Serum amyloid A increases following routine vaccination of healthy adult horses.

OBJECTIVES: To measure the effect of routine vaccination on serum amyloid A (SAA) concentration in apparently healthy horses. We hypothesized that routine vaccination would increase SAA in healthy horses. ANIMALS: 21 apparently healthy client-owned horses and 15 Kansas State University College of Veterinary Medicine-owned horses. METHODS: In experiment 1 (n = 8 horses), a blinded, randomized, prospective, crossover study was performed. Horses were either vaccinated (rabies, tetanus, West Nile, Eastern and Western equine encephalomyelitis, equine herpesvirus-1/-4, influenza) or administered saline, and SAA was measured at 6, 12, and 24 hours and daily until day 10 with a commercial lateral-flow immunoassay. In experiment 2 (n = 28 horses), a prospective, observational study measured SAA after vaccination at 12 and 24 hours and daily until day 10. A linear mixed-effect model with repeated measures over time blocked by horse tested the effect of treatment on SAA. A repeated-measures correlation tested the correlation between SAA and temperature. RESULTS: Over time, vaccinated horses had increased model-adjusted SAA compared to unvaccinated horses without clinical evidence of adverse reaction (P < .01). In experiment 1, the model-adjusted SAA after vaccination peaked on day 2 (median, 1,872 µg/mL; IQR, 1,220.8 to 2,402.5 µg/mL) and returned to normal (< 20 µg/mL) by day 9 (median, 6 µg/mL; IQR, 0.8 to 23.5 µg/mL) after vaccination. In experiment 2, vaccinated horses had increased SAA over time; temperature and SAA were not correlated (P = .78). CLINICAL RELEVANCE: Results of this study indicated that routine vaccination results in increased SAA concentration and provided evidence for a period of convalescence following vaccination. Measuring SAA for 10 days following vaccination cannot be used as an indicator of illness.

Determining the Economically Optimum Metaphylactic Strategy for Cattle Cohorts of Varied Demographic Characteristics.

Metaphylactic antibiotic use in feeder cattle is a common practice to control respiratory disease. Antimicrobial stewardship is important to ensure continued efficacy and to protect animal welfare. The objective of this study is to identify characteristics of cohorts of cattle that had not received metaphylaxis that would have benefited economically from the use of metaphylaxis. Cohorts (n = 12,785; 2,206,338 head) from 13 feedlots that did not receive metaphylaxis were modeled using an economic model to estimate net returns for three metaphylactic options. Logistic regression models with covariates for entry weight, sex, average daily weight gain, number of animals per cohort, and days on feed, with feedlot as a random effect, were used to determine the model-adjusted probability of cohorts benefiting economically from metaphylaxis. Most (72%) cohorts in this data set that had not received metaphylaxis at arrival would not economically benefit from metaphylaxis. Sex, entry weight category, number of cattle in the cohort, and average daily weight gain were associated with the likelihood of benefitting economically from metaphylaxis. The results illustrated that cattle cohort demographics influenced the probability that cohorts would benefit economically from metaphylaxis and the type of metaphylaxis utilized, and integrating this information has the potential to influence the metaphylaxis decision.

Epidemiological Factors Associated with Gross Diagnosis of Pulmonary Pathology in Feedyard Mortalities.

Respiratory disease continues to be the major cause of mortality in feedyard cattle, with bronchopneumonia (BP) and acute interstitial pneumonia (AIP) as the two most common syndromes. Recent studies described a combination of these pathological lesions with the presence of AIP in the caudodorsal lungs and BP in the cranioventral lungs of necropsied cattle. This pulmonary pathology has been described as bronchopneumonia with an interstitial pneumonia (BIP). The epidemiological characteristics of BIP in U.S. feedyard cattle are yet to be described. This study's objectives were to describe the agreement between feedyard clinical and necropsy gross diagnosis and to characterize epidemiological factors associated with four gross pulmonary diagnoses (AIP, BIP, BP, and Normal pulmonary tissue) observed during feedyard cattle necropsies. Systemic necropsies were performed at six feedyards in U.S. high plains region, and gross pulmonary diagnoses were established. Historical data were added to the dataset, including sex, days on feed at death (DOFDEATH), arrival weight, treatment count, and feedyard diagnosis. Generalized linear models were used to evaluate epidemiological factors associated with the probability of each pulmonary pathology. Comparing feedyard clinical diagnosis with gross pathological diagnosis revealed relatively low agreement and the frequency of agreement varied by diagnosis. The likelihood of AIP at necropsy was higher for heifers than steers and in the 100-150 DOFDEATH category compared with the 0-50 DOFDEATH (p = 0.05). The likelihood of BIP increased after the first treatment, whereas the DOFDEATH 0-50 category had a lower likelihood compared with the 150-200 category (p = 0.05). These findings highlight the importance of necropsy for final diagnosis and can aid the development of future diagnosis and therapeutic protocols for pulmonary diseases.

