Effect of Hair Coat Shedding Ability on Uterine Artery Hemodynamics in Angus Cattle

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.

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.

Effects of nutrient restriction and melatonin supplementation from mid-to-late gestation on maternal and fetal small intestinal carbohydrase activities in sheep

The objective of this experiment was to evaluate the effects of nutrient restriction and melatonin supplementation during mid-to-late gestation on maternal and fetal small intestinal carbohydrase activities in sheep. Ewes were randomly assigned to one of 4 dietary treatments arranged in a 2 × 2 factorial design. Ewes were fed to provide 100% (adequate; ADQ) or 60% (restricted; RES) of nutrient recommendations, and diets were supplemented with either no melatonin (control; CON) or 5 mg melatonin/d (melatonin; MEL). This resulted in 4 treatment groups: CON-ADQ (n = 7), CON-RES (n = 8), MEL-ADQ (n = 8), MEL-RES (n = 8). Treatments began on day 50 of gestation, and ewes were euthanized on day 130 for tissue collection. The maternal and fetal small intestine were collected and assayed for small intestinal carbohydrase activities. Data were analyzed using the GLM procedure of SAS with fetal sex, melatonin, nutrition, and the melatonin by nutrition interaction included in the model statement. There were no melatonin by nutrition interactions for maternal or fetal small intestinal protein concentration or carbohydrase activities (P ≥ 0.11). Dietary melatonin supplementation decreased (P = 0.03) maternal small intestinal protein concentration by 22.7% and increased (P = 0.03) maternal small intestinal glucoamylase, isomaltase, and maltase activity per gram protein by 45.5%, 41.3%, and 40.6%, respectively. Nutrient restriction from mid-to-late gestation did not influence (P ≥ 0.46) maternal small intestinal protein concentration, or maltase, isomaltase, and lactase activity. Maternal glucoamylase activity per gram intestine increased (P = 0.05) with nutrient restriction by 49.1%. Melatonin supplementation and maternal nutrient restriction did not influence (P ≥ 0.15) fetal small intestinal protein concentration, or glucoamylase, isomaltase, and lactase activity. Maternal nutrient restriction from mid-to-late gestation decreased (P = 0.05) fetal maltase activity per gram intestine by 20.5% but did not influence fetal maltase activity per gram protein. These data indicate that some maternal and fetal carbohydrases are influenced by nutrient restriction and melatonin supplementation in sheep. More information is needed to understand how nutritional and hormonal factors regulate digestive enzyme activity in ruminants to design improved maternal nutrition programs to optimize fetal growth and development while maintaining maternal productivity.

144 Nutritional advances in fetal and neonatal development: stage of gestation and placental nutrient supply

Placental and fetal development is especially sensitive to direct and indirect effects of the maternal environment. The duration and timing of environmental insults or stimuli in relation to the stage of gestation influences the phenotypic outcomes of offspring. Nutrient restriction during early gestation, such as developing heifers on low-input forage-based management schemes followed by nutrient re-alimentation at pregnancy confirmation, increased late-term uterine artery blood flow relative to maternal body weight compared with conventionally developed heifers. In this study, calf birth weights were not different between low-input vs conventionally developed heifers, which may indicate a compensatory mechanism to safeguard late-term fetal growth. In comparison, nutrient restriction during early to mid-gestation (from day 50 to 180 of pregnancy) decreased uterine artery blood flow, decreased fetal weight, and increased placental blood vessel density in both Brahman and Angus heifers. Moreover, the efficiency of uterine artery blood flow relative to fetal weight was improved in nutrient restricted dams versus adequate fed as well as Brahman vs Angus. These responses indicate improved placental nutrient supply following early to mid-gestation nutrient restriction. Apart from nutritional management, season and melatonin supplementation impacts placental nutrient supply in cattle. Specifically, spring calving heifers with increased uterine artery blood flow had heavier calves at birth compared with their fall calving counterparts. Although several seasonal environmental changes can influence performance and reproductive traits, specific changes in hormone concentrations as a result of photoperiod may alter blood distribution to the reproductive tract. This is apparent when supplementing dairy heifers and beef cows with melatonin during the last third of pregnancy, which increased uterine artery blood flow and calf weaning weights compared with non-supplemented controls. Elucidating the consequences of specific supplements on the continual plasticity of placental nutrient supply will allow us to determine important mediators of fetal growth and development.

