Herd Level Research Articles

Epidemiology of Bovine Hemorrhagic Bowel Syndrome in Belgium and The Netherlands.

Hemorrhagic bowel syndrome (HBS) is a poorly understood, sporadic and often fatal disease in cattle. Although, HBS is considered an important disease in dairy cattle, epidemiological data is largely lacking. This study describes the epidemiology of HBS in Belgium and the Netherlands, based on necropsy records from 2009 to 2022, and reports characteristics from 27 cows and 35 dairy operations with HBS, gathered through a survey. The annual incidence of HBS has a significantly increasing trend both at cow and herd level, with incidence above 3.2% in necropsied mature dairy cattle in the most recent years. Estimated herd-level incidence in the Netherlands was double the estimated incidence in Belgium, which might be explained by higher herd size in the Netherlands. Occurrence of HBS was most prevalent in fall, being 40.1% higher than the average of the other seasons. In 35 Flemish (Belgian) surveyed dairy herds with HBS, manifestation of HBS was mostly as solitary cases, and if multiple cases occurred, the time interval was highly variable. In addition, the majority of cows with HBS (61.1%; 16/26) were in more than 100 days lactation. In conclusion, HBS is an important and possibly emerging disease in dairy cattle in Belgium and the Netherlands.

Seroprevalence and herd-level associated factors of pathogenic Leptospira spp. circulating locally in dairy cattle in Uruguay

Leptospirosis is a zoonotic disease of worldwide importance. In Uruguay, it is endemic in cattle and primarily affects people with occupational exposure to livestock. The aim of this study was to determine the national seroprevalence and associated factors of local pathogen Leptospires in dairy cattle. A cross-sectional study was carried out. Herds were stratified by size (1–50, 51–250, and > 250 cattle), and up to 60 dairy cows per herd were randomly selected. A total of 4269 serum samples from 101 dairy herds were analyzed by microscopic agglutination test (MAT). A two-stage sampling design was used to estimate population seroprevalence of Leptospira spp. In order to determine the factors associated with the disease, herds with at least 1 seropositive animal were considered as case herds. Seroprevalence of Leptospira was 27.80% with a 95% CI [21.06, 34.54] at the animal level and 86.92% with a 95% CI [80.00, 93.75] at the herd level. The serology confirms the predominance of serogroups Sejroe and Pomona in our herd with the presence of incidental leptospires infection, in smaller proportion, but with a wide distribution at farm level. The population size and purchasing replacement of cows on dairy farms were associated with infection at farm level. The serologic studies confirmed that exposure to Leptospira spp. is endemic in our herds, and the spreading over dairy herds. Although the movement of purchased females and the size of the herd were associated with the disease, more studies should be conducted, to better understand the epidemiology of the disease and to highlight the possible risks to public health, especially in rural workers, farmers and veterinarians.

Sero-prevalence and Risk Factors Study of Foot and Mouth Disease and Farmers Perception on Vaccinating Cattle against the Disease in Sidama Region, South Ethiopia

Foot and mouth disease (FMD) is a severe, highly contagious viral disease of livestock that has a significant economic impact. A cross-sectional study was conducted from September 2019 to June 2020 in three selected districts of Sidama region, southern Ethiopia with the objectives of determining the sero-prevalence of cattle against foot and mouth disease virus (FMDV), identifying potential risk factors and assessing farmers' perception on vaccination against FMD. Purposive and systematic random sampling techniques were employed to select the districts and study animals, respectively. A total of 510 cattle were tested for FMDV antibodies using 3ABC-ELISA. The overall cattle and herd level sero-prevalence were 15.5% and 24.7%, respectively. Among the considered risk factors age, herd size, and season were significantly associated with the sero-positivity of FMDV (P<0.05). Out of 120 farmers interviewed84.2% had never vaccinated their cattle against FMDV. Inaccessibility (83.7%) and unaffordable cost (72.1%) of the vaccine were mentioned as leading causes for the low vaccination practice in the current study areas. Majority of the respondents (68.3%) don’t perceive vaccinating cattle against FMDV as one of the preventive measures. In districts with lower perception of farmers on vaccinating their cattle against FMDV, higher sero-prevalence of the disease were recorded. The present serological and questionnaire survey indicated that the presence of FMD sero-positive animals in the current study area. Therefore, an integrated strategy for disease control has to be designed and implemented which could include enhancing farmers’ perception about the use of vaccination in preventing FMD and government provision of vaccines at an affordable cost to the farmers.