Evaluation of predictive models to determine final outcome for feedlot cattle based on information available at first treatment for bovine respiratory disease.

OBJECTIVE: To evaluate predictive model ability to determine whether an animal finished the feeding period using data known at first treatment for bovine respiratory disease (BRD). Additional comparisons evaluated the potential benefits of predictions by adding weather data, utilizing balancing techniques, and creating models for individual feedyards. ANIMALS: This retrospective study included animal, pen, and feedyard data from 12 US feedyards from 2016 to 2021. The final dataset consisted of 96,382 BRD cases of which 14.2% did not finish the feeding phase. PROCEDURES: Five predictive models were trained and underwent threshold probability adjustment to maximize F1 score. Model performance was evaluated using accuracy, sensitivity specificity, positive and negative predictive values, and area under the receiver operating characteristics curve (AUC). RESULTS: Overall, model performance was low with a median AUC value of 0.675. The addition of weather data had little effect on AUC but resulted in more variation in sensitivity and specificity. Resampling the dataset had a limited effect on performance. Individual feedlot models had higher AUC values than others with the decision tree typically performing best in most feedyards. CLINICAL RELEVANCE: Results indicated some utility of predictive models evaluating BRD cases to predict cattle that did not finish the feeding phase. These models could be valuable in assisting health providers making decisions on individual cases.

Efficacy of high-level disinfection of endoscopes contaminated with Streptococcus equi subspecies equi with 2 different disinfectants.

BACKGROUND: Prevention of spread of Streptococcus equi subspecies equi (S. equi) after an outbreak is best accomplished by endoscopic lavage of the guttural pouch, with samples tested by culture and real time, quantitative polymerase chain reaction (qPCR). Disinfection of endoscopes must eliminate bacteria and DNA to avoid false diagnosis of carrier horses of S. equi. HYPOTHESIS/OBJECTIVES: Compare failure rates of disinfection of endoscopes contaminated with S. equi using 2 disinfectants (accelerated hydrogen peroxide [AHP] or ortho-phthalaldehyde [OPA]). The null hypothesis was that there would be no difference between the AHP and OPA products (based on culture and qPCR results) after disinfection. METHODS: Endoscopes contaminated with S. equi were disinfected using AHP, OPA or water (control). Samples were collected before and after disinfection and submitted for detection of S. equi by culture and qPCR. Using a multivariable logistic regression model-adjusted probability, with endoscope and day as controlled variables, the probability of an endoscope being qPCR-positive was determined. RESULTS: After disinfection, all endoscopes were culture-negative (0%). However, the raw unadjusted qPCR data were positive for 33% AHP, 73% OPA, and 71% control samples. The model-adjusted probability of being qPCR-positive after AHP disinfection was lower (0.31; 95% confidence interval [CI], -0.03-0.64) compared to OPA (0.81; 95% CI, 0.55-1.06), and control (0.72; 95% CI, 0.41-1.04). CONCLUSION AND CLINICAL IMPORTANCE: Disinfection using the AHP product resulted in significantly lower probability of endoscopes being qPCR-positive compared to the OPA product and control.

Retrospective analysis of risk and timing of death from right heart failure in United States and Canadian feedlot necropsied cattle.