107 Influence of chronic melatonin supplementation on bovine testis physiology

The objective was to evaluate the influence of melatonin supplementation on bovine testis biometrics, thermoregulation, and blood flow in two age groups. Mature and peri-pubertal bulls received four subdermal 24 mg melatonin implants (MEL; n = 5 and n = 6, respectively) or no implants (CON; n = 5 and n = 6, respectively) every 30 ± 4 d for 120 ± 5 d. Body weight, scrotal circumference (SC), testes temperature (average temperature of left and right testes as quantified with thermal imaging), and total testicular artery blood flow (TBF; total blood flow to left and right testes as measured with Doppler ultrasonography) were evaluated on d 60, 90, and 120 ± 4. On d 120, peri-pubertal bulls were castrated and total testes weight (TTW) determined. Data were analyzed using MIXED procedures of SAS specific for repeated measures with treatment, time, and the interaction as fixed effects and sire (peri-pubertal only) as a random effect. On d 120, peri-pubertal bull data were analyzed using MIXED procedures of SAS with treatment as a fixed effect and sire as a random effect, and relationships of TBF, SC, TTW, testes temperature, and ambient temperature assessed using CORR procedures of SAS. Body weight, testes temperature, TBF, and TBF as a proportion of SC changed over time in peri-pubertal (P &lt; 0.05) but not mature (P &gt; 0.05) bulls. On d 120, TBF was increased (P = 0.05) and TBF as a proportion of TTW tended (P = 0.10) to be increased in MEL (95.48 ± 14.63 mL/min and 0.29 ± 0.03 mL/min*g, respectively) compared to CON (65.06 ± 15.10 mL/min and 0.21 ± 0.03 mL/min*g, respectively) peri-pubertal bulls. TBF was positively correlated with SC (r = 0.59; P = 0.04) and TTW (r = 0.66; P = 0.02). Ambient temperature was positively correlated with testes temperature (r = 0.78; P &lt; 0.01). No other differences were identified (P &gt; 0.05). Limited alterations in testis physiology were observed in melatonin-supplemented bulls.

22 Comparison of vaginal microbiome and concentrations of estradiol at artificial insemination in Brangus heifers

The knowledge surrounding the bovine vaginal microbiome and its implications on fertility and reproductive traits remains incomplete. The objective of the current study was to characterize the bovine vaginal microbiome and estradiol concentrations at time of artificial insemination (AI). Brangus heifers (n = 78) underwent a 7-d Co-Synch + CIDR estrus synchronization protocol. At AI, a double guarded uterine culture swab was used to sample the anterior vaginal tract. Blood samples were collected by coccygeal venipuncture to determine concentrations of estradiol. Heifers were retrospectively classified as pregnant (n = 29) versus nonpregnant (n = 49) on day 35. Lastly, heifers were classified into low (1.1 - 2.5 pg/ml; n = 21), medium (2.6 - 6.7 pg/ml; n = 30), and high (7.2 - 17.6 pg/ml; n = 27) concentrations of estradiol. The vaginal bacterial community composition was determined through sequencing of the V4-V5 region from the 16S rRNA gene using the Illumina Miseq platform. ANOVA was used to compare the diversity metrics between treatment groups. PERMANOVA was utilized to determine variation in community structure. There were no statistical differences in the Shannon diversity index (alpha diversity; P = 0.336) or principal component analysis (beta diversity; P = 0.744) of pregnant versus nonpregnant animals. The vaginal microbiome of pregnant and nonpregnant animals was similar with the four most abundant phyla being Tenericutes, Proteobacteria, Fusobacteria, and Firmicutes. Overall bacterial community composition in animals with high, medium, or low concentrations of estradiol did not differ (P = 0.512). These results indicate that concentration of estradiol does not impact vaginal microbiome composition. In conclusion, the composition of the bovine vaginal microbiome, although dynamic, may not be directly linked to an animal’s reproductive ability.