The impact of controlling diseases of significant global importance on greenhouse gas emissions from livestock production

BackgroundA considerable body of evidence has reported the beneficial effects of improving productivity on reducing environmental impacts from livestock production. However, despite the negative impacts of animal diseases on reproduction, growth and milk production, there is little information available upon the impacts of animal disease on greenhouse gas emissions (GHGe). This study aimed to partially address this knowledge gap by investigating the effects of globally important vaccine-preventable diseases on GHGe from various livestock systems, namely: intensive dairy, extensive beef, commercial swine and backyard poultry production.MethodsSimple deterministic models were developed within Microsoft Excel to quantify the impacts of livestock disease on productivity (defined as total milk and/or meat yield, MMY) adjusted for disease prevalence both at the population level (high or low), and at the herd or flock level. Disease-induced changes in MMY were applied to the GHGe per kg of milk or meat according to the consequent changes in livestock populations required to maintain milk or meat production. Diseases investigated comprised foot and mouth, brucellosis, anthrax, lumpy skin disease, classical swine fever, porcine reproductive and respiratory syndrome (PRRS), low and high pathogenicity avian influenza (LPAI and HPAI), avian infectious bronchitis and Newcastle disease.ResultsAll diseases investigated had multifactorial impacts on total MMY, yet diseases that increased mortality in breeding or growing livestock (e.g. anthrax, classical swine fever and HPAI) showed greater impacts on GHGe per unit of milk or meat produced than those that primarily affecting yields or reproduction (e.g. brucellosis or LPAI). Prevalence also had considerable effects on potential GHGe. For example, maintaining backyard poultry meat production from a 100,000 hen population with 70% prevalence of HPAI increased GHGe by 11,255 MT CO2eq compared to a 30% prevalence at 3475 MT CO2eq above the baseline (0% prevalence). Effective reduction of the prevalence of PRRS in swine from 60 to 10%, FMD in beef cattle from 45 to 5% prevalence, or AIB in poultry from 75 to 20% prevalence would reduce GHGe intensities (CO2eq/kg CW) by 22.5%, 9.11% and 11.3% respectively.ConclusionsControlling livestock disease can reduce MMY losses at the farm level, which improves food security, reduces GHGe and enhances livestock system sustainability.

Humoral immune response profile of a cattle herd vaccinated with 5- and 10-times Bakirköy strain sheep pox vaccine under field conditions

Vaccination is the most effective control measure for Lumpy Skin Disease (LSD). The Bakırköy strain-derived sheep pox vaccine (SPPV) has been used against LSD in Türkiye since 2013. In this study, a cattle herd was vaccinated with SPPV and 35 cattle, of which 9 and 26 received 10 and 5 sheep doses, respectively, were followed for 200 days for humoral immune responses. Additionally, maternal antibodies in colostrum-fed calves were investigated. The humoral immune responses of naive and previously vaccinated cattle were compared to determine the effects of annual re-vaccination. Furthermore, the compatibility of the VNT and ELISA tests was analyzed. According to the results, on day 30 post-vaccination, 19 and 13 out of 35 cattle were positive for VNT and ELISA, respectively. The number of seropositive cattle was higher in the group that had been vaccinated in previous years than in naive cattle. No significant differences were observed in the number of positive cattle between the groups vaccinated with the 5- and 10- doses. In colostrum-fed calves grouped according to age, the seropositivity rate was 87 % (41/47) in the one-week-old group, while this rate was only 18 % (3/16) in the 3-month-old group. It was determined that vaccination at different stages in the last four months of pregnancy did not cause any difference in the number of seropositive calves in one-week-old calves fed with colostrum. The concordance between VNT and ELISA tests was lower in 5-dose vaccinated group than 10-dose vaccinated and colostrum-fed calves groups. This study provides insights into the effect of the vaccination strategy followed by Türkiye during its combat of LSD and revealed that annual repeated vaccination using heterologous vaccine has significant positive effects on humoral immun response at the herd level.

Comparison of diagnostic methods for assessment of Ostertagia ostertagi exposure in Norwegian dairy herds

BackgroundThe gastrointestinal nematode (GIN) Ostertagia ostertagi can cause severe disease in first season grazers (FSG) and impaired performance due to subclinical infections in adult cows. Diagnostic methods to assess exposure include faecal egg count and detection of specific antibodies using antibody-ELISAs resulting in an optical density ratio (ODR). Using the ELISA test on bulk tank milk (BTM) allows for a herd level diagnosis. Appropriate use of diagnostic methods for evaluation of O. ostertagi exposure is required to optimize herd parasite surveillance and aid in a sustainable control regime. The aim of this study was to describe the relationship between different diagnostic tests used to assess GIN exposure in Norwegian production systems. A cross-sectional field study was carried out in twenty herds in Norway in the fall of 2020. Serum and faecal samples were taken from 380 individuals, of which 181 were FSG and 199 were cows. In addition, milk was collected from every cow and one BTM sample was taken from each herd. Faecal egg counts were performed. The distribution of ODR values in individual samples within and between herds and the associations between BTM ODR and individual ODR values were described. The data were analysed using visual assessment of scatter plots, Pearson correlation coefficients and linear regression.ResultsA high variability of the within-herd individual ODR values in serum and milk in every herd was detected. The ODR in BTM explained a low degree of the variation in the individual serum and milk samples. When plotting the ODR results in milk or serum according to four BTM categories, the distribution of ODR values were notably different in the highest and lowest BTM categories. The correlation between individual milk and serum samples was moderate (r = 0.68), while the highest correlation (r = 0.81) was between the BTM ODR and the group average individual milk samples.ConclusionsA poor predictive ability for BTM ODR to assess individual ODR values in both FSG and cows was demonstrated. However, the study indicates that the evaluation by ELISA test on BTM to assess exposure to GIN could be useful in herds with a very high or low BTM ODR.

