Riley D. Messman

Gestational nutrient restriction can reduce fetal growth efficiency, while melatonin supplementation can mitigate some of these negative outcomes. This study investigated placental fatty acid (FA) transporter gene expression and maternal-fetal FA concentrations in cattle supplemented with dietary melatonin during late gestational nutrient restriction. Brangus heifers (n = 29) were fed a diet of 100% of National Research Council (NRC) requirements (ADQ) or 60% of NRC requirements (RES) from day 160 to day 240 of gestation. These groups were then randomly assigned to receive 20 mg of melatonin daily or no supplement, resulting in four treatment groups (ADQ-CON, n = 7; ADQ-MEL, n = 7; RES-CON, n = 7; RES-MEL, n = 8). On d 240, heifers underwent cesarean sections, in which amniotic fluid and blood samples from both the dam and fetus were collected to determine FA profiles. Placentomes were collected to determine transporter transcript abundance. Maternal concentrations of monounsaturated FA (P = 0.001) and total omega-3 (P = 0.041) were increased in RES versus ADQ fed dams. Melatonin supplementation did not alter maternal FA profiles (P ≥ 0.081). Fetal concentrations of total omega-6 (n-6) were increased (P < 0.05) in RES-CON versus ADQ-CON, whereas ADQ-MEL and RES-MEL did not differ. Fetal concentrations of total branch chain fatty acids (BCFA) were increased (P < 0.05) in ADQ-MEL versus RES-MEL. Interestingly, maternal concentrations of C16:0 were increased (P = 0.015) in RES vs ADQ fed dams, while the opposite was observed for amniotic fluid concentrations of C16:0 which were decreased (P = 0.003) in RES vs ADQ fed dams. Amniotic fluid concentrations of total BCFA were decreased (P = 0.019) in RES versus ADQ fed dams. Both caruncular and cotyledonary transcript abundance of CASR were decreased (P < 0.05) in RES-CON versus ADQ-CON, while melatonin supplementation rescued this depression in the cotyledon. Both caruncular and cotyledonary transcript abundance of SLC27A1 were increased (P < 0.05) in RES versus ADQ fed dams. These results indicate that maternal melatonin supplementation differentially altered placental FA transporter transcript abundance and fetal FA profiles, demonstrating context-dependent effects under adequate versus restricted maternal nutrition. Maternal nutrition during gestation, especially during key periods of fetal growth and development, is vital for producing a calf capable of meeting its genetic potential. Reduced growth efficiency in offspring is detrimental to producer profitability because maternal nutrient repartitioning prioritizes development of central nervous system over skeletal, muscular, and immune systems. Previous studies have investigated the use of melatonin supplementation to mitigate the effects of nutrient restriction during gestation. Melatonin increased fetal birth weights as well as negating cellular stress prior to birth. The present study investigated the effect of maternal nutrition and dietary melatonin supplementation on fatty acid concentrations and placental fatty acid transporters. Nutrient restriction increased maternal fatty acid concentrations, while melatonin did not influence maternal levels. Melatonin altered gene expression of nutrient transporters in the placenta leading to several nutrient restriction by melatonin interactions for fetal concentrations of fatty acids. In general, fetal fatty acids were altered in nutrient restricted animals supplemented with dietary melatonin. Furthermore, amnionic fluid experienced a depression in branch chain fatty acids when dams were nutrient restricted which was not rescued by melatonin supplementation.

The vaginal microbiota (VM) is the neonate’s first microbial exposure, playing a role in early health outcomes. However, the impact of VM disruption at parturition on neonatal microbial inoculation and passive transfer success remains unclear. Betadine lavages (BL) are commonly used to control reproductive tract infections but can induce microbial dysbiosis. Disrupting the VM before calving may reduce microbial competition during colonization, increasing the risk of pathogen establishment. This study aimed to determine whether VM dysbiosis affects neonatal bacterial communities and passive transfer in beef cow-calf pairs. Cows (n = 12) were randomly assigned to a control group (CON) or BL treatment group (BLG) two weeks before calving. BLG cows received 1-2 treatments based on calving date. Samples (dam colostrum, calf sera, dam-vaginal swab, dam-udder swab, dam-haircoat swab, and calf-nasal swab) were collected within 24 hours of birth and stored at -80°C. The V3-V4 region of the 16S rRNA gene was sequenced using Illumina MiSeq. Alpha diversity was assessed via two-way ANOVA, β-diversity via PERMANOVA, and taxonomic differences via LEfSe. IgG concentrations in calf serum and colostrum were analyzed using ELISA. Data were evaluated using the R software package (v. 2023.03 + 386). BL-induced VM dysbiosis did not alter α-diversity in the dam-vaginal (P = 0.42), dam-udder (P = 0.53), or dam-haircoat (P = 0.21) microbiota but did affect the calf-nasal microbiota (P = 0.03). Beta diversity was unchanged in the dam-vaginal (P = 0.66) and dam-udder (P = 0.56) microbiota but trended toward greater variation in BLG calf-nasal (P = 0.08) and dam-haircoat (P = 0.09) samples. BLG calves exhibited increased the relative abundance of the phylum Actinobacteria and decreased the relative abundance of the phylum Proteobacteria in the nasal microbiota compared with CON calves. Passive transfer status did not differ between groups (P = 0.88), but BLG dams had higher colostrum IgG concentrations than CON dams (P = 0.04), suggesting an immune response to pre-calving microbial disruption. Together, these results are indicative of microbial dysbiosis prior to parturition leading to an increased immune response in BLG dams which altered colostrum IgG. Thus, dam colostrum composition could drive immune responses against neonatal inoculating bacteria resulting in differing nasal microbial communities between BLG and CON calves.