OBJECTIVE: To evaluate the risk and timing of right heart failure (RHF) in feedlot cattle. ANIMALS: Study population consisted of 1,717,356 cattle (5,527 cohorts) in 13 US and Canadian feedlots. There were 1,336 RHF diagnosed at necropsy. PROCEDURES: Multivariable models were utilized to evaluate risk and timing of RHF death. RESULTS: Arrival year was associated with RHF and was influenced by arrival quarter on the magnitude of risk of RHF (P < .01), but no linear increase over years was identified. The impact of feedlot elevation on RHF was modified by breed (beef, dairy, or dairy-cross; P < .01) with beef cattle in the highest elevation category having 0.54 times the risk of RHF as dairy cattle in the same elevation category (LCL = 0.31; UCL = 0.962). Cattle that died due to RHF and were treated for bovine respiratory disease died 11 days (LCL = 1.33, UCL = 20.2 days) sooner than cattle never treated for bovine respiratory disease (P = .03). Cattle breed was associated with RHF timing (P = .01), and dairy-cross cattle RHF cases died approximately 37 days earlier (SE = 13.0 days; P = .01) compared to beef cattle. CLINICAL RELEVANCE: This research showed demographic factors associated with RHF and their respective influence on risk and timing of RHF. Risk rates of RHF were similar to previous research. This could allow for comparisons across different feedlot populations, using different diagnoses at necropsy and RHF risk/rates do not appear to be increasing.

No evidence for a negative association between bovine leukemia virus status and fertility in Kansas beef herds: a cross-sectional study.

OBJECTIVE: Determine the association between bovine leukemia virus (BLV) status and fertility in beef cows. BLV-status was defined using 3 different testing strategies (ELISA-, quantitative polymerase chain reaction- [qPCR], and high proviral load [PVL]-status). Fertility was defined as the overall probability of pregnancy as well as the probability of becoming pregnant in the first 21 days of the breeding season. ANIMALS: Convenience sample of 2,820 cows from 43 beef herds. PROCEDURES: The association of BLV-status with the probability of becoming pregnant was evaluated with a multivariable logistic regression analysis that used pregnancy status as a binary outcome, herd nested within ranch as a random effect, and BLV-status (ELISA-, qPCR-, and PVL-status as separate models) and potential covariates (eg, age, Body Condition Score [BCS] category, and interactions) as fixed effects. RESULTS: Raw data revealed that 55% (1,552/2,820) of cows were classified as BLV-positive by ELISA, and 95.3% (41/43) of herds had a least 1 ELISA-positive cow. Classification as BLV ELISA-positive was positively associated with the probability of being pregnant; however, when qPCR or PVL were used to classify BLV-status, there was no association with the probability of being pregnant. None of the methods of classifying BLV-status were associated with the probability of becoming pregnant in the first 21 days of the breeding season. CLINICAL RELEVANCE: This study did not find evidence that testing beef cows for BLV-status using ELISA, qPCR, or a cut-off of 0.9 PVL and removing test-positive cows will improve cowherd fertility as described by the probability of becoming pregnant during the breeding season or becoming pregnant during the first 21 days of the breeding season.

Evaluation of First Treatment Timing, Fatal Disease Onset, and Days from First Treatment to Death Associated with Bovine Respiratory Disease in Feedlot Cattle.

Bovine respiratory disease (BRD) is a frequent beef cattle syndrome. Improved understanding of the timing of BRD events, including subsequent deleterious outcomes, promotes efficient resource allocation. This study's objective was to determine differences in timing distributions of initial BRD treatments (Tx1), days to death after initial treatment (DTD), and days after arrival to fatal disease onset (FDO). Individual animal records for the first BRD treatment (n = 301,721) or BRD mortality (n = 19,332) were received from 25 feed yards. A subset of data (318-363 kg; steers/heifers) was created and Wasserstein distances were used to compare temporal distributions of Tx1, FDO, and DTD across genders (steers/heifers) and the quarter of arrival. Disease frequency varied by quarter with the greatest Wasserstein distances observed between Q2 and Q3 and between Q2 and Q4. Cattle arriving in Q3 and Q4 had earlier Tx1 events than in Q2. Evaluating FDO and DTD revealed the greatest Wasserstein distance between cattle arriving in Q2 and Q4, with cattle arriving in Q2 having later events. Distributions of FDO varied by gender and quarter and typically had wide distributions with the largest 25-75% quartiles ranging from 20 to 80 days (heifers arriving in Q2). The DTD had right-skewed distributions with 25% of cases occurring by days 3-4 post-treatment. Results illustrate temporal disease and outcome patterns are largely right-skewed and may not be well represented by simple arithmetic means. Knowledge of typical temporal patterns allows cattle health managers to focus disease control efforts on the correct groups of cattle at the appropriate time.

