Genetic parameters estimated at receiving for circulating cortisol, immunoglobulin G, interleukin 8, and incidence of bovine respiratory disease in feedlot beef steers

Bovine respiratory disease complex (i.e., shipping fever and bacterial bronchopneumonia) is a multifaceted respiratory illness influenced by numerous environmental factors and microorganisms. Bovine respiratory disease (BRD) is just one component of BRD complex. Because BRD is moderately heritable, it may be possible to reduce the incidence of BRD through genetic selection. The objectives of this study were to determine the heritability and associative genetic relationships among immune system traits (i.e., cortisol, total IgG, IgG isotypes, and IL-8) in cattle monitored for BRD incidence. At an average of 83 d after weaning (219 d age and mean = 221.7 kg [SD 4.34]), crossbred Bos taurus steer calves (n = 2,869) were received at a commercial feedlot in southeastern Colorado over a 2-yr period. At receiving, jugular blood samples were collected at 212 (yr 1) and 226 d (yr 2) of age for immune trait analyses. The BRD phenotype was defined as a binomial variable (0 = no and 1 = yes) and compared with immune system traits measured at receiving (prior to illness onset). An animal identified as BRD positive exhibited ≥ 2 clinical signs (i.e., eye or nasal discharge, cough, lethargy, rapid breathing, acute interstitial pneumonia, or acute upper respiratory syndrome and/or a rectal temperature > 39.7°C). Heritability and genetic correlation estimates for categorical variable BRD, cortisol, IgG, IgG1, IgG2, and IL-8 were estimated from a sire model using ASREML. Heritability estimates were low to moderate for BRD (0.17 ± 0.08), cortisol (0.13 ± 0.05), IgG (0.15 ± 0.05), IgG1 (0.11 ± 0.05), IgG2 (0.24 ± 0.06), and IL-8 (0.30 ± 0.06). A moderate negative genetic correlation was determined between BRD and cortisol (r_g = −0.19 ± 0.32). Moderate positive correlations were found between BRD with IgG (0.42 ± 0.28), IgG1 (0.36 ± 0.32), and IL-8 (r_g = 0.26 ± 0.26). Variation in the BRD phenotype and immune system traits suggested herd health improvement may be achieved through genetic selection.

Systematic Review of the Diagnostic Accuracy of Haptoglobin, Serum Amyloid A, and Fibrinogen versus Clinical Reference Standards for the Diagnosis of Bovine Respiratory Disease

BACKGROUND

Bovine respiratory disease (BRD) is a worldwide animal health concern especially in feedlot, dairy, and veal calves. One of the greatest challenges is the absence of a gold standard for achieving an accurate antemortem diagnosis. Various blood markers, including the acute-phase proteins (AAP), have been proposed as potential valuable tools for BRD diagnosis.

OBJECTIVES

To perform a systematic review of the literature to assess the accuracy of selected APP (haptoglobin [Hp], serum amyloid A [SAA], and fibrinogen [Fb]) as diagnostic tools for cattle with naturally occurring BRD when compared with clinical reference standards of diagnosis.

METHODS

This review was performed with eligible studies selected from CAB Abstract and MEDLINE from 1946 to 2015, as well as the "gray literature." Methodological quality of included studies was assessed using the QUADAS-2 tool developed for diagnostic accuracy studies. The accuracy parameters sensitivity (Se) and specificity (Sp) were obtained from the articles or through contact with the authors when not directly reported.

RESULTS

A total of 314 studies were identified, from them, 23 met inclusion criteria as diagnostic studies for naturally occurring BRD. Quality of studies showed high risk of bias for case selection (70% of articles) and unclear risk of bias for index test (65%), reference standard (74%), and flow and timing (61%). There were high concerns regarding applicability for case selection (61% of studies) and reference standards used for defining BRD (48%). The concerns regarding index test application were low (83% of the studies). Only 4-8 studies could be included in the meta-analysis for each APP. No pooled estimates or pooled accuracy measurements were performed due to the low number of studies and multiple differences between studies, including reference standard definitions.

CONCLUSIONS AND CLINICAL IMPORTANCE

On the basis of these findings, it is not possible to make conclusions regarding the accuracy of APP for BRD diagnosis. The reporting of accuracy of APP for BRD detection is inconsistent among studies. Recommendations to improve capability for future meta-analyses in this area include reporting studies on diagnostic tests following the Standard for the Reporting of Diagnostic Accuracy Studies (STARD), as well as trying to standardize BRD definition across future studies.

Bovine coronavirus (BCV) infections in transported commingled beef cattle and sole-source ranch calves

This study investigated bovine coronavirus (BCV) in both beef calves direct from the ranch and commingled, mixed-source calves obtained from an auction market. The level of BCV-neutralizing antibodies found in the calves varied among ranches in 2 different studies in a retained-ownership program (ROP), from the ranch to the feedlot. Calves with low levels of BCV-neutralizing antibodies (16 or less) were more likely to be treated for bovine respiratory disease (BRD) than those with higher titers. In 3 studies of commingled, mixed-source calves, BCV was recovered from calves at entry to the feedlot and the infections were cleared by day 8. The BCV was identified in lung samples [bronchoalveolar lavage (BAL) collection] as well as in nasal swabs. Calves with low levels of BCV-neutralizing antibodies at entry were most likely to be shedding BCV. Bovine coronavirus was isolated from both healthy and sick calves, but not from sick calves after 4 d arrival at the feedlot. Bovine coronavirus (BCV) should be considered along with other bovine respiratory viruses in the diagnosis of etiologies in bovine respiratory disease, especially for animals that become sick shortly after arrival. If approved vaccines are developed, it would be best to carry out vaccination programs before calves are weaned, giving them sufficient time to gain active immunity before commingling with other cattle.