Effect of supplementation with Saccharomyces boulardii CNCM I-1079 on vaccine response to an inactivated bacterial vaccine in young Japanese Black calves: A field trial.

Saccharomyces boulardii group (SB group) calves were fed 2.0 × 1010 CFU/day of S. boulardii in milk replacer after 2 wk of age. All calves received inactivated vaccine for Histophilus somni, Pasteurella multocida, and Mannheimia haemolytica at 3 wk of age and 3 wk later. After vaccination, the SB group calves showed significantly higher (mean difference: 1.56-fold) antibody titer against H. somni than the control group. The number of calves with the antibody titer above the cut-off value for M. haemolytica of the SB group was significantly higher than that of the control, and the percentage was twice as high. In addition, the mRNA transcription of IL4 and IL10 in peripheral blood mononuclear cells at the booster of the SB group was significantly higher than those of the control. In conclusion, S. boulardii may have positively affected immune responses to the inactivated multi-bacterial vaccine in young calves in the field.

Les veaux du groupe Saccharomyces boulardii (groupe SB) ont reçu 2,0 × 1010 UFC/jour de S. boulardii dans du lait de remplacement après l'âge de 2 semaines. Tous les veaux ont reçu un vaccin inactivé contre Histophilus somni, Pasteurella multocida et Mannheimia haemolytica à l'âge de 3 semaines et 3 semaines plus tard. Après vaccination, les veaux du groupe SB ont montré un titre d'anticorps contre H. somni significativement plus élevé (différence moyenne : 1,56 fois) que le groupe témoin. Le nombre de veaux avec un titre d'anticorps supérieur à la valeur seuil pour M. haemolytica du groupe SB était significativement plus élevé que celui du groupe témoin, et le pourcentage était deux fois plus élevé. De plus, la transcription de l'ARNm de l'IL4 et de l'IL10 dans les cellules mononucléaires du sang périphérique lors du rappel du groupe SB était significativement plus élevée que celles du groupe témoin. En conclusion, S. boulardii peut avoir affecté positivement les réponses immunitaires au vaccin multibactérien inactivé chez les jeunes veaux au champ.(Traduit par Docteur Serge Messier).

Limitations of bacterial culture, viral PCR, and tulathromycin susceptibility from upper respiratory tract samples in predicting clinical outcome of tulathromycin control or treatment of bovine respiratory disease in high-risk feeder heifers.

A cross-sectional prospective cohort study including 1026 heifers administered tulathromycin due to high risk of clinical signs of bovine respiratory disease (BRD), measured poor association between BRD clinical outcomes and results of bacterial culture and tulathromycin susceptibility from BRD isolates of deep nasopharyngeal swabs (DNS) and adequate association with viral polymerase chain reaction (PCR) results from nasal swabs. Isolation rates from DNS collected on day-0 and at 1st BRD-treatment respectively were: Mannheimia haemolytica (10.9% & 34.1%); Pasteurella multocida (10.4% & 7.4%); Mycoplasma bovis (1.0% & 36.6%); and Histophilus somni (0.7% & 6.3%). Prevalence of BRD viral nucleic acid on nasal swabs collected exclusively at 1st BRD-treatment were: bovine parainfluenza virus type-3 (bPIV-3) 34.1%; bovine viral diarrhea virus (BVDV) 26.3%; bovine herpes virus type-1 (BHV-1) 10.8%; and bovine respiratory syncytial virus (BRSV) 54.1%. Increased relative risk, at 95% confidence intervals, of 1st BRD-treatment failure was associated with positive viral PCR results: BVDV 1.39 (1.17-1.66), bPIV-3 1.26 (1.06-1.51), BHV-1 1.52 (1.25-1.83), and BRSV 1.35 (1.11-1.63) from nasal swabs collected at 1st BRD-treatment and culture of M. haemolytica 1.23 (1.00-1.51) from DNS collected at day-0. However, in this population of high-risk feeder heifers, the predictive values of susceptible and resistant isolates had inadequate association with BRD clinical outcome. These results indicate, that using tulathromycin susceptibility testing of isolates of M. haemolytica or P. multocida from DNS collected on arrival or at 1st BRD-treatment to evaluate tulathromycin clinical efficacy, is unreliable.

Aldsulfin, a novel unusual anti-mannheimiosis epithiodiketopiperazine antibiotic produced by Lasiodiplodia pseudotheobromae FKI-4499.

An anti-mannheimiosis agent, aldsulfin, was isolated from a culture broth of the fungus Lasiodiplodia pseudotheobromae FKI-4499, together with a known compound, lasiodipline C, using bioassay-guided fractionation. Spectroscopic analysis of aldsulfin, using NMR, mass spectrometry, and CD analyses revealed it to be an epithiodiketopiperazine with an unstable and unusual hemithioaminal moiety. Aldsulfin showed antibacterial activity against Mannheimia haemolytica and Pasteurella multocida.

Effect of apo-lactoferrin on leukotoxin and outer membrane vesicles of Mannheimia haemolytica A2.

