Association between maternal growth in the pre-conception and early gestational period of nulliparous dairy heifers with anti-Müllerian hormone in their female offspring.

Anti-Müllerian hormone (AMH) is secreted by granulosa cells of healthy, growing follicles and is positively correlated with the ovarian reserve. Maternal and environmental factors, such as nutrition, disease, parity and endocrine disruptors, are thought to have a profound impact on ovarian reserve development during early foetal life. For genetic progress, it can be advantageous to breed dairy replacements from heifers to expedite the generation interval; however, there is some evidence that nulliparous animals produce female offspring with smaller ovarian reserves compared with multiparous animals. The objective of this prospective, observational study was to determine whether maternal growth in the pre-conception and early gestational period of nulliparous dairy heifers is associated with pre-weaning AMH concentrations in their female offspring. Our hypothesis was that excessive growth in this period would negatively impact AMH concentrations. Seasonal, pasture-based dairy heifer calves (n = 156) born from nulliparous dams, from six Irish farms, were blood sampled at an average of 60 days of age in spring 2022 and tested for AMH. Mixed-effects linear regression models were constructed with Box-Cox transformed AMH concentration as the dependent variable. The independent variables tested included maternal average daily gain (ADG) from pre-breeding examination (PBE) to pregnancy diagnosis (PD) between 30 and 60 days in calf (DIC), ADG from PBE to PD over 60 DIC and ADG between the two PDs. Calf breed and age at sampling were forced into the models, and the farm was treated as a random effect in all models. We found that as ADG increased from the pre-breeding period to their first PD visit, the AMH concentration in their offspring reduced. However, ADG explained only a small amount of the variation in AMH concentrations (marginal R2 = 0.041). In conclusion, the results of our study suggest that excessive growth prior to conception and in early gestation of nulliparous heifers could impact the ovarian reserve of their female offspring, and may imply that farmers should avoid excessive growth in the immediate pre-breeding and early gestational periods.

Determining the clinical utility of a single pre-breeding examination for predicting subsequent reproductive performance in seasonal pasture-based dairy heifers.

Heifers that conceive early in the breeding season are key to the maintenance of a compact calving pattern in seasonal dairy herds. The purpose of this prospective observational study was to determine whether a single pre-breeding examination is useful in predicting future reproductive and calving performance in dairy heifers. This evaluation was based on a matrix of easily measurable variables which could be applied to seasonal, pasture-based dairy heifers. The matrix variables were; body weight (≥55% mature body weight at mating start date), body condition score (≥3.5), and the presence of a corpus luteum. Seasonal, pasture-based dairy heifers (n = 572) on six commercial dairy farms were examined at an average of 28 days prior to the breeding season. At this examination, they were classified as READY (meeting all three of the above criteria), INTERMEDIATE (meeting one or two of the above criteria) or PROBLEM (meeting none of the above criteria) based on the matrix and then exposed to a routine artificial insemination (AI) breeding period followed by bull breeding depending on individual farm management. Subsequent pregnancy status was determined by transrectal ultrasonography initially at 30-60 days in calf (DIC), and confirmed at over 60 DIC. After the breeding season, 519 (96%) of heifers were determined to be pregnant, of which 345 (64%) became pregnant within the first three weeks of the breeding season. Farmers collected calving data; including calving difficulty score, from the heifers the following spring. A logistic regression model was used to analyse the association between the matrix categories and the following outcomes: reproductive (21 day submission rate, 1st AI conception rate, 3 wk and 6 wk in calf rate) and calving (assistance and dystocia). Heifers classified as PROBLEM had significantly lower odds of conceiving to the first AI serve and of becoming pregnant within the first three and six weeks of the breeding season (P ≤ 0.05). In conclusion, the proposed matrix could be practically useful for classifying heifers prior to the breeding season.

A preliminary analysis of the variation in circulating 25-hydroxycholecalciferol concentrations in peri-partum spring-calving dairy cows.

