Thermotolerance capabilities, blood metabolomics, and mammary gland hemodynamics and transcriptomic profiles of slick-haired Holstein cattle during mid lactation in Puerto Rico.

Holstein cattle carrying a prolactin receptor gene mutation (SLICK) exhibit short and sleek hair coats (short-haired Holstein [SLK]) enhancing thermotolerance and productivity compared with wild type-haired Holstein (WT) under tropical conditions. The objectives were to unravel the physiological and molecular mechanisms that confer an advantage to this slick genotype in Puerto Rico and determine potential correlations between metabolites and physiological variables. At 160 ± 3 DIM we compared vaginal temperatures (VT) and voluntary solar radiation exposure (VSRE) during 48 h between 9 SLK and 9 WT Holsteins, whereas a subsample of 7 SLK and 7 WT were used to assess udder skin temperature, mammary gland hemodynamics and transcriptomics, and blood plasma untargeted metabolomics at a single time point. The SLK cattle showed lower VT throughout the day and greater VSRE at 1000 h and 1100 h compared with their WT counterparts. Total mammary blood flow (MBF) was greater in SLK Holsteins compared with WT. The metabolite 9-nitrooctadecenoic acid was identified as a potential biomarker for MBF; moreover, SLK cattle had greater amounts of this metabolite in their plasma. Prostaglandin D2 synthase (PTGS) was upregulated in the slick mammary gland, while plasma prostaglandin D2 was positively correlated with milk yield and increased in SLK Holsteins compared with WT. Interestingly, the arachidonic acid metabolism pathway was enriched in the mammary gland transcriptome and perturbed in the blood metabolome in the SLK Holsteins. In conclusion, SLK Holsteins exhibited lower body temperatures, greater VSRE, enhanced blood supply to the mammary gland, and alterations in genes and metabolites involved in arachidonic acid metabolism at the mammary gland and blood plasma. The usage of the SLK Holstein cattle genetics in dairy operations could be a feasible alternative to mitigate the adverse consequences of heat stress.

Bovine neonatal microbiome origins: a review of proposed microbial community presence from conception to colostrum.

In recent years, there has been an influx of research evaluating the roles of the reproductive tract microbiota in modulating reproductive performance. These efforts have resulted in a breadth of research exploring the bovine reproductive tract microbiota. The female reproductive tract microbiota has been characterized during the estrus cycle, at timed artificial insemination, during gestation, and postpartum. Additionally, there are recently published studies investigating in-utero inoculation of the bovine fetus. However, critical review of the literature to understand how the microbial shifts during a dam's lifecycle could impact neonatal outcomes is limited. This review demonstrates a consistency at the phyla level throughout both the maternal, paternal, and neonatal microbiomes. Moreover, this review challenges the current gestational inoculation hypothesis and suggests instead a maturation of the resident uterine microbiota throughout gestation to parturition. Recent literature is indicative of microbial composition influencing metabolomic parameters that have developmental programming effects in feed utilization and metabolic performance later in life. Thus, this review enumerates the potential origins of neonatal microbial inoculation from conception, through gestation, parturition, and colostrum consumption while introducing clear paucities where future research is needed to better understand the ramifications of the reproductive microbiome on neonates.

Effects of prenatal and postnatal melatonin supplementation on overall performance, male reproductive performance, and testicular hemodynamics in beef cattle.

Melatonin has been documented to alleviate compromised pregnancies and enhance livestock performance traits. The objective of this study was to determine the effect of prenatal and postnatal melatonin supplementation on overall calf performance and dam milking traits in relation to calves, molecular factors involved in growth and metabolism of calves, along with testicular physiology and fertility traits in subsequent bulls. On days 190, 220 and 250 of gestation, dams (N = 60) were administered either two subdermal ear melatonin implants (preMEL) or no implants (preCON). After parturition, birth weights were recorded and calves were blocked based on prenatal treatment and sex. Calves received either melatonin implants (posMEL) or none (posCON) on days 0, 30, and 60 of age. On day 60 of lactation, a subset of dams (N = 32) were selected based on age, weight, and calf sex for milk collection and analysis. At weaning, (day 210 postnatally) calf weight, morphometric data, liver samples, and loin samples were collected. At 12 mo of age, bull (N = 30) scrotal circumference, scrotal temperature, and testicular artery measurements were recorded. Milk yield and fat percent from dams tended to decrease in the preMEL group (P < 0.07) compared with preCON group. Prenatal melatonin administration did not affect (P = 0.95) calf birth weight and similarly calf weaning weight was unaffected (P < 0.10) by prenatal or postnatal melatonin supplementation. Blood analysis demonstrated that plasma concentrations of melatonin were not different (P = 0.12) in dams; however, an increase (P < 0.001) in plasma concentrations of melatonin was observed in posMEL vs. posCON calves. A tendency (P < 0.10) for decreased MYF5 and MYOD1 expression in loin muscle was observed in the posMEL calves. Prenatal and postnatal melatonin administration did not affect subsequent bull scrotal measurements or testicular hemodynamics (P ≥ 0.14). Administering supplemental melatonin via implants during the prenatal and postnatal phase did not alter performance characteristics in offspring. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature might have attributed to a lack of differences in melatonin levels during the prenatal phase. In the postnatal period, the level of developmental plasticity appears to be too low for melatonin properties to be effective.

