Hormonal profile prior to luteolysis modulates the uterine luminal transcriptome in the subsequent cycle in beef cross-bred cows†.

Sex steroid concentrations modulate endometrial function and fertility in cattle. Our objective was to compare the post-estrus luminal transcriptome of cows that were exposed to contrasting concentrations of progesterone (P4) before luteolysis that displayed estrus and ovulated spontaneously. Cross-bred beef cows received either (1) a new CIDR and GnRH (day -9; high progesterone treatment; HP4; n = 16) or (2) a previously used CIDR, PGF2α, and GnRH (low progesterone treatment; LP4; n = 24). All cows received PGF2α at CIDR removal (day -2). Ovarian ultrasonography and blood collections were performed on days -9, -2, -0.5, and 0 (day of observed estrus), and days 4, 7, and 14 for measurement of ovarian structures, P4, and estradiol (E2). Luminal epithelial cells were collected using a cytology brush on days 4, 7, and 14 for RNAseq. On day -2, CL area and concentrations of P4 were greater, while on day -0.5, concentrations of E2 were decreased in HP4. Ovarian structures and hormonal concentrations were similar on days 4, 7, or 14 (P > 0.05). There were enriched pathways in HP4 related to activation and signaling of the innate immune system at day 4, downregulation in the network involved in the extracellular matrix remodeling at day 7, and exacerbated inflammatory response as well as differentiation and activation of macrophages at day 14 (Benjamini-Hochberg P-value ≤ 0.05). In conclusion, manipulation of pre-luteolysis sex steroid concentrations altered the post-estrus luminal transcriptome even though all cows showed estrus and ovulated spontaneously.

Pre-estrus progesterone does not affect post-estrus luminal metabolome in cross-bred beef cows.

In brief: The concentration of progesterone through the estrous cycle modulates uterine function to affect the luminal metabolome. This paper reports that the dynamic changes in the bovine uterine luminal metabolome during diestrus are independent of the concentration of progesterone in the previous cycle. Abstract: In cattle, the concentration of sex steroids modulates uterine function, which is reflected in the composition of the luminal metabolome. Ultimately, the uterine luminal metabolome influences embryonic growth and development. Our objectives were (i) to compare the luminal metabolome 4, 7, and 14 days after estrus of cows that were exposed to greater (HP4; n = 16) vs lower (LP4; n = 24) concentrations of progesterone before displaying estrus and ovulating spontaneously and (ii) to identify changes in the luminal concentration of metabolites across these time points. Luminal epithelial cells and fluid were collected using a cytology brush, and gene expression and metabolite concentrations were assessed by RNAseq and targeted mass spectrometry, respectively. Metabolome profile was similar between treatments within each of days 4, 7, and 14 (false discovery rate (FDR): ≥ 0.1). Concentrations of 53 metabolites changed, independent of treatment, across the diestrus. Metabolites were mostly lipids (40 out 53) and the greatest concentrations were at day 14 (FDR: ≤ 0.1). On day 7, the concentration of putrescine and the gene expression of ODC1, PAOX, SLC3A2, and SAT1 increased (P ≤ 0.05). On day 14, the concentration of 3 ceramides, 4 glucosylceramides, and 12 sphingomyelins and the expression of SGMS2 were increased, in addition to the concentration of choline and 20 phosphatidylcholines. Collectively, the post-estrus concentration of luminal metabolites changed dynamically, independent of the concentration of sex steroids on the previous cycle, and the greatest magnitude changes were on day 14 when lipid metabolism was the most enriched pathway.

Bulls fed a high-gain diet decrease blastocyst formation after in vitro fertilization.

In brief: Paternal high-gain diet reduces blastocyst development following in vitro fertilization and embryo culture but does not affect gene expression or cellular allocation of resultant blastocysts. Abstract: Bulls used in cattle production are often overfed to induce rapid growth, early puberty, and increase sale price. While the negative consequences of undernutrition on bull sperm quality are known, it is unclear how a high-gain diet influences embryo development. We hypothesized that semen collected from bulls fed a high-gain diet would have a reduced capacity to produce blastocysts following in vitro fertilization. Eight mature bulls were stratified by body weight and fed the same diet for 67 days at either a maintenance level (0.5% body weight per day; n = 4) or a high-gain rate (1.25% body weight per day; n = 4). Semen was collected by electroejaculation at the end of the feeding regimen and subjected to sperm analysis, frozen, and used for in vitro fertilization. The high-gain diet increased body weight, average daily gain, and subcutaneous fat thickness compared to the maintenance diet. Sperm of high-gain bulls tended to have increased early necrosis and had increased post-thaw acrosome damage compared with maintenance bulls, but diet did not affect sperm motility or morphology. Semen of high-gain bulls reduced the percentage of cleaved oocytes that developed to blastocyst stage embryos. Paternal diet had no effect on the number of total or CDX2-positive cells of blastocysts, or blastocysts gene expression for markers associated with developmental capacity. Feeding bulls a high-gain diet did not affect sperm morphology or motility, but increased adiposity and reduced the ability of sperm to generate blastocyst-stage embryos.

Understanding placentation in ruminants: a review focusing on cows and sheep.

