Respiratory illness in young and adult cattle caused by bovine viral diarrhea virus subgenotype 2b in singular and mixed bacterial infection in a BVDV-vaccinated dairy herd.

Bovine respiratory disease (BRD) is a common global health problem in dairy cattle. The definitive diagnosis of BRD is complex because its etiology involves several predisposing and determining factors. This report describes the etiology of a BRD outbreak in a dairy herd in the mesoregion of Central Eastern Paraná, which simultaneously affected young (calves and heifers) and adult (cows) Holstein-Friesian cattle. Nine biological samples, consisting of five lung samples from two cows and three suckling calves, and four nasal swab samples from heifers, were used for etiological diagnosis. The nucleic acids extracted from lung fragments and nasal swabs were subjected to PCR and RT-PCR assays for partial amplification of the genes of five viruses [bovine viral diarrhea virus (BVDV), bovine alphaherpesvirus 1 (BoAHV1), bovine respiratory syncytial virus (BRSV), bovine parainfluenza virus 3 (BPIV-3), and bovine coronavirus (BCoV)] and four bacteria (Mycoplasma bovis, Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni) involved in the etiology of BRD. All nine biological samples from the animals with BRD tested negative for BoAHV1, BRSV, BPIV-3, BCoV, and H. somni. Therefore, the involvement of these microorganisms in the etiology of BRD outbreak can be ruled out. It was possible to identify the presence of BVDV and M. bovis in singular and mixed infections of the lower respiratory tract in cattle. BVDV was also identified in two nasal swabs: one as a single etiological agent and the other in association with two bacteria (P. multocida and M. haemolytica). The phylogenetic analysis conducted in the nucleotide sequence of the 5'UTR region and Npro gene of the BVDV amplicons demonstrated that the BVDV field strains of this BRD outbreak belong to subgenotype 2b. To the best of our knowledge, this is the first report of BVDV-2b involvement in the etiology of BRD in Brazil. Finally, it is necessary to highlight that the cattle were obtained from an open dairy herd with biannual vaccinations for BVDV-1a and - 2a.

Association of passive immunity and genetic composition, health, and performance of tropical dairy calves.

This retrospective cohort study aimed to identify risk factors for the failure of transfer of passive immunity (FPI) in preweaned dairy calves, explore its associations with morbidity, mortality, genetics, and determine a standardized cut-off point for FPI. Analyzing data from 6011 calves, factors such as sire predicted transmitted ability for milk (PTA), birth season, retained placenta (RP), total serum protein concentration (TSP), morbidity (neonatal calf diarrhea - NCD, bovine respiratory disease - BRD, tick-borne disease - TBD), mortality, and average daily weight gain (ADG) were considered. The calves were categorized into predominantly Gyr (PG) and predominantly Holstein (PH) genetic composition groups. Multivariate mixed logistic regression revealed optimal TSP cut-off points for predicting morbidity (7.6 g/dL) and mortality (6.9 g/dL). PH calves exhibited 1.35 times higher odds of FPI and 1.48 times greater odds of disease. Calves from multiparous cows and those born to dams with RP had increased FPI odds. Disease prevalence was 53%, with 41% NCD, 18% BRD, and 10% TBD. Season, parity, PTA, and birth weight were associated with disease odds, though FPI was not a reliable predictor. The mortality percentage was 6%, with PH calves and those with a positive PTA having higher odds. The ADG was 0.64 kg, and FPI-affected calves gained less weight. The study compared and identified various risk factors that potentially impact calf immunity. However, the use of a standardized cut-off point for FPI assessment was not effective in predicting morbidity and mortality at this specific farm.

A comprehensive molecular analysis of bovine coronavirus strains isolated from Brazil and comparison of a wild-type and cell culture-adapted strain associated with respiratory disease.

Bovine coronavirus (BCoV) has dual tropisms that can trigger enteric and respiratory diseases in cattle. Despite its global distribution, BCoV field strains from Brazil remain underexplored in studies investigating the virus's worldwide circulation. Another research gap involves the comparative analysis of S protein sequences in BCoV isolates from passages in cell lines versus direct sequencing from clinical samples. Therefore, one of the objectives of our study was to conduct a comprehensive phylogenetic analysis of BCoV strains identified from Brazil, including a respiratory strain obtained during this study, comparing them with global and ancestral BCoV strains. Additionally, we performed a comparative analysis between wild-type BCoV directly sequenced from the clinical sample (nasal secretion) and the cell culture-adapted strain, utilizing the Sanger method. The field strain and multiple cell passage in cell culture (HRT-18) adapted BCoV strain (BOV19 NS) detected in this study were characterized through molecular and phylogenetic analyses based on partial fragments of 1,448 nt covering the hypervariable region of the S gene. The analyses have demonstrated that different BCoV strains circulating in Brazil, and possibly Brazilian variants, constitute a new genotype (putative G15 genotype). Compared with the ancestral prototype (Mebus strain) of BCoV, 33 nt substitutions were identified of which 15 resulted in non-synonymous mutations (nine transitions and six transversions). Now, compared with the wild-type strain was identified only one nt substitution in nt 2,428 from the seventh passage onwards, which resulted in transversion, neutral-neutral charge, and one substitution of asparagine for tyrosine at aa residue 810 (N810Y).