The objective of this study was to evaluate winter hair coat shedding ability and its association with uterine artery hemodynamics. Fall calving, artificially inseminated purebred Angus females (n = 29) were observed once monthly by two trained technicians for winter hair coat shedding and given a visual hair shedding score of 1 to 5 with 1 indicating 100% shed, 2 = 75%, 3 = 50%, 4 = 25%, and 5 indicating 0% shedding of winter hair coat. Month of first shedding (MFS) was determined once a female reached an average hair shedding score of ≤ 3.5 from March until July of 2019 and 2020. Uterine artery blood flow (ABF) was determined using color Doppler ultrasonography at d 150, 180, 210, and 240 of gestation. Total uterine artery (summation of ipsilateral and contralateral arteries) and ipsilateral uterine ABF, diameter, resistance and pulsatility index (PI) were analyzed using repeated measures of the MIXED procedure of SAS with significance declared at P ≤ 0.05. Fixed effects included MFS, day, year, and the respected interactions with covariates of dam body weight, ambient temperature and order of cows ultrasonography examination considered as a random effect. No significant MFS by day of gestation interaction (P > 0.32) was observed for total or ipsilateral ABF (P > 0.23). A MFS by day of gestation (P < 0.04) interaction was observed for both ipsilateral artery diameter and PI, in which females that shed by May had smaller artery diameter (0.74 vs. 0.85 cm) at day 180 of gestation and greater PI (P < 0.02; 1.48 vs. 1.03) at day 150 of gestation compared to June. Shedding ability had an effect on ipsilateral uterine artery development and pulsatility during gestation, possibly affecting the amount of nutrients distributed to the prenatal fetus and subsequent birth weight of the calf from females that shed by May.

The knowledge surrounding the bovine vaginal microbiota and its implications on fertility and reproductive traits remains incomplete. The objective of the current study was to characterize the bovine vaginal bacterial community and estradiol concentrations at the time of artificial insemination (AI). Brangus heifers (n = 78) underwent a 7-d Co-Synch + controlled internal drug release estrus synchronization protocol. At AI, a double-guarded uterine culture swab was used to sample the anterior vaginal tract. Immediately after swabbing the vaginal tract, blood samples were collected by coccygeal venipuncture to determine concentrations of estradiol. Heifers were retrospectively classified as pregnant (n = 29) vs. nonpregnant (n = 49) between 41 and 57 d post-AI. Additionally, heifers were classified into low (1.1 to 2.5 pg/mL; n = 21), medium (2.6 to 6.7 pg/mL; n = 30), and high (7.2 to 17.6 pg/mL; n = 27) concentration of estradiol. The vaginal bacterial community composition was determined through sequencing of the V4 region from the 16S rRNA gene using the Illumina Miseq platform. Alpha diversity was compared via ANOVA and beta diversity was compared via PERMANOVA. There were no differences in the Shannon diversity index (alpha diversity; P = 0.336) or Bray–Curtis dissimilarity (beta diversity; P = 0.744) of pregnant vs. nonpregnant heifers. Overall, bacterial community composition in heifers with high, medium, or low concentrations of estradiol did not differ (P = 0.512). While no overall compositional differences were observed, species-level differences were present within pregnancy status and estradiol concentration groups. The implications of these species-level differences are unknown, but these differences could alter the vaginal environment thereby influencing fertility and vaginal health. Therefore, species-level changes could provide better insight rather than overall microbial composition in relation to an animal’s reproductive health.