Mammals differ regarding their placentae, but in all species placental trophoblasts interact intimately with the uterine endometrium to mediate the transfer of nutrients from the mother to the embryo/fetus through the closely juxtaposed microcirculatory systems of the uterus and placenta. Placentation in ruminants is intermediate between the non-invasive type, as observed in the epitheliochorial placenta of pigs, and the invasive type, as observed in the haemochorial placentae of mice and humans. In ruminants, placental trophoblast cells invade uterine endometrial tissue, but invasion is believed to be limited to the endometrial luminal epithelium (LE). In the LE there are varying degrees of syncytialisation among species, with syncytialisation being more extensive in sheep than cows. The hallmarks of placentation in ruminants include: (1) an extended period in which conceptuses (embryos and associated placental membranes) elongate and must be supported by secretions (histotroph) from the uterus; (2) a cascade involving an array of adhesion molecules that includes integrin-mediated attachment of the conceptus trophoblast to the endometrial LE for implantation; (3) syncytialisation of the developing early placenta, a process for which there is currently limited understanding; and (4) development of placentomes that define the cotyledonary placentae of cows and sheep, and provide haemotrophic support of fetal development.

Early juvenile but not mid-to-late prenatal nutrition controls puberty in heifers but neither impact adult reproductive function†.

Objectives were to test the hypothesis that pre- and post-natal nutrition in the bovine female, independently or interactively, affect age at puberty and functional characteristics of the estrous cycle of sexually mature offspring. Brangus and Braford (n = 97) beef cows bearing a female fetus were fed to achieve body condition scores of 7.5-8 (H, obese), 5.5-6 (M, moderate), or 3-3.5 (L, thin) by the start of the third trimester and maintained until parturition. Heifer offspring were weaned and fed to gain weight at either a high (H; 1 kg/day) or a low (L; 0.5 kg/day) rate between 4 and 8 months of age, then fed the same diet during a common feeding period until puberty, which resulted in compensatory growth of heifers in the L group. Heifers (n = 95) from the H postnatal diet reached puberty 2 months earlier (12 ± 0.4 months; P = 0.0002) than those from the L postnatal diet (14 ± 0.4 months). Estrous cycles of a subgroup of postpubertal heifers (n = 53) were synchronized to evaluate antral follicle count (AFC), rate of growth and size of the pre-ovulatory follicle, size of corpus luteum and ovary, endometrial thickness, and plasma concentrations of progesterone and estradiol-17ß (E2). Although there was a trend for postnatal H heifers to have greater AFC and plasma concentrations of E2 compared to L heifers, neither pre- nor post-natal nutrition affected any other physiological or hormonal variables, including short-term fertility. Postnatal nutritional effects on pubertal age remained the dominant observed feature.

Interactions of circulating estradiol and progesterone on changes in endometrial area and pituitary responsiveness to GnRH†.

Changes in circulating progesterone (P4) and estradiol (E2) during proestrus produce dynamic changes in endometrial function and pituitary release of gonadotropins. Independent and combined effects of P4 and E2 on endometrium and pituitary were evaluated. In a preliminary study, an exogenous hormone model of proestrus was created by removal of corpus luteum and follicles ≥5 mm followed by gradual removal of intravaginal P4 implants during 18 h and treatment with increasing doses of estradiol benzoate during 48 h to mimic proestrus using high E2 (n = 9) or low E2 (n = 9). Decreased P4, increased E2, and increased endometrial area (EA) simulated proestrus in high-E2 cows and this was used subsequently. The main experiment used a 2 × 2 factorial design with: high E2 and low P4 (n = 11); high E2 and high P4 (n = 11); low E2 and high P4 (n = 11); low E2 and low P4 (n = 10). At 48 h, gonadotropin-releasing hormone (GnRH)-induced luteinizing hormone (LH) and follicle stimulating hormone (FSH) release was determined. Variables were analyzed using PROCMIXED of Statistical Analysis System. The EA increased dramatically during 48 h only in high-E2 and low-P4 cows. For FSH, high-E2 cows had greater area under the curve (AUC) and FSH peak after GnRH than low E2, with mild negative effects of high P4. For LH, concentration at peak and AUC were 2-fold greater in high E2 compared to low-E2 groups, with low P4 also 2-fold greater than high-P4 groups. Thus, maximal changes in uterus and pituitary during proestrus depend on both low P4 and high E2, but different physiologic responses are regulated differently by E2 and P4. Changes in endometrium depend on low P4 and high E2, whereas GnRH-induced FSH secretion primarily depends on high E2, and GnRH-induced LH secretion is independently increased by high E2 or reduced by high P4.

Genomic merit for reproductive traits. II: Physiological responses of Holstein heifers.