23 Comparison of vaginal microbiome and concentrations of estradiol at artificial insemination in Brangus heifers

The knowledge surrounding the bovine vaginal microbiome and its implications on fertility and reproductive traits remains incomplete. The objective of the current study was to characterize the bovine vaginal microbiome and estradiol concentrations at time of artificial insemination (AI). Brangus heifers (n = 78) underwent a 7-day Co-Synch + CIDR estrus synchronization protocol. At AI, a double guarded uterine culture swab was used to sample the anterior vaginal tract. Blood samples were collected by coccygeal venipuncture to determine concentrations of estradiol. Heifers were retrospectively classified as pregnant (n = 29) versus nonpregnant (n = 49) on day 35. Lastly, heifers were classified into low (1.1 - 2.5 pg/ml; n = 21), medium (2.6 - 6.7 pg/ml; n = 30), and high (7.2 - 17.6 pg/ml; n = 27) concentrations of estradiol. The vaginal bacterial community composition was determined through sequencing of the V4-V5 region from the 16S rRNA gene using the Illumina Miseq platform. ANOVA was used to compare the diversity metrics between treatment groups. PERMANOVA was utilized to determine variation in community structure. There were no statistical differences in the Shannon diversity index (alpha diversity; P = 0.336) or principal component analysis (beta diversity; P = 0.744) of pregnant versus nonpregnant animals. The vaginal microbiome of pregnant and nonpregnant animals was similar with the four most abundant phyla being Tenericutes, Proteobacteria, Fusobacteria, and Firmicutes. Overall bacterial community composition in animals with high, medium, or low concentrations of estradiol did not differ (P = 0.512). These results indicate that concentration of estradiol does not impact vaginal microbiome composition. In conclusion, the composition of the bovine vaginal microbiome, although dynamic, may not be directly linked to an animal’s reproductive ability.

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.

281 Effects of feeding endophyte-infected tall fescue seed to Angus steers on ergovaline concentration, lipid oxidation, and skeletal metmyoglobin reductase activity

This study was aimed to determine the ergovaline concentration, lipid oxidation, and skeletal metmyoglobin reductase activity in Angus steers fed with endophyte-infected tall fescue seed. Animals were blocked into light (n = 4, 205.5 ± 7.4 kg), medium (n = 5, 231.3 ± 8.2 kg), and heavy (n = 3, 272.7 ± 8.4 kg) groups and randomly assigned to either a KY31 seed treatment (6796 ppb ergovaline; 20 µg/kg BW; E+; n = 6) or a KY32 control (&lt; 100 ppb; E-; n = 6) by Calan® gates during a 70-d feeding period from June to August of 2015 (period 1), followed by a 150-d resting period and another 64-d feeding period from January to March of 2016 (period 2). In both periods, there was a 2-way treatment × time interaction for ergovaline concentration in blood (P = 0.002 and 0.022, respectively), with E+ steers having 0.59 to 0.95 nM more than E- steers on d 3 (P &lt; 0.001). In period 1, TBARS values were greater in blood serum of E+ steers than in that of E- steers (6.56 vs. 2.56 µM MDA; P = 0.048) and an overall increase in MDA from d 0 (2.39 µM) to d 3 (7.59 µM) was also observed (P = 0.049). At slaughter, E+ steers had a blood TBARS value of 2.27 µM, greater than 1.15 µM in E- steers (P = 0.013). In postmortem muscle, the TBARS value was 0.68 and 0.77 µg/kg for E- and E+ steers, respectively (P = 0.239). There was no effect of endophyte-infected tall fescue seed on metmyoglobin reductase in longissimus thoracis (4.82 µM/min/g in E- muscle vs. 3.93 µM/min/g in E+ muscle; P = 0.484). Therefore, feeding endophyte-infected tall fescue seed increased ergovaline concentration and oxidative stress in the blood of Angus steers.

