Consumption of endophyte-infected tall fescue results in a syndrome of negatively altered physiological systems, collectively known as fescue toxicosis. Another challenge to endophyte-infected tall fescue -based beef cattle operations is that the soils often are selenium (Se) poor, necessitating the need to provide supplemental Se. To test the general hypothesis that different forms of supplemental Se would ameliorate the negative effects of fescue toxicosis, predominately-Angus steers (BW = 183 ± 34 kg) were randomly selected from herds of fall-calving cows grazing an endophyte-infected tall fescue pasture and consuming vitamin-mineral mixes that contained 35 ppm Se as sodium selenite (ISe), SELPLEX (OSe), or an 1:1 blend of ISe and OSe (MIX). Steers were commonly weaned and depleted of Se for 98 d. Steers were assigned (n = 8 per treatment) to the same Se-form treatments upon which they were raised and subjected to summer-long common grazing of an endophyte-infected tall fescue pasture (0.51 ppm ergot alkaloids: ergovaline plus ergovalinine; 10.1 ha). Selenium treatments were administered by daily top-dressing 85 g of vitamin-mineral mix onto 0.23 kg soyhulls, using in-pasture Calan gates. The first project objective was to determine the effect of forms of supplemental Se on whole blood Se, serum prolactin, liver glutamine synthetase (GS) activity, carcass parameters, and growth performance (Experiment 1). In Experiment 1, whole blood Se increased for all treatments from day 0 to 22 and then did not change. Across periods, MIX and OSe steers had greater whole blood Se than ISe steer. Compared to ISe steers, MIX and OSe steers had more serum prolactin. Liver GS mRNA, protein content, and activity were greater in MIX and OSe steers than ISe steers. However, the ADG and carcass parameters were not affected by Se treatments. The second project objective was to determine the effect of forms of supplemental Se on serum clinical parameters of Experiment 1 steers (Experiment 2). In Experiment 2, across periods, MIX steers had more serum albumin than OSe, and ISe steers, respectively. Serum alkaline phosphatase (ALP) activity was greater in MIX and OSe steers. In addition, blood urea nitrogen (BUN), serum sodium, phosphorus, and magnesium concentration were affected by Se treatments. Partial correlation analysis revealed that serum albumin, BUN, and ALP activity were correlated with whole blood Se concentration. The third project objective was to evaluate the hepatic transcriptome profiles of Experiment 1 steers using microarray and targeted RT-PCR analyses (Experiment 3). In Experiment 3, bioinformatic analysis of microarray data indicated that hepatic glutamate/glutamine, proline, arginine, and citrulline metabolism was affected by different forms of supplemental Se. The mRNA expression of critical proteins involved in glutamate/glutamine (GLS2, GLUD1, GLUL), proline (PYCR1, ALDH18A1), and urea (ARG1, ARG2, OAT, NAGS, OTC, ORNT1) metabolism were differentially expressed by Se treatments. Collectively, we conclude that consumption of 3 mg Se/d as OSe or MIX forms of Se in vitamin-mineral mixes 1) increased whole blood Se content, an indicator of greater whole-body Se assimilation; 2) increased serum prolactin, albumin, and ALP, the reduction of which are hallmarks of fescue toxicosis; and 3) altered hepatic nitrogen metabolism, as indicated by changes in key enzymes of glutamate/glutamine, proline, and urea metabolism. However, 4) these positive effects on metabolic parameters were not accompanied by increased growth performance.