Fertility traits were recently added to the evaluation of genetic merit, allowing for the selection of Holstein cattle with improved reproductive performance. In the current study, we investigated the associations among genomic merit for daughter pregnancy rate (GDPR) and heifer conception rate (GHCR) and physiological responses during proestrus and diestrus. Holstein heifers (n = 99) were classified based on GDPR [high = 3.26 ± 0.76 (1.6 to 5.3), n = 48; low = -0.17 ± 0.75 (-1.8 to 1.0), n = 51] and GHCR [high = 2.75 ± 0.77 (1.5 to 5.5), n = 49; low = 0.06 ± 0.67 (-2.1 to 1.2), n = 50]. Heifers were fitted with an automated estrous detection device, were treated with PGF2α for synchronization of estrus, and received either artificial insemination or embryo transfer at detected estrus. Blood was sampled at the time of PGF2α treatment, within 24 h of the onset of estrus (d 0), and on d 7, 14, 19 ± 2, 28, and 35. Blood samples from all heifers were analyzed for concentrations of estradiol (d 0) and progesterone (on the day of PGF2α treatment and d 0, 7, and 14). Blood samples from heifers pregnant on d 38 ± 3 were analyzed for concentrations of progesterone (d 0, 7, 14, 19 ± 2, 28, and 35), pregnancy-specific protein B (d 19 ± 2, 28, and 35), and insulin-like growth factor 1 (d 0, 7, 14, 19 ± 2, 28, and 35). Expression of mRNA for interferon-stimulated gene 15 in peripheral leukocytes isolated from blood collected on d 19 ± 2 was determined. Ovaries were scanned by ultrasound daily from d 0 to 4 or until ovulation was detected. Heifers with low GHCR tended to be less likely to be detected in estrus (78.0 vs. 91.8%). Estradiol concentration on d 0 was greater for heifers with high GDPR (4.53 ± 0.23 vs. 3.79 ± 0.23 pg/mL). The ovulatory follicle was larger for heifers with high GDPR (16.28 ± 0.33 vs. 14.55 ± 0.35 mm), whereas heifers with high GHCR tended to have smaller ovulatory follicles (15.00 ± 0.31 vs. 15.83 ± 0.37 mm). Heifers with high GDPR tended to be more likely to ovulate within 96 h of the onset of estrus (90.7 vs. 75.0%). Among heifers pregnant on d 38 ± 3, GDPR and GHCR were not associated with mRNA expression for interferon-stimulated gene 15. Heifers with high GDPR had greater concentration of pregnancy-specific protein B from d 28 to 35 (3.03 ± 0.15 vs. 2.48 ± 0.1 ng/mL). Heifers with high GHCR tended to have greater insulin-like growth factor 1 concentration from d 7 to 35 (108.0 ± 3.2 vs. 97.7 ± 4.2 ng/mL). Our results suggest that selection for Holstein cattle for GDPR may have positive effects on reproductive performance through changes in ovarian follicle development and steroidogenesis. Although selection of Holstein cattle for GHCR may negatively affect estrous expression by affecting ovarian follicle growth, selection for GHCR may improve reproductive performance by altering the somatotropic axis.

An in vivo model to assess the thermoregulatory response of lactating Holsteins to an acute heat stress event occurring after a pharmacologically-induced LH surge.

Hyperthermia occurring 10-12 h after LH surge reduces quality of maturing oocyte, thereby reducing fertility. Objective was to examine consequences of an acute heat stress and the influence of certain hormones on the thermoregulatory responses of lactating cows during this critical period. Between the months of February through May, cows were transported to a facility and maintained at a temperature-humidity index (THI) of 65.9 ±â€¯0.2 (thermoneutral) or exposed to changes in THI to simulate what may occur during an acute heat stress event (71-86 THI; heat stress); cows were rapidly cooled thereafter. Mixed model regressions with repeated measures were used to test respiration rates (RR) and rectal temperature (RT). Within 40 and 110 min of increasing THI, RR increased in a quadratic fashion (P < 0.001); RT increased by 0.04 ±â€¯0.1 °C (P < 0.001) per unit THI. Changes in RR lagged THI and preceded rises in RT. Average THI 3-days before treatment (prior THI) influenced RR (P = 0.050) and RT (P < 0.001) changes. Increased RR was more noticeable in heat-stressed cows when prior THI was in the 40 s. Rectal temperature of heat-stressed cows was 0.8 ±â€¯0.02 °C lower when prior THI was in the 40 s versus low 60 s. Levels of progesterone and luteinizing hormone before treatment were predictive of thermoregulatory response in heat-stressed cows. Rapid cooling decreased RR by 0.6 ±â€¯0.1 bpm (P < 0.001) and RT by 0.02 ±â€¯0.002 °C per min (P < 0.002). Speed and magnitude of thermoregulatory changes to an acute heat stress and after sudden cooling emphasizes importance of strategic cooling before ovulation. Efforts to do so when prior THI approaches levels expected to induce mild stress are especially important. Respiration rate is a useful indicator of the degree of hyperthermia a lactating cow is experiencing.

Colony-stimulating factor 2 acts from days 5 to 7 of development to modify programming of the bovine conceptus at day 86 of gestation†.