Previous studies have examined maternal melatonin implants in fall calving Mississippi cattle during the third trimester of pregnancy. These studies have shown increased maternal uterine blood flow without any change in calf birth weight when supplemented with melatonin implants. However, calf weaning weights were increased in calves born to melatonin supplemented dams vs. their control counterparts. The objective of this study was to examine offspring performance following maternal melatonin supplementation (prenatal) and/or postnatal calf melatonin supplementation in spring calving Montana cattle. Calf performance and weight at weaning were not affected by maternal or postnatal melatonin supplementation. However, dam milk yield and fat percent were decreased in the melatonin supplemented dams. Maternal and postnatal melatonin supplementation did not affect bull measurements of reproductive performance. Interestingly, maternal concentrations of melatonin were not different between dam treatment groups; however, postnatal melatonin supplementation increased calf concentrations of melatonin. In this study, dams were implanted in winter months, whereas calves were implanted in the spring months. Seasonal differences involving photoperiod and ambient temperature may attribute to a lack of differences in melatonin levels during the prenatal phase.

Melatonin in Health and Disease: A Perspective for Livestock Production.

Mounting evidence in the literature indicates an important role of endogenous and exogenous melatonin in driving physiological and molecular adaptations in livestock. Melatonin has been extensively studied in seasonally polyestrous animals whereby supplementation studies have been used to adjust circannual rhythms in herds of animals under abnormal photoperiodic conditions. Livestock undergo multiple metabolic and physiological adaptation processes throughout their production cycle which can result in decreased immune response leading to chronic illness, weight loss, or decreased production efficiency; however, melatonin's antioxidant capacity and immunostimulatory properties could alleviate these effects. The cardiovascular system responds to melatonin and depending on receptor type and localization, melatonin can vasodilate or vasoconstrict several systemic arteries, thereby controlling whole animal nutrient partitioning via vascular resistance. Increased incidences of non-communicable diseases in populations exposed to circadian disruption have uncovered novel pathways of neurohormones, such as melatonin, influence health, and disease. Perturbations in immune function can negatively impact the growth and development of livestock which has been examined following melatonin supplementation. Specifically, melatonin can influence nutrient uptake, circulating nutrient profiles, and endocrine profiles controlling economically important livestock growth and development. This review focuses on the physiological, cellular, and molecular implications of melatonin on the health and disease of domesticated food animals.

Maternal nutrient restriction and dietary melatonin alter neurotransmitter pathways in placental and fetal tissues.

INTRODUCTION: Recent research indicates an important role in the placental fetal brain axis, with a paucity of information reported in large animals. Melatonin supplementation has been investigated as a potential therapeutic to negate fetal growth restriction. We hypothesized that maternal nutrient restriction and melatonin supplementation would alter neurotransmitter pathways in fetal blood, cotyledonary and hypothalamus tissue. METHODS: On day 160 of gestation, Brangus heifers (n = 29 in fall study; n = 25 in summer study) were assigned to one of four treatments: adequately fed (ADQ-CON; 100% NRC recommendation), nutrient restricted (RES-CON; 60% NRC recommendation), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL; RES-MEL). Placentomes, fetal blood, and hypothalamic tissue were collected at day 240 of gestation. Neurotransmitters were analyzed in fetal blood and fetal and placental tissues. Transcript abundance of genes in the serotonin pathway and catecholamine pathway were determined in fetal hypothalamus and placental cotyledon. RESULTS: Serotonin was increased (P < 0.05) by 12.5-fold in the blood of fetuses from RES dams versus ADQ in the fall study. Additionally, melatonin supplementation increased (P < 0.05) neurotransmitter metabolites and transcript abundance of the monoamine oxidase A (MAOA) enzyme in the cotyledon. In the summer study, plasma dopamine and placental dopamine receptors were decreased (P < 0.05) in RES dams versus ADQ. DISCUSSION: In conclusion, these data indicate novel evidence of the presence of neurotransmitters and their synthesis and metabolism in the bovine conceptus, which could have greater implications in establishing postnatal behavior.

Seasonal and temporal variation in the placenta during melatonin supplementation in a bovine compromised pregnancy model.