PSII-35 Melatonin supplementation and restricted nutrition do not affect chorionic somatomammotropin (CSH) concentration in ovine placenta from mid- to late- gestation

Melatonin plays a role as a vasodilator. Vasoactive and angiogenic factors are expressed by placental binucleate cells (BNC) and produce chorionic somatomammotropin (CSH), known to impact fetal and placental growth. We hypothesized that melatonin supplementation and restricted nutrition from mid- to late-gestation would alter CSH concentration and some characteristics of BNC in placenta. At day 50 of gestation, ewes carrying singletons were randomly assigned to a 2 × 2 factorial design and were fed either an adequate (ADQ; 100% NRC; n = 15) or restricted (RES; 60% NRC; n = 15) diet supplemented with 0 (CON, n = 14) or 5 mg of melatonin (MEL; n = 16). Placentomes were collected on day 130 of gestation and preserved in formalin for histological analysis. Cotyledon (COT) were snap frozen for western immunoblotting analyses. Tissue sections were stained using biotinylated Dolichos Biflurus (DBA; a marker of fetal membrane) lectin and fluorescein labeled Texas red-avidin and fluorescein labeled Griffonia Simplifolica (BS) lectin (a marker of BNC). The number, area, and diameter of BNC in COT were determined by image analysis. For immunoblotting, protein was extracted from COT in SDS phosphate buffer, loaded equally, and separated on 12.5% polyacrylamide gels. Protein was transferred to PVDF membranes and incubated with rabbit anti-CSH. Bands were visualized and imaged. Data were analyzed using Proc Mixed procedure of SAS. Melatonin supplementation and restricted nutrition did not affect BNC number, area, or diameter, or CSH protein expression. While we reject our hypothesis that melatonin supplementation and nutrient restriction would alter the CSH concentration and BNC characteristics in COT, we continue to evaluate if the BNC produce angiogenic or vasoactive factors that may influence placental and mammary gland functions in sheep.

PSII-7 Uterine artery hemodynamics and placentome quantification during maternal nutrient restriction in beef cattle

Proper fetal nutrition via adequate uteroplacental blood flow is critical for maximizing fetal development and reducing mortality. However, our understanding of adaptations during maternal nutrient restriction is incomplete. The purpose of this study was to determine the effect of nutrient restriction during mid to late gestation on utero-placental hemodynamics and placentome morphometrics in gestating beef cattle. Animals (n = 10) were randomly assigned one of 2 treatments: Control (CON; 100% NRC Requirements) vs Restricted Feed (NR; 60% of NRC Requirements) from 140 to 240 days of gestation. Hemodynamic parameters were collected by Doppler ultrasonography 1 week prior to slaughter from the ipsilateral and contralateral uterine arteries, after which, total uterine artery blood flow was calculated. Six animals (n = 3 per treatment) were slaughtered on day 240 of gestation (Group 1) and the remaining 4 animals were slaughtered on 265 ± 15 days (Group 2). Placentome tissues were harvested for weight and number determination. Placentome number decreased (P = 0.01) in nutrient restricted (49 ± 6) versus control (83 ± 6) fed dams. There was an interaction between treatment and group in which ipsilateral diameter increased (P &lt; 0.05) in group 2 NR animals versus group 2 CON animals while there was no difference between NR and CON in group 1. There was no difference (P = 0.30) in total uterine artery blood flow in fetal weight, which averaged 212 ± 37 mL/min*kg in nutrient restricted versus 153 ± 34 mL/min*kg in control fed dams. In summary, these data indicate limited alterations in uterine artery blood flow and fetal weight in nutrient restricted dams during the last half of gestation. The decrease in placentome number with no difference in placentome weight could indicate larger placentomes in nutrient restricted dams were able to compensate for the reduction in total number.