Vitamin D has a well-established role in regulating the intestinal absorption of minerals but its association with immunity has not been extensively explored in livestock. Although an optimal circulating concentration of 30 ng/ml 25-hydroxycholecalciferol (25(OH)D) is proposed for immune function, it is unknown if this vitamin D concentration is sufficient, particularly for cows under a pasture-based, spring-calving dairy production system. The objectives of this retrospective analysis were to assess circulating vitamin D concentrations in a total of 843 bio-banked serum samples from Holstein-Friesian dairy cows enrolled from 12 spring-calving, pasture-based dairy farms in Ireland. Mean 25(OH)D concentrations were 36.3 ng/ml at calving, 30.7 ng/ml at 7 days post-partum (DPP), and 38.3 ng/ml at 21 DPP. However, mean concentrations masked significant inter-farm and inter-individual variation (P < 0.05). In fact, the proportion of cows with vitamin D insufficiency of < 30 ng/ml was found to be 33.8%, 55.5% and 19.5% at each time point, respectively. In addition, 25(OH)D concentrations correlated positively with immune cell populations (monocytes and lymphocytes) and negatively with blood urea and non-esterified fatty acids (NEFA) at 7 DPP. This is the first report of 25(OH)D concentrations in pasture-based peripartum dairy cows and we show a high degree of variation across farms and between individual animals. Sub-optimal concentrations of vitamin D in some post-partum cows may predispose cattle to multiple metabolic or infectious diseases, and therefore further work is now warranted.

Cow-level prevalence and risk factors for estrus detection inaccuracy in seasonal calving pasture-based dairy cows.

High submission rates and pregnancies per AI are essential to ensure compact calving is achieved in seasonal calving pasture-based systems. Estrus detection inaccuracy (EDI) is one area that negatively impacts pregnancies per AI as it increases the inseminations per pregnancy with little probability of conception, while also having the potential to disrupt established pregnancies. The aims of this cross-sectional study were to provide cow-level estimates of EDI prevalence and determine cow-level risk factors for EDI in seasonal calving pasture-based systems. A total of 1071 milk samples were obtained from 984 cows on 19 farms in spring 2018 and analyzed by radioimmunoassay to determine the progesterone concentration at the time of artificial insemination. Based on a validation study on a subset of cows, an inaccurate estrus detection was described as a concentration of progesterone in foremilk of ≥3 ng/ml which corresponded to a composite milk progesterone value of 5 ng/ml. To investigate selected risk factors for EDI, we conducted statistical analyses using two multivariate logistic regression models, stratifying by insemination number (first versus repeat). The overall prevalence of EDI was 4.7% with a prevalence of 3.3% of EDI at first insemination and 14.1% at repeat insemination. Absence of a mounting abrasion (Adjusted odds ratio (AOR) = 3.0) was a significant risk factor for EDI on first insemination while abnormal preceding repeat interval (AOR = 9.5), the absence of an observed standing estrus (AOR = 12.5) and the absence of a mounting abrasion (AOR = 4.1) were significant risk factors for EDI on repeat insemination. The results indicate that cow-level estimated prevalence of EDI in a selection of pasture-based herds was low at first insemination but higher for repeat insemination. It confirms that certain cow-level risk factors existed for EDI, thus providing preliminary evidence for potential future investigation into the targeted use of on-farm progesterone assays in pasture-based herds.

Relationship between plasma concentrations of IGF-I and clinical endometritis, and response to progesterone synchrony in dairy cows during early lactation.