The Role of Mycoplasma bovirhinis in the Development of Singular and Concomitant Respiratory Infections in Dairy Calves from Southern Brazil.

The role of Mycoplasma bovirhinis in the development of pulmonary disease in cattle is controversial and was never evaluated in cattle from Latin America. This study investigated the respiratory infection dynamics associated with M. bovirhinis in suckling calves from 15 dairy cattle herds in Southern Brazil. Nasal swabs were obtained from asymptomatic (n = 102) and calves with clinical manifestations (n = 103) of bovine respiratory disease (BRD) and used in molecular assays to identify the specific genes of viral and bacterial disease pathogens of BRD. Only M. bovirhinis, bovine coronavirus (BCoV), ovine gammaherpesvirus 2 (OvGHV2), Histophilus somni, Pasteurella multocida, and Mannheimia haemolytica were detected. M. bovirhinis was the most frequently diagnosed pathogen in diseased (57.8%; 59/102) and asymptomatic (55.3%; 57/103) calves at all farms. BCoV-related infections were diagnosed in diseased (52%; 53/102) and asymptomatic (51.4%; 53/103) calves and occurred in 93.3% (14/15) of all farms. Similarly, infectious due to OvGHV2 occurred in diseased (37.2%; 38/102) and asymptomatic (27.2%; /28/103) calves and were diagnosed in 80% (12/15) of all farms investigated. Significant statistical differences were not identified when the two groups of calves were compared at most farms, except for infections due to OvGHV2 that affected five calves at one farm. These results demonstrated that the respiratory infection dynamics of M. bovirhinis identified in Southern Brazil are similar to those observed worldwide, suggesting that there is not enough sufficient collected data to consider M. bovirhinis as a pathogen of respiratory infections in cattle. Additionally, the possible roles of BCoV and OvGHV2 in the development of BRD are discussed.

Draft genome sequence of Mannheimia haemolytica strain Oliden, isolated from a calf lung infection in Argentina.

We present the draft genome sequence of a Mannheimia haemolytica strain isolated from a postmortem lung lesion from a calf diagnosed with bovine respiratory disease. The genome sequence was 2,749,707-bp long with 2,909 putative protein-encoding genes.

Neglected bacterial infections associated to bovine respiratory disease in lactating cows from high-yielding dairy cattle herds.

Bovine respiratory disease (BRD) is a multifactorial and predominantly multietiological disease that affects dairy cattle herds worldwide, being more frequent in young animals. The occurrence of BRD was investigated in lactating cows from two high-yielding dairy herds in southern Brazil. To determine the etiology of the clinical cases of acute respiratory disease, nasal swab samples were collected from cows with clinical signs of BRD and evaluated using PCR and RT-PCR for nucleic acid detection of the main BRD etiological agents, including Mycoplasma bovis, Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, bovine respiratory syncytial virus, bovine coronavirus, bovine viral diarrhea virus, bovine alphaherpesvirus 1, and bovine parainfluenza virus 3. Only three microorganisms (M. bovis, H. somni, and P. multocida) were identified in both single and mixed infections. We concluded that 40.0% of the cows were infected with M. bovis and 75.0% with H. somni in herd A. Considering both single and mixed infections, the analyses performed in herd B showed that 87.5%, 25.0%, and 50.0% of the cows were infected with M. bovis, H. somni, and P. multocida, respectively. M. bovis and H. somni are considered fastidious bacteria and laboratory diagnosis is neglected. Subsequently, most clinical cases of mycoplasmosis and histophilosis in cattle remain undiagnosed. This study demonstrates the importance of M. bovis and H. somni infections in adult cows with BRD. These results highlight the importance of including these bacteria in the group of etiological agents responsible for the occurrence of BRD in cattle, especially in adult cows with unfavorable immunological conditions, such as recent calving and peak lactation.

Oral meloxicam given as an ancillary treatment at respiratory disease diagnosis was not associated with growth, clinical scores, or ultrasound scores in preweaned dairy calves.

Objective: To assess the efficacy of a single dose of oral meloxicam as an ancillary therapy to an antibiotic given at the time of respiratory disease identification on average daily gain (ADG), behavioral attitude, clinical respiratory, and lung ultrasound scores in preweaned dairy calves. Animals: 215 male and female Holstein, Jersey, and crossbred preweaned calves enrolled between 1 and 14 days of age at study enrollment on a single commercial dairy in the western US. Methods: The study took place from March 4, 2021, to November 21, 2021. In this double-blind placebo-controlled study, calves were given an antibiotic (1.1 mL of tulathromycin/kg, SC, once) and either a placebo (1 mg of lactose monohydrate/kg, in a gelatin capsule) or oral meloxicam (1 mg/kg) at the time of respiratory disease identification. Behavioral attitude, clinical respiratory, and lung ultrasound scores and ADG were assessed in preweaned dairy calves at different time points including the next health examination, 1 week later, or at weaning. Results: There was no association between treatment (placebo vs meloxicam) on ADG or respiratory disease status at weaning (P > .05). There was no effect of treatment on behavioral attitude, clinical respiratory, or lung ultrasound scores at the next health examination or 1 week later (P > .05). Clinical Relevance: The present study did not provide evidence that oral meloxicam given once is beneficial for growth, behavioral attitude, or clinical or lung ultrasound scores.