Pilot study on the distribution of caseous lymphadenitis in Korean native goats and the relationship between sex and age in disease occurrence

Caseous lymphadenitis (CLA) caused by Corynebacterium pseudotuberculosis is a chronic disease that affects goats. The Korean native goat (KNG) is the most popular goat breed raised in Korea. In this study, the distribution of CLA in the KNG population and the relevance of sex and age in disease development were determined. From March 2020 to February 2021, 1,177 KNGs from 110 farms were assessed. The distribution of CLA in animals was determined by a veterinary inspector who performed gross examinations of goat carcasses and confirmed diagnoses via polymerase chain reaction and bacteriological examination. The CLA detection rate in the KNG population was 19.80%, and more than half of the farms were affected by the disease (56.36%). A statistically significant difference was observed among the sex groups, with castrated males (13.98%) having the lowest detection rate, followed by intact males (22.48%) and females (24.09%), suggesting that castration has a positive effect on reducing the risk of CLA (p < 0.05). In terms of age groups, an increased detection rate of 28.16% was observed in the late adult (>2 years) group. Phylogenetic analysis indicated that the RNA polymerase beta subunit-encoding gene can effectively differentiate biovar ovis from biovar equi and can be used for further epidemiological studies of C. pseudotuberculosis. This is the first nationwide surveillance study of CLA distribution to confirm the continuous occurrence of CLA in Korean goat farms. Future studies should include risk factor analyses of CLA based on herd levels to prevent and control this disease in Korea.

Sero-prevalence of contagious bovine pleuropneumonia in dryland of Borana, southern Oromia, Ethiopia

Ethiopia is one of the largest African countries where livestock farming represent a relevant resource for the economy and the livelihood of the population. Contagious bovine pleuropneumonia (CBPP) is among the transboundaries animal disease that is hindering cattle farming in Ethiopia. Due to the limited resources of veterinary services, disease control and surveillance is discontinuous and occasional field investigations of target areas contribute to depict disease spreading in the country. The study was conducted to determine the seroprevalence, at herd and animal level, and identify the risk factors involved in CBPP diffusion and persistence in the Borana pastoral zone. A total of 498 serum samples were collected from 120 cattle herds and tested using competitive Enzyme-Linked Immunosorbent Assay (c-ELISA). Of 120 herds sampled, 37 (30.83%; (95% CI = 22.73–39.91%) were tested positive to CBPP antibody. Out of 498 sera samples tested 46 (9.24%; 95% CI = 6.84–12.13%) were positive. The highest prevalence was observed in Teltele (12/95; 12.90%; 95% CI = 6.7–21%) followed by Yabello (12/104; 11.54%; 95% CI = 6.1–19.3%) and Arero (10/91; 10.99%; 95% CI = 95% CI = 5.4–19.3%), whereas the lowest prevalence was observed in Gomole (5/101; 6.42%; 95% CI = 1.6–11.2%) and Dubluk (7/109; 4.95%; 95% CI = 2.6–12.8%) districts and statistically not significant (p > 0.05). Results of multivariate logistic regression analysis revealed that, age, herd movement and herd size of the animals had statistically significant effect on sero-positivity to CBPP (p < 0.05). Sex, season and body condition were not significantly (p > 0.05) associated with the occurrence of CBPP. The study confirms that CBPP is persistent in the territory and remain as a major problem that affects health and productivity of cattle. Therefore, awareness creation to the pastoralists in the study area about the effect of CBPP and designing appropriate control methods has a paramount importance to improve the health and productivity of cattle production in the area.

Mapping brucellosis risk in Kenya and its implications for control strategies in sub-Saharan Africa