PSVIII-3 Maternal nutrient restriction during mid-to-late gestation alters adipogenic gene expression in subcutaneous and perirenal adipose tissue of fetal beef cattle offspring

Proper maternal nutrition during gestation is an important determinant of fetal and long-term developmental programming. Transcriptional networks involved in economically important processes such as adipogenesis and overall growth of the offspring are particularly susceptible to developmental perturbations and programming. Low quality forages or insufficient maternal nutrient supplementation during gestation are scenarios that can negatively affect fetal growth and development by altering the regulation of these networks. Therefore, the purpose of this study was to determine the effect of maternal nutrient restriction during mid-to-late gestation on mRNA expression of genes involved in growth and adipogenesis in fetal back fat (BF), and perirenal adipose tissue (PR). A total of six multiparous, commercial cows were equally divided into one of two dietary treatments: Control (CON; fed 100% of NRC recommendations) vs. Restricted Feed (RES; fed 60% of NRC recommendations) from 140 to 240 days of gestation. The animals were euthanized on day 240 of gestation for fetal tissue collection and qPCR analysis using TaqMan® gene expression assays. Relative mRNA quantification was determined using the Delta-Delta Ct method. Differences between Least Square Means were compared using the PDIFF option of the MIXED procedure of SAS (9.4). PPARg expression was increased (P = 0.009) in BF tissue in the RES group compared to the CON group. IGF-1 expression tended to increase (P = 0.076), and IGF-1R expression tended to decrease (P = 0.055) in fetal BF. In PR tissue, CEBPA and IGF-1 expression decreased (P ≤ 0.043) in RES compared to CON. These findings suggest that as a result of a compromised fetal environment, the PR and BF depots are differentially regulated in a manner that may persist into postnatal life and warrants further investigation.

380 Effects of estradiol benzoate on reproductive characteristics in beef cows

Ovulation prompted by exogenous GnRH may cause the release of sub-mature oocytes and lead to decreased pregnancy rates. Inclusion of estradiol benzoate (EB) has improved pregnancy rates. The objective was to determine if EB affects blood perfusion of follicles, CL, or uterus, concentrations of estradiol, or incidence of standing estrus. Forty-seven suckled beef cows were synchronized (GnRH+CIDR on d -9, PGF2a+CIDR removal on d -2, expected estrus=d 0). On d -1, 24 of 47 cows received an injection of EB (1mg/2mL) while the other 23 remained as a control group. Ovaries were evaluated via Doppler ultrasonography on d -1, 0, 6, 14, and 21. A laser Doppler probe was used to measure blood perfusion of the uterus on d -1, 0, and 6. Only cows that exhibited estrus (n = 29) were evaluated on d 14 and 21. Images were analyzed via ImageJ software to determine mean area of perfusion. Blood samples were collected on d -1 and 0 and analyzed for concentrations of estradiol using RIA. Using SAS, MIXED and FREQ were used to determine the influence of treatment on blood perfusion and estradiol, and incidence of standing estrus, respectively. Treatment with EB increased (P &lt; 0.001) the number of cows exhibiting standing estrus compared to control (21/24 vs 8/23, respectively). Treatment of EB did not (P &gt; 0.10) alter blood perfusion of the follicles or uterus on any day or perfusion of the CL on d 6. However, EB increased (P &lt; 0.036) the size of the CL on d 14 (25.06±1.7 vs 6.06±3.7) and tended (P &lt; 0.097) to increase the size of the CL on d 21. Treatment of EB increased (P &lt; 0.003) concentrations of estradiol on d 0 compared to control (21.35±4.49 vs 9.44±4.61 pg/mL). In conclusion, treatment with EB may play a role in changing the CL after ovulation.

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.

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.