The first aim of this study was to evaluate the relationship between the concentrations of plasma insulin-like growth factor-I (IGF-I) in the transition period and the incidence of clinical endometritis postpartum. The second aim was to evaluate the relationship between the concentration of plasma IGF-I in the transition period and the estrous synchrony response and pregnancy rate to a controlled internal drug release (CIDR) protocol. A total of 402 dairy cows, 250 multiparous and 152 primiparous, were enrolled. A blood sample was taken from all cows 2 and 1 wk precalving and wk 1, 3, 4, and 5 postcalving for subsequent analysis of IGF-I. Vaginal discharge score as a measurement of uterine health was recorded in wk 3, 4, and 5 postcalving. Estrous cycles of all cows were synchronized on ≥37 d in milk (mean = 59; range 37-93) using an 8-d CIDR protocol. All cows were scanned at 32 to 35 d after insemination to confirm pregnancy. Data were analyzed using Proc Mixed and Proc Logistic models in SAS (version 9.3; SAS Institute Inc., Cary, NC). Plasma IGF-I concentrations were significantly greater in the primiparous cows than in the multiparous cows, both before and after calving, and were therefore analyzed separately. In multiparous cows plasma IGF-I concentrations postcalving were significantly lower among cows with uterine infection than in those without infection, and multiparous cows with a plasma IGF-I concentration less than 40 ng/mL 1 wk after calving were 3 times more likely to suffer from a uterine infection 4 to 5 weeks postcalving (odds ratio 2.8; 95% confidence interval 1.0-7.6). Plasma IGF-I concentrations were significantly greater after calving in the 121 primiparous cows that exhibited estrus post-CIDR protocol (mean 125 ng/mL) than in the 25 primiparous cows that did not respond (mean 95 ng/mL). Multiparous cows with greater plasma IGF-I concentrations postcalving had a significantly greater chance of conceiving (mean plasma IGF-I concentration of conceiving cows = 86 ng/mL; nonconceiving = 70 ng/mL). These results show an association between greater concentrations of plasma IGF-I postcalving and response to CIDR protocol in primiparous animals (mean plasma IGF-I concentration of responders = 116 ng/mL; nonresponders = 95 ng/mL). In contrast no association was detected between concentrations of plasma IGF-I in relation to the response to the CIDR protocol in multiparous cows. In conclusion, changes in circulating concentrations of plasma IGF-I early postpartum may help predict reproductive status of dairy cows.

Purulent vaginal discharge diagnosed in pasture-based Holstein-Friesian cows at 21 days postpartum is influenced by previous lactation milk yield and results in diminished fertility.

In a subset of dairy cows, prolonged pathological uterine inflammation results in purulent vaginal discharge (PVD), which can have negative consequences for both fertility and milk production. However, unlike for intensive systems, analysis of the effects of PVD in predominantly pasture-based herds is limited. The objective of this study was to assess the effect of PVD in spring-calving, pasture-based dairy cows on production and reproduction indices, stratified according to previous full-lactation milk yield. We assessed clinical disease as defined by vaginal mucus score (VMS) in 440 Holstein-Friesian cows from 5 farms. Cows were categorized as healthy (VMS 0) or having PVD (VMS 1-3) at 21 d postpartum. We recorded 305-d milk, milk protein, and milk fat yields (kg) before and after disease diagnosis, as well as fertility data, such as services per conception and the calving-conception period (CCP). Using SAS 9.4 (SAS Institute Inc., Cary, NC), we analyzed data using PROC MIXED, PROC PHREG, and PROC LOGISTIC to determine the least squares means differences and hazard and odds ratios between the groups, respectively. Overall, a 60% prevalence of PVD was recorded at 21 d postpartum. Milk yield and milk constituents were similar between all VMS categories and between healthy cows and cows with PVD. Although cows in the 4 VMS categories had statistically similar CCP, cows with PVD had a significantly longer CCP than healthy cows on average (9 d). The hazard ratio for cows with PVD was 0.66, indicating a 34% higher risk of a prolonged CCP than healthy cows. Odds ratio analysis determined that cows with PVD were 3 times more likely not to conceive at all, twice as likely not to conceive at first service, twice as likely not to conceive by 100 d postpartum, and 3 times more likely to fail to conceive before 150 d postpartum compared with healthy cows. Cows were retrospectively categorized as having low or high milk yield, based on whether they were above or below the median 305-d milk yield of the study population (6,571 kg) in the lactation before vaginal mucus scoring. Based on a univariate odds ratio, high-yield cows were 1.6 times more likely to present with PVD in the subsequent lactation. The number of services per conception did not differ between healthy and PVD cows in the low- and high-yield groups. In the high-yield group, cows with PVD were 4.9 times more likely not to conceive, 2.7 times more likely to require multiple services to conceive, 2.1 times more likely to remain not pregnant by 100 d postpartum, and 4.4 times more likely to remain not pregnant by 150 d postpartum. The CCP was also significantly longer in cows with PVD than their healthy counterparts (115.9 ± 4.9 and 104 ± 7.4 d, respectively). In conclusion, PVD significantly increased the CCP in all cows, but to a greater extent in cows with a high milk yield in the lactation before disease diagnosis.