The first goal of the current research was to determine whether gene expression profiles differed between whole pituitaries of growing beef steers grazing pastures containing high (HE) or low (LE) amounts of toxic endophyte-infected tall fescue. The global (microarray analysis) and selected targeted (RT-PCR) mRNA expression patterns of pituitaries collected from beef steers (BW = 266 ± 15.5 kg) that had been randomly assigned to undergo summer-long grazing (89 to 105 d) of either HE (0.52 ppm ergot alkaloids) or LE (< 0.03 ppm ergot alkaloids) pastures were compared. Gene expression data were subjected to one-way ANOVA. The pituitaries of HE steers had 542 differentially expressed genes, and the pattern of altered gene expression was dependent on treatment. Targeted RT-PCR analysis corroborated these findings, including decreased expression of DRD2, PRL, POU1F1, GAL, and VIP and that of POMC and PCSK1, respectively. Canonical pathway analysis (Integrated Pathway Analysis, IPA) identified HE-dependent alteration in signaling of additional pituitary-derived hormones, including growth hormone and GnRH. In conclusion, consumption of endophyte-infected tall fescue alters the pituitary transcriptome profiles of steers in a manner consistent with their negatively affected physiological parameters. The second goal of this project was to test the hypothesis that sodium selenite (ISe), SEL-PLEX (OSe), vs. a 1:1 blend (MIX) of ISe and OSe in a basal vitamin-mineral (VM) mix would differentially alter pituitary transcriptome profiles in growing beef steers (BW = 183 ± 34 kg) commonly grazing an endophyte-infected tall fescue (HE) pasture. Steers were randomly selected from herds of fall-calving cows grazing HE pasture and consuming VM mixes that contained 35 ppm Se as either ISe, OSe, or MIX forms. Steers were weaned, depleted of Se for 98 d, and subjected to summer-long common grazing of a 10.1 ha HE pasture containing 0.51 ppm ergot alkaloids. Steers were assigned (n = 8) to the same Se-form treatments on which they were raised. Selenium treatments were administered by daily top-dressing 85 g of VM mix onto 0.23 kg soyhulls, using in-pasture Calan gates. Pituitaries were collected at slaughter and changes in global (microarray) and selected (RT-PCR) mRNA expression patterns determined. The effects of Se treatment on relative gene expression were subjected to one-way ANOVA. The form of Se affected the expression of 542 annotated genes. Integrated Pathway Analysis found a canonical pathway network between prolactin and POMC/ACTH/ α-MSH synthesis-related proteins, and that mitochondrial dysfunction was a top-affected canonical pathway. Targeted RT-PCR analysis found that the relative abundance of mRNA encoding prolactin and POMC/ACTH/ α-MSH synthesis-related proteins was affected by the form of Se, as were mitochondrial dysfunction-related proteins OSe steers appeared to have a greater prolactin synthesis capacity vs. ISe steers through decreased dopamine receptor D2 signaling, whereas MIX steers had a greater prolactin synthesis capacity and release potential by increasing TRH concentrations than ISe steers. OSe steers also had a greater ACTH and α-MSH synthesis potential than ISe steers. We conclude that form of Se in VM mixes affected genes responsible for prolactin and POMC/ACTH/α-MSH synthesis, and mitochondrial function in pituitaries of growing beef steers commonly grazing an HE pasture. The third goal was to test the hypothesis that sodium selenite (ISe), SEL-PLEX (OSe), vs. a 1:1 blend (MIX) of ISe and OSe in a basal vitamin-mineral (VM) mix would differentially alter selenoprotein profiles in pituitaries and livers of growing beef steers commonly grazing an endophyte-infected tall fescue (HE) pasture (i.e., the same steers used in Goal 2). The effects of Se treatment on relative gene expression were subjected to one-way ANOVA. The mRNA content of 6 selenoproteins in the pituitary was affected by Se treatments, along with two selenoprotein P receptors, whereas the expression of two selenoproteins was altered in the liver. We conclude that the change in selenoprotein gene expression in pituitaries indicates that OSe steers have a greater potential capacity to manage against oxidative damage, maintain cellular redox balance, and have a better quality control of protein-folding in their pituitaries than ISe steers. The change in selenoprotein gene expression by the liver indicates that MIX steers have a greater redox signaling capacity and capacity to manage oxidative damage than ISe steers.

Transitioning cattle from a high-forage to a high-concentrate diet increases the risk for ruminal acidosis and is often related to decreased feed intake, which compromises animal health and performance. Since control of feed intake and rumen motility are closely related, we hypothesized that a reduction in rumen motility may be associated with a reduction in feed intake during this transition. Computer programs were created to analyze feed disappearance and rumen pressure data for feeding behavior as well as identification and characterization of rumen contractions, respectively. This method enabled timely analysis of large datasets and removed subjectivity associated with manual analysis. In the second part of this series, cattle were moderately transitioned from a 70% to a 90% concentrate diet, and SARA was induced. Although, reductions in feed intake were modest, on day 2 of high-grain feeding, animals slowed feed consumption rate and displayed a reduction in rumen contraction frequency, amplitude, and duration. Next, an abrupt transition from 50% to 90% concentrate was used to induce ruminal acidosis and cause some animals to stop eating. The abrupt increase in dietary concentrate was also associated with reductions in rumen motility. Patterns of ruminal pH, viscosity, and motility changes were related to when cattle reduced feed intake. Endotoxin quantification in blood samples from the ruminal vein, portal vein, and mesenteric artery suggested the point of endotoxin translocation into blood was across the ruminal epithelium. Additionally, the greater the concentration of endotoxin in the plasma, the more likely animals were to go “off-feed.” By understanding the physiological and behavioral mechanisms by which cattle adapt to high-grain diets, we can improve animal health and performance through these diet transitions.