Compromised pregnancies result in a poorly functioning placenta restricting the amount of oxygen and nutrient supply to the fetus resulting in intrauterine growth restriction (IUGR). Supplementing dietary melatonin during a compromised pregnancy increased uteroplacental blood flow and prevented IUGR in a seasonal-dependent manner. The objectives were to evaluate seasonal melatonin-mediated changes in temporal alterations of the bovine placental vascularity and transcript abundance of clock genes, angiogenic factors, and nutrient sensing genes in 54 underfed pregnant Brangus heifers (Fall, n = 29; Summer, n = 25). At day 160 of gestation, heifers were assigned to treatments consisting of adequately fed (ADQ-CON; 100% NRC; n = 13), nutrient restricted (RES-CON; 60% NRC; n = 13), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL, n = 13; RES-MEL, n = 15). The animals were fed daily at 0900 hours until day 240 where Cesarean sections were performed in the morning (0500 hours) or afternoon (1300 hours) for placentome collections. In both seasons, we observed a temporal alteration of the core clock genes in the cotyledonary tissue in a season-dependent manner. In the fall, ARNTL, CLOCK, NR1D1, and RORA transcript abundance were decreased (P ≤ 0.05) in the afternoon compared to the morning; whereas in the summer, ARNTL, PER2, and RORA expression were increased (P ≤ 0.05) in the afternoon. Interestingly, in both seasons, there was a concomitant temporal increase (P ≤ 0.05) of cotyledonary blood vessel perfusion and caruncular melatonin receptor 1A transcript abundance. Melatonin supplementation did not alter the melatonin receptor 1A transcript abundance (P > 0.05), however, in the summer, melatonin supplementation increased cotyledonary VEGFA, CRY1, and RORA (P ≤ 0.05) transcript abundance. In addition, during the summer the placentomes from underfed dams had increased average capillary size and HIF1α transcript abundance compared to those adequately fed (P ≤ 0.05). In conclusion, these data indicate increased cotyledonary blood vessel size and blood distribution after feeding to better facilitate nutrient transport. Interestingly, the maternal nutritional plane appears to play a crucial role in regulating the bovine placental circadian clock. Based on these findings, the regulation of angiogenic factors and clock genes in the bovine placenta appears to be an underlying mechanism of the therapeutic effect of dietary melatonin supplementation in the summer.

Maternal nutrient restriction during the last trimester of pregnancy impairs the fetal development, increases morbidity and mortality, and reduces its performance in adult life. Animals with compromised pregnancies exhibit a reduction in uterine blood flow thereby limiting the nutrients available for the fetus to grow and develop. Melatonin, a hormone that many people use as a sleep aid, could be a solution as a potential therapeutic in cattle since it has antioxidant properties and has been shown to regulate blood flow and rescue fetal weight during compromised pregnancies. In the current study, we examined the changes in placental vascularity and gene expression when supplementing underfed dams with dietary melatonin during late gestation in a group of fall-calving and spring-calving heifers. Contrary to our hypothesis melatonin did not control the placental circadian clock gene network, while maternal nutrient restriction disrupted the gene expression in the placenta. Furthermore, this study found that gene expression in the placenta is seasonally dependent.

Effects of Maternal Nutrient Restriction and Melatonin Supplementation on Cardiomyocyte Cell Development Parameters Using Machine Learning Techniques.

The objective of the current study was to examine the effects of maternal feed restriction and melatonin supplementation on fetal cardiomyocyte cell development parameters and predict binucleation and hypertrophy using machine learning techniques using pregnant beef heifers. Brangus heifers (n = 29) were assigned to one of four treatment groups in a 2 × 2 factorial design at day 160 of gestation: (1) 100% of nutrient requirements (adequately fed; ADQ) with no dietary melatonin (CON); (2) 100% of nutrient requirements (ADQ) with 20 mg/d of dietary melatonin (MEL); (3) 60% of nutrient requirements (nutrient-restricted; RES) with no dietary melatonin (CON); (4) 60% of nutrient requirements (RES) with 20 mg/d of dietary melatonin (MEL). On day 240 of gestation, fetuses were removed, and fetal heart weight and thickness were determined. The large blood vessel perimeter was increased in fetuses from RES compared with ADQ (p = 0.05). The total number of capillaries per tissue area exhibited a nutrition by treatment interaction (p = 0.01) where RES-MEL increased capillary number compared (p = 0.03) with ADQ-MEL. The binucleated cell number per tissue area showed a nutrition by treatment interaction (p = 0.010), where it was decreased in RES-CON vs. ADQ-CON fetuses. Hypertrophy was estimated by dividing ventricle thickness by heart weight. Based on machine learning results, for the binucleation and hypertrophy target variables, the Bagging model with 5 Decision Tree estimators and 3 Decision Tree estimators produced the best results without overfitting. In the prediction of binucleation, left heart ventricular thickness feature had the highest Gin importance weight followed by fetal body weight. In the case of hypertrophy, heart weight was the most important feature. This study provides evidence that restricted maternal nutrition leads to a reduction in the number of cardiomyocytes while melatonin treatment can mitigate some of these disturbances.

Oxidative stress biomarkers and free amino acid concentrations in the blood plasma of moderately exercised horses indicate adaptive response to prolonged exercise training.

