Prevalence of respiratory disease in Irish preweaned dairy calves using hierarchical Bayesian latent class analysis

Development and Progression of Bovine Respiratory Disease Measured Using Clinical Respiratory Scoring and Thoracic Ultrasonography in Preweaned Calves on Dairy Farms in the United Kingdom: A Prospective Cohort Study

The respiratory health of preweaned calves is an important determinant of their health, welfare, and future performance. This prospective cohort study measured bovine respiratory disease (BRD) on 16 dairy farms, including 476 calves in South-west England. Wisconsin and California respiratory scoring and thoracic ultrasonography were performed repeatedly at 7 ± 0.89 day intervals (mean ± SD) at 0-56 days of age (n = 3344 examinations). Cases were localized to the upper or lower respiratory tract, or both, and classified as new, repeat, or chronic. Prevalence and incidence were calculated. Multivariate modeling of factors associated with repeated measurements was performed. Increasing age (OR = 1.05, 95% CI 1.04-1.06) and fecal score (Score 2, OR = 1.78, 95% CI 1.14-2.77) were associated with a lower odds of a healthy BRD subtype, whereas increasing serum total protein (OR = 0.97, 95% CI 0.96-0.99) was protective. Older (OR 1.08, 95% CI 1.06-1.09), male (OR 1.69, 95% CI 1.01-2.84) calves with elevated Wisconsin respiratory scores (≥5, OR 5.61, 95% CI 3.38-9.30) were more likely to have elevated thoracic ultrasound scores. BRD remains common in calves born in UK dairy herds, requiring precise identification and management if preweaning health is to be optimized.

Developing a tool to assess the health-related quality of life in calves with respiratory disease: tool refinement and construct validity testing

Bovine respiratory disease (BRD) is a major source of morbidity and mortality in calves and detection of the disease can be challenging. Diagnostic tools for BRD are typically based on the assessment of clinical signs. As experience of disease is associated with a poor quality of life and this poor emotional experience can be expressed in observable behaviour patterns, a quality-of-life approach might identify new indicators of disease. Health-related quality of life (HRQOL) approaches are widely used in human medicine but are rarely used in livestock. This study aimed to refine and validate an HRQOL tool for calves with BRD that had been created in a previous study. The tool contained 13 items/indicators across two domains (clinical signs and behavioural expression). One hundred preweaned dairy-bred calves were scored daily using the HRQOL tool and also using the industry-recognised Wisconsin health score as a 'gold standard'. The score assigned to each of the 13 items of the HRQOL tool was summed to give an accumulated HRQOL score for each calf/day. To refine the tool, the items within the tool were compared to each other to identify high levels of correlation or redundancy. This resulted in the retention of three items within the clinical signs domain (body and head posture, respiratory effort and ear carriage) and four within the behavioural expression domain (vigour, movement to feed, motivation at feed and volume of feed consumed). To determine whether the refined HRQOL tool could successfully differentiate sick from healthy animals, the Wisconsin score was used to create two matched groups of 28 'sick' and 28 'healthy' calves. There was a significant difference in the HRQOL scores between the two groups (H = 14.09, df = 1, P = 0.000) suggesting that the new tool could differentiate between 'healthy' and 'sick' calves. In terms of the two domains, there was a significant difference (P < 0.001) between the 'healthy' and 'sick' calves for the overall HRQOL tool score for the clinical signs domain, but there was no significant difference (P = 0.154) between 'healthy' and 'sick' calves in the overall HRQOL score for the behavioural expression domain; however, the combined tool was the most accurate. Overall, this study has demonstrated that the new HRQOL tool can differentiate between sick and healthy calves. Some or all of the indicators could be used alongside existing disease-detection tools for preweaned calves. However, future work would be needed to validate this HRQOL tool in other production systems.