Determining Frequency of Common Pulmonary Gross and Histopathological Findings in Feedyard Fatalities.

Pulmonary disease is often associated with feedlot cattle mortality, and the most common syndromes include bronchopneumonia, acute interstitial pneumonia, and bronchopneumonia with an interstitial pneumonia. The study objective was to utilize gross necropsy and histopathology to determine the frequency of pulmonary lesions from three major syndromes and agreement between gross and histopathological diagnosis. A cross sectional, observational study was performed at six U.S. feedyards using a full systematic necropsy to assess mortalities during summer 2022. A subset of mortalities had four lung samples submitted for histopathological diagnosis. Gross necropsy was performed on 417 mortalities, 402 received a gross diagnosis and 189 had a histopathological diagnosis. Descriptive statistics were used to evaluate pulmonary diagnosis frequency based on method (gross/histopathology), and generalized linear mixed models were used to evaluate agreement between histopathological and gross diagnoses. Using gross diagnosis, bronchopneumonia represented 36.6% of cases with acute interstitial pneumonia and bronchopneumonia with an interstitial pneumonia representing 10.0% and 35.8%, respectively. Results identified bronchopneumonia with an interstitial pneumonia as a frequent syndrome which has only been recently reported. Histopathological diagnosis had similar findings; bronchopneumonia represented 32.3% of cases, with acute interstitial pneumonia and bronchopneumonia with an interstitial pneumonia representing 12.2% and 36.0%, respectively. Histopathological diagnosis tended (p-VALUE = 0.06) to be associated with gross diagnosis. Pulmonary disease was common and both diagnostic modalities illustrated three primary syndromes: bronchopneumonia, acute interstitial pneumonia, and bronchopneumonia with an interstitial pneumonia with similar frequencies. Improved understanding of pulmonary pathology can be valuable for evaluating and adjusting therapeutic interventions.

Image Classification and Automated Machine Learning to Classify Lung Pathologies in Deceased Feedlot Cattle.

Bovine respiratory disease (BRD) and acute interstitial pneumonia (AIP) are the main reported respiratory syndromes (RSs) causing significant morbidity and mortality in feedlot cattle. Recently, bronchopneumonia with an interstitial pattern (BIP) was described as a concerning emerging feedlot lung disease. Necropsies are imperative to assist lung disease diagnosis and pinpoint feedlot management sectors that require improvement. However, necropsies can be logistically challenging due to location and veterinarians' time constraints. Technology advances allow image collection for veterinarians' asynchronous evaluation, thereby reducing challenges. This study's goal was to develop image classification models using machine learning to determine RS diagnostic accuracy in right lateral necropsied feedlot cattle lungs. Unaltered and cropped lung images were labeled using gross and histopathology diagnoses generating four datasets: unaltered lung images labeled with gross diagnoses, unaltered lung images labeled with histopathological diagnoses, cropped images labeled with gross diagnoses, and cropped images labeled with histopathological diagnoses. Datasets were exported to create image classification models, and a best trial was selected for each model based on accuracy. Gross diagnoses accuracies ranged from 39 to 41% for unaltered and cropped images. Labeling images with histopathology diagnoses did not improve average accuracies; 34-38% for unaltered and cropped images. Moderately high sensitivities were attained for BIP (60-100%) and BRD (20-69%) compared to AIP (0-23%). The models developed still require fine-tuning; however, they are the first step towards assisting veterinarians' lung diseases diagnostics in field necropsies.

Stochastic, individual animal systems simulation model of beef cow-calf production: development and validation.

