Fetal programming effect of rumen-protected methionine on primiparous Angus × Simmental offspring's performance and skeletal muscle gene expression.

Primiparous Angus × Simmental dams (n = 22) with an average body weight (BW) of 449 ±â€…32 kg of BW were divided based on two nutritional treatments: control (CTRL) and rumen-protected methionine (RPM). The control group received bermudagrass hay, corn gluten, and soybean hulls pellets supplementation (base diet); whereas the RPM group received the base diet in addition to 0.07% of DM of RPM at a fixed rate during the last trimester of gestation and the first ~80 d of lactation, in which calves (n = 17) were early weaned. Only male calves were included in this study. After weaning, calves born to RPM dams also received RPM from weaning (day 1) to day 100. Blood sampling and skeletal muscle biopsies for subsequent quantitative polymerase chain reaction (PCR) analysis were conducted on days 1, 25, 50, and 100 on calves. Quantitative PCR data were analyzed using GLIMMIX, and blood metabolites concentrations, BW, and body condition score (BCS) were analyzed using the MIXED procedure of SAS. There was no difference in maternal BW and BCS between treatments. Glucose and blood metabolites that served as biomarkers for liver health (e.g., aspartate transaminase, albumin, alkaline phosphatase, and alanine transaminase) were in the normal levels for all calves (P > 0.40). Calves in the RPM group had a greater expression of adipogenic genes (e.g., PPARG, LPL, and CEBPD) at day 100 compared with CTRL (P < 0.01). In addition, DNA methylation (DNMT1) and oxidative stress-related genes (SOD2 and NOS3) in the RPM group were upregulated at day 100 compared with CTRL (P < 0.01). These results may suggest that calves born to primiparous dams exposed to RPM supplementation are more prone to develop greater adipose tissue than CTRL calves. Furthermore, RPM supplementation may improve methylation processes, as shown by the upregulation of DNMT1. The results shown in our study aim at expanding the knowledge on fetal programming and early-life growth and development of beef cattle under supplementation with RPM.

Plane of nutrition plays a critical role in fetal and postnatal growth in beef cattle offspring. Methionine, a limiting amino acid in ruminants, is also involved in DNA methylation due to its role as S-adenosyl methionine precursor. A complete randomized design experiment was conducted to assess the fetal programming effect of rumen-protected methionine (RPM) supplementation on beef cattle. Calves born to primiparous beef heifers, that individually received RPM during the last trimester of gestation and lactation, had a greater expression of genes related to adipose tissue development, oxidative stress, and DNA methylation compared with those born to dams that did not receive rumen-protected supplementation. No difference in animal performance or blood parameters that serve as biomarkers for liver health status was detected. Our results suggest that maternal supplementation with RPM during the last trimester of gestation and lactation, and supplementation to the offspring after early weaning, could potentially increase adipose tissue development on male calves.

Hepatic transcript profiling in beef cattle: Effects of rumen-protected niacin supplementation.

The objective of our study was to assess the effect of rumen-protected niacin supplementation on the transcriptome of liver tissue in growing Angus × Simmental steers and heifers through RNA-seq analysis. Consequently, we wanted to assess the known role of niacin in the physiological processes of vasodilation, detoxification, and immune function in beef hepatic tissue. Normal weaned calves (~8 months old) were provided either a control diet or a diet supplemented with rumen-protected niacin (6 g/hd/d) for a 30-day period, followed by a liver biopsy. We observed a significant list of changes at the transcriptome level due to rumen-protected niacin supplementation. Several metabolic pathways revealed potential positive effects to the animal's liver metabolism due to administration of rumen-protected niacin; for example, a decrease in lipolysis, apoptosis, inflammatory responses, atherosclerosis, oxidative stress, fibrosis, and vasodilation-related pathways. Therefore, results from our study showed that the liver transcriptional machinery switched several metabolic pathways to a condition that could potentially benefit the health status of animals supplemented with rumen-protected niacin. In conclusion, based on the results of our study, we can suggest the utilization of rumen-protected niacin supplementation as a nutritional strategy could improve the health status of growing beef cattle in different beef production stages, such as backgrounding operations or new arrivals to a feedlot.

miRNA expression profiles of peripheral white blood cells from beef heifers with varying reproductive potential.