An Innovative Approach: The Usage of N-Acetylcysteine in the Therapy of Pneumonia in Neonatal Calves

NAC has mucolytic, antioxidant, and antimicrobial effects in living organisms. However, the therapeutic effects of NAC on clinical recovery among neonatal calves with respiratory diseases have not yet been studied. Our study represents the first investigation of the effects of NAC in neonatal calves with pneumonia. The objective of this work was to observe the effects of NAC in the treatment of neonatal pneumonia, including its ability to reduce the clinical score, shorten the duration of the treatment, and improve the overall health condition of neonatal calves. For this study, calves were divided into two groups: a treatment group that received NAC and amoxicillin with clavulanic acid, and a control group that received amoxicillin with clavulanic acid (antimicrobial only). The findings of this study indicate that NAC treatment significantly shortened the time to resolution (p < 0.001), compared to the results in the group without NAC treatment. Generally, NAC-supplemented therapy reduced the recovery time by more than 27 h (or slightly more than one day), compared to that in the antimicrobial-only group. Our study presents the first reported usage of NAC in therapy for respiratory disorders.

Performance of various interpretations of clinical scoring systems for diagnosis of respiratory disease in dairy calves in a temperate climate using Bayesian latent class analysis

Bovine respiratory disease (BRD) presents a challenge to farmers all over the globe, not only because it can have significant impacts on welfare and productivity, but also because diagnosis can prove challenging. Several clinical scoring systems have been developed to aid farmers in making consistent early diagnosis, 2 examples being the Wisconsin (WCS) and the California (CALIF) systems. Neither of these systems were developed in or for use in a temperate environment. As environment may lead to changes in BRD presentation, the weightings and cutoffs designed for one environmental presentation of BRD may not be appropriate when used in a temperate climate. Additionally, the interpretation of the scores recorded varies between studies; this may also influence conclusions. Hence, the objective of this work was to investigate the sensitivity (Se) and specificity (Sp) of these tests in a temperate climate and investigate the influence of varying the interpretation on the performance of the WCS. In this prospective study, 98 commercial spring-calving dairy farms were recruited (40 randomly, 58 targeted) and visited. Thoracic ultrasound and WCS were performed on 20 randomly sampled calves between 4 and 6 wk of age on each farm. On a subset of 32 farms, the CALIF score was also undertaken. The data were then used in a hierarchical Bayesian latent class model to estimate the Se and Sp of 5 different interpretations of the Wisconsin clinical score and 1 interpretation of the California clinical score. In total, 1,936 calves were examined. The Se of the Wisconsin score varied from 0.336 to 0.577 depending on the interpretation used, and the Sp varied from 0.943 to 0.977. The Se of the California score was 0.563 (95% Bayesian credible interval [BCI]: 0.452, 0.681) and the Sp was 0.919 (95% BCI: 0.899, 0.937). In conclusion, the performances of the clinical scores in a temperate environment were similar to previously published work from more extreme climates; however, the performance varied widely depending on the score interpretation. Authors should justify their use of a particular clinical score interpretation to improve clarity in publications.

Summer scour syndrome in weaned dairy calves: case series

BACKGROUND

Summer scour syndrome (SSS) is a recently identified pathological condition affecting weaned dairy and dairy-beef calves during their first grazing season in Ireland. The syndrome is characterised by diarrhoea, weight loss, weakness, and can ultimately lead to death in some calves. Oral and oesophageal ulcerations are present in some cases. This study aimed to characterise a series of SSS cases in weaned dairy-bred calves on Irish commercial farms.

RESULTS

Five farms with calves having unexplained diarrhoea at grass were referred by private veterinary practitioners (PVP) following preliminary testing to exclude coccidiosis and parasitic gastroenteritis. Farms were visited within 2 to 5 days following PVP's referrals, or 2 days to 3 weeks relative to the onset of clinical signs. Farm management data, grass and concentrate samples, and biological samples from 46 calves (8 to 10 calves/farm) displaying clinical signs were collected. Two farms were subsequently found positive for coccidiosis and/or had chronic pneumonia problems after a thorough herd investigation and were designated as non-case farms (NCF). The remaining three farms were deemed typical SSS outbreaks (case farms; CF). Mean rumen fluid pH per farm ranged from 6.67 to 7.09 on CF, and 6.43-6.88 on NCF. Mean rumen fluid ammonia concentrations ranged from 17.6 to 29.6 mg/L and 17.2-45.0 mg/L on CF and NCF, respectively. Corresponding blood ammonia concentrations ranged from 129 to 223 µmol/L and 22-25 µmol/L. Mean blood copper and molybdenum concentrations were within normal range on all farms. Grass crude protein concentrations on the paddocks where the calves had grazed, and were currently grazing on the day of visit ranged from 137 to 148 g/kg DM and 106-177 g/kg DM, respectively on CF, and 160-200 g/kg DM and 151-186 g/kg DM, respectively on NCF. On CF, inorganic nitrogen fertiliser was applied 1 to 3 weeks pre-grazing, whereas on the two NCF, inorganic nitrogen fertiliser was applied 2 to 3 weeks pre-grazing on one farm and no fertiliser was applied on the other.