Oxidative stress caused by routine physical stressors may negatively impact the performance of equine athletes; thus, the present study identifies oxidative biomarkers in the blood plasma of exercising horses. Stock-type horses were subject to a standardized moderate-intensity exercise protocol 3 times per week for 8 wk. Exercise protocol followed NRC guidelines consisting of 30% walk, 55% trot, and 15% canter, with a target heart rate (HR) of 90 BPM. Blood plasma was collected in wk 1, 2, 7, and 8 immediately before and 0, 30, 60, and 90 min after exercise and analyzed for total antioxidant capacity (TAC), thiobarbituric acid reactive substance (TBARS), glutathione peroxidase activity (GPx), and superoxide dismutase activity (SOD). Data were analyzed as repeated measures with wk, d, time, and their interactions as fixed effects. The TAC on day 2 (0.40 mM Trolox) was 7.5% greater than on day 3 (P = 0.013). There were wk × d × time interactions for SOD, TBARS, and GPx (P < 0.001). The TBARS remained at pre-exercise baseline (d-1 wk-1; 2.7 µM malondialdehyde) for most collection times within weeks 1, 7, and 8 (P ≥ 0.058); however, TBARS increased by 0.24 to 0.41 µM on day 2 of week 2 post-exercise (P < 0.001) and remained similarly elevated on day 3 pre- and immediately post-exercise (P < 0.001). The GPx similarly remained at baseline (172.6 µM/min; P ≥ 0.621) but increased by 48.18 to 83.4 µM/min at most collection times on days 1 and 2 of week 2 (P ≤ 0.023). The SOD remained at baseline (167.2 U/ mL; P ≥ 0.055) until increasing by 11.28 to 15.61 U/mL at 30 min post-exercise on day 1, week 1 and at most collection times on day 3, week 8 (P ≤ 0.043). Amino acids with antioxidant properties such as Met, Tyr, and Trp drastically decreased from weeks 2 to 8 (P < 0.001). Met and Tyr also decreased from -60 to 90 min (P < 0.047), whereas there was no time effect on Trp concentration (P = 0.841). The current study indicates the time-dependent nature of oxidative stress concerning persistent stressors such as exercise.

Performance horses are subjected to numerous stressors. These stressors may subsequently impact their overall performance. The present study measured oxidative stress biomarkers in the blood of exercising horses. Horses were moderately exercised over an 8-wk period and blood plasma was collected to measure total antioxidant capacity (TAC), thiobarbituric acid reactive substance (TBARS), glutathione peroxidase activity (GPx), and superoxide dismutase activity (SOD). Amino acid concentration was also evaluated. The TAC was greater on day 2 vs. day 3. The TBARS remained at pre-exercise (baseline) at most times except for increasing on day 2 of week 2 post-exercise. The GPx also remained at baseline for most times but increased on days 1 and 2 of week 2. The SOD remained at baseline until increasing at 30 min post-exercise on day 1, week 1 and at most collection times on day 3, week 8. Amino acids with antioxidant properties drastically decreased from weeks 2 to 8. Horses are exposed to a variety of physical stressors on a regular basis that may produce similar effects in the equine stress response. Understanding the response in the equine athlete when exposed to new stressors is crucial in determining how to prevent oxidative damage in future athletes.

Differences in bovine placentome blood vessel density and transcriptomics in a mid to late-gestating maternal nutrient restriction model.

INTRODUCTION: Prenatal development is reliant on a functioning placenta, which can be influenced by maternal nutrition. Moreover, the variation in cotyledonary capacity within an animal has not been fully examined to date. Therefore, the purpose of this study was to determine the effect of (1) placentome size and (2) maternal nutrient restriction on molecular, microscopic, and macroscopic features of bovine placentomes during late gestation. METHODS: Pregnant cows (n = 6) were placed into one of 2 treatments: CON (100% NRC) vs RES (60% of NRC) from day 140 until slaughter at day 240 of gestation. Placentomes of various sizes were perfused to assess macroscopic blood vessel density of the cotyledon. Microscopic imaging and RNA extraction for sequencing was performed. RESULTS: Macroscopic blood vessel density relative to placentome weight was not different (P = 0.42) among small, medium, or large placentomes. Cotyledonary microscopic blood vessel number, area, and perimeter was increased (P < 0.005) in high versus low blood perfusion areas. Differential expressed gene (DEG) analysis showed 209 upregulations and 168 downregulations in the RES group (P ≤ 0.0001). Gene Ontology (GO) analysis showed that downregulated enriched terms were involved in blood vessel and mesenchymal stem cells development, whereas upregulated enriched terms were involved with translation and ribosomal function. DISCUSSION: This study demonstrates that placentome function is uniform across various placentome sizes within an animal. However, microscopic heterogeneity exists within each placentome. Maternal nutrient constraints alter placental transcriptomics which may yield compensatory mechanisms involved in nutrient transport including increased perimeter.