Colony-stimulating factor 2 (CSF2) is an embryokine that improves competence of the embryo to establish pregnancy and which may participate in developmental programming. We tested whether culture of bovine embryos with CSF2 alters fetal development and alleviates abnormalities associated with in vitro production (IVP) of embryos. Pregnancies were established by artificial insemination (AI), transfer of an IVP embryo (IVP), or transfer of an IVP embryo treated with 10 ng/ml CSF2 from day 5 to 7 of development (CSF2). Pregnancies were produced using X-sorted semen. Female singleton conceptuses were collected on day 86 of gestation. There were few morphological differences between groups, although IVP and CSF2 fetuses were heavier than AI fetuses. Bicarbonate concentration in allantoic fluid was lower for IVP than for AI or CSF2. Expression of 92 genes in liver, placenta, and muscle was determined. The general pattern for liver and placenta was for IVP to alter expression and for CSF2 to sometimes reverse this effect. For muscle, CSF2 affected gene expression but did not generally reverse effects of IVP. Levels of methylation for each of the three tissues at 12 loci in the promoter of insulin-like growth factor 2 (IGF2) and five in the promoter of growth factor receptor bound protein 10 were unaffected by treatment except for CSF2 effects on two CpG for IGF2 in placenta and muscle. In conclusion, CSF2 can act as a developmental programming agent but alone is not able to abolish the adverse effects of IVP on fetal characteristics.

Circulating microRNA as candidates for early embryonic viability in cattle.

Blood-borne extracellular vesicles (i.e., exosomes and microvesicles) carrying microRNAs (miRNAs) could make excellent biomarkers of disease and different physiologic states, including pregnancy status. We tested the hypothesis that circulating extracellular vesicle-derived miRNAs might differentiate the pregnancy status of cows that had maintained pregnancy to Day 30 from non-pregnant cows or from those that exhibited embryonic mortality between Days 17 and 30 of gestation. Cows were randomly assigned for artificial insemination with fertile semen (n = 36) or dead semen (n = 8; control group) on Day 0 (day of estrus). Blood was collected from all animals on Day 0 and on Days 17 and 24 after artificial insemination. Cows receiving live sperm were retrospectively classified as pregnant on Day 30 (n = 17) or exhibiting embryonic mortality between Days 17 and 30 (n = 19). Extracellular vesicles from Day 17 and 24 samples were isolated from serum using ultra-centrifugation, and their presence was confirmed by nanoparticle tracking and Western blot analyses (for CD81) prior to RNA extraction. MicroRNA sequencing was performed on pregnant, embryonic-mortality, and control cows (n = 4 per day), for a total of 24 independent reactions. In total, 214 miRNAs were identified in serum, 40 of which were novel. Based on differential abundance parameters, we identified 32 differentially abundant loci, representing 27 differentially abundant mature miRNA. At Days 17 and 24, specific miRNAs (e.g., miR-25, -16b, and -3596) were identified that differentiated the pregnancy status. In summary, we identified several circulating extracellular vesicles derived miRNAs that differ in abundance between embryonic mortality and pregnant cows.

Placental PAGs: gene origins, expression patterns, and use as markers of pregnancy.

Pregnancy-associated glycoproteins (PAGs) are abundantly expressed products of the placenta of species within the Cetartiodactyla order (even-toed ungulates). They are restricted to this order and they are particularly numerous in the Bovidae. The PAGs exhibit a range of temporal and spatial expression patterns by the placental trophoblasts and probably represent a group of related proteins that perform a range of distinct functions in the epitheliochorial and synepitheliochorial placental forms. This review presents an overview of the origins of the PAGs, a summary of PAG expression patterns, and their use as markers of pregnancy status. Speculations about their putative role(s) in pregnancy are also presented.

The WNT signaling antagonist Dickkopf-1 directs lineage commitment and promotes survival of the preimplantation embryo.

Successful embryonic development is dependent on factors secreted by the reproductive tract. Dickkopf-1 (DKK1), an antagonist of the wingless-related mouse mammary tumor virus (WNT) signaling pathway, is one endometrial secretory protein potentially involved in maternal-embryo communication. The purpose of this study was to investigate the roles of DKK1 in embryo cell fate decisions and competence to establish pregnancy. Using in vitro-produced bovine embryos, we demonstrate that exposure of embryos to DKK1 during the period of morula to blastocyst transition (between d 5 and 8 of development) promotes the first 2 cell fate decisions leading to increased differentiation of cells toward the trophectoderm and hypoblast lineages compared with that for control embryos treated with vehicle. Moreover, treatment of embryos with DKK1 or colony-stimulating factor 2 (CSF2; an endometrial cytokine known to improve embryo development and pregnancy establishment) between d 5 and 7 of development improves embryo survival after transfer to recipients. Pregnancy success at d 32 of gestation was 27% for cows receiving control embryos treated with vehicle, 41% for cows receiving embryos treated with DKK1, and 39% for cows receiving embryos treated with CSF2. These novel findings represent the first evidence of a role for maternally derived WNT regulators during this period and could lead to improvements in assisted reproductive technologies.

Impact of the Sire on Pregnancy Loss.

For over a century, scientists have attempted to develop techniques to accurately predict the fertility potential of a male's semen sample. In most livestock species, the sire is responsible for multiple pregnancies per year and up to hundreds of thousands of pregnancies if used for artificial insemination. Use of subfertile or infertile sires can have devastating impacts in regard to the reproductive efficiency of a cow herd. Despite the rapid expansion of fertility studies through advancements in molecular, genomic, and computer techniques, our understanding of male fertility is still far from complete. This article will provide an overview of the impact of the sire in pregnancy loss.