Uterine disease and its effect on subsequent reproductive performance of dairy cattle: a comparison of two cow-side diagnostic methods.

The aim of this study was to compare vaginal mucus scoring and ultrasonographic assessment of uterine content as predictors of future reproductive performance of dairy cows. Holstein-Friesian cows (n = 493) from seven commercial dairy farms were enrolled in this study. All cows received one prebreeding examination (PBE) between 21 and 38 days after parturition. During the PBE, vaginal mucus was scored (MS) and the transrectal ultrasonographic examination of the uterus to assess content (UTS) took place. The MS was scored on a scale of 0 to 3 using a Metricheck device and appearance of the uterus on transrectal ultrasound was scored on a scale of 0 to 4 based on the presence and consistency of intraluminal fluid. Other data collected from each cow included the farm ID (F_ID), conception rate to first service, length of breeding window, lactation number, calving month, body condition score (BCS) at calving, BCS loss after calving, BCS at PBE, days in milk at PBE, 305 day milk yield, economic breeding index (EBI), EBI fertility subindex and EBI health subindex. For each cow these parameters were analyzed using univariate Cox proportional hazard model to evaluate the effect of variables on the reproductive performance, measured as positive pregnancy status (PS) at the end of the breeding season. Receiver-operating characteristic analysis of the diagnostic tests compared with each other took place as well. Cows with positive UTS were 7.75 times more likely to have a positive MS as well (P < 0.01). The PS hazard ratios for cows with UTS0, 1, 2, 3, and 4 were 1; 0.84; 0.53; 0.78; 0.28, respectively (P < 0.001). For the cows with MS0, 1, 2, and 3, the PR hazard ratios were 1; 1.02; 0.51; 0.75; respectively (P = 0.01). Conception rate to first service, breeding window, and PS were significantly better for the cows with UTS0, 1 and 2 compared with the cows with UTS3-4 and MS2+3 (68%; 18%, [P = 0.020]; 29; 75 days, [P = 0.001]; 95%; 55%; [P = 0.010], respectively). There was a significant effect of days in milk at PBE in relation to the subsequent PS (P = 0.04). Cows in lactation number 5 or more were less likely (r = 0.69) to get in calf before the end of the breeding season than cows in their first lactation. Cows that calved later in the season were less likely to become pregnant before the end of the breeding season (P < 0.03). Younger cows (lactation <5) and cows with MS and UTS scores of 0 and -1 had significantly better reproductive performance (P < 0.04). Receiver-operating characteristic analysis showed that MS did not always reflect UTS, but cows with positive UTS were 7.75 times more likely to have a positive MS (P < 0.01) and a high UTS had a larger negative effect on time to PS than a high MS (P < 0.05). In conclusion, both prebreeding vaginal mucus evaluation with the Metricheck device and an ultrasound scan of the uterus serve as a good predictor of the subsequent PS. There is overlap between the two systems, but the best predictor for future reproductive outcome of the cow is a combination of both.

The effect of parturition induction treatment on interval to calving, calving ease, postpartum uterine health, and resumption of ovarian cyclicity in beef heifers.