Reproductive performance is the most critical factor affecting production efficiency in the cow-calf industry. Heifers with low reproductive efficiency may fail to become pregnant during the breeding season or maintain a pregnancy. The cause of reproductive failure often remains unknown, and the non-pregnant heifers are not identified until several weeks after the breeding season. Therefore, improving heifer fertility utilizing genomic information has become increasingly important. One approach is using microRNAs (miRNA) in the maternal blood that play an important role in regulating the target genes underlying pregnancy success and thereby in selecting reproductively efficient heifers. Therefore, the current study hypothesized that miRNA expression profiles from peripheral white blood cells (PWBC) at weaning could predict the future reproductive outcome of beef heifers. To this end, we measured the miRNA profiles using small RNA-sequencing in Angus-Simmental crossbred heifers sampled at weaning and retrospectively classified as fertile (FH, n = 7) or subfertile (SFH, n = 7). In addition to differentially expressed miRNAs (DEMIs), their target genes were predicted from TargetScan. The PWBC gene expression from the same heifers were retrieved and co-expression networks were constructed between DEMIs and their target genes. We identified 16 differentially expressed miRNAs between the groups (p-value ≤0.05 and absolute (log2 fold change ≥0.05)). Interestingly, based on a strong negative correlation identified from miRNA-gene network analysis with PCIT (partial correlation and information theory), we identified miRNA-target genes in the SFH group. Additionally, TargetScan predictions and differential expression analysis identified bta-miR-1839 with ESR1 , bta-miR-92b with KLF4 and KAT2B, bta-miR-2419-5p with LILRA4, bta-miR-1260b with UBE2E1, SKAP2 and CLEC4D, and bta-let-7a-5p with GATM, MXD1 as miRNA-gene targets. The miRNA-target gene pairs in the FH group are over-represented for MAPK, ErbB, HIF-1, FoxO, p53, mTOR, T-cell receptor, insulin and GnRH signaling pathways, while those in the SFH group include cell cycle, p53 signaling pathway and apoptosis. Some miRNAs, miRNA-target genes and regulated pathways identified in this study have a potential role in fertility; other targets are identified as novel and need to be validated in a bigger cohort that could help to predict the future reproductive outcomes of beef heifers.

Transcriptomic dataset from peripheral white blood cells of beef heifers at weaning.

Reproductive failure of replacement breeding animals is one of the leading causes of loss to the beef production industry. The losses are further increased due to the inability to diagnose the reproductive potential of the beef heifer prior to the breeding season until the pregnancy outcome. To overcome this problem, a system to discriminate beef heifers with varying reproductive potential as early and accurately as possible is demanded. The omics technologies, such as transcriptomics, could predict the future reproductive potential of beef heifers. Therefore, this manuscript provides the gene expression profile dataset using RNA-Seq identified from peripheral white blood cells (PWBC) of beef heifers at weaning. To accomplish this, the blood samples were collected at the time of weaning, processed to extract the PWBC pellet and stored at - 80 °C until further processing. After the breeding protocol (artificial insemination (AI) followed by natural bull service) and pregnancy diagnosis, the heifers that were pregnant to AI (n = 8) or remained open (n = 7) were utilized for this study. Total RNA was extracted from PWBC collected at the time of weaning from these samples and subjected to sequencing using the Illumina Nova-Seq platform. High-quality sequencing data was analyzed using a bioinformatic workflow based on FastQC and MultiQC for quality control, STAR for read alignment, and DESeq2 for differential expression analysis. Genes were considered significantly differentially expressed after adjustment with Bonferroni correction (padj ≤ 0.05) and absolute (log2 fold change) ≥ 0.5. Raw and processed RNA-Seq data were deposited and made publicly available on the gene expression omnibus database (GEO; GSE221903). To our knowledge, this is the first dataset investigating the change in the gene expression level as early as weaning to predict the future reproductive outcome in beef heifers. Interpretation of the main findings based on this data is reported in a research article titled "mRNA Signatures in Peripheral White Blood Cells Predicts Reproductive Potential in Beef Heifers at Weaning" [1].

mRNA Signatures in Peripheral White Blood Cells Predict Reproductive Potential in Beef Heifers at Weaning.