In Sub-Saharan Africa (SSA), effective brucellosis control is limited, in part, by the lack of long-term commitments by governments to control the disease and the absence of reliable national human and livestock population-based data to inform policies. Therefore, we conducted a study to establish the national prevalence and develop a risk map for Brucella spp. in cattle to contribute to plans to eliminate the disease in Kenya by the year 2040. We randomly generated 268 geolocations and distributed them across Kenya, proportionate to the area of each of the five agroecological zones and the associated cattle population. Cattle herds closest to each selected geolocation were identified for sampling. Up to 25 cattle were sampled per geolocation and a semi-structured questionnaire was administered to their owners. We tested 6,593 cattle samples for Brucella immunoglobulin G (IgG) antibodies using an Enzyme-linked immunosorbent assay (ELISA). We assessed potential risk factors and performed spatial analyses and prevalence mapping using approximate Bayesian inference implemented via the integrated nested Laplace approximation (INLA) method. The national Brucella spp. prevalence was 6.8% (95% CI: 6.2–7.4%). Exposure levels varied significantly between agro-ecological zones, with a high of 8.5% in the very arid zone with the lowest agricultural potential relative to a low of 0.0% in the agro-alpine zone with the highest agricultural potential. Additionally, seroprevalence increased with herd size, and the odds of seropositivity were significantly higher for females and adult animals than for males or calves. Similarly, animals with a history of abortion, or with multiple reproductive syndromes had higher seropositivity than those without. At the herd level, the risk of Brucella spp. transmission was higher in larger herds, and herds with a history of reproductive problems such as abortion, giving birth to weak calves, or having swollen testes. Geographic localities with high Brucella seroprevalence occurred in northern, eastern, and southern regions of Kenya all primarily characterized by semi-arid or arid agro-ecological zones dominated by livestock pastoralism interspersed with vast areas with mixed livestock-wildlife systems. The large spatial extent of our survey provides compelling evidence for the widespread geographical distribution of brucellosis risk across Kenya in a manner easily understandable for policymakers. Our findings can provide a basis for risk-stratified pilot studies aiming to investigate the cost-effectiveness and efficacy of singular and combined preventive intervention strategies that seek to inform Kenya’s Brucellosis Control Policy.

Does knowledge of blood calcium concentration at 2 days postpartum affect decisions of calcium supplementation?

Delaying oral Ca supplementation might benefit cows with low blood Ca concentrations at 4 d in milk (DIM), a time when reduced blood total Ca (tCa) is associated with negative health and production outcomes. To implement a targeted approach to manage subclinical hypocalcemia (SCH) at the herd level, it is important to identify which cows benefit from supplemental Ca. Therefore, our objective was to determine if SCH diagnosis at 2 DIM could inform decisions of oral Ca supplementation at 2 and 3 DIM based on milk yield and 4 DIM blood Ca concentration. Data were analyzed from a previously conducted randomized controlled trial on multiparous cows (n = 518) from 4 farms in New York State. Cows were randomly assigned to 1 of 2 treatment groups at calving: (1) control (CON; no Ca supplementation, n = 259) or (2) bolus (BOL; 43 g of oral Ca administered at 2 and 3 DIM postcalving, n = 259). For each parity group (2, 3, 4+), we used generalized linear mixed models to identify serum tCa concentrations at 2 DIM that maximized the difference in milk yield to diagnose SCH. Cows were classified as normocalcemic (NC; parity 2 tCa >1.9 mmol/L, parity 3 tCa >1.87 mmol/L, n = 327; parity ≥4 had no defining threshold) or SCH (parity 2 tCa ≤1.9 mmol/L, parity 3 tCa ≤1.87 mmol/L, n = 58; parity ≥4 had no defining threshold). Parity 2 and 3 cows were further classified into 1 of 4 SCH-treatment groups (SCHTRT) based on 2 DIM SCH status and random treatment allocation: (1) NC-CON, n = 165, (2) SCH-CON, n = 28, (3) NC-BOL, n = 162, or (4) SCH-BOL, n = 30. Generalized linear mixed models were used to analyze the difference in milk yield for the first 10 wk of lactation and tCa at 4 DIM between SCHTRT groups with separate analyses performed for parities 2 and 3. Mean milk yield differed between SCHTRT groups for both parities. For parity 2, SCH-CON and SCH-BOL cows produced more milk than NC-CON and NC-BOL cows with SCH-CON producing 50.9 (95% confidence interval [CI] = 48.4, 53.4) kg/d, SCH-BOL 51.7 (49.1, 54.2) kg/d, NC-CON 47.5 (46.3, 48.7) kg/d, and NC-BOL 47.2 (45.8, 48.5) kg/d of milk. Milk yield was also different between SCHTRT groups for parity 3 with SCH-BOL cows producing more milk than NC-CON and NC-BOL cows. In parity 3, SCH-BOL cows produced 56.3 (95% CI = 53.1, 59.3) kg/d, SCH-CON 51.7 (48.6, 54.7) kg/d, NC-BOL 50.6 (49.0, 52.2) kg/d, and NC-CON 48.7 (46.9, 50.5) kg/d of milk. For both parities, SCH-CON and SCH-BOL cows had lower tCa at 2 DIM than NC-CON and NC-BOL cows. At 4 DIM, tCa concentrations were similar for all SCHTRT groups respective to parity. Our results suggest that although delayed Ca bolus administration does not improve blood Ca concentration when compared with controls, it does support increased milk production in parity 3 cows regardless of Ca status at 2 DIM. Thus, knowledge of blood Ca at 2 DIM should not affect decisions of Ca supplementation in this parity of cows.