Bovine respiratory syncytial virus infection in feedlot cattle cases in Argentina.

Although bovine respiratory syncytial virus (BRSV) infection has been reported in cattle in Argentina, it has not been associated with pneumonia in Argentina. We report here 5 cases of bovine pneumonia associated with BRSV. Autopsies were performed on 35 beef cattle with gross and/or microscopic lesions of pneumonia from 3 commercial feedlots. Lung samples in 5 of 35 animals were BRSV-positive by reverse-transcription nested PCR. The lungs of 2 of these 5 animals were coinfected with Mannheimia haemolytica, and 1 with bovine viral diarrhea virus 1. Microscopically, the lungs of 3 of the 5 BRSV PCR-positive animals had fibrinosuppurative bronchopneumonia, with or without pleuritis; 2 of the 5 had interstitial pneumonia. We conclude that BRSV is part of the bovine respiratory disease complex in Argentina.

Possible Association of Bovine Gammaherpesvirus 6 with Pulmonary Disease in a Cow.

Bovine gammaherpesvirus 6 (BoGHV6), previously known as bovine lymphotropic virus, is a member of the Macavirus genus, subfamily Gammaherpesvirinae. Other members of the genus Macavirus include viruses that produce malignant catarrhal fever (MCF) in mammalian hosts, collectively referred to as the MCF virus (MCFV) complex, and the porcine lymphotropic herpesvirus (PLHV). However, the current role of BoGHV6 in the development of diseases and/or disease syndromes remains uncertain and controversial. This paper investigated the participation of BoGHV6 in the development of pulmonary disease in a cow with interstitial pneumonia by histopathology and molecular testing. Tissue antigens of common viral agents of respiratory diseases and Mycoplasma bovis were not identified by immunohistochemistry. Additionally, molecular assays designed to amplify common bacterial and viral pathogens of pulmonary disease did not amplify the nucleic acids of these agents. However, a pan-PCR assay amplified the DNA of the herpesvirus polymerase gene, while the specific BoGHV6 nested-PCR assay amplified the partial fragment of the BoGHV6 polymerase gene derived from the pulmonary tissue with interstitial pneumonia. Phylogenetic analysis revealed that the BoGHV6 strain herein identified had 99.8% nucleotide (nt) sequence identity with reference strains of BoGHV6, but only 72.2-73.5% and 67.9-68.6% nt identity with reference strains of MCFV and PLHV, respectively. Consequently, these results suggest that BoGHV6 was associated with the pulmonary disease observed in this cow.

Effects of autolyzed yeast on leukocyte oxidative metabolism and pneumonia occurrence in feedlot steers / Efeito da levedura autolisada no metabolismo oxidativo leucocitário e na ocorrência de pneumonia em novilhos terminados em confinamento

Although yeast supplementation has shown an immunostimulant effect in feedlot cattle, the question remains whether it influences the occurrence of the bovine respiratory disease complex (BRD) in feedlot cattle. Therefore, our objective was to evaluate whether dietary supplementation with autolyzed yeast affects the efficiency of blood phagocytes, reducing inflammation and the occurrence of BRD in feedlot cattle. A randomized experimental trial was conducted with whole steers with half Angus blood for 106 days: control (n=10): diet without yeast; Y4 (n=12): yeast diet (4g per animal per day); and Y7 (n=7): yeast diet (7g per animal per day). On Days 0, 14, 42, 70, and 105, blood count, leukocyte oxidative metabolism, serum haptoglobin, frequency of nasal secretion and orbital temperature were evaluated. On slaughter day, a lung evaluation was performed. On Days 42 and 70 of feedlot finishing, the treated animals showed increased leukocyte oxidative metabolism (D42 P=0.04; D70 P=0.02) compared to the control group. These animals had a lower frequency of mucopurulent nasal secretion, lower orbital temperature and reduced pneumonia occurrence than the treated groups (P=0.05) with less lung lesion severity (P=0.01), allowing us to infer that the autolyzed yeast improves blood phagocytic function and decreases the inflammation and BRD of feedlot steers, especially at a dose of 4g.