Reproductive failure is a major contributor to inefficiency within the cow-calf industry. Particularly problematic is the inability to diagnose heifer reproductive issues prior to pregnancy diagnosis following their first breeding season. Therefore, we hypothesized that gene expression from the peripheral white blood cells at weaning could predict the future reproductive potential of beef heifers. To investigate this, the gene expression was measured using RNA-Seq in Angus-Simmental crossbred heifers sampled at weaning and retrospectively classified as fertile (FH, n = 8) or subfertile (SFH, n = 7) after pregnancy diagnosis. We identified 92 differentially expressed genes between the groups. Network co-expression analysis identified 14 and 52 hub targets. ENSBTAG00000052659, OLR1, TFF2, and NAIP were exclusive hubs to the FH group, while 42 hubs were exclusive to the SFH group. The differential connectivity between the networks of each group revealed a gain in connectivity due to the rewiring of major regulators in the SFH group. The exclusive hub targets from FH were over-represented for the CXCR chemokine receptor pathway and inflammasome complex, while for the SFH, they were over-represented for immune response and cytokine production pathways. These multiple interactions revealed novel targets and pathways predicting reproductive potential at an early stage of heifer development.

Machine Learning-Based Co-Expression Network Analysis Unravels Potential Fertility-Related Genes in Beef Cows.

Reproductive failure is still a challenge for beef producers and a significant cause of economic loss. The increased availability of transcriptomic data has shed light on the mechanisms modulating pregnancy success. Furthermore, new analytical tools, such as machine learning (ML), provide opportunities for data mining and uncovering new biological events that explain or predict reproductive outcomes. Herein, we identified potential biomarkers underlying pregnancy status and fertility-related networks by integrating gene expression profiles through ML and gene network modeling. We used public transcriptomic data from uterine luminal epithelial cells of cows retrospectively classified as pregnant (P, n = 25) and non-pregnant (NP, n = 18). First, we used a feature selection function from BioDiscML and identified SERPINE3, PDCD1, FNDC1, MRTFA, ARHGEF7, MEF2B, NAA16, ENSBTAG00000019474, and ENSBTAG00000054585 as candidate biomarker predictors of pregnancy status. Then, based on co-expression networks, we identified seven genes significantly rewired (gaining or losing connections) between the P and NP networks. These biomarkers were co-expressed with genes critical for uterine receptivity, including endometrial tissue remodeling, focal adhesion, and embryo development. We provided insights into the regulatory networks of fertility-related processes and demonstrated the potential of combining different analytical tools to prioritize candidate genes.

Co-Expression Network and Integrative Analysis of Metabolome and Transcriptome Uncovers Biological Pathways for Fertility in Beef Heifers.

Reproductive failure remains a significant challenge to the beef industry. The omics technologies have provided opportunities to improve reproductive efficiency. We used a multistaged analysis from blood profiles to integrate metabolome (plasma) and transcriptome (peripheral white blood cells) in beef heifers. We used untargeted metabolomics and RNA-Seq paired data from six AI-pregnant (AI-P) and six nonpregnant (NP) Angus-Simmental crossbred heifers at artificial insemination (AI). Based on network co-expression analysis, we identified 17 and 37 hub genes in the AI-P and NP groups, respectively. Further, we identified TGM2, TMEM51, TAC3, NDRG4, and PDGFB as more connected in the NP heifers' network. The NP gene network showed a connectivity gain due to the rewiring of major regulators. The metabolomic analysis identified 18 and 15 hub metabolites in the AI-P and NP networks. Tryptophan and allantoic acid exhibited a connectivity gain in the NP and AI-P networks, respectively. The gene-metabolite integration identified tocopherol-a as positively correlated with ENSBTAG00000009943 in the AI-P group. Conversely, tocopherol-a was negatively correlated in the NP group with EXOSC2, TRNAUIAP, and SNX12. In the NP group, α-ketoglutarate-SMG8 and putrescine-HSD17B13 were positively correlated, whereas a-ketoglutarate-ALAS2 and tryptophan-MTMR1 were negatively correlated. These multiple interactions identified novel targets and pathways underlying fertility in bovines.

Vacuum Packaging Can Extend Fresh Color Characteristics of Beef Steaks during Simulated Display Conditions.