Prediction of persistency for day 305 of lactation at the moment of the insemination decision.

When deciding on the voluntary waiting period of an individual cow, it might be useful to have insight into the persistency for the remainder of that lactation at the moment of the insemination decision, especially for farmers who consider persistency in their reproduction management. Currently, breeding values for persistency are calculated for dairy cows but, to our knowledge, prediction models to accurately predict persistency at different moments of insemination are lacking. This study aimed to predict lactation persistency for DIM 305 at different insemination moments (DIM 50, 75, 100, and 125). Available cow and herd level data from 2005 to 2022 were collected for a total of 20,508 cows from 85 herds located in the Netherlands and Belgium. Lactation curve characteristics were estimated for every daily record using the data up to and including that day. Persistency was defined as the number of days it takes for the milk production to decrease by half during the declining stage of lactation, and calculated from the estimated lactation curve characteristic 'decay'. Four linear regression models for each of the selected insemination moment were built separately to predict decay at DIM 305 (decay-305). Independent variables included the lactation curve characteristics at the selected insemination moment, daily milk yield, age, calving season, parity group and other herd variables. The average decay-305 of primiparous cows was lower than that of multiparous cows (1.55 *10-3 vs. 2.41*10-3, equivalent to a persistency of 447 vs. 288 days, respectively). Results showed that our models had limitations in accurately predicting persistency, although predictions improved slightly at later insemination moments, with R2 values ranging between 0.27 and 0.41. It can thus be concluded that, based only on cow and herd milk production information, accurate prediction of persistency for DIM 305 is not feasible.

Milk β-hydroxybutyrate metrics and its consequences for surveillance of hyperketonaemia on commercial dairy farms.

Dairy cows that are unable to adapt to a change in their metabolic status are at risk for hyperketonaemia (HK). Reported HK herd level prevalences range a lot and we hypothesized that this is partly due to differences in used tests and monitoring protocols. Insights in milk β-hydroxybutyrate (BHB) metrics can potentially explain why the reported incidences or prevalences vary between test strategies. Automated collection and repeated analyses of individual milk samples with the DeLaval Herd Navigator™ (HN) provides real-time data on milk BHB concentrations. We aimed to use that information to gain insight in BHB metrics measured in milk from 3 to 60 days in milk (DIM). Using different cut-offs (0.08, 0.10 and 0.15 mmol/L), 5 BHB metrics were determined. Furthermore, the impact of 4 arbitrary test protocols on the detected incidence of HK was assessed. We used HN data of 3,133 cows from 35 herds. The cumulative incidence of HK between 3 and 60 DIM varied between 30.5 and 76.7% for different cut-off values. We found a higher HK incidence for higher parity cows. The first elevated BHB concentrations were roughly found between one and two weeks after calving. For higher parity cows the maximum BHB concentrations were higher, the onset of HK was earlier after calving, and the number of episodes of HK was higher. It appeared that the sensitivity of a HK test protocol can be increased by increasing the testing frequency from once to twice a week. Also extending the number of days of the test window from 4-14 to 4-21 days enhances the chance to find cows experiencing HK. In conclusion, HN data provided useful insights in milk BHB metrics. The chosen cut-off value had a large effect on the reported metrics which explains why earlier reported incidences or prevalences vary such a lot. Differences in test period and sample selection also had a large impact on the observed HK incidence. We suggest to take this in consideration while evaluating whether HK is an issue on farm level and use a uniform protocol for benchmarking of HK between farms.

PSX-15 Precision Beef Dry Matter Intake Estimation on Extensive Rangelands

Abstract Predicting dry matter intake (DMI) for beef cattle on extensive rangelands presents a significant challenge to determining stocking rates. Traditionally, DMI is estimated by taking full body weight (BW) multiplied by a percentage selected based on animal class, production phase, and forage quality, which introduces tremendous levels of accumulated error at the herd level. Animal Unit Months (AUMs) are utilized to simplify the determination of stocking rate (animal units per area per a specific period of time) of pastures. This challenge represents a tremendous opportunity to leverage precision technology to account for individual animal variation in BW and growth, with subsequent impacts on herd-level decisions. Therefore, the objective of this study was to utilize precision livestock technology (PLT) collected data to build a precision system model (PSM) to evaluate the differences in predicted DMI using either initial BW, expected mid-season BW, or PLT measured BW. The PSM model was built utilizing BW data measured using SmartScale (C-Lock Inc.) for 60 days during the summers of 2021 and 2022 on Angus yearling steers (average initial BW 393.71 ± 39.01 and 315.23 ± 53.91 kg, n = 130 and 124, for year 2021 and 2022, respectively) on native pastures at the South Dakota State University Cottonwood Field Station. The PSM evaluated total forage consumption and deterministically estimated hectares of pasture required to meet the herd forage demands relative to available biomass (kg/ha). the PSM estimated 4.49% and 6.94% more DMI at the herd level compared with using initial BW for years 2021 and 22, respectively, and 1.64% less DMI than mid-season BW in 2021. This resulted in an additional 14.03 and 17.95 ha required for years 2021 and 22, respectively, according to PSM estimates compared with initial BW, while animals were understocked by 5 and 0.3 ha for 2021 and 2022, respectively, using mid-season BW. Individuals expressed a divergent growth rate, resulting in greater misalignment between static and PSM predicted DMI as the grazing period progressed (Menendez et al., 2023), indicating greater opportunities for targeted grazing management in long grazing periods. Therefore, applying precision data provides more precise DMI estimates and demonstrates the advantages and disadvantages of herd-level estimates. The use of PSM helps to identify high-leverage precision tools to minimize a performance gap like overgrazing extensive rangeland systems and demonstrates the critical need to develop robust data-collection and processing steps to leverage continuously collected PLT data.