The dam vaginal microbiota is the first major microbial inoculating community within the neonate. The composition of the dam vaginal microbiota has implications in calf commensal microbiota development. Alterations of the dam microbial community prior to parturition could alter inoculating communities and immune responses in both the dam and calf. Thus, authors aimed to elucidate the microbial community composition of the bovine dam vaginal and calf nasal microbiota post-partum after utilizing betadine lavages (BL). The dam vaginal and calf nasal microbial communities and immune responses were evaluated at 0-, 15-, 30- and 60-day post-partum. Microbiota composition of the dam haircoat, udder, and IgG in the colostrum/calf sera were also evaluated at day 0. Serial BLG prior to parturition did not alter the alpha diversity of the dam-vaginal microbiota but did alter the calf-nasal microbiota at parturition (P = 0.03). Dams receiving BLG prior to calving had increased colostrum IgG concentrations compared to CON dams (P =0.04). These results suggest physiological insults (BLG) prior to parturition led to an increased immune response which altering dam colostrum IgG. Thus, neonatal colostrum consumption could drive immune responses against inoculating bacteria resulting in differing nasal microbial communities between treatment groups. The beta diversity of the calf nasal microbiota was significantly different at day 0 compared to all other timepoints (P = 0.006). The calf nasal beta diversity at day 15 was similar to day 30 (P = 0.38) but significantly different compared to day 60 (P = 0.006). There was no effect of time on altering the alpha (P = 0.60) or beta (P = 0.06) diversity of the dam vaginal microbiota. The calf nasal microbiota was different from the dam vaginal microbiota at all timepoints post-partum, regardless of treatment. At day 15, the alpha and beta diversity of calves was altered compared to day 0, suggestive of a reinoculation timepoint between 0 and 14 days of age. Together, this data contributes to the paucity within beef cattle dam-calf post-partum microbiota literature and provides directionality for future research objectives within this field.

Researchers have investigated several factors that could alter fetal growth, including nutrient restriction (Valiente et al., 2021), hair shedding (Gray et al., 2011), and extreme hot and cold temperatures (Davidson et al., 2022). Hot temperatures and increased humidity percentages in the southeast United States caused researchers to investigate the hair coats of Angus cattle in the commercial production setting. An improvement in fiber digestibility and calf birth and weaning weights has been observed in Angus dams that shed 50% of the winter hair coat by May (Gray et al., 2011; Burnett et al., 2021). Our objective of this experiment was to investigate the nutrient digestibility of Angus calves born to cows that on average, shed early compared to calves from cows that shed later. Newly weaned, purebred Angus bull calves (early; n = 6, late; n = 6) were housed in metabolism crates for 10 d. Prior to the trial, calves had a 14 d adaption period to a 14% CP textured feed (CPC 14% Developer, CPC Commodities, Fountain Run, KY) and offered ad libitum Cynodon dactlyon hay and water. After 3 d crate acclimation period, urine, feces, orts, and hay samples were collected for 7 d. Concentrate was offered at 0.25% of average BW. Approximately 5% samples were taken of feces, and urine samples had 1-1.5% of 25% metaphosphoric acid added to prevent ammonia volatilization, and both collections were composited by animal. Orts were collected at 0600 h daily, dried, and composited by animal. Laboratory analysis included dry matter (DM), organic matter (OM), Ash, neutral detergent fiber (NDF), acid detergent fiber (ADF), Kjeldahl N (CP), and fat. Data were analyzed using the GLM procedure of SAS 9.4 in a completely randomized design with calf as the experimental unit. Significant (P ≤ 0.05) means were separated using Fischer’s protected LSD. The model for intake included average daily DM and OM (kg) and adjusted by body weight (BW%). For digestibility analysis, the model included: DM, OM, ash, NDF, ADF, hemi-cellulose (HC), CP, and fat. The N retention model included: N retained (g/d), N retained/consumed (%), and N retained/DM intake (%). There were no differences between early or late calves for DM intake (5.502 ± 0.2774 kg/d; 2.251 ± 0.1247 %BW), or OM intake (5.199 ± 0.2591 kg/d; 2.128 ± 0.1166 %BW). There were no differences in digestibility for either group for DM, OM, Ash, NDF, ADF, HC, CP, or fat (Table 1.). There were also no differences in N retention in either group of calves (3.686 ± 2.0242 g/d; 4.366 ± 2.3964 %; 0.064 ± 0.0355 %). Replication and further research are needed in this area to adequately understand factors influencing nutrient digestibility in calves born from early and late shedding dams.