Packaging technology is evolving, and the objectives of this study were to evaluate instrumental surface color, expert color evaluation, and lipid oxidation (TBARS) on beef longissimus lumborum steaks packaged in vacuum-ready packaging (VRF) or polyvinyl chloride (PVC) overwrap packaging. Paired strip loins (Institutional Meat Purchasing Specifications # 180) were cut into 2.54-cm-thick steaks and assigned randomly to one of two packaging treatments, VRF or PVC. Steaks packaged in VRF were lighter in color (p < 0.05) as the display period increased, whereas steaks packaged in PVC became darker (p < 0.05). Redness (a*) values were greater (p < 0.05) for PVC steaks until day 5, whereas VRF steaks had a greater (p < 0.05) surface redness from day 10 to 35 of the display period. Calculated spectral values of red to brown were greater (p < 0.05) for steaks in VRF than PVC. In addition, expert color evaluators confirmed VRF steaks were less brown and less discolored (p < 0.05) from day 5 to 35 of the display. Nonetheless, lipid oxidation was greater (p < 0.05) for PVC steaks from day 10 through day 35 of the display. Results from this study suggest that the use of vacuum packaging for beef steaks is plausible for maintaining surface color characteristics during extended display periods.

Surface Color Variations of Ground Beef Packaged Using Enhanced, Recycle Ready, or Standard Barrier Vacuum Films.

With current meat industry efforts focused on improving environmental influencers, adopting sustainable packaging materials may be an easier transition to addressing the sustainability demands of the meat consumer. With the growing popularity of vacuum-packaged meat products, the current study evaluated instrumental surface color on fresh ground beef using vacuum packaging films, recycle-ready film (RRF), standard barrier (STB) and enhanced barrier (ENB). Ground beef packaged using ENB barrier film was lighter (L*), redder (a*) and more vivid (chroma) than all other packaging treatments during the simulated display period (p < 0.05). By day 12 of the simulated retail display, the ground beef surface color became lighter (L*), more yellow (b*), less red (a*), less vivid (chroma) and contained greater forms of calculated metmyoglobin, oxymyoglobin (p < 0.05). The current results suggest that barrier properties of vacuum packaging film for ground beef are pivotal for extending the surface color during fresh shelf-life conditions.

Impact of Packaging Film and Beef Trimmings on Ground Beef Shelf Life.

Fresh beef storage in the retail setting can be presented in a variety of packaging methods, and identifying an alternative such as vacuum packaging to current traditional methods could potentially increase shelf life and reduce meat waste. The objective of this study was to identify the influence of packaging film and lean trimming sources on fresh ground beef surface color during a simulated retail display period. There were no differences (p > 0.05) in surface color redness (a*), yellowness (b*), chroma, or hue angle regardless of packaging film or lean trimmings. However, thiobarbituric acid reactive substances (TBARS) were greater (p < 0.05) for packages containing a greater percentage of CULL beef trimmings regardless of packaging film. In addition, pH values of ground beef packages did not differ (p > 0.05) among packaging film or lean trimming blends. Visual color did not differ (p > 0.05) throughout the simulated retail display period regardless of beef trimmings or packaging film. Microbial spoilage organisms were greater (p < 0.05) after the simulated display period. These results suggest that ground beef presented in a simulated retail setting using an alternative packaging platform, such as vacuum packaging, is plausible.

Complete Blood Count Analysis on Beef Cattle Exposed to Fescue Toxicity and Rumen-Protected Niacin Supplementation.

Offspring born to dams genetically tested for resistance to fescue toxicity were separated in groups based on their dams' resistance level (tolerant vs. susceptible). Rumen-protected niacin (RPN) is proposed as a potential alleviator for vasoconstriction produced by fescue toxicity. Complete blood count (CBC) analysis was utilized for detection of significant responses to treatments applied. Our objectives were as follows: (a) to analyze changes in CBC due to fescue toxicity, maternal resistance level, and RPN in growing offspring; and (b) to assess the effects of maternal resistance level when consuming endophyte-infected tall fescue seeds in addition to RPN in offspring performance. Body weight, average daily gain, or health status were not improved by RPN or the genetic test to detect fescue toxicity resistance. Typical signs of alkaloids intoxication and heat stress were noticed in offspring. Particularly, rectal temperature was greater for susceptible control heifers. Results showed that susceptible control offspring presented signs of anemia denoted by low mean corpuscular hemoglobin (MCH) and mean corpuscular volume (MCV). High levels of white blood cells (WBC) and basophils in combination to low neutrophils to lymphocytes ratio were the signs of infection or inflammation detected in the CBC analysis, especially in tolerant niacin steers. Furthermore, offspring of control heifers had a greater percentage of reticulocytes and RDW, denoting signs of anemia.