121 Quantifying Genetic Relationships to Maintain Genetic Diversity in the Canadian Dairy Population

Abstract Intensive selection pressure coupled with the use of a limited number of high genetic merit sires has resulted in reduced effective population size and increased levels of inbreeding in dairy cattle populations. The increased rate of inbreeding amplifies the frequency of recessive deleterious alleles, possibly leading to inbreeding depression in economically important traits, such as disease resistance, fertility and production. To better understand the relationship of available and active breeding sires to Canadian herds, quantifying genetic relationships between these groups could prove insightful. The genetic relationship value (R-value) represents the average number of alleles identical by descent shared between an animal and a reference population and is currently estimated based on pedigree information. Furthermore, the average R-value indicates the relationship of a sire to the rest of the population. Estimating the R-value between sires and individual herds may offer a more refined tool for producers to select sires that are less related to their specific herds. The aim of this study was to quantify and characterize R-values between individual sires and individual herds within the Canadian Holstein population. To quantify R-values, a dataset comprised of 11,914 sires born between 1953 and 2020 and 584,740 active cows born between 1997 and 2022 from 5,592 herds was considered. Active cows were defined as those currently alive, on milk recording, and actively contributing to the national milk inventory. Active sires were considered those used to breed the active cows. All data were provided by Lactanet Canada and analyses were carried out on PEDIG using the par2 program for relationship estimation. Results indicate that herd-level R-values (i.e., R-values estimated using individual sires and individual herds) showed variation. The R-value of individual sires to individual herds containing active cows ranged from 0.43% to 32.38. This result indicates that outbred sires are available to individual farmers when the population is considered at the herd level, and that the development of herd-level R-values may provide a selection tool which promotes the use of less related sires. Next steps include developing and estimating genomic R-values and comparing them with the pedigree-based R-values for the genotyped Canadian Holstein population. By better understanding of the relationship of available breeding sires to individual Canadian herds, a simple tool for producers to identify sires which are less related to their herds can be developed.

Evaluation of anthelmintic resistance in Oklahoma beef cattle herds and assessment of composite sampling for herd level fecal egg count reduction testing

Beef cow-calf producers submitted fecal samples for fecal egg count reduction (FECR) tests. Anthelmintic administration practices were not controlled, and producers were encouraged to follow standard procedures for each herd. Fecal egg counts (FEC) were determined using the Wisconsin method with alimit of detection of 1 egg per gram (EPG). Inclusion criteria included a pretreatment FEC of 25 EPG. A FECR of ≤ 90% was considered indicative of resistance. Seventeen herds submitted a total of 19 sample sets. All major classes of anthelmintics were represented except for levamisole. Injectable, pour-onand oral as well as original label and generic products were represented. Sample sets from 3 herds were excluded from the final analysis based on inadequate pretreatment FEC. Of the 16 sample sets included in the final analysis, 13 exhibited resistance based on the arithmetic mean of individual FECR tests (FECRT). In addition to individual FEC, composite samples for each herd were created using 1 gram of feces from each animal. Four grams of each composite sample were used to determine a composite FEC. Composite samples from 13 herds were included in the final analysis and 11 of 13 exhibited resistance. There was complete agreement between the individual and composite samples for the detection of resistance. Based on the results of this small survey, apparent anthelmintic resistance appears to be widespread in beef cow-calf herds in Oklahoma. Composite sampling appears to be an effectivemethod for detection of herd level resistance.