The aim of this study was to compare the effects of two parturition induction protocols with a nontreated control group, on interval to calving, calving ease, postpartum uterine health, and ovarian cyclicity in beef heifers. At Day 285 of gestation, 81 crossbred recipient beef heifers carrying purebred Simmental fetuses, were blocked by live-weight, body condition score, expected calving date and fetal sex, and assigned to one of three groups: (1) control (CON; no induction treatment, n = 29); (2) induction with corticosteroids (CORT; n = 27); or (3) induction with corticosteroids plus prostaglandin (CORT + PG; n = 25). Interval from induction to calving in hours and calving ease on a scale of 1 to 5 were recorded. Vaginal mucus samples were collected on Day 21 and Day 42 after calving (Day 0) by means of a Metricheck and scored on a scale of 0 to 3. Reproductive tract examinations were conducted on Day 21 and Day 42 after calving, and uterine cytology samples were obtained on Day 21. A positive cytologic sample was defined as greater than 18% neutrophils in the sample obtained via a cytobrush technique. Cows were considered to have resumed ovarian cyclicity if the presence of the CL was confirmed. Data were analyzed using the Mixed (normally distributed data) and Genmod (nonparametric data) procedures of SAS (v. 9.3). The interval from treatment to calving was longer (P < 0.0001) for CON (161.9 ± 15.12 hours) animals compared with CORT (39.7 ± 11.64 hours) or CORT + PG (32.6 ± 12.10 hours), which did not differ. Treatment did not affect calving difficulty score. There was also no difference in incidence of retained placenta between the three groups. At Day 21 postpartum, cytology score tended to be higher for both induced groups (48%) compared with the control animals (24%), but this was not the case for vaginal mucus score (CON 52%, CORT 70%, and CORT + PG 52%). A higher proportion of CON had an involuted uterus by Day 21 postpartum (69%) compared with both induced groups (CORT 48%, CORT + PG 32%). Day 21 ovarian cyclicity was higher in both CON (52%) and CORT (59%) compared with CORT + PG (29%). By Day 42, there was no difference in ovarian cyclicity or uterine involution between CON and CORT; however, a positive relationship was observed between uterine involution score on Day 21 and return to cyclicity on Day 42 in these two groups. There was a negative relationship between uterine involution score and return to cyclicity in the CORT + PG group, and these animals were slower (P < 0.05) to resume cyclicity by Day 42 with a larger proportion animals having evidence of having resumed postpartum ovarian cyclicity in both CON (P = 0.03) and CORT compared with CORT + PG on Day 42. In conclusion, the use of corticosteroid-based treatments is an effective strategy to advance parturition in full term dams and does not have a negative effect on calving progress or dam health. However, when prostaglandin is also included in the protocol, these treatments may lead to greater delay in uterine involution with increased chance of uterine infection and slower resumption of ovarian cyclicity.

DNA methylation dynamics at imprinted genes during bovine pre-implantation embryo development.

BACKGROUND: In mammals, maternal differentially methylated regions (DMRs) acquire DNA methylation during the postnatal growth stage of oogenesis, with paternal DMRs acquiring DNA methylation in the perinatal prospermatagonia. Following fusion of the male and female gametes, it is widely accepted that murine DNA methylation marks at the DMRs of imprinted genes are stable through embryogenesis and early development, until they are reprogrammed in primordial germ cells. However, the DNA methylation dynamics at DMRs of bovine imprinted genes during early stages of development remains largely unknown. The objective of this investigation was to analyse the methylation dynamics at imprinted gene DMRs during bovine embryo development, from blastocyst stage until implantation. RESULTS: To this end, pyrosequencing technology was used to quantify DNA methylation at DMR-associated CpG dinucleotides of six imprinted bovine genes (SNRPN, MEST, IGF2R, PLAGL1, PEG10 and H19) using bisulfite-modified genomic DNA isolated from individual blastocysts (Day 7); ovoid embryos (Day 14); filamentous embryos (Day 17) and implanting conceptuses (Day 25). For all genes, the degree of DNA methylation was most variable in Day 7 blastocysts compared to later developmental stages (P < 0.05). Furthermore, mining of RNA-seq transcriptomic data and western blot analysis revealed a specific window of expression of DNA methylation machinery genes (including DNMT3A, DNMT3B, TRIM28/KAP1 and DNMT1) and proteins (DNMT3A, DNMT3A2 and DNMT3B) by bovine embryos coincident with imprint stabilization. CONCLUSION: The findings of this study suggest that the DNA methylation status of bovine DMRs might be variable during the early stages of embryonic development, possibly requiring an active period of imprint stabilization.

Effects of physiological and/or disease status on the response of postpartum dairy cows to synchronization of estrus using an intravaginal progesterone device.

