. This is supportive of a regulatory relationship between ovarian GnRH and steroidogenesis. This work is supported by AFRI Grant No.2018-67016-27578 from USDA. USDA is an equal opportunity provider and employer.

Abstract The relationship of ovarian reserve parameters to fertility in mammalian females continues to be debated. We demonstrated improved uterine function, creating an environment that is more supportive of early embryonic development in beef heifers with increased numbers of follicles. In the present study we hypothesized that timing of luteolysis differs between heifers with increased compared to heifers with diminished numbers of follicles. Angus heifers (n = 20/ group) were classified as low (14.7 ± 1.1) or high (32 ± 1.1) antral follicle number based on ovarian ultrasonography, and artificially inseminated (d0) following a Select Synch protocol. At d16 after insemination, heifers were slaughtered, and reproductive tracts collected. Tracts were flushed with 20 mL of physiological saline to determine pregnancy status by presence of a conceptus and endometrial samples from the horn ipsilateral to the CL were frozen for determination of transcript abundance. Real-time RT-PCR was performed to determine relative transcript abundance of oxytocin receptor (OXTR) and interferon-stimulated gene-15 (ISG15) with glyceraldehyde-3-phospate dehydrogenase as the endogenous reference gene. Transcript abundance was analyzed using the MIXED procedure of SAS with follicle group, pregnancy status and the interaction as fixed effects. Transcript abundance of ISG15 was greater in pregnant endometrium than non-pregnant endometrium (2.75 ± 0.25 vs 0.16 ± 0.22-fold; P < 0.0001) with no influence of follicle group or the interaction. The interaction of follicle group and pregnancy status influenced OXTR transcript abundance (P = 0.06). Luteolytic mechanisms were activated in non-pregnant heifers with diminished numbers of follicles (1.46 ± 0.25-fold) and were not activated in pregnant heifers (0.06 ± 0.22-fold) or heifers with increased numbers of follicles that were not pregnant (0.32 ± 0.30-fold). These data indicate a wider window of recognition of pregnancy in beef heifers with increased numbers of ovarian follicles. USDA is an equal opportunity provider and employer.