CONCLUSION

These findings suggest that copper or molybdenum toxicity, and ruminal acidosis are not the primary causes of SSS. High blood ammonia concentrations and the timing and level of inorganic nitrogen fertiliser application to paddocks pre-grazing, warrant further investigation.

A Bayesian finite mixture model approach to evaluate dichotomization method for correlated ELISA tests

In diagnostic accuracy studies, a commonly employed approach involves dichotomizing continuous data and subsequently analyzing them using a Bayesian latent class model (BLCM), often relying on binomial or multinomial distributions, rather than preserving their continuous nature. However, this procedure can inadvertently lead to less reliable outcomes due to the inherent loss of information when converting the original continuous measurements into binary values. Through comprehensive simulations, we demonstrated the limitations and disadvantages of dichotomizing continuous biomarkers from two correlated tests. Our findings highlighted notable disparities between the true values and the model estimates as a result of dichotomization. We discovered the crucial significance of selecting a reference test with high diagnostic accuracy in test evaluation in order to obtain reliable estimates of test accuracy and prevalences. Our study served as a call to action for veterinary researchers to exercise caution when utilizing dichotomization.

A systematic review of the relationship between housing environmental factors and bovine respiratory disease in preweaned calves - Part 2: Temperature, relative humidity and bedding

Bovine respiratory disease (BRD) is a challenge in all housed farming systems that raise calves. Farm to farm variation in BRD prevalence can be partially attributed to variation in host immunity, pathogens and housing environment. Unlike host immunity and BRD pathogens, housing environment has not been well investigated. The objective of this systematic review was to identify the measurable environmental variables associated with BRD in housed preweaned calves. Pubmed, CAB Direct and Scopus databases were searched. To be considered for inclusion publications had to be published in English, before 24 November, 2022 and include at least one measurable/ manipulated environmental variable and a standardized method of BRD detection. In total 12 publications were included in this review. In this second part of the systematic review the environmental variables identified were; temperature (9 publications); relative humidity (8 publications); bedding (5 publications); ventilation (1 publication); air CO2 concentration (1 publication) and air velocity (4 publications). Of the publications that were examined a statistically significant relationship to BRD was identified in 4/9 publications examining temperature, 3/8 examining relative humidity, 2/4 examining air velocity, 2/5 examining bedding, 0/1 examining ventilation rates and 0/1 examining CO2 concentration. From this review it is clear high airspeed at calf level should be avoided as should deep, wet pack bedding. The relationship between BRD prevalence and both high and low temperature requires more investigation to identify temperature thresholds associated with increased risk of BRD as well as the most influential modifiers. An optimal environment for housed calves could not be clearly identified in this review.

Invited review: Bovine neonatal morbidity and mortality-Causes, risk factors, incidences, sequelae and prevention

The neonatal period may be defined as the first month of the calf's life; it may be considered part of the fourth trimester. It is the most hazardous due to the immaturity of the neonate's immune system and the environmental challenge from infections, the main causes of both bovine neonatal morbidity and mortality. The five most common morbidities causing mortality in neonatal calves are, in descending order, gastrointestinal infections, respiratory infections, abomasal disorders, umbilical infections and developmental abnormalities. This review describes the aetiology, incidence, risk factors and sequelae of these common morbidities and highlights current preventive strategies both at farm and national levels.