As consumers have become increasingly interested in where their food comes from and how it is grown, the cattle and beef industry is without exception. Many consumers are beginning to question traditional animal husbandry practices and on-farm animal welfare protocol. It is essential that the food system meets new demands and understands consumer views. In order to address these concerns, the industry has rallied around the Beef Quality Assurance (BQA) program to set the standard for cattle welfare and beef quality, with the explicit goal of improving consumer confidence. The goal of this research is to determine if cattle producers would be willing to participate in animal welfare verification programs based on BQA to ensure that cattle are being raised in accordance with industry standards. Data were collected through an online survey sent to a national sample of cattle producers. The survey was designed to determine specific producer demographics that would be inclined to participate, their opinions of the BQA program, and using fractional factorial design to assess what components of a program would most likely encourage producer participation.

Nutrient restriction is a relatively common production insult to pregnancy in cattle. Recently, melatonin supplementation has been investigated as a possible therapeutic to rescue the negative effects of nutrient restriction. Neurotransmitters have been implicated as having negative programming effects in mouse and human pregnancies, manifested as metabolic and neurologic disorders. The role of neurotransmitters in fetal development has only begun to be understood in mice and humans. Neurotransmitters have not been analyzed in cattle, much less within the context of a compromised pregnancy. Brangus heifers were allotted to one of four treatments (ADQ-CON, RES-CON, ADQ-MEL, RES-MEL) in either Fall 2019 or Summer 2020. Cesarian sections, at day 240 of gestation, allowed for fetal and placental tissues to be collected for neurotransmitter and gene expression analysis. Alterations to neurotransmitter pathways were observed in a seasonally dependent manner. Future investigation is needed into the implications of altered neurotransmitters on post-natal life.

Assisted reproductive technologies, such as estrus synchronization and embryo transfer, can aid producers in improving genetics by increasing the number of progeny produced from elite females. The success of embryo transfer is dependent on a viable, competent embryo and a recipient with a receptive uterine environment. Follicular development and luteinization are pertinent for the recipient to establish a functional corpus luteum (CL) that can produce adequate concentrations of progesterone (P4) and provide a uterine environment conducive for the establishment of pregnancy. The objective of this study was to determine if exogenous follicle stimulating hormone (FSH), would increase the number of CL, size and blood perfusion of the largest CL, as well as circulatory concentrations of P4.

Seminal plasma is commonly known to serve as a transport medium for sperm as it moves through the female reproductive tract for fertilization, however, more recent evidence demonstrates seminal plasma induces an expansive inflammatory response in the uterus. Murine models have found this inflammatory response is important for clearing pathogens and poor-quality sperm, eliciting the secretion of cytokines, chemokines, and embryokines that aid in embryo attachment and growth, placental angiogenesis, and blunting maternal immunity to the embryo. However, there is minimal research on the impacts of seminal plasma uterine priming in bovine, and more specifically embryo growth, uterine blood flow, offspring growth and metabolism, and production efficiency. There is significant evidence that malnutrition and environmental stress during gestation alters uterine blood flow resulting in poor placental efficiency and poor fetal growth and development which persists postnatally. Animal production is vital in providing high-quality protein for human consumption but recent challenges of public misconception, consumer preferences, high input costs, and environmental impacts threaten the security of these production systems. Growth efficiency is imperative for improving economic and environmental sustainability, and in turn ensuring the longevity of animal production systems. Knowing the impact of seminal plasma on the uterus, and its potential role in placental efficiency and subsequent offspring growth and metabolic function, and the negative impacts these can have on economic and environmental sustainability drive the need to better understand seminal plasma uterine priming in bovine.