A stochastic, individual animal systems simulation model describing U.S. beef cow-calf production was developed and parameterized to match typical U.S. Angus genetics under cow-calf production conditions in the Kansas Flint Hills. Model simulation results were compared to available actual, multivariate U.S. cow-calf production data reported according to beef cow-calf standardized performance analysis (SPA) methodology through North Dakota State University's CHAPS program to assess model validity. Individual animal nutrition, reproduction, growth, and health characteristics, as well as production state are determined on a daily time step. Any number of days can be simulated. These capabilities allow for decision analysis and assessment of long-run outcomes of various genetic, management, and economic scenarios regarding multiple metrics simultaneously. Parameterizing the model to match Kansas Flint Hills production conditions for the years 1995 through 2018, 32 different genetic combinations for mature cow weight and peak lactation potential were simulated with 100 iterations each. Sire mature cow weight genetics ranged from 454 to 771 kg in 45 to 46 kg increments. Sire peak lactation genetics were considered at 6.8, 9, 11.3, and 13.6 kg/d for all eight mature cow weights. Utilizing model results for the years 2000 to 2018, raw model results were assessed against actual historical cow-calf production data. Exploratory factor analysis was applied to interpret the underlying factor scores of model output relative to actual cow-calf production data. Comparing modeled herd output with CHAPS herd data, median average calf weaning age, average cow age, percent pregnant per cow exposed, and percent calf mortality per calf born of model output was 3.4 d greater, 0.2 yr greater, 1 percentage point less, and 1.7 percentage points greater, respectively. Subtracting the median CHAPS pre-weaning average daily gain from the median modeled pre-weaning average daily gain for each of the eight respective mature cow weight genetics categories, and then calculating the median of the eight values, the median difference was -0.21 kg/d. Performing the same calculation for birth weight and adjusted 205 d weaning weight, the modeled data was 4.9 and 48.6 kg lighter than the CHAPS data, respectively. Management and genetic details underlying the CHAPS data were unknown.

Nasopharyngeal Bacterial Prevalence and Microbial Diversity at First Treatment for Bovine Respiratory Disease (BRD) and Its Associations with Health and Mortality Outcomes in Feedyard Cattle.

Bovine respiratory disease (BRD) is an economically important disease in feedyards influencing both animal welfare and antimicrobial utilization. Major pathogens associated with BRD have been identified in previous research, but little information is available on the relationship between nasopharyngeal microbiota and health outcomes. The objective of this study was to identify potential associations between nasopharyngeal microbiota and antimicrobial resistance patterns of clinical cases that lived or died compared to non-diseased controls. Enrolled animals were subdivided based on clinical disease status and case outcome (subsequent mortality). Deep nasopharyngeal swabs were collected on enrolled animals and submitted for bacterial isolation, antimicrobial susceptibility determination, and metagenomics analysis. Enrolled cattle were represented in three groups: animals at first treatment for BRD that subsequently died (BRDM, n = 9), animals at first treatment for BRD that subsequently lived (BRDL, n = 15), and animals that were never treated for BRD during the feeding phase (CONT, n = 11). Antimicrobial resistance patterns for Pasteurella multocida illustrated cattle in each outcome category had isolates that were pan-susceptible or only showed resistance to oxytetracycline. The relative abundance of species and genera illustrated few differences among the three outcomes. Higher alpha diversity was identified in BRDL compared to CONT at the species level, and both BRDL and BRDM showed increased alpha diversity compared to CONT at the general level. Overall, this work illustrated nasopharyngeal microbiota showed relatively few differences among BRD cases that lived or died compared to animals without BRD.

Cross-sectional study to describe bovine leukemia virus herd and within-herd ELISA prevalence and bovine leukemia virus proviral load of convenience-sampled Kansas beef cow-calf herds.