Embora a suplementação com leveduras tenha demonstrado efeito imunoestimulante em bovinos, permanece-se a dúvida se ela influencia na ocorrência do complexo doença respiratória bovina (CDRB) em bovinos confinados. Portanto, objetivou-se avaliar se a suplementação dietética com levedura autolisada influencia a eficiência de fagócitos sanguíneos, reduzindo inflamações e a ocorrência de CDRB em bovinos confinados. Realizou-se um ensaio experimental randomizado com 36 novilhos inteiros 1/2 sangue Angus por 106 dias: controle (n=10): dieta sem levedura; Y4 (n=12): dieta com levedura (4g por animal por dia); e Y7 (n=7): dieta com levedura (7g por animal por dia). Nos dias 0, 14, 42, 70 e 105, hemograma, metabolismo oxidativo de leucócitos, haptoglobina sérica, frequência de secreção nasal e temperatura orbital foram avaliados. No dia do abate, foi realizada avaliação pulmonar. Nos dias 42, e 70 de terminação em confinamento, os animais tratados apresentaram aumento do metabolismo oxidativo dos leucócitos (D42 P=0,04; D70 P=0,02) em relação ao grupo controle. Esses animais apresentaram menor frequência de secreção nasal mucopurulenta, menor temperatura orbital, menor ocorrência de pneumonias (P=0,05) com menor gravidade das lesões pulmonares (P=0,01), permitindo inferir que a levedura autolisada na dieta melhorou a eficiência dos fagócitos sanguíneos, reduzindo inflamações e a ocorrência de CDRB, especialmente na dosagem de 4g.

Effect of Saccharomyces cerevisiae in a culture or lysate on innate immunity and ruminal and intestinal morphology of steers finished in feedlot / Efeito da Saccharomyces cerevisiae em cultura ou lisada na imunidade inata, na morfologia ruminal e intestinal de novilhos terminados em confinamento

The objective of this study was to evaluate whether the administration of two classes of Saccharomyces cerevisiae improved the health of feedlot-finished steers. A total of 33 Angus-Nellore blood ½ steers (body weight of 350 ± 10 kg and 11 ± 5 months old) fed an energy diet were evaluated at the beginning (0 and 16 days), middle (44 and 72 days), and end (100) of the feedlot based on the inflammatory status and health of the respiratory and digestive tracts. Inflammation and innate immunity were measured using leukocyte oxidative metabolism (OM), serum haptoglobin levels, and the neutrophil-to-lymphocyte ratio. Respiratory health was verified based on nasal secretion, rectal temperature, and lung lesions during slaughter. The digestive health was verified by histomorphology of the rumen and intestine. The treatments were as follows: Saccharomyces cerevisiae in culture (CUL n=12), S. cerevisiae in the autolyzed form (AUT n=10), and control diet (CON, n=11). In the CUL group, OM increased by 7% on average, with lower indicators of respiratory disease and inflammatory status in the intermediate and final stages of the feedlots. The ruminal papillae of these animals were 30% thinner than those of the CON group and had lower ruminitis scores. Although AUT promoted a 10% increase in OM and a lower inflammatory status in the intermediate and final stages of the feedlot, steers showed more indicators of respiratory diseases than those in the CUL group. The duodenal villus area and jejunal villus height in the AUT group still increased by 25 and 15%, respectively. Its effect on the ruminal papilla was subtle, only decreasing the ruminitis score. We concluded that both groups of S. cerevisiae improved the health of animals compared with the control group, indicating that supplementation with S. cerevisiae cultures resulted in the decreased alteration of rumen papillae, compatible with a lower occurrence of subclinical ruminal acidosis syndrome (SARA), reflecting immunological gains and a lower occurrence of bovine respiratory disease (BRD). The S. cerevisiae autolysate showed a higher intestinal effect and lower activity in the rumen papillae. Although this treatment showed an immunological gain similar to a yeast culture, it reflected the lower health of the respiratory tract.(AU)

O objetivo do trabalho foi avaliar se a administração de duas classes de Saccharomyces cerevisiae melhoram a saúde de novilhos terminados confinados. Um total de 33 novilhos ½ sangue Angus-Nelore, (350 ±10 kg peso vivo e 11± 5 meses de vida) alimentados com dieta energética foram avaliados no início (0 e 16 dias), meio (44 e 72 dias) e final (100) de confinamento, por meio de indicadores de inflamação e saúde do trato respiratório e digestório. A inflamação e imunidade inata foram aferidas por metabolismo oxidativo de leucócitos (MO); teores séricos de haptoglobina e razão neutrófilo:linfócito. A saúde respiratória foi verificada por secreção nasal, temperatura retal e lesões pulmonares no abate. E a saúde digestória foi verificada por histomorfologia do rúmen e intestino. Os tratamentos foram: Saccharomyces cerevisiae na forma de cultura (CUL n=12), S. cerevisiae na forma autolisada (AUT n=10) e dieta controle (CON n=11). O CUL apresentaram incremento médio de 7% no MO, menores indicadores de doença respiratória e de status inflamatório na fase intermediária e final do confinamento. As papilas ruminais destes animais era 30% mais delgada que o CON, e apresentavam menor escore de ruminite. Apesar do AUT promover incremento de 10% no MO e menor status inflamatório na fase intermediária e final do confinamento também, os novilhos apesentaram mais indicadores de doenças respiratórias que o CUL. O AUT ainda aumentou 25% da área de vilosidade de duodeno, e 15% na altura da vilosidade jejunal. Sua ação em papila ruminal foi tênue, minimizando apenas o escore de ruminite. Concluiu-se que ambas as classes de S. cerevisiae aumentaram a saúde dos animais em relação ao CON, destacando-se a suplementação com cultura de S. cerevisiae, que resultou em menor alteração de papilas ruminais compatíveis com menor ocorrência de SARA, melhores resultados do sistema imunológico e menor ocorrência de CRB. O autolisado de S. cerevisiae demonstrou maior efeito intestinal, com atuação de menor impacto em papila ruminal. E apesar de ter ganho imunológico similar ao encontrado ao CUL, apresentou menor influência na saúde do trato respiratório.(AU)