Rewiring of gene expression in circulating white blood cells is associated with pregnancy outcome in heifers (Bos taurus).

Infertility is a challenging phenomenon in cattle that reduces the sustainability of beef production worldwide. Here, we tested the hypothesis that gene expression profiles of protein-coding genes expressed in peripheral white blood cells (PWBCs), and circulating micro RNAs in plasma, are associated with female fertility, measured by pregnancy outcome. We drew blood samples from 17 heifers on the day of artificial insemination and analyzed transcript abundance for 10,496 genes in PWBCs and 290 circulating micro RNAs. The females were later classified as pregnant to artificial insemination, pregnant to natural breeding or not pregnant. We identified 1860 genes producing significant differential coexpression (eFDR < 0.002) based on pregnancy outcome. Additionally, 237 micro RNAs and 2274 genes in PWBCs presented differential coexpression based on pregnancy outcome. Furthermore, using a machine learning prediction algorithm we detected a subset of genes whose abundance could be used for blind categorization of pregnancy outcome. Our results provide strong evidence that transcript abundance in circulating white blood cells is associated with fertility in heifers.

Preconditioning beef cattle for long-duration transportation stress with rumen-protected methionine supplementation: A nutrigenetics study.

In general, beef cattle long-distance transportation from cow-calf operations to feedlots or from feedlots to abattoirs is a common situation in the beef industry. The aim of this study was to determine the effect of rumen-protected methionine (RPM) supplementation on a proposed gene network for muscle fatigue, creatine synthesis (CKM), and reactive oxygen species (ROS) metabolism after a transportation simulation in a test track. Angus × Simmental heifers (n = 18) were stratified by body weight (408 ± 64 kg; BW) and randomly assigned to dietary treatments: 1) control diet (CTRL) or 2) control diet + 8 gr/hd/day of top-dressed rumen-protected methionine (RPM). After an adaptation period to Calan gates, animals received the mentioned dietary treatment consisting of Bermuda hay ad libitum and a soy hulls and corn gluten feed based supplement. After 45 days of supplementation, animals were loaded onto a trailer and transported for 22 hours (long-term transportation). Longissimus muscle biopsies, BW and blood samples were obtained on day 0 (Baseline), 43 (Pre-transport; PRET), and 46 (Post-transport; POST). Heifers' average daily gain did not differ between baseline and PRET. Control heifer's shrink was 10% of BW while RPM heifers shrink was 8%. Serum cortisol decreased, and glucose and creatine kinase levels increased after transportation, but no differences were observed between treatments. Messenger RNA was extracted from skeletal muscle tissue and gene expression analysis was performed by RT-qPCR. Results showed that AHCY and DNMT3A (DNA methylation), SSPN (Sarcoglycan complex), and SOD2 (Oxidative Stress-ROS) were upregulated in CTRL between baseline and PRET and, decreased between pre and POST while they remained constant for RPM. Furthermore, CKM was not affected by treatments. In conclusion, RPM supplementation may affect ROS production and enhance DNA hypermethylation, after a long-term transportation.

Evaluation of age, weaning weight, body condition score, and reproductive tract score in pre-selected beef heifers relative to reproductive potential.