Impacts of learning experiences within an online extension initiative on application of research-based principles by beef stakeholders.

The objective of this study was to evaluate, characterize and quantify the learning experiences and subsequent application of research-based technologies by beef producers upon conclusion of an online extension certification program (44 Farms International Beef Cattle Academy, IBCA). Upon conclusion of the program, paricipants were invited to complete a structured interview. Interview transcripts (n = 19) were coded, categorized, and merged into four overarching themes: Strengths, Struggles, Courses, and Geographical origin. Within Strengths, the most frequent codes were Connections, Application, and Instructor Experience, with 61, 53, and 50 coded segments respectively. Within Struggles, the most frequent codes were Time Management, Level of Knowledge, and Language issues, with 27, 18, and 15 coded segments, respectively. For Courses in the program, the most frequently mentioned were Nutrition, Reproduction, and Genetics, with 35, 28, and 24 coded segments respectively. Correlation between codes was evaluated using Pearson and only statistically significant (P ≤ 0.05) correlations were included in the matrices for network analysis. Interpretation of the generated network analysis map (P ≤ 0.05; Q = 0.468) including all four categories of codes revealed close relationships between Application and the Strengths of Time management, Instructor Experience, and Connections. Application was also directly related to the Courses of Reproduction and Genetics, and the Struggle of Student Engagement and Guidance. Geographical origin was an important factor mediating different correlations. Developing countries (Brazil, Panama, Dominican Republic, and South Africa) were more closely related to the Struggle of Tuition cost, which, in turn was related to the perceived Prestige of the program. In Europe (Romania, Germany, and Kazakhstan), a stronger correlation to the Struggles of Material Relevance and Language Issues was described. Collectively, these results support the positive impact of a comprehensive and interactive extension initiative to leverage application of research-based principles by beef stakeholders around the world. Further, these outcomes indicate that the most valued aspects of the program regarding application are related to interpersonal experience with faculty and peers of the industry (Instructor Experience and Connections) and that perception of struggles and strengths is greatly influenced by socio-cultural aspects of the learning community.

Reproductive microbiome and cytokine profiles associated with fertility outcomes of postpartum beef cows.

Shifts from commensal bacteria (for example, Lactobacillus in the phylum Firmicutes) within the reproductive tract have been associated with changes in local reproductive immune responses and decreased fertility in humans. The objective of this study was to characterize the microbiome and cytokine concentrations before artificial insemination (AI) in vaginal and uterine flushes from postpartum beef cows. Twenty Bos indicus-influenced beef cows (approximately 60 d postpartum and free of reproductive, health, or physical issues) were enrolled. The B. indicus prostaglandin (PG) 5-d + controlled intervaginal drug-releasing estrus synchronization protocol was initiated on day -8 of the study with timed AI on d0. Blood samples were collected on days -3, -1, and 28 via coccygeal venipuncture. Vaginal and uterine flushes were collected on days -3 and -1. Based on days 28 pregnancy status determined by transrectal ultrasonography, cows were identified as either Open (n = 13) or Pregnant (n = 7). Bacterial community analyses were conducted targeting the V4 hypervariable region of the 16S rRNA gene. Cytokine analyses were performed using the RayBiotech Quantibody Bovine Cytokine Array Q1 and MyBioSource ELISA kits per the manufacturer's instructions. Statistical analyses for bacteria relative abundance were conducted using PROC NPAR1WAY and for cytokine concentrations using PROC GLM in SAS 9.4. Uterine concentrations of interferon γ, interleukin (IL)1α, and IL21 were greater in Open than in Pregnant cows (P < 0.05). Regardless of pregnancy status, uterine IL13 increased from days -3 to -1 (9.76 vs. 39.48 ± 9.28 pg/mL, respectively; P < 0.05). Uterine relative abundance of the phylum Firmicutes decreased from days -3 to -1 in Open cows (60.4% ± 0.9% vs. 48.5% ± 3.2%; P = 0.004). In Open cows, the genus Blautia decreased in relative abundance within the uterus from days -3 to -1 (2.1% ± 0.2% vs. 0.9% ± 0.1%; P = 0.002). Uterine relative abundance of the phylum Tenericutes increased from days -3 to -1 in Pregnant cows (1.0% ± 0.1% vs. 7.6% ± 4.1%; P = 0.002). In Pregnant cows, the genus Ureaplasma tended to increase within the uterus from days -3 to -1 (0.08% ± 0.06% vs. 7.3% ± 4.1%; P = 0.054). These findings suggest a distinct difference in the reproductive microbiome and cytokine profiles before AI for resulting Open vs. Pregnant cows.

Efficiently producing cattle to feed a growing population can come with many challenges. A few challenges occur soon after a cow has given birth, and subsequent reproductive performance can be impacted. Bacteria within the reproductive tract can trigger an immune response and together play a role in affecting fertility in cows. The objectives of this experiment were to distinguish the commensal vs. harmful bacteria that reside in the reproductive tract and to characterize the immune response in beef cattle via uterine and vaginal flushes. The results demonstrated that bacteria within the reproductive tract of beef cattle changes before breeding. The current study also suggests that changes in immune response before breeding can be associated with fertility outcomes. Additional research may be worthwhile to evaluate management tactics to positively shift bacteria within the reproductive tract and reduce inflammatory immune responses to improve fertility and increase reproductive efficiency. Future research is necessary to identify the causes of bacterial shifts and how it relates to pregnancy establishment.