Prevalence of three Mycoplasma sp. by multiplex PCR in cattle with and without respiratory disease in central Mexico.

This study aimed to identify Mycoplasma bovis, Myc. dispar, and Myc. bovirhinis, which are involved in bovine respiratory disease through a multiplex PCR as an alternative to culture's features that hamper Mycoplasma isolation. Nasal swabs were taken from 335 cattle with and without respiratory disease background (RDB) from dairy herds in the central region of Mexico. Each sample was divided in two; the first part was processed for the direct DNA extraction of the nasal swab and the second for Mycoplasma isolation, culture, and then the multiplex PCR was performed. In the nasal swabs, Myc. bovis was identified in 21.1%; Myc. dispar, in 11.8%; and Myc. bovirhinis, in 10.8% in cattle with RDB. Isolates were identified as Myc. bovis, 20.1%; Myc. dispar, 11.8%; and Myc. bovirhinis, 6.1%. There is a strong correlation between the presence of Mycoplasma identified by PCR and the clinical history of the disease (ρ < 0.0000). In animals without RDB, Myc. bovirhinis was the only species detected in 6.1% of the samples processed directly for multiplex PCR, and in 2% of the isolates. There is an excellent correlation (kappa 0.803) between the isolation and the 16S PCR and a high correlation (kappa 0.75) between the isolation and the multiplex PCR. Therefore, we conclude that the PCR multiplex test is highly sensitive and may be used for the diagnosis and surveillance of the three species in biological samples and mycoplasma isolates.

Diagnostic accuracy of Wisconsin and California scoring systems to detect bovine respiratory disease in preweaning dairy calves under subtropical environmental conditions.

Bovine respiratory disease (BRD) is a multifactorial disease which causes short- and long-term negative effects. Early detection is crucial for a prompt response to therapy, as well as to decrease mortality risk. Clinical scoring systems have been developed mostly in North America for screening calves at risk or suspected of having BRD, and these tools have also been applied in subtropical and tropical countries. However, it has been unknown whether these scoring systems had the same accuracy in tropical environmental conditions. Therefore, this study evaluated the accuracy of 4 different field techniques, as well as serum haptoglobin (HAP), to diagnose BRD in Holstein dairy calves in subtropical conditions. The tests used to diagnose BRD were thoracic ultrasound (TUS; positive if consolidation depth ≥1 cm), thoracic auscultation (AUSC; positive if crackles, wheezes, or silent areas were present), Wisconsin score (WISC; ≥2 categories with scores of ≥2), and California score (CALIF; positive if total score ≥5). Also, HAP was measured and classified as positive if ≥15 mg/dL. Heifers between 30 d of age and weaning (n = 482), residing on 17 commercial dairies in São Paulo state, were enrolled in this study. Bayesian latent class models were used with informative priors to evaluate the accuracy of TUS, AUSC, and HAP, and noninformative priors for the accuracy of WISC and CALIF. The percentage of calves positive for each test on each farm ranged from 0 to 56% for WISC, 11-51% for CALIF, 0-72% for TUS, 0-32% for AUSC, and 0-100% for HAP. The sensitivity (Se; 95% credible interval) and specificity (Sp) for WISC were 77.9% (64.8-90.2) and 81.9% (76.3-88.2). For CALIF, the Se was 67.1% (53.6-80.1) and Sp 79.1% (73.9-84.6). For TUS Se was 59.8% (46.5-73.1) and Sp was 84.8% (80.0-89.5), and for AUSC, Se was 58.8% (41.3-79.8) and Sp was 98.6% (95.7-99.9). The Se and Sp of HAP was 67.6% (55.3-78.8) and 46.7% (41.4-52.2), respectively. The performance of the scoring systems was similar to, or better than, the performance found in North American studies, despite the fact that calves were in a tropical environment.