Abstract P247: ACE2/ACE Imbalance in the Placental Circulation in an Ovine Model of Intrauterine Growth Restriction

Intrauterine growth restriction (IUGR) has been linked to the development of cardiovascular complications in the offspring. We have previously shown that in an ovine model of IUGR placental blood flow, in both umbilical and uterine artery, was decreased in diet-restricted dams. Angiotensin-converting enzyme (ACE), its metabolite Ang II and the receptor AT1 constitute the vascular-detrimental axis or renin angiotensin system, while ACE2, its metabolite Ang-(1-7) and Mas receptor constitute vasoprotective axis. This study tested the hypothesis that IUGR induces ACE2/ACE imbalance in the placental circulation. In ewe lambs, IUGR was accomplished by providing 60% of the nutrient requirement (RES) while the control group received adequate nutrients (CON) from day 50 to day 130 of gestation. At day 130, plasma samples were collected from umbilical artery (Um-A) and vein (Um-V), uterine artery (Ut-A) and vein (Ut-V), and jugular vein (J-V). ACE and ACE2 enzyme activities were determined by using enzyme-specific fluorogenic substrates, and enzyme-selective inhibitors, captopril and MLN-4760, respectively. Activities were expressed as percent inhibition by the respective inhibitors. ACE2 activity is decreased in the plasma obtained from Um-A (16±2), Um-V (29±4) and Ut-V (31±3) but not in Ut-A of RES group, compared to the CON group (Um-A 25±3, Um-V 42±2 and Ut-V 43±2, P<0.05, P<0.02 and P<.01, respectively, n=5). This resulted in decreased ACE2/ACE (CON: Um-A 0.43±0.03, Um-V 0.84±0.08 and Ut-V 0.82±0.05, and RES: Um-A 0.26±0.02, Um-V 0.46±0.05 and Ut-V 0.5±0.03, P<0.002, P<0.004, P<0.001, respectively). ACE activity was unchanged (n=5) in all four samples of placental circulation. In the J-V plasma ACE2 was decreased (24±2 vs 31±6, NS) and ACE was increased (68±4 vs 54±6, P<0.05) in RES group compared to CON (n=5). This resulted in decreased ACE2/ACE (CON: 0.58±0.04 and RES: 0.3±0.02). These observations suggest that IUGR induces ACE2/ACE imbalance. In the maternal systemic circulation it is largely due to increased ACE, while in the placental circulation it is due to decreased ACE2. Hyperactivity of ACE/Ang II/AT1 receptor pathway due attenuated opposing activity of ACE2 may restrict blood flow to the placental tissues during development.

Uteroplacental secretion of progesterone and estradiol-17β in an ovine model of intrauterine growth restriction

Using a mid to late gestation model of intrauterine growth restriction, uteroplacental secretion of progesterone and estradiol-17β were examined. From day 50 to 130 of gestation, 31 ewe lambs were allocated to receive 100% (ADQ) or 60% (RES) of nutrient requirements. At day 130, umbilical and uterine artery blood flows were determined and blood samples were collected from maternal saphenous artery, gravid uterine vein, umbilical vein, and umbilical artery. Uteroplacental secretion of progesterone was increased in RES compared to ADQ fed dams. There was a net secretion and net metabolism of estradiol-17β in RES, and ADQ fed dams, respectively. In relation to steroid synthesis, cotyledonary abundance of steroidogenic acute regulatory protein was greater in RES compared with ADQ fed dams, while abundance of aromatase was not different between dietary treatments. Caruncular aldo-keto reductase 1C abundance was less in RES compared to ADQ fed dams. The increase in progesterone secretion, therefore, is due in part to an increase in synthesis and a decrease in placental catabolism. Caruncular cytochrome P450 3A, which catalyzes the conversion of estrogens to catechol-estrogens, was in lesser abundance in RES compared to ADQ fed dams. Opposite responses in estradiol-17β uteroplacental secretion compared with metabolism may be mediated through placental estrogen metabolism via cytochrome P450 enzymes.