OBJECTIVE: Determine bovine leukemia virus (BLV) seroprevalence of adult female cattle in Eastern Kansas beef herds and the proviral load (PVL) of those cattle found to be ELISA positive. ANIMALS: Convenience sample of 2,845 cows from 44 beef herds. PROCEDURES: BLV serostatus was determined using an ELISA antibody test (gp-51; IDEXX). BLV quantitative PCR (qPCR) status and PVL were determined utilizing a qPCR test (SS1 qPCR test; CentralStar Laboratories). The association of age, herd size, and body condition score (BCS) category on the probability of being BLV positive was evaluated with a multiple variable logistic regression analysis that used BLV status as a binary outcome, herd nested within ranch as a random effect, and BCS, herd size, and age category as fixed effects. RESULTS: Forty-two of 44 herds had at least 1 BLV ELISA-positive cow (95.5% herd seroprevalence). Overall, 1,564 of the 2,845 cows were BLV ELISA positive (55.0% individual animal prevalence). No association between BLV ELISA status and herd size or BCS was identified. When evaluated by age, the model-adjusted probability of being BLV ELISA positive was lowest for heifers (1 year of age, first parity) and increased until 5 to 6 years of age. Of the 1,564 ELISA-positive animals, 838 were qPCR positive (53.6%). The model-adjusted probability of being qPCR positive was not associated with age, herd size, or BCS category. CLINICAL RELEVANCE: This study indicated that BLV-seropositive status both as a herd classification and individual animal classification was very common in this population. Because the percentage of BLV-seropositive cows varied between herds and by age, this study provides evidence that it is essential for investigators to control for herd and age in any analysis of the association of BLV serostatus and health and production outcomes of interest. Some BLV ELSIA-seropositive cows were classified as BLV negative by qPCR, and risk factors may differ between classification status by ELISA and qPCR.

Impact of Water Sources and Shared Fence Lines on Bovine Respiratory Disease Incidence in the First 45 Days on Feed.

Bovine respiratory disease (BRD) is a frequent disease in feedlot cattle, but little is known on the role of pen housing conditions. The objective of this research is to use a retrospective analysis with data from 10 U.S. feedlots to determine potential associations between BRD risk during the first 45 days after arrival with pen-level management factors including the number of water sources, shared water sources, and shared fence lines. Generalized linear mixed models were used to evaluate associations between management factors, cattle demographics, and BRD incidence. The effect of shared water sources on BRD risk was modified by arrival weight and cohort size (p < 0.05). Cattle with two water sources had lower BRD morbidity (5.55% ± 0.98) compared to cattle with one water source (8.80% ± 1.50) when arrival weight was 227 kg to 272 kg, while there were few differences in heavier weight cattle. Cattle with two water sources had lower BRD morbidity (3.11% ± 0.56) compared to one water (5.50% ± 0.10) when cohort size was 100−175 head, but there were no BRD morbidity differences when bigger or smaller cohorts were evaluated. Shared fence lines and water sources were associated with BRD risk; however, no biologically meaningful results were identified. The number of water sources was associated with BRD risk, and effects were modified by cohort size and arrival weight.

Predicting Bovine Respiratory Disease Risk in Feedlot Cattle in the First 45 Days Post Arrival.

Bovine respiratory disease (BRD) is the leading cause of morbidity in feedlot cattle. The ability to accurately identify the expected BRD risk of cattle would allow managers to detect high-risk animals more frequently. Five classification models were built and evaluated towards predicting the expected BRD risk (high/low) of feedlot cattle within the first 45 days on feed (DOF) and incorporate an economic analysis to determine the potential health cost advantage when using a predictive model compared with standard methods. Retrospective data from 10 U.S. feedlots containing 1733 cohorts representing 188,188 cattle with known health outcomes were classified into high- (≥15% BRD morbidity) or low- (<15%) BRD risk in the first 45 DOF. Area under the curve was calculated from the test dataset for each model and ranged from 0.682 to 0.789. The economic performance for each model was dependent on the true proportion of high-risk cohorts in the population. The decision tree model displayed a greater potential economic advantage compared with standard procedures when the proportion of high-risk cohorts was ≤45%. Results illustrate that predictive models may be useful at delineating cattle as high or low risk for disease and may provide economic value relative to standard methods.

The failure mode of a mechanically loaded equine medial femoral condyle analog with a void and the impact of lag and neutral screw placement.