Melatonin alters bovine uterine artery hemodynamics, vaginal temperatures, and fetal morphometrics during late gestational nutrient restriction in a season-dependent manner.

The objectives were to examine melatonin-mediated changes in temporal uterine blood flow (UBF), vaginal temperatures (VTs), and fetal morphometrics in 54 commercial Brangus heifers (Fall, n = 29; Summer, n = 25) during compromised pregnancy. At day 160 of gestation, heifers were assigned to one of the four treatments consisting of adequately fed (ADQ-CON; 100% National Research Council [NRC]; n = 13), global nutrient restricted (RES-CON; 60% NRC; n =13), and ADQ or RES supplemented with 20 mg/d of melatonin (ADQ-MEL, n = 13; RES-MEL, n = 15). In the morning (0500 hours; AM) and afternoon (1300 hours; PM) of day 220 of gestation, UBF was determined via Doppler ultrasonography, while temperature data loggers attached to progesterone-free controlled internal drug releases were used to record VTs. At day 240 of gestation, heifers underwent cesarean sections for fetal removal and morphometrics determination. The UBF and VT data were analyzed using repeated measures of analysis of variance (ANOVA), while the morphometrics was analyzed using the MIXED procedure of SAS. Seasons were analyzed separately. In Fall, a nutrition by treatment interaction was observed, where the RES-CON heifers exhibited reduced total UBF compared with ADQ-CON (5.67 ± 0.68 vs. 7.97 ± 0.54 L/min; P = 0.039). In Summer, MEL heifers exhibited increased total UBF compared with the CON counterparts (8.16 ± 0.73 vs. 6.00 ± 0.70 L/min; P = 0.048). Moreover, there was a nutrition by treatment by time interaction in VT for Fall and Summer heifers (P ≤ 0.005). In Fall, all groups had decreased VT in the morning compared with the afternoon (P < 0.05). Whereas, in Summer, VT increased for ADQ-CON and RES-CON (P < 0.0001) from morning to afternoon, the ADQ-MEL and RES-MEL remained constant throughout the day (P = 0.648). Furthermore, the RES-MEL-PM exhibited decreased VT compared with ADQ-CON-PM (38.91 ± 0.09 vs. 39.26 ± 0.09 °C; P = 0.018). Lastly, in Fall, a main effect of nutrition was observed on fetal weights, where the RES dams had fetuses with decreased body weight when compared with ADQ (24.08 ± 0.62 vs. 26.57 ± 0.64 kg; P = 0.0087). In Summer, a nutrition by treatment interaction was observed on fetal weights where the RES-CON dams had fetuses with reduced weight when compared with ADQ-CON and RES-MEL (P < 0.05). In summary, nutrient restriction decreased UBF and melatonin supplementation increased UBF depending on the season. Additionally, melatonin appeared to decrease VT and rescue fetal weights when supplemented in the Summer.

Effects of administration of exogenous estradiol benzoate on follicular, luteal, and uterine hemodynamics in beef cows.

Objectives of these two experiments were to determine if exogenous estradiol benzoate (EB) affects follicular, luteal, and uterine hemodynamics. In both experiments, 77 estrous-synchronized beef cows were assigned to one of two treatments: 1) Control (CON) or, 2) an injection of 1 mg EB the day before expected estrus (Day 0; Experiment 1) or on the day of estrus (Day 1; Experiment 2). There was transfer of an embryo (Day 7) into cows that expressed estrus. In Experiment 1, estradiol concentrations in circulation at Day 0 were greater in EB-treated cows (P = 0.003); however, concentrations of progesterone were only greater (P = 0.03) at Day 21 in cows of the EB-treated compared to those in the CON group. The follicular and luteal blood perfusion was similar, however, treatment with EB resulted in a greater uterine blood perfusion. In Experiment 2, treatment with EB did not affect size or blood perfusion of the corpus luteum (CL) on Day 7, 14, and 21. Only on Day 21, however, did pregnant cows have a larger CL than non-pregnant cows (P = 0.02). Blood perfusion to the CL was greater (P < 0.05) in all cows on Day 21 compared to 7 or 14 and those determined to be pregnant on Day 35 tended (P = 0.06) to have greater CL blood perfusion only on Day 21 compared to non-pregnant cows. In conclusion, EB treatment resulted in a greater blood perfusion of the uterus, and only affected the CL on Day 21 in Experiment 2.

Melatonin-induced changes in the bovine vaginal microbiota during maternal nutrient restriction.