PSVI-16 Conditioning Dairy Cows to a Virtual Fencing System Is Compatible with Animal Welfare

Abstract Virtual fencing (VF) enables livestock grazing without physical fences by conditioning animals to an audio tone (AT) followed by an electric pulse (EP) that is up to 25 times weaker than conventional electric fencing (EF). However, the operating principle of a virtual fencing system raises concerns about animal welfare. Therefore, the present study investigated the learning process of dairy cows in a virtual fencing environment and its effects on animal behavior and welfare. Twenty lactating cows were divided into four groups of five individuals each (2x VF; 2x EF), balanced by lactation stage (203 ± 62 days) and age (3.7 ± 1.5 lactations). All cows were accustomed to daily grazing with EF but were naïve to VF. Each group grazed in a separate paddock for 3 days of acclimation (P0) and 21, 14, 14, and 7 days of experimental treatment (P1-4). All paddocks were electrically fenced, and of similar vegetation structure and botanical composition. During P1-P4, a virtual boundary was activated within each paddock of the VF groups, and a second electric fence was set up within each paddock of the EF groups to maintain comparable paddock sizes. All cows were fitted with a VF collar (Nofence AS, Batnfjordsøra, Norway) and an IceQube pedometer (Peacock Technology Ltd, Stirling, UK). The sensors continuously tracked cow positions, the daily numbers of AT and EP, and activity behavior, respectively. Throughout P0-P4, daily milk yield, feed intake, and body weight were recorded. A total of 26 milk samples were collected per cow to determine milk cortisol concentrations. Behavioral observations were conducted for 2 h on 23 days to record agonistic behaviors, vocalizations, and excretions. During P1-P4, each cow received an average of 1.9 ± 3.3 AT and 0.1 ± 0.7 EP per day. The total number of stimuli ranged from 37 to 225 AT and 3 to 11 EP per cow throughout the experimental period, indicating individual variations in learning (P &amp;lt; 0.003). Within the first three days after virtual fence activation, most cows learned the concept of the VF system. The conditioning of the cows was successful at herd level after three repetitions at a new virtual boundary, reflected by a decreasing ratio of mean EP/AT from 20 to 3, 2, and 0 % with each paddock change. Milk yield and cortisol, feed intake, body weight, and cow activity did not differ between VF and EF groups. Overall, there were a mean of 11.2 vocalizations and 5.9 displacements more per cow in the VF groups (P &amp;lt; 0.05), but similar across P0-P4. Our results suggest that learning the virtual fencing system did not lead to lasting adverse effects on cow welfare.

Antimicrobial resistance of Escherichia coli in the UK: comparison of single vs. pooled samples from healthy pigs.

This study compared the antimicrobial resistance (AMR) of Escherichia coli detected from single samples vs. pooled samples at herd level. The national monitoring dataset included isolates from one sample per pig holding, whereas the research study included isolates from pooled samples of 10 pigs per holding. In both datasets, caecal samples were collected from healthy pigs randomly selected at slaughterhouses and plated on non-selective and antibiotic selective media. Resistance against a panel of nine antibiotics was compared between datasets by generalized linear mixed effects models (GLMMs) and by bootstrapped generalized linear model (GLM) to account for pooling. The highest proportion of resistant E. coli was observed against tetracycline and ampicillin in both datasets. In non-selective media, single and pooled samples showed similar results, but the bootstrapped GLM detected significantly lower resistance to ciprofloxacin and nalidixic acid in the national dataset. In selective media, a significantly greater proportion of resistant isolates was observed in the research dataset for ceftazidime (OR: 0.05, 95%CI=0.01-0.42) and nalidixic acid (OR: 0.15, 95%CI=0.05-0.51). The results suggest that one sample per holding provides similar information on AMR at herd level as pooled samples for most of the tested antibiotics, although less resistance to ciprofloxacin, ceftazidime, and nalidixic acid was detected.

Total and pathogen-specific serum Immunoglobulin G concentrations in neonatal beef calves, Part 1: Risk factors.

Maternal antibodies, delivered to the calf via colostrum, are crucial to prevent calfhood diseases and death. However, knowledge regarding the factors influencing this transfer of total and specific Immunoglobulin G (IgG) against common enteric and respiratory disease pathogens under current production conditions is sparse. The objectives of this study were to determine risk factors influencing total and pathogen-specific immunoglobulin G (IgG) concentrations against Escherichia coli (E. coli), bovine Rotavirus (BRoV), Cryptosporidium parvum (C. parvum), Bovine Viral Diarrhea Virus type 1 and 2 (BVDV), Parainfluenza Virus Type 3 (PI-3), Bovine Respiratory Syncytial Virus (BRSV), and Bovine Herpesvirus type 1 (BHV-1) in the serum of newborn beef calves. A total of 420 serum samples were collected from 1- to 7-day-old beef calves born on 6 farms in Alberta, Canada. Samples were analyzed by radial immunodiffusion for total IgG concentration and by enzyme-linked immunosorbent assays for pathogen-specific IgG concentrations against E. coli, BRoV, C. parvum, BVDV, PI-3, BRSV, and BHV-1. Multivariable multilevel linear and logistic regression models were built to evaluate dam- and calf-level risk factors associated with total and pathogen-specific IgG concentrations, failed transfer of passive immunity (FTPI; serum IgG < 10g/L), and inadequate transfer of passive immunity (ITPI; serum IgG < 24g/L). Farm was included as a random effect in all models to account for clustering at the herd level. Of the 420 calves included in this study, 5% (n=20) and 18% (n=75) of calves had FTPI and ITPI, respectively. Receiving colostrum intervention (i.e., being fed colostrum or colostrum product by either bottle or tube) was the most consistent risk factor for low total IgG concentration and significantly increased the odds of FTPI (Odds ratio (OR): 6.1, 95% CI: 2.0-18.9) and ITPI (OR: 4.8, 95% CI: 2.1-10.8). Calves born to cows consistently had higher pathogen-specific IgG concentrations (P<0.0001), compared to calves born from heifers, and calves born to vaccinated dams had significantly higher BRoV, BVDV, and BHV-1-specific IgG concentrations. Interestingly, E.coli-specific IgG concentrations were associated with dam vaccination only in cows but not in heifers, which was likely due to differing vaccination strategies used. This study highlights the need to review and refine protocols with respect to dam vaccination and colostrum intervention on cow-calf operations.