OBJECTIVE: To determine the failure method of simulated equine medial femoral condyle (MFC) subchondral bone defects under compression and the influence of screw placement on failure resistance. STUDY DESIGN: In vitro study. SAMPLE POPULATION: Composite disks (CD) simulating the moduli of yearling bone in the MFC. METHODS: Four CD conditions were tested, all with a 12.7 mm void (n = 6 per condition): intact (no void), void only, void with a 4.5 mm screw placed in neutral fashion, and void with a 4.5 mm screw placed in lag fashion. Composite disks of each condition were tested under monotonic compression to 6000 N and cyclic compression to 10 000 cycles. Observable failure, load at first observable failure, and displacement at peak 2000 N load were compared among conditions. RESULTS: Specimens failed by cracking at the superior aspect of the void or the screw exit hole. After monotonic loading, cracks were observed 6/6 CD with a void, 6/6 CD with a void/lag screw, and 5/6 CD with a void/neutral screw. After cyclical testing, cracks were noted only on the superior aspect of 6/6 CD with a void and 3/6 CD with a void/lag screw. Displacement at peak load was 0.06 mm (intact), 0.32 mm (void), 0.24 mm (void/lag screw), and 0.11 mm (void/neutral screw). CONCLUSION: Model MFC voids failed by superior cracking that was resisted by lag and neutral screw placement. CLINICAL SIGNIFICANCE: Neutral screws may be an acceptable treatment for subchondral lucencies in the MFC.

Evaluation of Strategies to Improve the Environmental and Economic Sustainability of Cow-Calf Production Systems.

Grazing cow-calf production systems account for 60 to 70% of the greenhouse gas emissions of U.S. beef production. The objective of this analysis was to evaluate the importance of management strategies (cow maintenance energy requirements, reproductive efficiency, forage nutritive value, and forage yield) on the sustainability of cow-calf production systems using a sensitivity analysis in a production systems model. The Beef Cattle Systems Model was used to simulate a cow-calf production system in the Kansas Flint Hills using Angus genetics over a 24 year time period. The model was modified to create variation among cow herds in the base net energy for the maintenance requirement (NEm_Req), postpartum interval (PPI), grazed forage digestibility (Forage_TDN), and forage yield per hectare (Forage_Yield). The model was run for 1000 iterations/herds of a 100-cow herd. A stepwise regression analysis in conjunction with standardized regression analysis was used to identify important predictors of an indicator of greenhouse gas (GHG) emission intensity, dry matter intake per kilogram weaned, and two indicators of economic sustainability, winter feed use and returns over variable costs, using R statistical software. The most important predictor of DMI per kilogram weaned was calf weaning weight followed by NEm_Req, whereas returns over variable costs were primarily influenced by kilograms weaned per cow exposed and total purchased feed (supplement + winter feed), which were strongly influenced by NEm_Req and Forage_Yield, respectively. In conclusion, decreasing the net energy required for maintenance improved both economic and environmental sustainability, and increasing forage yield and length of the grazing season improved economic sustainability, implying that these strategies should be primary targets to enhance the sustainability of cow-calf production systems.

Retrospective analysis of cohort risk factors and feeding phase timing associated with noninfectious heart disease deaths in U.S. feedlot cattle.

Heart disease, specifically congestive heart failure, has become of increased interest to geneticists and cattle feeders. Data on cohort associations of risk factors related to heart disease and when heart disease deaths occur in U.S. feedlot cattle are limited. The study objectives were to 1) determine potential associations between feedlot cohort demographics and the risk of at least one noninfectious heart disease (NIHD) death occurrence and 2) determine potential association between feedlot cohort demographics and the timing of NIHD deaths during the feeding phase. Data were downloaded from commercial feedyard software and analyzed by constructing a generalized linear mixed model for both analyses. A binomial and Gaussian distributions for risk of NIHD death and timing of NIHD were utilized as link functions for their respective models. Our study population consisted of 28,950 cohorts (representing 4,596,205 cattle) that were placed in 22 U.S. commercial feedlots from January 01, 2016, to January 01, 2019. There were 3,282 cases of NIHD deaths from a population of 75,963 cattle that died during the 3-yr study period. Average cohort arrival weight's effect on NIHD probability was influenced by arrival quarter and arrival year of placement (P < 0.01). Cohorts with steers were associated with a greater probability of at least one NIHD death (2.38%) compared with heifers (1.95%; P < 0.01). Increasing cohort size was associated with an increased probability of a cohort having at least one NIHD death (P < 0.01). The probability of a cohort having at least one NIHD death increased with increasing DOF categories from 1.51% in cattle fed 100 to 175 d, to 2.12% in cattle fed 176 to 250 d, and 2.87% for cattle fed 251 to 326 d. Cattle > 326 DOF were no different in the probability of a NIHD death compared with the other feeding categories. Timing of a NIHD death had a mean and median occurrence of 110 DOF with an interquartile range of 64 to 153 DOF. The effect of arrival weight on days at death was influenced by year placed with heavier cattle generally decreasing the model adjusted means of DOF at NIHD death. Arrival quarter was influenced by year placed on model adjusted means on the timing of a NIHD death. Steers with NIHD died later compared with heifers (P < 0.01) diagnosed with NIHD. In conclusion, multiple factors are associated with the probability and timing of a NIHD death. Probability of having at least one NIHD death within a cohort was low, and half of the deaths occurred before 110 DOF.