Morbidity and mortality in Holstein calves from birth to 145 days of age on a large dairy farm in Brazil / Morbidade e mortalidade em bezerras da raça Holandesa do nascimento aos 145 dias de vida, em uma grande fazenda produtora de leite no Brasil

The present study aimed to investigate the morbidity and mortality associated with the most common diseases during the rearing period of Holstein calves in a high-production dairy farm. The calves (n = 600) were allocated to three groups based on age: G1 (1-7 days, n = 216), G2 (30-40 days, n = 188), and G3 (69-85 days, n = 196). They were evaluated over 60 days at eight different times. The morbidity rates were 47.67% (286/600) for diarrhea, 73.00% (438/600) for bovine respiratory disease (BRD), and 3.83% (23/600) for umbilical inflammation (UI). The mortality rate was 2.33% (14/600) for all the animals studied. The morbidity differed in the groups, with higher rates of diarrhea (78.85%, 166/216) and UI (6.94%, 15/216) in G1, and the highest rate of BRD in G3 (79.59%, 156/196). Diarrhea was associated with the occurrence of BRD in G1 and G2. Even in farms with good management practices, there is high morbidity associated with diarrhea and BRD, with the morbidity rate for diarrhea decreasing and that for BRD increasing as the animals get older. In addition, diarrhea is an important risk factor for BRD, especially in younger animals.(AU)

O presente estudo objetivou investigar a morbidade e a mortalidade associadas às doenças mais comuns no período de criação de bezerras da raça Holandesa, em uma fazenda leiteira de alta produção. As bezerras (n = 600) foram alocadas em três grupos de acordo com a idade: G1 (1-7 dias, n = 216); G2 (30-40 dias, n = 188); G3 (69-85 dias, n = 196). Os animais foram avaliados durante 60 dias, em oito momentos diferentes. A morbidade foi de 47,67% (286/600) para diarreia, 73,00% (438/600) para doença respiratória bovina (DRB) e 3,83% (23/600) para inflamação umbilical (IU). A taxa de mortalidade foi de 2,33% (14/600), para o total de animais avaliados. A morbidade foi diferente entre os grupos, com maior frequência de diarreia (78,85%, 166/216) e IU (6,94%, 15/216) no G1, sendo a maior ocorrência de DRB no G3 (79,59%, 156/196). A diarreia foi associada à DRB no G1 e no G2. Mesmo em fazendas com boas práticas de manejo, há alta morbidade por diarreia e DRB, com a taxa de morbidade por diarreia diminuindo e a de DRB aumentando à medida que os animais envelhecem. Além disso, a diarreia é um importante fator de risco para DRB, especialmente em animais mais jovens.(AU)

Assessment of Plasma Zinc and Total Leukocyte Count in Calves Experimentally Infected with Mannheimia haemolytica.

Mannheimia haemolytica is the main bacterial pathogen isolated in bovine respiratory disease (BRD), a common disease affecting calves before weaning. Previous research has shown that experimental infection with bovine herpesvirus 1, a respiratory virus, decreases plasma zinc (Zn) levels. However, changes in plasma Zn concentrations in calves experimentally infected with M. haemolytica have not been studied thus far. The objective of this study was to evaluate the effect of experimental infection with M. haemolytica on plasma Zn concentration in calves. Total leukocyte count and bovine respiratory disease (BRD) clinical score were also evaluated. We conducted a 6-day trial in 14 male Holstein calves randomly assigned to one of two groups, experimental (EG, n = 8) and control (CG, n = 6). Animals in EG were intrabronchially inoculated with M. haemolytica (6.5 × 106 CFU/mL) on day 0 of the trial. Plasma Zn levels were affected by time, treatment, and time by treatment interaction, being lower in EG compared with CG on days 1, 2, and 3. Differences in total leukocyte count were significant on day 1, observing a tendency on day 3. BRD clinical score differed between groups, being higher in EG throughout the trial. We conclude that experimental M. haemolytica infection reduced plasma Zn concentration in clinically ill calves, suggesting that the clinical condition of animals (healthy/ill) should be considered to better interpret plasma Zn values.

An Assessment of Secondary Clinical Disease, Milk Production and Quality, and the Impact on Reproduction in Holstein Heifers and Cows from a Single Large Commercial Herd Persistently Infected with Bovine Viral Diarrhea Virus Type 2.

The aim of this study was to evaluate secondary clinical disease, milk production efficiency and reproductive performance of heifers and cows persistently infected (PI) with bovine viral diarrhea virus type 2 (BVDV type 2). PI animals (n = 25) were identified using an antigen capture ELISA of ear notch samples. They were distributed into three age groups: ≤ 12 (n = 8), 13 to 24 (n = 6) and 25 to 34 (n = 11) months old. A control group of BVDV antigen ELISA negative female cattle that were age matched to the PI animals was utilized from the same herd. The PI group had a 1.29 higher odds ratio for diarrhea than controls (p = 0.001, IC95% = 1.032-1.623) and 1.615 greater chance of developing bovine respiratory disease (BRD) (p = 0.012, IC95% = 1.155-2.259). The age at first insemination (p = 0.012) and number of insemination attempts required to establish the first pregnancy (p = 0.016) were both higher for PI than controls. Milk production was higher for control cows than PI cows during most of the sampling periods. Somatic cell counts (SCC) were higher in PI cows than the controls at all sampling points across lactation (p ≤ 0.042). PI cattle had a higher incidence of disease, produced less milk, a higher SCC, and poorer reproductive performance than control cattle in this study.