Monitoring of Body Condition in Dairy Cows to Assess Disease Risk at the Individual and Herd Level.

A retrospective longitudinal study assessing the explanatory and predictive capacity of body condition score (BCS) in dairy cows on disease risk at the individual and herd level was carried out. Data from two commercial grazing herds from the Argentinean Pampa were gathered (Herd A = 2100 and herd B = 2600 milking cows per year) for 4 years. Logistic models were used to assess the association of BCS indicators with the odds for anestrus at the cow and herd level. Population attributable fraction (AFP) was estimated to assess the anestrus rate due to BCS indicators. We found that anestrus risk decreased in cows calving with BCS ≥ 3 and losing ≤ 0.5 (OR: 0.07-0.41), and that anestrus rate decreased in cohorts with a high frequency of cows with proper BCS (OR: 0.22-0.45). Despite aggregated data having a good explanatory power, their predictive capacity for anestrus rate at the herd level is poor (AUC: 0.574-0.679). The AFP varied along the study in both herds and tended to decrease every time the anestrous rate peaked. We conclude that threshold-based models with BCS indicators as predictors are useful to understand disease risk (e.g., anestrus), but conversely, they are useless to predict such multicausal disease events at the herd level.

Enhancing bovine abortion surveillance: A learning experience

Abortions and perinatal mortalities (APM) substantially affect cattle industry efficiency. Various infectious and noninfectious factors have been associated with bovine APM worldwide. Infections are often considered pivotal due to their abortifacient potential, leading laboratories to primarily investigate relevant infectious agents for APM cases. Some infectious causes, such as Brucella abortus, have also a zoonotic impact, necessitating monitoring for both animal and human health. However, underreporting of bovine APM is a global issue, affecting early detection of infectious and zoonotic causes. Previous studies identified factors influencing case submission, but regional characteristics may affect results. In Belgium, farmers are obliged to report cases of APM within the context of a national brucellosis monitoring program. The inclusion criteria for this monitoring program cover abortions (gestation length of 42-260 d) and perinatal mortalities of (pre)mature calves following a gestation length of more than 260 d, which were stillborn or died within 48 h after birth. The objective of the present study was to describe the evolution in submission of APM cases within a mandatory abortion monitoring program in relation to subsidized initiatives in the northern part of Belgium. Based on the proportion of APM submissions versus the proportion of bovine reproductive females, an APM proportion (APMPR) was calculated, and factors at both animal and herd level that may influence this APMPR were explored by using linear models. This evaluation revealed that the APMPR increased with the introduction of an extensive analytical panel of abortifacient agents and a free on-farm sample collection from 0.44% to 0.94%. Additionally, an increase of the APMPR was associated with an outbreak of an emerging abortifacient pathogen (Schmallenberg virus; 1.23%), and the introduction of a mandatory eradication program for bovine viral diarrhea virus (BVDv; 1.20%). The APMPR was higher in beef compared with dairy cattle, and it was higher in winter compared with fall, spring, and summer. Smaller herds categorized in the first quartile had a higher APMPR compared with larger herds. Herds that submitted an APM in the previous year had a higher APMPR in the next year compared with herds without an APM submission. Finally, herds for which there was evidence of the presence of BVDv had a higher APMPR compared with herds without evidence of the presence of BVDv. In conclusion, the number of APM submissions increased after the introduction of a free on-farm sample collection and an extensive pathogen screening panel. Production type (beef), season (winter), smaller herd size, previous APM, and presence of BVDv seemed to have a positive effect on APMPR. However, even under mandatory circumstances, APM still seems to be underreported, since the APMPR was lower than the expected minimal rate of 2%. Therefore, further research is necessary to identify the drivers that convince farmers to submit APM cases to improve submission rates and ensure an efficient monitoring program for APM and eventually associated zoonotic pathogens.