Evaluation of specific immunoglobulin A in nasal secretions and neutralizing antibodies in serum collected at multiple time points from young beef calves following intranasal or subcutaneous administration of a modified-live bovine respiratory syncytial virus vaccine.

OBJECTIVE: To determine anti-bovine respiratory syncytial virus (BRSV) antibody titers for nasal secretions and serum from beef calves following administration of a modified-live (MLV) BRSV vaccine. ANIMALS: 60 healthy newborn purebred beef calves. PROCEDURES: Calves were randomly assigned to 1 of 3 groups: intranasal (IN)-SC (IN MLV BRSV vaccine within 24 hours of birth and SC MLV BRSV vaccine at 2 months of age), SC-IN (SC MLV BRSV vaccine within 24 hours of birth and IN MLV BRSV vaccine at 2 months of age), or NO-IN (no vaccine within 24 hours of birth and IN MLV BRSV vaccine at 2 months of age). Nasal secretion and serum samples were collected for determination of anti-BRSV antibodies within 24 hours of birth and 2 and 6 months of age. RESULTS: Titers of anti-BRSV IgA antibodies in nasal secretions and BRSV neutralizing antibodies in serum were similar among groups at each sampling time. Within 24 hours of birth, nasal anti-BRSV IgA titers were negligible. At 2 months, mean nasal anti-BRSV IgA titers for calves in IN-SC, SC-IN, and NO-IN groups were 192.84, 224.49, and 114.71, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Concentrations of anti-BRSV IgA antibodies in the nasal secretions and BRSV neutralizing antibodies in the serum of young beef calves following an MLV BRSV vaccine protocol that consisted of IN or SC vaccine within 24 hours of birth and vice versa at 2 months of age were not different from that following only an IN MLV BRSV vaccine at 2 months of age. However, the lack of any differences may have been attributed to other factors.

Detection of bovine inflammatory cytokines IL-1ß, IL-6, and TNF-α with a multiplex electrochemiluminescent assay platform.

Commercially available bovine-specific assays are limited in number, and multiplex assays for this species are rare. Our objective was to develop a multiplex assay for the bovine inflammatory cytokines IL-1ß, IL-6, and TNF-α using the Meso Scale Discovery U-PLEX platform. "Do-It-Yourself" ELISA kits that contained polyclonal antibodies, both unlabeled and biotinylated, and the specific recombinant bovine cytokine standard, were purchased for each of these three cytokines. The biotinylated antibodies were coupled to linkers that bind to specific locations within each well of the U-PLEX plate. Unique linkers were used for each of the cytokines. The unlabeled antibodies were conjugated with electrochemiluminescent labels to serve as detection antibodies. Each cytokine assay was optimized individually prior to performing an optimization on the multiplex assay containing reagents for all three cytokines. To calculate cytokine concentrations, standard curves were developed using the recombinant cytokines and were run concurrently on each plate. Standard curves for IL-1ß and TNF-α were run at concentrations ranging from 0 to 50,000 pg/mL, and for IL-6 from 0 to 10,000 pg/mL. The average lowest level of detection concentration measured by the standard curves were 5.3 pg/mL, 0.92 pg/mL, and 22.34 pg/mL for IL-1ß, IL-6, and TNF-α respectively, as determined by data from seven plates containing bovine plasma samples from a combination of healthy and diseased cattle. The U-PLEX platform was a viable means to develop custom analyte- and species-specific multiplex assays using privately developed or purchased sets of commercially available reagents.