PHYSIOLOGY AND ENDOCRINOLOGY SYMPOSIUM: Alterations in uteroplacental hemodynamics during melatonin supplementation in sheep and cattle

Compromised placental function can result in fetal growth restriction which is associated with greater risk of neonatal morbidity and mortality. Large increases in transplacental nutrient and waste exchange, which support the exponential increase in fetal growth during the last half of gestation, are dependent primarily on the rapid growth and vascularization of the uteroplacenta. The amplitude of melatonin secretion has been associated with improved oxidative status and altered cardiovascular function in several mammalian species; however, melatonin mediated alterations of uteroplacental capacity in sheep and cattle are lacking. Therefore, our laboratories are examining uteroplacental blood flow and fetal development during maternal melatonin supplementation. Using a mid- to late-gestation ovine model of intrauterine growth restriction, we examined uteroplacental blood flow and fetal growth during supplementation with 5 mg/d of dietary melatonin. Maternal nutrient restriction decreased uterine arterial blood flow, while melatonin supplementation increased umbilical arterial blood flow compared with non-supplemented controls. Although melatonin treatment did not rescue fetal weight in nutrient restricted ewes; we observed disproportionate fetal size and fetal organ development. Elevated fetal concentrations of melatonin may result in altered blood flow distribution during important time points of development. These melatonin specific responses on umbilical arterial hemodynamics and fetal development may be partially mediated through vascular melatonin receptors. Recently, we examined the effects of supplementing Holstein heifers with 20 mg/d of dietary melatonin during the last third of gestation. Uterine arterial blood flow was increased by 25% and total serum antioxidant capacity was increased by 43% in melatonin supplemented heifers vs. non-supplemented controls. In addition, peripheral concentrations of progesterone were decreased in melatonin supplemented heifers vs. non-supplemented controls. Using an in vitro model, melatonin treatment increased the activity of cytochrome P450 2C, a progesterone inactivating enzyme, which was blocked by treatment with the melatonin receptor antagonist, luzindole. Elucidating the consequences of specific hormonal supplements on the continual plasticity of placental function will allow us to determine important endogenous mediators of offspring growth and development.

Effects of body condition score (BCS) on steroid- and eicosanoid-metabolizing enzyme activity in various mare tissues during winter anoestrus

The objective of this study was to determine the activity of steroid- and eicosanoid-metabolizing enzymes in horses with varying BCSs. The BCSs of twenty non-pregnant, anoestrous mares were determined prior to euthanasia, and tissue samples were collected from the liver, kidney, adrenal gland, ovary and endometrium. Cytochrome P450 1A (CYP1A), 2C (CYP2C), 3A (CYP3A) and uridine 5'-diphospho-glucuronosyltransferase (UGT) activities were determined using luminogenic substrates. The MIXED procedure of SAS was used to test the effect of BCS on enzyme activity and differences between tissues. Activity of CYP1A in adrenals was increased (p ≤ .05) in BCS 5 versus BCSs 4 and 6. Activity of CYP1A in the liver was increased (p = .05) in BCS 4 versus BCSs 5 and 6. Activity of CYP1A was 100-fold greater (p < .0001) in the liver than in the adrenal, ovary and kidney. Activity of CYP2C was 100-fold greater (p < .0001) in the liver than in the adrenal, ovary and endometrium. Activity of CYP3A was only detectable in the liver. Activity of UGT in the kidney was decreased (p = .02) in BCS 4 versus BCSs 5 and 6. Activity of UGT was threefold greater (p < .0001) in the liver than in the kidney, whereas activity of UGT was ninefold greater (p < .0001) in the kidney than in the ovary and endometrium. In general, BCS did not alter the activity of steroid- and eicosanoid-metabolizing enzymes in horses. However, tissue differences in these enzymes indicated abundant hepatic metabolism in horses, which is similar to other livestock species.

Supplementation of corn dried distillers' grains plus solubles to gestating beef cows fed low-quality forage: II. Impacts on uterine blood flow, circulating estradiol-17β and progesterone, and hepatic steroid metabolizing enzyme activity