Efeito dos anticorpos maternos sobre a resposta imune induzida pela vacinação em bezerros Holandeses / Effect of maternal antibodies on vaccine-induced immune responses in Holstein calves

Objetivou-se avaliar o efeito dos anticorpos (ACs) maternos sobre resposta imune humoral induzida pela vacinação em bezerros Holandeses. Bezerros foram distribuídos aleatoriamente em quatro grupos: G1 - vacinados no D14 e D44 (n=6); G2 - vacinados no D90 e D120 (n=5); G3 - vacinados no D180 e D210 (n=8); controle: não vacinado (n=5). Utilizaram-se 5mL de vacina comercial (Cattle Master Gold FP5+L5® - Zoetis, Brasil), por via subcutânea. Foi realizada vírus neutralização (VN) no momento da vacinação, booster e 30 dias após a revacinação. Não foram observadas diferenças entre controle e G1 ou G2 para a frequência de soropositivos ou títulos de ACs contra os vírus respiratórios (P≥0,05). G3 apresentou maior produção de ACs em relação ao controle para BoHV-1 (P<0,01), BRSV (P<0,01) e BPIV-3 (P=0,02) após o booster (D240). A análise no tempo também demonstrou aumento nos títulos de ACs no G3 (P≤0,05). O perfil clínico revelou broncopneumonia apenas no grupo controle (n=4/5) entre 80-135 dias de vida. A imunidade colostral e a vacinal apresentaram perfis inversamente proporcionais, com maior produção de ACs aos seis meses de idade. Devido à precocidade da doença respiratória, estudos complementares são necessários para esclarecer o papel da resposta imune celular na vacinação diante dos ACs maternos.(AU)

This research aimed to evaluate the effect of colostral antibodies (ABs) on the humoral immune response induced by vaccination in Holstein calves. Twenty-four calves were randomly assigned into four groups: G1 - vaccinated on D14 and D44 (n= 6); G2 - on D90 and D120 (n= 5); G3 - on D180 and D210 (n= 8); Control: unvaccinated (n= 5). Commercial vaccine (Cattle Master Gold FP5+L5® - Zoetis, Brazil) was administered subcutaneously (5mL). Virus neutralization test (VN) was performed at the time of vaccination, booster and 30 days after booster to determine AB titers. No differences were observed between control and G1 or G2 for seropositive frequencies and ABs titers (P≥ 0.05). G3 showed higher AB production than control for BoHV-1 (P< 0.01), BRSV (P< 0.01) and BPIV-3 (P= 0.02) after booster (D240). Overtime analysis also exhibited increase in AB titers in G3 (P≤ 0,05). Bronchopneumonia was identified in the control group (n= 4/5) between 80-135 days of life. The colostral and vaccinal immunity presented inversely proportional profiles, with higher production of ABs at 6 months of age. Due to the precocity of respiratory disease further studies are required to clarify the role of cellular immune response to vaccination in face of maternal ABs.(AU)

Efeito dos anticorpos maternos sobre a resposta imune induzida pela vacinação em bezerros Holandeses / Effect of maternal antibodies on vaccine-induced immune responses in Holstein calves

Objetivou-se avaliar o efeito dos anticorpos (ACs) maternos sobre resposta imune humoral induzida pela vacinação em bezerros Holandeses. Bezerros foram distribuídos aleatoriamente em quatro grupos: G1 - vacinados no D14 e D44 (n=6); G2 - vacinados no D90 e D120 (n=5); G3 - vacinados no D180 e D210 (n=8); controle: não vacinado (n=5). Utilizaram-se 5mL de vacina comercial (Cattle Master Gold FP5+L5® - Zoetis, Brasil), por via subcutânea. Foi realizada vírus neutralização (VN) no momento da vacinação, booster e 30 dias após a revacinação. Não foram observadas diferenças entre controle e G1 ou G2 para a frequência de soropositivos ou títulos de ACs contra os vírus respiratórios (P≥0,05). G3 apresentou maior produção de ACs em relação ao controle para BoHV-1 (P<0,01), BRSV (P<0,01) e BPIV-3 (P=0,02) após o booster (D240). A análise no tempo também demonstrou aumento nos títulos de ACs no G3 (P≤0,05). O perfil clínico revelou broncopneumonia apenas no grupo controle (n=4/5) entre 80-135 dias de vida. A imunidade colostral e a vacinal apresentaram perfis inversamente proporcionais, com maior produção de ACs aos seis meses de idade. Devido à precocidade da doença respiratória, estudos complementares são necessários para esclarecer o papel da resposta imune celular na vacinação diante dos ACs maternos.(AU)