Altering the composition of the bovine vaginal microbiota has proved challenging, with recent studies deeming the microbiota dynamic due to few overall changes being found. Therefore, the objectives of this study were to determine whether gestational age, endogenous progesterone, maternal nutrient restriction, or dietary melatonin altered the composition of the bovine vaginal microbiota. Brangus heifers (n = 29) from timed artificial insemination to day 240 of gestation were used; at day 160 of gestation, heifers were assigned to either an adequate (ADQ; n = 14; 100% NRC requirements) or restricted (RES; n = 15; 60% NRC requirements) nutritional plane and were either supplemented with dietary melatonin (MEL; n = 15) or not supplemented (CON; n = 14). Samples for vaginal microbiota analysis were taken on day 0 (prior to artificial insemination), day 150 (prior to dietary treatments), and day 220 of gestation (60 d post-treatment initiation) using a double guarded culture swab. The vaginal bacterial overall community structure was determined through sequencing the V4 region of the 16S rRNA gene using the Illumina Miseq platform. Alpha diversity was compared via 2-way ANOVA; ß diversity was compared via PERMANOVA. The linear discriminant analysis for effect size (LEfSe) pipeline was utilized for analysis of taxonomic rank differences between bacterial communities. Gestational age, progesterone concentration, and maternal nutritional plane did not alter α or ß diversity of the vaginal microbiota. However, gestational age resulted in compositional changes at the order, family, and genus level. Moreover, dietary melatonin supplementation did not alter α diversity of the vaginal microbiota but did alter ß diversity (P = 0.02). Specifically, melatonin altered the composition at the genus level and increased the prevalence of aerobic bacteria in the vaginal tract. To date, melatonin is the first hormone associated with altering the composition of the bovine vaginal microbiota.

Effects of administering exogenous bovine somatotropin to beef heifers during the first trimester on conceptus development as well as steroid- and eicosanoid-metabolizing enzymes.

The aim of this study was to evaluate the effect of bovine somatotropin (bST) on fetal and placental development during the first third of gestation in beef heifers. Angus heifers (n = 97) were randomly assigned to either receive a 500-mg injection of bST (BST) biweekly on days 0, 15, 29, 43, and 57 of gestation or not receive bST (CTL) throughout the experiment. Body weight (BW) was assessed on days -9, -3, 0, 15, 22, 29, 43, 50, 57, 64, and 77, while blood samples were collected on days 0, 22, 50, and 64. Pregnancy status was determined via transrectal ultrasonography on days 29 and 64. A subset of pregnant heifers (BST, n = 7; CTL, n = 5) were harvested on day 84, and complete gravid reproductive tracts and liver tissue were collected for analysis. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A), and uridine 5'-diphospho-glucuronosyltransferase (UGT) activities were determined. Mean change in BW and average daily gain of heifers between fixed-time artificial insemination (day 0) and day 77 did not differ between treatments (P ≥ 0.05). Mean concentrations of insulin-like growth factor 1 (IGF-1) were greater (P < 0.001) in BST (347 ± 27.7 ng/mL) compared with CTL (135 ± 32.8 ng/mL) heifers. Mean placental weight, fetal membrane weight, uterine weight, and ovarian and corpus luteum (CL) weights, as well as fetal morphometric data, did not differ (P ≥ 0.05) between treatments. However, BST heifers had greater (P = 0.03) quantities of combined fetal fluid compared with CTL (521.6 ± 22.9 vs. 429.6 ± 27.14 g, respectively). Tendencies were observed for BST heifers to have reproductive tracts with fewer placentomes (P = 0.08) and fetuses with greater umbilical diameters (P = 0.09) compared with CTL. The activity of CYP1A did not differ (P ≥ 0.05) within the maternal and fetal liver, caruncle, cotyledon, or CL tissue samples between treatments. Furthermore, CYP3A activity was only observed in maternal liver samples and was not different between treatments (P ≥ 0.05). Interestingly, CYP2C activity was greater (P = 0.01) in the liver of BST vs. CTL heifers, and UGT activity was greater (P = 0.02) in the CL from BST heifers compared with CTL. In conclusion, the administration of bST during the first third of gestation increased plasma concentrations of IGF-1, which resulted in an increase in fetal fluid, decrease in placentome number, and greater umbilical diameter, but failed to alter fetal development.

Vaginal bacterial community composition and concentrations of estradiol at the time of artificial insemination in Brangus heifers.

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.

Temporal transcript abundance of clock genes, angiogenic factors and nutrient sensing genes in bovine placental explants.

Recent research has shown expression of clock genes in peripheral tissue explants, targeting multiple pathways leading to the entrainment of circadian rhythms. Temporal variations are not solely regulated by photoperiod, but factors such as maternal feed availability can entrain fetal circadian clock. Currently, a paucity of information exists for clock gene expression and short-term temporal transcript abundance in the bovine placenta, which is essential for proper offspring development. Therefore, the objective of this study was to determine the effect of early to mid-gestational nutrient restriction on clock genes, angiogenic factors, and nutrient sensing genes mRNA transcript abundance in placental explants during a 24 h period. Placentomes from adequately fed and nutrient restricted heifers were collected via Cesarean section at day 180 of gestation; separated into caruncular and cotyledonary tissue and placed in culture media for a 24 h period. The mRNA transcript abundance of clock genes (ARNTL, CRY1, and PER2), angiogenic factors (HIF1A and VEGFA), and nutrient sensing genes (NAMPT and NR3C1) was determined every 4 h. Clock genes were expressed in caruncular and cotyledonary explant tissue. The caruncular explant transcript abundance of the clock genes was not influenced by time (P > 0.05); while ARNTL abundance decreased over time in the cotyledon explant (P < 0.05). A main effect of time was observed for HIF1A, VEGFA, and NR3C1 in the caruncular tissue (P < 0.05). Although, angiogenic factors and nutrient sensing genes in cotyledonary tissue displayed evident temporal variation in transcript abundance (P < 0.05). Nutrient restriction did not alter (P > 0.15) mRNA transcript abundance of clock genes, angiogenic factors, or nutrient sensing genes in either caruncular or cotyledonary tissue. Interestingly, these data may indicate limited transmission and synchronization of maternal and fetal temporal variations in transcript abundance. These findings demonstrate that multiple timepoint collections are needed in future studies due to the innate existence of temporal oscillations observed in the bovine placenta.