BACKGROUND: Artificial insemination is a preferred breeding method for beef heifers as it advances the genetic background, produces a predictive and profitable calving season, and extends the heifer's reproductive life span. As reproductive efficiency in heifers is key for the success of beef cattle production systems, following artificial insemination, heifers are exposed to a bull for the remainder of the breeding season. Altogether, up to 95% of heifers might become pregnant in their first breeding season. Heifers that do not become pregnant at the end of the breeding season represent an irreparable economical loss. Additionally, heifers conceiving late in the breeding season to natural service, although acceptable, poses serious losses to producers. To minimize losses due to reproductive failure, different phenotypic parameters can be assessed and utilized as selection tools. Here, we tested the hypothesis that in a group of pre-selected heifers, records of weaning weight, age at weaning, age at artificial insemination, and age of dam differ among heifers of varied reproductive outcomes during the first breeding season. RESULTS: None of the parameters tested presented predictive ability to discriminate the heifers based on the response variable ('pregnant to artificial insemination', 'pregnant to natural service', 'not pregnant'). Heifers categorized with body condition score = 6 and reproductive tract score ≥ 4 had the greatest proportion of pregnancy to artificial insemination (49% and 44%, respectively). Furthermore, it was notable that heifers presenting body condition score = 6 and reproductive tract score = 5 presented the greatest pregnancy rate at end of the breeding season (89%). Heifers younger than 368 d at the start of the breeding season did not become pregnant to artificial insemination. Those young heifers had 12.5% chance to become pregnant in their first breeding season, compared to 87.5% if the heifers were older than 368 days. CONCLUSION: Our results suggest that beef heifers with body condition score = 6 and reproductive tract score ≥ 4 are more likely to become pregnant to artificial insemination. Careful assessment should be undertaken when developing replacement heifers that will not reach 12 months of age by the beginning of the breeding season.

Plasma metabolomic profiles differ at the time of artificial insemination based on pregnancy outcome, in Bos taurus beef heifers.

Infertility remains the most prevalent reason for cattle being removed from production environments. We utilized metabolomic profiling to identify metabolites in the blood plasma that may be useful in identifying infertile heifers at the time of artificial insemination (AI). Prior to AI, phenotypic parameters including body condition, weight, and reproductive organ measurements were collected. These were determined not effective at differentiating between fertile and infertile heifers. Analysis of the resulting metabolomic profiles revealed 15 metabolites at significantly different levels (T-test P ≤ 0.05), with seven metabolites having a greater than 2-fold difference (T-test P ≤ 0.05, fold change ≥2, ROC-AUC ≥ 0.80) between infertile and fertile heifers. We further characterized the utility of using the levels of these metabolites in the blood plasma to discriminate between fertile and infertile heifers. Finally, we investigated the potential role inflammation may play by comparing the expression of inflammatory cytokines in the white blood cells of infertile heifers to that of fertile heifers. We found significantly higher expression in infertile heifers of the proinflammatory markers tumor necrosis factor alpha (TNFα), interleukin 6 (IL6), and the C-X-C motif chemokine 5 (CXCL5). Our work offers potentially valuable information regarding the diagnosis of fertility problems in heifers undergoing AI.

Transcriptome profiles in peripheral white blood cells at the time of artificial insemination discriminate beef heifers with different fertility potential.

BACKGROUND: Infertility is a longstanding limitation in livestock production with important economic impact for the cattle industry. Female reproductive traits are polygenic and lowly heritable in nature, thus selection for fertility is challenging. Beef cattle operations leverage estrous synchronization in combination with artificial insemination (AI) to breed heifers and benefit from an early and uniform calving season. A couple of weeks following AI, heifers are exposed to bulls for an opportunity to become pregnant by natural breeding (NB), but they may also not become pregnant during this time period. Focusing on beef heifers, in their first breeding season, we hypothesized that: a- at the time of AI, the transcriptome of peripheral white blood cells (PWBC) differs between heifers that become pregnant to AI and heifers that become pregnant late in the breeding season by NB or do not become pregnant during the breeding season; and b- the ratio of transcript abundance between genes in PWBC classifies heifers according to pregnancy by AI, NB, or failure to become pregnant. RESULTS: We generated RNA-sequencing data from 23 heifers from two locations (A: six AI-pregnant and five NB-pregnant; and B: six AI-pregnant and six non-pregnant). After filtering out lowly expressed genes, we quantified transcript abundance for 12,538 genes. The comparison of gene expression levels between AI-pregnant and NB-pregnant heifers yielded 18 differentially expressed genes (DEGs) (ADAM20, ALDH5A1, ANG, BOLA-DQB, DMBT1, FCER1A, GSTM3, KIR3DL1, LOC107131247, LOC618633, LYZ, MNS1, P2RY12, PPP1R1B, SIGLEC14, TPPP, TTLL1, UGT8, eFDR≤0.02). The comparison of gene expression levels between AI-pregnant and non-pregnant heifers yielded six DEGs (ALAS2, CNKSR3, LOC522763, SAXO2, TAC3, TFF2, eFDR≤0.05). We calculated the ratio of expression levels between all gene pairs and assessed their potential to classify samples according to experimental groups. Considering all samples, relative expression from two gene pairs correctly classified 10 out of 12 AI-pregnant heifers (P = 0.0028) separately from the other 11 heifers (NB-pregnant, or non-pregnant). CONCLUSION: The transcriptome profile in PWBC, at the time of AI, is associated with the fertility potential of beef heifers. Transcript levels of specific genes may be further explored as potential classifiers, and thus selection tools, of heifer fertility.

