Rebecca R. Payton

Reproductive efficiency is largely impacted during heifer development, which generally requires nutrient supplementation for proper maturation. Nutritional status can also influence inflammation within the reproductive tract. Therefore, we hypothesized that cytokine concentrations in uterine luminal fluid (ULF) will be impacted by protein supplementation following exposure to semen via artificial insemination (AI). Commercial heifers (n = 60) were utilized to determine the effects of protein supplementation and AI on cytokine concentrations in ULF. Heifers were randomly assigned to one of three crude protein (CP) treatments (11%, 15%, and 19% overall CP) via supplementation: (1) CON (10% CP), (2) P20 (20% CP), and (3) P40 (40% CP). All heifers underwent estrus synchronization and ULF was collected 14 d after insemination. Cytokine profiles were constructed in MetaboAnalyst 5.0, and R Studio was used for individual cytokine analyses. Control heifers had increased (p = 0.05) MIP-1β concentrations (148.7 ± 123.9 pg) over P20 heifers (42.3 ± 123.9 pg), and P40 heifers (75.5 ± 123.9 pg) had intermediate concentrations. Semen exposure (1877 ± 550 pg) showed a trend (p = 0.06) to increase concentrations of IP-10 compared with heifers who were not inseminated (1556 ± 550 pg). In conclusion, although protein supplementation and semen exposure had minimal effects on overall cytokine profiles, MIP-1β, IP-10, and MIP-1α were identified as potential key regulators of uterine inflammation during early gestation.

Elevated body temperature (HEAT) in sexually receptive females is a normal part of the periovulatory microenvironment. The objective was to identify direct (first 6 h) and delayed (4 h or 18 h of recovery) effects at 41 °C exposure during in vitro maturation (IVM) on transcripts involved in steroidogenesis, oocyte maturation, or previously impacted by elevated temperature using targeted RNA-sequencing. Most transcripts (72.3%) were impacted in the first 2 to 4 hIVM. Twelve of the fifteen transcripts first impacted at 4 hIVM had a higher abundance and three had a lower abundance. Direct exposure to 41 °C impacted the transcripts related to progesterone production and signaling, germinal vesicle breakdown, oocyte meiotic progression, transcriptional activity and/or alternative splicing, cell cycle, cumulus expansion, and/or ovulation. Three transcripts demonstrated a delayed impact; changes were not seen until the COCs recovered for 4 h. The use of multidimensional scaling plots to ‘visualize’ samples highlights that oocytes exposed to an acute elevation in temperature are more advanced at the molecular level during the initial stages of maturation. Described efforts represent important steps towards providing a novel insight into the dynamic physiology of the COC in the estrual female bovid, during HEAT and after body temperature returns to baseline.

Nutrient requirements for lactation often lead to a negative energy balance accompanied by reduced body condition and fertility in cattle. A previous study identified an increased abundance of serum metabolites associated with tissue mobilization and reactive oxygen species (ROS) generation in postpartum beef cows with a thin versus moderate body condition. No studies, however, have measured ROS levels in the serum and follicular fluid of postpartum beef cows for comparison with body condition. We hypothesized that beef cows with a thin body condition would have elevated levels of ROS, as indicated by hydrogen peroxide (H₂O₂), in serum and preovulatory follicular fluid. Serum and follicular fluid samples from thin (n = 12), moderate (n = 11), and obese (n = 16) cows underwent a H₂O₂ bioluminescence assay. Levels of H₂O₂ in each biofluid were then assessed to determine relationships with cow body condition and serum or follicular fluid metabolites. Levels of H₂O₂ did not differ among body condition categories. In thin cows, the serum H₂O₂ level was positively related to the abundance of 3 metabolites with antioxidant activity. Among all animals, the follicular fluid H₂O₂ level was positively associated with the abundance of 13 metabolites, many of which had antioxidant roles. The results suggest an impact of postpartum beef cow metabolism on ROS levels in preovulatory follicular fluid or serum and highlight the need for additional studies to further investigate this potential impactor of reproductive efficiency and sustainable beef production.

Replacement heifer development is one of the most critical components in beef production. The composition of the ideal uterine environment could maximize fertility and reproductive efficiency. Our hypothesis was that protein supplementation would affect the uterine environment of beef heifers without inhibiting development or reproduction. To test the effects of dietary supplementation on these outcomes, a randomized complete block design with repeated measures was implemented. Angus heifers (n = 60) were blocked by body weight (BW) and randomly assigned to one of three supplemental protein treatment groups (10% (CON), 20% (P20), and 40% (P40)). Mixed model ANOVAs were used to determine whether protein supplementation treatments, time, and the interaction or protein supplementation, semen exposure, and the interaction influenced uterine luminal fluid (ULF) and pregnancy outcomes. Amino acids (AAs) were impacted (p < 0.001), specifically, the essential AAs: Arg, Iso, Leu, Val, His, Lys, Met, Phe, Trp. Protein supplementation influenced multiple AAs post-insemination: Arg (p = 0.03), CC (p = 0.05), 1-MH (p = 0.001), and Orn (p = 0.03). In conclusion, protein supplementation did not affect the reproductive development via puberty attainment or the timing of conception even with alterations in growth. However, uterine AA concentrations did change throughout development and protein supplementation influenced ULF d 14 post-insemination, which may affect the conception rates.

Induced ovulation of small pre-ovulatory follicles reduced pregnancy rates, embryo survival, day seven embryo quality, and successful embryo cleavage in beef cows undergoing fixed-time artificial insemination. RNA-sequencing of oocytes and associated cumulus cells collected from pre-ovulatory follicles 23 h after gonadotropin-releasing hormone (GnRH) administration to induce the pre-ovulatory gonadotropin surge suggested reduced capacity for glucose metabolism in cumulus cells of follicles ≤11.7 mm. We hypothesized that the follicular fluid metabolome influences metabolic capacity of the cumulus-oocyte complex and contributes to reduced embryo cleavage and quality grade observed following induced ovulation of small follicles. Therefore, we performed a study to determine the correlation between pre-ovulatory follicle diameter and follicular fluid metabolome profiles in lactating beef cows (Angus, n = 130). We synchronized the development of a pre-ovulatory follicle and collected the follicular contents approximately 20 h after GnRH administration. We then performed ultra-high performance liquid chromatography—high resolution mass spectrometry (UHPLC-HRMS) metabolomic studies on 43 follicular fluid samples and identified 38 metabolites within pre-ovulatory follicles of increasing size. We detected 18 metabolites with a significant, positive correlation to follicle diameter. Individual and pathway enrichment analysis of significantly correlated metabolites suggest that altered glucose and amino acid metabolism likely contribute to reduced developmental competence of oocytes when small pre-ovulatory follicles undergo induced ovulation.