The objective of this study was to investigate the effects of supplementing dried distillers' grains plus solubles (DDGS) during late gestation on uterine blood flow (BF), circulating steroid hormones and hepatic steroid metabolizing enzymes, and calf and placental weights. Multiparous beef cows were randomly divided into a control group (CON; = 15) consuming a diet containing 90% corn stover and 10% corn silage (DM basis) for ad libitum intake and a treatment group (SUP; = 12) consuming the same diet and DDGS (0.3% of BW). Corn silage inclusion was increased to 30% as gestation progressed to meet increasing caloric requirements. Ipsilateral and contralateral uterine BF and cross-sectional area (CSA) of each uterine artery were measured by Doppler ultrasonography on d 180, 216, and 246 of pregnancy. Contralateral BF and CSA increased ( < 0.01) as gestation advanced. Ipsilateral BF and CSA was affected by a treatment × day of gestation interaction ( < 0.05). A main effect of treatment ( = 0.02) and day ( < 0.01) was observed for total BF; BF increased over time and SUP cows had greater BF than CON cows. Circulating concentrations of both progesterone (P4) and estradiol-17β (E2) were affected by an interaction of treatment and day ( < 0.01). Concentrations of circulating E2 steadily increased throughout the study and were greater in CON cows than in SUP cows by d 242. Concentrations of P4 also increased over time; P4 of CON cows was greater than that of SUP cows by d 242. Uridine 5'-diphospho-glucuronosyltransferase (UGT) and cytochrome P450 1A (CYP1A) activity increased with advancing gestation ( < 0.01). There was greater UGT activity ( < 0.05) and a trend for greater CYP1A activity ( = 0.06) in SUP cows than in CON cows. Activity of cytochrome P450 3A was greater ( < 0.01) in SUP cows and decreased ( < 0.05) with advancing gestation. Supplementing DDGS to cows fed low-quality forage during late gestation increased uterine BF but decreased circulating E2 and P4 concentrations and altered hepatic steroid metabolizing enzyme activity. It was anticipated that enzyme activity would reflect circulating hormone levels; however, our data suggests the observed increases in BF are not driven by alterations in hormone concentration. Therefore, further research is warranted to elucidate the underlying mechanisms.

The effect of follicular wave on fertility characteristics in beef cattle

The objectives of this experiment were to determine the effects of follicular wave (first or second) on diameter of the dominant follicle, concentrations of progesterone and estradiol and the hepatic enzymes that inactivate them, thickness of the endometrium, and pregnancy rates to AI. Beef heifers ( = 101) and cows ( = 106) were randomly assigned to 1 of 2 treatments: insemination to the first follicular wave (FFW) or insemination to the second follicular wave (SFW). Estrous cycles of females were synchronized to ensure appropriate timing for the treatments. The MIXED procedure of SAS was used for analysis. A similar proportion of females in each treatment responded to presynchronization; however, females in the FFW group ovulated in response to the first injection of GnRH of the CO-Synch protocol more frequently. Only females ( = 94) that properly responded to ovulation synchronization were included in further analyses. Cows in the FFW group tended ( 0.06) to have larger ovulatory follicles 36 h post-PGF of the CO-Synch protocol compared to cows in the SFW group (14.22 ± 0.42 and 11.83 ± 0.49, respectively), whereas heifers were similar between treatment groups. Three d prior to AI, circulating concentrations of progesterone were lesser ( 0.01) in females in the FFW (3.63 ± 0.80 ng/mL) than in the SFW (7.12 ± 0.83 ng/mL), whereas concentrations of estradiol tended ( 0.08) to be greater in those in the FFW (82.72 ± 6.48 pg/mL) than in the SFW (65.55 ± 6.74 pg/mL). Concentrations of cytochrome P450 1A in the liver were lesser ( 0.01) in females in the FFW than those in the SFW (0.68 ± 0.08 vs. 0.96 ± 0.06, respectively). Endometrial thicknesses were similar between treatments but were thicker ( < 0.0001) in cows (9.73 ± 0.24 mm) than heifers (7.22 ± 0.26 mm). When considering all females or only those that were properly presynchronized, pregnancy rates were similar between treatments. However, when evaluating females that ovulated to the assigned follicular wave, there was a treatment by parity interaction ( = 0.04) with heifers in the FFW having a lesser pregnancy rate (25.9%) than heifers in the SFW (72.0%) while cows in both treatment groups were intermediate (45.4% in FFW and 50.0% in SFW). The differences in concentrations of steroids between treatment groups may affect fertility of heifers; however, additional research is necessary.