Impact of a killed Tritrichomonas foetus vaccine on clearance of the organism and subsequent fertility of heifers following experimental inoculation.

Tritrichomonas foetus is a sexually transmitted reproductive pathogen of cattle that causes transient infertility, early embryonic death, metritis, pyometra, and sporadic abortions. The objective of this research was to assess the impact on reproductive health of vaccinating naïve heifers with a killed T. foetus vaccine (TrichGuard) before experimental exposure followed by breeding. A total of 40 beef heifers were randomly assigned into two treatment groups. Heifers where then vaccinated with two doses of TrichGuard or sham vaccinated with 0.9% sterile saline according to their respective groups. Sixty days following vaccination or sham vaccination, heifers were intravaginally inoculated with 2 × 106 organisms of a cloned isolate of T. foetus of bovine origin (CDTf-4) during synchronized estrus. Three days following inoculation of T. foetus, bulls free of T. foetus were introduced for natural breeding. Three bulls were maintained with the 40 heifers (20 vaccinated; 20 sham vaccinated) for a 49-day breeding season. Cervical mucous samples were obtained from each heifer at Day 0 and at 29 additional time points throughout the study for T. foetus culture. Pregnancy assessments were performed routinely by using transrectal palpation and ultrasonography. Pregnancies were detected in 19/20 (95%) vaccinated heifers and 14/20 (70%) sham-vaccinated heifers (P = 0.046). Only 4/20 (20%) of the sham-vaccinated heifers gave birth to a live calf compared with 10/20 (50%) of the vaccinated heifers (P = 0.048). Thus, embryonic or fetal loss was detected in 9/19 (47%) vaccinated heifers and 10/14 (71%) sham-vaccinated heifers (P = 0.153). The interval of time between inoculations with T. foetus and conceptions of pregnancies that were maintained until birth did not differ significantly between groups (vaccinated = 18.7 days; sham-vaccinated = 17.3 days; P = 0.716). The infectious challenge in this study proved to be very rigorous as a positive culture was detected from all heifers. The culture-positive results on the last culture day did not differ significantly (P = 0.115) between vaccinated heifers (63.9 days) and sham-vaccinated heifers (79.2 days). All uterine culture samples collected from the 26 nonpregnant heifers on Day 207 postinoculation did not result in the detection of T. foetus. These findings indicate that the killed, whole cell vaccine used in this study (TrichGuard) was effective in improving reproductive health evidenced by significantly reducing losses associated with T. foetus infections.

Evaluation of reproductive protection against bovine viral diarrhea virus and bovine herpesvirus-1 afforded by annual revaccination with modified-live viral or combination modified-live/killed viral vaccines after primary vaccination with modified-live viral vaccine.