Progesterone treatments are used to increase submission rates in postpartum dairy cows; however, in many cases the protocol is used as a blanket therapy for all cows without regard for physiological or disease state. The objective of this study was to identify the physiological or disease classes of cows that respond well (or not) to synchronization of estrus via progesterone. Dairy cows (n = 402) were monitored peri and postpartum to establish their physiological or disease status. Animals were classified as having negative energy balance, clinical lameness, uterine infection (UI), anovulatory anestrus, high somatic cell counts, and healthy (H). Blood samples were collected at five different time points and analyzed for metabolites. All animals received an 8-day controlled internal drug release protocol, which included GnRH at insertion and PGF2α the day before removal. Response to the protocol was determined by visual observation of estrus synchronization. Conception rate was determined by ultrasonography between Days 32 and 35 after artificial insemination. Animals without UI were 1.9 times more likely to respond and two times more likely to be confirmed pregnant than those with UI. There was no relationship between negative energy balance and clinical lameness in the visual estrous response, but both conditions were associated with reduced conception rates. Dairy cows in anovulatory anestrus responded successfully to the protocol in both estrous response and conception rates. High glutathione peroxidase concentrations had a positive effect on conception rates, whereas high non-esterified fatty acids and beta-hydroxybutyrate had a negative effect on the estrous response. In conclusion, disease and physiological states of dairy cows determined the response to progesterone-based synchronization. The more disease or physiological problems the cows had, the lower the estrous response and conception rates; cows with these problems were not ideal candidates for synchronization. Both anestrus and healthy dairy cows were good responders to progesterone-based synchronization.

Complete genomic sequence analyses of the first group A giraffe rotavirus reveals close evolutionary relationship with rotaviruses infecting other members of the Artiodactyla.

Group A Rotaviruses (RVA) have been established as significant contributory agents of acute gastroenteritis in young children and many animal species. In 2008, we described the first RVA strain detected in a giraffe calf (RVA/Giraffe-wt/IRL/GirRV/2008/G10P[11]), presenting with acute diarrhoea. Molecular characterisation of the VP7 and VP4 genes revealed the bovine-like genotypes G10 and P[11], respectively. To further investigate the origin of this giraffe RVA strain, the 9 remaining gene segments were sequenced and analysed, revealing the following genotype constellation: G10-P[11]-I2-R2-C2-M2-A3-N2-T6-E2-H3. This genotype constellation is very similar to RVA strains isolated from cattle or other members of the artiodactyls. Phylogenetic analyses confirmed the close relationship between GirRV and RVA strains with a bovine-like genotype constellation detected from several host species, including humans. These results suggest that RVA strain GirRV was the result of an interspecies transmission from a bovine host to the giraffe calf. However, we cannot rule out completely that this bovine-like RVA genotype constellation may be enzootic in giraffes. Future RVA surveillance in giraffes may answer this intriguing question.

The influence of cow and management factors on reproductive performance of Irish seasonal calving dairy cows.

Herd management record analysis facilitates accurate assessment of the current herd reproductive status; a crucial decision making tool to implement effective change. To determine the relative importance of cow and management factors on reproductive indices in moderate-yielding Irish seasonal-calving dairy herds, breeding records of 1173 cows were collected from 10 seasonal calving herds between 2007 and 2009. Backward-stepwise multivariable logistic regression analysis was utilised to determine the effect of cow factors including parity, calving timing, days post partum, heat detection accuracy and herd factors including herd size and heat detection efficiency on key reproductive indices. Mean farm six-week pregnancy and end of season not-in-calf rate were 46% (range 14-72%) and 22% (range 3-40%), respectively. Oestrous detection efficiency (P<0.001), timing of calving (P<0.001) relative to start of breeding, history of abnormal repeat intervals (P<0.001) and length of post partum interval (P<0.001) were each associated with lower six-week pregnancy rates. Timing of calving (P<0.001) and history of abnormal repeat intervals (P<0.001) were associated with higher not-in-calf rates. Herd size and cow parity were not associated (P>0.05) with either outcome when factors including existing calving pattern and heat detection accuracy and efficiency were accounted for. The existing spread in calving pattern, heat detection quality and length of voluntary waiting period were the most influential factors that reduced fertility performance in seasonal-calving herds.