Productive and physiological responses of feedlot cattle receiving different sources of Ca salts of fatty acids in the finishing diet.

This study evaluated productive and physiological responses in feedlot cattle receiving a finishing diet that included Ca salts of palm oil (CSPALM), or a blend of Ca salts of palm, cottonseed, and soybean oils (CSMIX). Ninety yearling steers were housed in 15 pens equipped with Calan-gate feeders (6 steers/pen). Steers within each pen were stratified by shrunk body weight (BW; 410 ±â€…3.3 kg across pens) on d 0 and assigned to receive a total-mixed ration (TMR) containing (dry matter basis) 2.2% of CSPALM (n = 30), 2.2% of CSMIX (n = 30), or no supplemental fat (CON; n = 30). Individual TMR intake was evaluated weekly. Blood samples were collected on d 0, 28, 56, 91, 119, and 147. Samples of the Longissimus muscle (LM) were collected on d 84 via biopsy. Upon slaughter on d 148, hot carcass weight (HCW) was recorded to estimate final BW (63% dressing), and one LM steak sample (2.54 cm thickness) was removed from the right side of each carcass. Steer ADG was greater (P = 0.02) for CSMIX compared with CSPALM and tended to be greater (P = 0.09) for CSMIX compared with CON. The gain:feed ratio was greater (P ≤ 0.05) for CSMIX compared with CSPALM and CON, and carcass LM area was less (P = 0.01) for CSPALM compared with CSMIX and CON. No treatment effects were detected (P ≥ 0.21) for TMR intake, final BW, and other carcass merit traits including marbling. Mean plasma cholesterol concentrations were greater (P < 0.01) in CSMIX and CSPALM compared with CON, and mRNA expression of adipocyte fatty acid binding protein in the LM on d 84 was greater (P ≤ 0.04) in CSPALM compared with CSMIX and CON. No treatment effects were detected (P ≥ 0.15) for plasma concentrations of glucose, insulin, insulin-like growth factor I, and leptin, nor for other LM genes associated with marbling and muscle growth. Concentrations of total fatty acids (FA) in plasma and LM steak samples were greater (P < 0.01) in CSMIX compared with CSPALM and CON, and greater (P < 0.01) in the LM samples of CSPALM compared with CON. Steers receiving CSMIX had greater (P < 0.01) concentrations of polyunsaturated and ω-6 FA in plasma and LM steak samples compared with CSPALM and CON. Supplementing CSMIX improved gain efficiency and FA profile in the LM of feedlot steers compared with the CON diet, but the same responses were not observed when CSPALM was offered. Perhaps the advantages from CSMIX supplementation resulted from increasing the supply of polyunsaturated and ω-6 FA to the finishing diet.

Supplemental fat has been provided to feedlot cattle to increase energy density of their diets, and may yield nutraceutical advantages if includes polyunsaturated fatty acids (FA). Alternatively, carcass quality can be improved when the fat supplement is based on saturated and monounsaturated FA. Hence, this experiment evaluated a blend of saturated, monounsaturated, and polyunsaturated FA to improve both performance and carcass merit in feedlot cattle. Steers received a finishing diet that included this blend (CSMIX), a source of saturated and monounsaturated FA (CSPALM), or no supplemental fat (CON). Growth rate and gain efficiency were improved in steers that received CSMIX compared with CSPALM and CON, and these traits did not differ between the latter treatments. Inclusion of CSMIX increased FA concentrations in the circulation of steers throughout the 147-day study and in Longissimus muscle (LM) samples collected after slaughter. This increase in FA concentrations was associated with greater accumulation of polyunsaturated and ω-6 FA, suggesting that CSMIX resulted in LM with FA profile deemed more beneficial for human consumption. Collectively, supplementing CSMIX to feedlot steers improved gain efficiency and FA composition in the LM, and these advantages may be associated with increased supply of polyunsaturated ω-6 FA to the finishing diet.

Follicular determinants of pregnancy establishment and maintenance.

Synchronization of dominant follicle development and control of ovulation/oocyte retrieval are commonly used assisted reproductive technologies in both cattle and humans. The final maturation of the dominant follicle is intimately tied to the final maturation of the oocyte, preovulatory secretion of estradiol, preparation of follicular cells for luteinization, postovulatory secretion of progesterone and endocrine control of the oviductal and uterine environment for gamete and embryo development. The physiological maturity of a dominant/ovulatory follicle can affect the establishment and maintenance of pregnancy. Premature induction of the ovulatory process can reduce pregnancy rates and increase late embryonic/fetal mortality in cattle, which is likely mediated through inadequate oocyte competence and a compromised maternal environment. Oocyte competence increases with follicular maturity and is dependent upon acquisition of a complete complement of mRNA transcripts and establishment of the appropriate epigenetic marking of the oocyte genome before the preovulatory gonadotropin surge. Preovulatory secretion of estradiol is a reflection of follicular maturity and affects the oocyte, follicular cells, oviduct and uterus. The corpus luteum is a continuation of follicular maturation and rate of progesterone secretion following ovulation is linked to fertility. Advancements in our understanding of how the follicular microenvironment affects pregnancy establishment and maintenance will improve the efficiency of assisted reproductive technologies in all species. The purpose of this review is to discuss how follicular microenvironment, oocyte competence, preovulatory secretion of estradiol and postovulatory secretion of progesterone can affect pregnancy establishment and embryo/fetal survival, with an emphasis on cattle.