In-vitro produced embryos (IVP) differ greatly from in-vivo derived embryos (IVD) in gene expression, metabolism, development, and cryotolerance which limit the widespread use of this technology. In-vitro maturation (IVM) is one of the most important components for successful in-vitro embryo development. Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) have been found to be essential during oocyte maturation and thus female fertility. These proteins are oocyte secreted factors (OSFs) and are produced with pro- and mature protein regions where the pro-regions are thought to aid in protein folding and dimerization where heterodimerization the two proteins has been termed cumulin (Motterhead et al., 2015). Cumulin was found to have significant effects on oocyte maturation, blastocyst rate and hatching rates. However, only recombinant mature forms of these proteins are available commercially and making pro-mature GDF9 and BMP15 as well as pro- and mature cumulin is problematic. A few studies have evaluated the mature versions finding slight, although non-significant effects on oocyte maturation and blastocyst rates. However, none have studied the effects of using both mature GDF9 and BMP15 on bovine oocytes; thus, it was tested in this thesis. For the first experiment we hypothesized cumulus–oocyte complexes (COCs) matured for 23 h in maturation media supplemented with the mature proteins would increase blastocyst development, decreased lipid levels, and increased mitochondrial activity. Additionally, cryopreservation of embryos induces oxidative damage. However, studies have shown adding individual antioxidants to cryopreservation medium help alleviate post-thaw oxidative stress by reducing the accumulation of reactive oxygen species (ROS) and detoxifying lipid peroxidation (Tarin and Trounson, 1993; Lane et al., 2002; Takahashi et al., 2013). Few studies have evaluated effects using combinations of antioxidants supplemented in slow-freezing media. For the second experiment we further hypothesized blastocysts slow frozen with antioxidants would have increased cryotolerance compared to controls. For the first experiment, bovine embryos were IVP in three treatment groups, J: a commercial IVM media, T: control (TCM 199 supplemented with gonadotrophins), and TGB: control supplemented with GDF9 (200 ng/µL) and BMP15 (100 ng/µL). For experiment 2, only IVM groups T and TGB were used. Embryos were produced in five then four replicates, respectively, from abattoir ovaries, oocytes were matured, fertilized with frozen-thawed semen from one of three bulls, and presumptive zygotes were cultured for 7-8 days. For experiment 1, stage 6–9 blastocysts were stained with Nile Red or Mitotracker Red CMX-Rosamine to evaluate lipid content and mitochondrial polarity, respectively, utilizing confocal microscopy at ×40. Five slices per embryo were evaluated and averaged for fluorescence. Blastocyst rates, Nile Red (sqrt transformed, outliers removed), and Mitotracker data were analyzed by an ANOVA and means separated by Tukey HSD. For experiment 2 stage 6–9 blastocysts were slow frozen then thawed in a 2x2 factorial and evaluated for re-expansion 24 hours post-thaw. Results indicate that there was no difference for blastocyst rates for experiment 1 and 2 (J: 26.7 0.02%, T: 26.9 0.02%, TGB: 24.2 0.031%, P > 0.1; and T: 22.0 0.020%, TGB: 21.8 0.024%, P > 0.1; respectively). TGB’s Nile Red fluorescence intensity was significantly lower (5.09 2.16 AFU, P < 0.0001) than T (12.0 2.11) and J (11.05 2.18). MitoTracker fluorescence was similar among all treatments (P > 0.05). There was no significant interactions or main effects seen between cryopreservation groups; however, T/AO (52.9 0.05%, n = 37) and T/C (39.8 0.05%, n =38) having on average a 13.1% higher re-expansion rate and AO overall had on average 6.2% higher re-expansion rates. There was no difference seen between TGB/AO and TGB/C. These results suggest that the mature forms of GDF9 and BMP15 supplemented during oocyte maturation can lower lipid content of resulting embryos, however they do not increase blastocyst rates, mitochondrial activity, or re-expansion rates after cryopreservation.