Oxylipin concentrations in bovine corpora lutea during maternal recognition of pregnancy.

The objective was to determine the effects of pregnancy status on oxylipin profiles and eicosanoid metabolizing enzymes and in corpora lutea (CL) or endometrial (caruncle; CAR and intercaruncle; IC) tissues. Angus crossed cattle were synchronized with the CO-Synch protocol and artificially inseminated (AI). Sixteen days after AI, cattle were euthanized, and reproductive tracts collected from 6 non-pregnant and 6 pregnant cows. Oxylipin profiles and concentrations of progesterone (P4) were obtained from CL tissues. The activity of cytochrome P450 1A (CYP1A) and UDP-glucuronosyltransferase (UGT) enzymes were determined using specific luminogenic substrates. Data were analyzed using the MIXED procedure of SAS, and the model included pregnancy status. Corpora lutea of pregnant cattle contained greater (P < 0.05) concentrations of 9,10-DiHODE, 15,16-DiHODE, and 9,10-DiHOME. These oxylipins have been observed to increase cellular proliferation and vasodilation. Activity of CYP1A in the CL and UGT in CAR and IC was not different (P > 0.05) between pregnant and non-pregnant cattle. In the CL, activity of UGT was decreased (P < 0.05) in pregnant vs. non-pregnant cattle. The decrease in CL UGT activity during pregnancy indicates alterations in local hormone metabolism, while no differences in CL weight nor amount of P4 in CL were different between pregnant and non-pregnant cattle. Moreover, the increase in specific concentrations of oxylipins in the CL may indicate a novel pathway of steroid and eicosanoid metabolism during maternal recognition of pregnancy.

Effect of chronic melatonin supplementation during mid to late gestation on maternal uterine artery blood flow and subsequent development of male offspring in beef cattle.

The objective of the current study was to examine the effects of supplemental melatonin implants on uterine artery blood flow from mid to late gestation in beef cattle and subsequent development of their male offspring. Commercial beef heifers (n = 32) and cows (n = 25) were bred via artificial insemination and assigned to 1 of 2 groups supplemented with melatonin implants (MEL) or without (CON) at day 180, 210, and 240 of gestation. Uterine artery blood flow was determined using color Doppler ultrasonography. A subset of 12 crossbred heifers (n = 6 MEL; n = 6 CON) underwent Cesarean sections on day 243 ± 2 of gestation to allow for placentome collection. Maternal and fetal serum were collected to analyze melatonin concentrations. The remaining cattle were allowed to calve and at weaning (195 ± 2 d of age), bull calves (n = 15) were castrated and testicular tissue harvested for seminiferous tubule analysis. Heifer uterine artery blood flow was increased (P = 0.009) at day 240 of gestation in MEL compared with CON heifers. Cow uterine artery blood flow was increased (P = 0.003) in MEL compared with CON cows irrespective of gestational day. Maternal and fetal concentrations of melatonin were increased (P < 0.05) in MEL compared with CON heifers. The percent of placentome capillary area per mm2 was decreased (P = 0.019) in MEL compared with CON heifers, while cotyledonary ANGPT1 mRNA tended to increase (P = 0.095) in MEL compared with CON heifers. At weaning, body weight of male offspring and their scrotal circumference were increased (P < 0.05) in calves born to MEL compared with CON dams, while seminiferous tubule diameter and area were not different (P > 0.40) between treatments. In summary, melatonin supplementation increased uterine artery blood flow in mid to late gestating cattle, but this was not accompanied by an increase in fetal weight. Alterations in postnatal development of bulls, including increased body weight and scrotal circumference, warrants future investigations related to attainment of puberty and subsequent fertility of offspring born to melatonin supplemented dams.

Maternal nutrient restriction alters uterine artery hemodynamics and placentome vascular density in Bos indicus and Bos taurus.