Short Communication: Influence of estrus activity and reproductive tract size and position scores on fertility in Bos indicus and Bos taurus suckled beef cows.

The primary objective of this study was to determine if estrus activity and reproductive tract size and position score (SPS) are associated with pregnancy outcomes in Bos indicus (Nelore) and Bos taurus (Angus) beef cows. In study 1, multiparous Nelore cows (n = 1,280) were artificially inseminated at a fixed time (FTAI, day 0) using an estradiol and progesterone (P4)-based estrus synchronization protocol. In study 2, multiparous Angus cows (n = 764) were artificially inseminated at a fixed time (FTAI, day 0) using a gonadotropin-releasing hormone and P4-based estrus synchronization protocol. Estrus activity was assessed using Estrotect heat detector patches and scored on day 0 using the following scoring system: 0 (patch was lost, most likely due to repeated mounting), 1 (<25% activation), 2 (≥25%, <50% activation), 3 (≥50%, <75% activation), or 4 (>75% activation) where patch scores of 1 and 2 signified no or limited estrus activity, whereas scores of 0, 3, and 4 had increased estrus activity. Reproductive tract SPS were assigned on day 0 as SPS1: small and compact resting within the pelvic cavity; SPS2: intermediate, resting partially outside the pelvic cavity; and SPS3: larger and resting outside the pelvic cavity. Pregnancy diagnosis was performed by ultrasound on day 30 and 100 after FTAI. Cows were determined as undergoing pregnancy loss if a viable embryo with heartbeat was detected at day 30 but was no longer present at day 100. Pregnancy rate at day 30 was influenced by estrus activity and SPS in both Nelore (P = 0.004) and Angus (P = 0.009) cows. Specifically, cows with smaller reproductive tracts (SPS1) had greater (P < 0.001) pregnancy rate when estrus was expressed before FTAI. There was no effect of estrus activity nor reproductive tract size on pregnancy loss between day 30 and 100 for both breeds. In summary, estrus activity before FTAI may influence reproductive outcomes differently depending on size and position of the reproductive tract at time of breeding.

The livelihood of a cow-calf producer relies on reproductively sound cattle that give birth to live offspring once a year. Two factors, pregnancy rate and pregnancy loss, are informative measures of fertility. Herein, the authors identified that pregnancy rates are interactively influenced by estrus activity and reproductive tract size and position scores. Specifically, cows with smaller reproductive tracts that exhibited estrus activity had greatest pregnancy rates. Neither estrus activity, reproductive tract size and position score, nor their interaction were associated with pregnancy loss.

Supplementing a blend of magnesium oxide to feedlot cattle: effects on ruminal, physiological, and productive responses.

This experiment evaluated ruminal, physiological, and productive responses of feedlot cattle consuming a corn-based finishing diet that included different levels of a magnesium oxide (MG) blend. Yearling cattle (58 heifers and 62 steers) were ranked by sex and initial body weight (BW; 407 ± 3.1 kg), and allocated to 4 groups of 30 animals each. Groups were housed in one of four drylot pens (30 × 12 m) equipped with GrowSafe automated feeding systems (Model 6000E, 4 bunks/pen) during the experiment (days -14 to 117). On day 0, groups were randomly assigned to receive a total-mixed ration without (CON; n = 30) or with the inclusion (as-fed basis) of MG at 0.25% (MG25; n = 30), 0.50% (MG50; n = 30), or 0.75% (MG75; n = 30) until slaughter on day 118. Individual feed intake was recorded daily, and BW was recorded every 14 d and prior to slaughter (day 117). Blood samples were collected on days 0, 28, 56, 84, and 112, and hair samples were collected on days 0, 56, and 112 from the tail-switch. On day 42, eight rumen-cannulated steers (BW = 492 ± 8.0 kg) were housed with yearling cattle (1 pair/pen). Pairs rotated among groups every 14 d, resulting in a replicated 4 × 4 Latin square design (n = 8/treatment; days 42 to 98). Rumen pH was measured on days 7 and 14 of each period (0800, 1200, 1600, and 2000 h). Orthogonal contrasts were used to determine if inclusion of MG (0%, 0.25%, 0.50%, or 0.75% of the diet) yielded linear or quadratic effects, and to explore overall effect of MG supplementation (CON vs. MG25 + MG50 + MG75). No treatment differences were noted (P ≥ 0.31) for BW gain, feed intake, or feed efficiency. Cattle supplemented with MG tended to have less carcass marbling (P = 0.07) compared with CON. Inclusion of MG linearly increased (P < 0.01) mean plasma concentrations of magnesium and tended to linearly decrease (P = 0.09) mean plasma concentrations of haptoglobin. Cattle supplemented with MG had greater (P < 0.01) mean plasma concentrations of cortisol compared with CON. Hair cortisol concentration did not differ between treatments on day 56 (P ≥ 0.25) and linearly decreased (P < 0.01) with MG inclusion on day 112 (treatment × day; P = 0.02). Inclusion of MG linearly increased (P = 0.03) mean rumen pH, but these outcomes were mostly noted during the last two sampling of the day (treatment × hour; P = 0.02). Collectively, supplemental MG was effective in controlling rumen pH in cattle receiving a corn-based finishing diet, but without improvements in feedlot performance and carcass merit.