The objective of this study was to compare reproductive protection in cattle against bovine viral diarrhea virus (BVDV) and bovine herpesvirus 1 (BoHV-1) provided by annual revaccination with multivalent modified-live viral (MLV) vaccine or multivalent combination viral (CV) vaccine containing temperature-sensitive modified-live BoHV-1 and killed BVDV when MLV vaccines were given pre-breeding to nulliparous heifers. Seventy-five beef heifers were allocated into treatment groups A (n=30; two MLV doses pre-breeding, annual revaccination with MLV vaccine), B (n=30; two MLV doses pre-breeding, annual revaccination with CV vaccine) and C (n=15; saline in lieu of vaccine). Heifers were administered treatments on days 0 (weaning), 183 (pre-breeding), 366 (first gestation), and 738 (second gestation). After first calving, primiparous cows were bred, with pregnancy assessment on day 715. At that time, 24 group A heifers (23 pregnancies), 23 group B heifers (22 pregnancies), and 15 group C heifers (15 pregnancies) were commingled with six persistently infected (PI) cattle for 16days. Ninety-nine days after PI removal, cows were intravenously inoculated with BoHV-1. All fetuses and live offspring were assessed for BVDV and BoHV-1. Abortions occurred in 3/23 group A cows, 1/22 group B cows, and 11/15 group C cows. Fetal infection with BVDV or BoHV-1 occurred in 4/23 group A offspring, 0/22 group B offspring, and 15/15 group C offspring. This research demonstrates efficacy of administering two pre-breeding doses of MLV vaccine with annual revaccination using CV vaccine to prevent fetal loss due to exposure to BVDV and BoHV-1.

Efficacy of multivalent, modified- live virus (MLV) vaccines administered to early weaned beef calves subsequently challenged with virulent Bovine viral diarrhea virus type 2.

BACKGROUND: Vaccination of young calves against Bovine viral diarrhea virus (BVDV) is desirable in dairy and beef operations to reduce clinical disease and prevent spread of the virus among cattle. Although protection from clinical disease by multivalent, modified-live virus (MLV) vaccines has been demonstrated, the ability of MLV vaccines to prevent viremia and viral shedding in young calves possessing passive immunity is not known. The purpose of this study was to compare the ability of three different MLV vaccines to prevent clinical disease, viremia, and virus shedding in early weaned beef calves possessing maternal immunity that were vaccinated once at 45 days prior to challenge with virulent BVDV 2. RESULTS: At 45 days following vaccination, calves that received vaccines B and C had significantly higher BVDV 1 and BVDV 2 serum antibody titers compared with control calves. Serum antibody titers for BVDV 1 and BVDV 2 were not significantly different between control calves and calves that received vaccine D. Following BVDV 2 challenge, a higher proportion of control calves and calves that received vaccine D presented viremia and shed virus compared with calves that received vaccines B and C. Rectal temperatures and clinical scores were not significantly different between groups at any time period. Calves that received vaccines B and C had significantly higher mean body weights at BVDV 2 challenge and at the end of the study compared with control calves. CONCLUSIONS: Moderate to low maternally-derived BVDV antibody levels protected all calves against severe clinical disease after challenge with virulent BVDV 2. Vaccines B and C induced a greater antibody response to BVDV 1 and BVDV 2, and resulted in reduced viremia and virus shedding in vaccinated calves after challenge indicating a greater efficacy in preventing virus transmission and reducing negative effects of viremia.

Effect of exercise and environmental terrain on development of the digital cushion and bony structures of the bovine foot.

OBJECTIVE: To determine whether exercise on alternative terrain affects the development of the digital cushion and bony structures of the bovine foot. ANIMALS: 20 weaned bull calves. PROCEDURES: Two-month-old calves were randomly allocated to an exercise or control group. For 4 months, the control group was maintained in grass paddocks, and the exercise group was maintained in a 0.8-km lane with a mixed terrain of dirt, stones (0.32- to 0.95-cm pea gravel and 5-cm crusher run), and grass. Water and food for the exercise group were located at opposite ends of the lane; calves were fed twice daily, which ensured they walked 3.2 km/d. Pedometers were applied to all calves to measure distance traveled. All calves were slaughtered at 6 months of age. The right forefeet and hind feet were harvested for MRI and CT evaluation. RESULTS: Control calves walked a mean of 1.1 km daily, whereas the exercised calves walked a mean of 3.2 km daily. Mean digital cushion volume and surface area were 25,335 mm(3) and 15,647 mm(2), respectively, for the exercised calves and 17,026 mm(3) and 12,745 mm(2), respectively, for the control calves. When weight was controlled, mean digital cushion volume and surface area for the exercise group were increased by 37.10% and 18.25%, respectively, from those for the control group. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that exercise on alternative terrain increased the volume and surface area of the digital cushion of the feet of dairy calves, which should make them less susceptible to lameness.