The objective was to examine uterine artery blood flow (UBF) as well as macroscopic and microscopic placentome vascular density in nutrient-restricted Angus and Brahman heifers. Angus (n = 6) and Brahman (n = 6) heifers were bred to a single sire and pregnancy confirmed at 30-d postbreeding. Heifers were randomly assigned to 1 of 2 dietary treatments consisting of 100% (control-fed; CON; n = 6) or 60% (total nutrient-restricted; RES; n = 6) based from net energy requirements for gestating heifers. Nutritional treatments were imposed from days 50 to 180 of gestation. On day 175 of gestation, UBF was collected ipsilateral and contralateral to the conceptus via Doppler ultrasonography. Heifers underwent Cesarean sections for collection of 2 adjacent placentomes on day 180 of gestation. The primary cotyledonary artery of 1 placentome was perfused with Alexa Fluor 647 Con A conjugate to examine macroscopic cotyledonary vascular density via an in vivo imaging system. The second placentome was fixed for microscopic immunofluorescence labeling of capillaries and separated into maternal (caruncle) and fetal (cotyledon) components for determination of angiogenic factor mRNA expression. Main effects of nutritional treatment and breed are reported in the absence of a significant nutritional treatment by breed interaction. Ipsilateral UBF was decreased (P < 0.05) by 48% in RES vs. CON, whereas breed did not influence ipsilateral UBF. Contralateral UBF was not different between nutritional treatments; however, contralateral UBF was decreased (P < 0.05) by 63% in Brahman vs. Angus cattle. Macroscopic cotyledonary vascular density was increased (P < 0.05) by 36% in RES vs. CON and 82% in Brahman vs. Angus heifers. Percent capillary area and capillary perimeter were increased (P < 0.05) in RES vs. CON and increased (P < 0.05) in Brahman vs. Angus heifers. Dietary treatments did not alter angiogenic factor expression; however, transcript abundance of caruncle and cotyledon ANGP1, FLT1, and KDR was increased (P < 0.05) in Brahman vs. Angus heifers. In summary, these data indicate compensatory responses in macroscopic and microscopic placentome blood vessel density during maternal nutrient restriction-induced reductions in UBF. Moreover, a greater macroscopic density of cotyledonary blood vessels was observed in Brahman vs. Angus heifers.

Pre-breeding beef heifer management and season affect mid to late gestation uterine artery hemodynamics.

The objective of the present study was to evaluate the effects of beef heifer development practices and the influence of season on uterine artery hemodynamics during mid to late gestation. Metrics of uterine artery blood flow (BF) of fall calving and spring calving crossbred beef heifers (n = 27) developed on either a low-input (LOW|FALL n = 6; LOW|SPRING n = 6) or a conventional (CON|FALL n = 9; CON|SPRING n = 6) heifer development scheme were evaluated. Heifer body weight (BW) was measured every 30 days, and uterine BF, arterial diameter (AD), pulsatility index (PI), and resistance index were measured for uterine arteries ipsilateral and contralateral to the conceptus on days 180, 210, and 240 of gestation. Calf birth weight was assessed at parturition. Repeated-measures ANOVA was performed. There were significant treatment × season (P = 0.0001) and season × day (P = 0.003) interactions on heifer BW. Main effects of season (P = 0.04) and gestational day (P = 0.0001) were observed on contralateral BF, and there was a season × day interaction (P = 0.03) on ipsilateral BF. As such, there was a season × day interaction on total blood flow (TBF; P = 0.05), whereby TBF increased as gestation progressed and spring calving heifers displayed increased TBF. However, when adjusted for BW, an additional main effect of treatment was observed (P = 0.0007) in which LOW heifers had increased TBF compared with CON heifers. Correspondingly, LOW heifers displayed increased AD compared with CON heifers, and spring calving heifers had greater AD than fall calving females. There was also a main effect of season on calf birth weight (P = 0.02). It was concluded that developing replacement heifers with low-input management schemes does not yield compromised uteroplacental hemodynamics compared with traditionally developed females when nutrition during gestation is adequate. Furthermore, spring calving 2-year-old heifers have increased uteroplacental BF compared with their fall calving counterparts. Our results imply that producers who seek to decrease development costs by feeding replacements to lighter target breeding weights may do so without compromising mid to late gestation uterine BF when heifers are not nutrient restricted during pregnancy.

Impacts of Maternal Nutrition on Vascularity of Nutrient Transferring Tissues during Gestation and Lactation.

As the demand for food increases with exponential growth in the world population, it is imperative that we understand how to make livestock production as efficient as possible in the face of decreasing available natural resources. Moreover, it is important that livestock are able to meet their metabolic demands and supply adequate nutrition to developing offspring both during pregnancy and lactation. Specific nutrient supplementation programs that are designed to offset deficiencies, enhance efficiency, and improve nutrient supply during pregnancy can alter tissue vascular responses, fetal growth, and postnatal offspring outcomes. This review outlines how vascularity in nutrient transferring tissues, namely the maternal gastrointestinal tract, the utero-placental tissue, and the mammary gland, respond to differing nutritional planes and other specific nutrient supplementation regimes.