Acidosis is a common digestive disorder in feedlot cattle consuming high-grain diets, resulting in excessive accumulation of organic acids and pH reduction in the rumen. Sub-acute acidosis is the most prevalent form of acidosis in feedlot cattle, and it is difficult to diagnose due to limited clinical signs, but directly impairs cattle health and productivity. This study evaluated the inclusion of a blend of magnesium oxide (MG) into feedlot diets, a novel neutralizing agent to control rumen pH and mitigate sub-acute acidosis. More specifically, cattle received a corn-based diet with the inclusion of MG at different levels (0%, 0.25%, 0.50%, or 0.75% of the diet). Ruminal pH increased as dietary MG inclusion increased, particularly as cattle consumed feed toward the end of the day. Concentrations of plasma haptoglobin and cortisol in the tail-switch hair decreased as dietary MG inclusion increased, indicating that MG supplementation reduced inflammatory and chronic stress resultant from sub-acute acidosis. However, no benefits from MG were noted for cattle productive traits, including growth rate, feed efficiency, and carcass merit traits. Therefore, supplemental MG appears to be effective in controlling rumen pH in cattle receiving a corn-based finishing diet, but without improvements in feedlot performance and carcass quality.

Positive relationship of rectal temperature at fixed timed artificial insemination on pregnancy outcomes in beef cattle.

The overarching aim was to examine the relationship of rectal temperature at fixed time artificial insemination (FTAI) on pregnancy outcomes in a typical breeding season with expected pregnancy rates approaching 50% using Bos indicus and Bos taurus cattle. This represents a continuum of steps to test the hypothesis that elevated body temperature at or around insemination is functionally important to maximize pregnancy outcomes. Rectal temperature of Bos indicus cattle at FTAI ranged from 37.0 to 40.9 °C; 60.6% were hyperthermic. Positive factors impacting pregnancy outcomes were rectal temperature at FTAI, body condition, and estrus patch scores. Rectal temperature at FTAI was positively associated with pregnancy outcomes (P < 0.0001); per each 1 °C increase pregnancy odds increased 1.9 times (95% CI: 1.4 to 2.6). Highest pregnancy outcomes occurred with rectal temperatures exceeding 40 °C (P = 0.0004). Rectal temperature before FTAI in Bos taurus cattle ranged from 37.8 to 41.8 °C; 43.3% were hyperthermic. Factors impacting pregnancy were rectal temperature at FTAI, estrus activity, parity, and ambient conditions on day of FTAI. Rectal temperature of Bos taurus cattle at FTAI was positively associated with pregnancy (P = 0.0286); odds increased 1.45 times (95% CI: 1.0 to 2.0) per each 1 °C increase. Highest pregnancy outcomes occurred with rectal temperatures at FTAI exceeding 40 °C (P = 0.057). Moreover, positive relationship of rectal temperature at FTAI to pregnancy persisted in estrual females (71.25% of total; P = 0.0408; OR 1.5; 95% CI: 1.0 to 2.2). Mindful that 1) elevated temperatures observed in Bos indicus and Bos taurus cattle directly promote meiotic resumption of the oocyte in vitro and that 2) in vivo hyperthermia alters intrafollicular components which others have shown to potentiate ovulation and promote meiotic resumption, it is biologically plausible that an acute elevation in body temperature at or around time of insemination is functionally important to maximize pregnancy outcomes.

Reproductive efficiency remains a major challenge for beef producers with 35% to 55% of females failing to become pregnant after a single insemination. While basis for failure is multi-factorial, heightened estrus activity matters for pregnancy outcomes, even when synchronizing ovulation for fixed time artificial insemination. Body temperature increases of 1.5 °C+ are common during estrus. We hypothesize that higher estrous-associated temperatures (HEAT) at/near insemination are functionally important to maximize pregnancy outcomes. Elevated temperatures equivalent to what is observed in females exhibiting HEAT have been shown to induce oocyte meiotic resumption. An acute episode of hyperthermia after the LH surge alters intrafollicular components known to potentiate ovulation and affect the oocyte. Effort to examine the relationship of rectal temperature at fixed time artificial insemination with pregnancy outcomes in a breeding season with expected pregnancy rates >50% represents a next step in the continuum of hypothesis testing. The positive relationship of rectal temperature at insemination with pregnancy outcomes that was discovered adds to foundational knowledge. Because the degree of hyperthermia is related to highest pregnancy outcomes, a case is made for HEAT to be biologically and functionally important to maximize pregnancy outcomes in cattle.