This research aimed to evaluate the effect of colostral antibodies (ABs) on the humoral immune response induced by vaccination in Holstein calves. Twenty-four calves were randomly assigned into four groups: G1 - vaccinated on D14 and D44 (n= 6); G2 - on D90 and D120 (n= 5); G3 - on D180 and D210 (n= 8); Control: unvaccinated (n= 5). Commercial vaccine (Cattle Master Gold FP5+L5® - Zoetis, Brazil) was administered subcutaneously (5mL). Virus neutralization test (VN) was performed at the time of vaccination, booster and 30 days after booster to determine AB titers. No differences were observed between control and G1 or G2 for seropositive frequencies and ABs titers (P≥ 0.05). G3 showed higher AB production than control for BoHV-1 (P< 0.01), BRSV (P< 0.01) and BPIV-3 (P= 0.02) after booster (D240). Overtime analysis also exhibited increase in AB titers in G3 (P≤ 0,05). Bronchopneumonia was identified in the control group (n= 4/5) between 80-135 days of life. The colostral and vaccinal immunity presented inversely proportional profiles, with higher production of ABs at 6 months of age. Due to the precocity of respiratory disease further studies are required to clarify the role of cellular immune response to vaccination in face of maternal ABs.(AU)

Molecular characterization of Brazilian wild-type strains of bovine respiratory syncytial virus reveals genetic diversity and a putative new subgroup of the virus.

Background: Bovine orthopneumovirus, formerly known as bovine respiratory syncytial virus (BRSV), is frequently associated with bovine respiratory disease (BRD).Aim: To perform the molecular characterization of the G and F proteins of Brazilian wild-type BRSV strains derived from bovine respiratory infections in both beef and dairy cattle.Materials and Methods: Ten BRSV strains derived from a dairy heifer rearing unit (n = 3) in 2011 and steers of three other feedlots (n = 7) in 2014 and 2015 were analyzed. For the BRSV G and F partial gene amplifications, RT-nested-PCR assays were performed with sequencing in both directions with forward and reverse primers used.Results: The G gene-based analysis revealed that two strains were highly similar to the BRSV sequences representative of subgroup III, including the Bayovac vaccine strain. However, the remaining seven Brazilian BRSV strains were diverse when compared with strains representative of the BRSV I to VIII subgroups. The central hydrophobic region of the Brazilian BRSV G gene showed the replacement of conserved cysteines and other residues of importance to antibody reactivity. The deduced F gene amino acid sequences from the Brazilian BRSV strains showed changes that were absent in the representative sequences of the known subgroups. Viral isolation on the nasopharyngeal swab suspensions failed to isolate BRSV.Conclusion: Results suggest that these strains represent a putative new subgroup of BRSV with mutations observed in the immunodominant region of the G protein. However, further studies on these Brazilian BRSV strains should be performed to establish their pathogenic potential.

Influence of therapeutic use of feedgrade tetracyclines in combination with tulathromycin metaphylaxis on animal health and performance of Holstein steer calves.

Feedgrade chlortetracycline (CTC) and oxytetracycline (OTC) are approved for use in beef cattle diets for the control of bovine respiratory disease (BRD). The objectives of this experiment were to compare CTC and OTC, administered according to label, for the treatment of BRD in Holstein calves and to characterize the influence of tulathromycin metaphylaxis in combination with tetracycline treatment. Summer-placed Holstein steer calves (n = 6,800) were randomly assigned to one of four treatments (11 blocks; initial BW = 140 ± 18 kg) as they passed through the squeeze chute at initial processing in a commercial feedlot. Treatments consisted of: (i) CTC and tulathromycin metaphylaxis (CTC+TUL), (ii) OTC and tulathromycin metaphylaxis (OTC+TUL), (iii) tulathromycin metaphylaxis only (TUL), or (iv) CTC only (CTC). Cattle were fed for an average of 118 d. Tetracycline feeding was instituted based on visual assessment of the attending veterinarian in accordance with the veterinary feed directive. When applicable, CTC was fed as a top-dress at a rate of 4 g CTC·steer-1·d-1 for 5 consecutive days, beginning on 6 d on feed (DOF). Three 5-d pulses were delivered to CTC+TUL and CTC cattle, with a 48-h time lapse between pulses. Cattle on OTC+TUL were administered 4 g OTC·steer-1·d-1 as part of a complete diet for 14 consecutive days beginning on 10 DOF. Within the first 30 d of the feeding period, BRD first pulls were reduced (P = 0.001) for CTC+TUL, OTC+TUL, and TUL relative to CTC alone. Percentage of BRD first pulls and total morbidity were lowest (P = 0.001) for CTC+TUL across the feeding period, with OTC+TUL and TUL being intermediate, and CTC alone exhibiting the highest percentage. Death loss and railers were not influenced (P ≥ 0.58) by treatment. Dry matter intake was greater (P = 0.001) for CTC+TUL than all other treatments. Final BW and ADG were greatest for CTC+TUL, lowest for TUL alone, and intermediate for the remaining treatments (P < 0.05) on a deads-and-railers-out basis. Deads-and-railers-in ADG was greatest (P < 0.05) for CTC+TUL compared to all other treatments. Feed conversion was not influenced (P ≥ 0.22) by treatment. In the current study, supplementation of OTC in combination with tulathromycin metaphylaxis did not benefit health over tulathromycin alone. Results suggest that CTC in combination with tulathromycin metaphylaxis reduces morbidity in Holstein steers calves, which may lead to improved performance.