Mannheimia haemolytica serotype A2 is the principal cause of pneumonic mannheimiosis in ovine and caprine livestock; this disease is a consequence of immune suppression caused by stress and associated viruses and is responsible for significant economic losses in farm production worldwide. Gram-negative bacteria such as M. haemolytica produce outer membrane (OM)-derived spherical structures named outer membrane vesicles (OMVs) that contain leukotoxin and other biologically active virulence factors. In the present study, the relationship between M. haemolytica A2 and bovine lactoferrin (BLf) was studied. BLf is an 80 kDa glycoprotein that possesses bacteriostatic and bactericidal properties and is part of the mammalian innate immune system. Apo-BLf (iron-free) showed a bactericidal effect against M. haemolytica A2, with an observed minimal inhibitory concentration (MIC) of 16 µM. Sublethal doses (2-8 µM) of apo-BLf increased the release of OMVs, which were quantified by flow cytometry. Apo-BLf modified the normal structure of the OM and OMVs, as observed through transmission electron microscopy. Apo-BLf also induced lipopolysaccharide (LPS) release from bacteria, disrupting OM permeability and functionality, as measured by silver staining and SDS and polymyxin B cell permeability assays. Western blot results showed that apo-BLf increased the secretion of leukotoxin in M. haemolytica A2 culture supernatants, possibly through its iron-chelating activity. In contrast, holo-BLf (with iron) did not have this effect, possibly due to differences in the tertiary structure between these proteins. In summary, apo-BLf affected the levels of several M. haemolytica virulence factors and could be evaluated for use in animals as an adjuvant in the treatment of ovine mannheimiosis.

Association between antimicrobial drug class for treatment and retreatment of bovine respiratory disease (BRD) and frequency of resistant BRD pathogen isolation from veterinary diagnostic laboratory samples.

Although 90% of BRD relapses are reported to receive retreatment with a different class of antimicrobial, studies examining the impact of antimicrobial selection (i.e. bactericidal or bacteriostatic) on retreatment outcomes and the emergence of antimicrobial resistance (AMR) are deficient in the published literature. This survey was conducted to determine the association between antimicrobial class selection for treatment and retreatment of BRD relapses on antimicrobial susceptibility of Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni. Pathogens were isolated from samples submitted to the Iowa State University Veterinary Diagnostic Laboratory from January 2013 to December 2015. A total of 781 isolates with corresponding animal case histories, including treatment protocols, were included in the analysis. Original susceptibility testing of these isolates for ceftiofur, danofloxacin, enrofloxacin, florfenicol, oxytetracycline, spectinomycin, tilmicosin, and tulathromycin was performed using Clinical and Laboratory Standards Institute guidelines. Data were analyzed using a Bayesian approach to evaluate whether retreatment with antimicrobials of different mechanistic classes (bactericidal or bacteriostatic) increased the probability of resistant BRD pathogen isolation in calves. The posterior distribution we calculated suggests that an increased number of treatments is associated with a greater probability of isolates resistant to at least one antimicrobial. Furthermore, the frequency of resistant BRD bacterial isolates was greater with retreatment using antimicrobials of different mechanistic classes than retreatment with the same class. Specifically, treatment protocols using a bacteriostatic drug first followed by retreatment with a bactericidal drug were associated with a higher frequency of resistant BRD pathogen isolation. In particular, first treatment with tulathromycin (bacteriostatic) followed by ceftiofur (bactericidal) was associated with the highest probability of resistant M. haemolytica among all antimicrobial combinations. These observations suggest that consideration should be given to antimicrobial pharmacodynamics when selecting drugs for retreatment of BRD. However, prospective studies are needed to determine the clinical relevance to antimicrobial stewardship programs in livestock production systems.

Development of Bacterial Therapeutics against the Bovine Respiratory Pathogen Mannheimia haemolytica.

Bovine respiratory disease (BRD) is a major cause of morbidity and mortality in beef cattle. Recent evidence suggests that commensal bacteria of the bovine nasopharynx have an important role in maintaining respiratory health by providing colonization resistance against pathogens. The objective of this study was to screen and select bacterial therapeutic candidates from the nasopharynxes of feedlot cattle to mitigate the BRD pathogen Mannheimia haemolytica In a stepwise approach, bacteria (n = 300) isolated from the nasopharynxes of 100 healthy feedlot cattle were identified and initially screened (n = 178 isolates from 12 different genera) for growth inhibition of M. haemolytica Subsequently, selected isolates were evaluated for the ability to adhere to bovine turbinate (BT) cells (n = 47), compete against M. haemolytica for BT cell adherence (n = 15), and modulate gene expression in BT cells (n = 10). Lactobacillus strains had the strongest inhibition of M. haemolytica, with 88% of the isolates (n =33) having inhibition zones ranging from 17 to 23 mm. Adherence to BT cells ranged from 3.4 to 8.0 log10 CFU per 105 BT cells. All the isolates tested in competition assays reduced M. haemolytica adherence to BT cells (32% to 78%). Among 84 bovine genes evaluated, selected isolates upregulated expression of interleukin 8 (IL-8) and IL-6 (P < 0.05). After ranking isolates for greatest inhibition, adhesion, competition, and immunomodulation properties, 6 Lactobacillus strains from 4 different species were selected as the best candidates for further development as intranasal bacterial therapeutics to mitigate M. haemolytica infection in feedlot cattle.IMPORTANCE Bovine respiratory disease (BRD) is a significant animal health issue impacting the beef industry. Current BRD prevention strategies rely mainly on metaphylactic use of antimicrobials when cattle enter feedlots. However, a recent increase in BRD-associated bacterial pathogens that are resistant to metaphylactic antimicrobials highlights a pressing need for the development of novel mitigation strategies. Based upon previous research showing the importance of respiratory commensal bacteria in protecting against bronchopneumonia, this study aimed to develop bacterial therapeutics that could be used to mitigate the BRD pathogen Mannheimia haemolytica Bacteria isolated from the respiratory tracts of healthy cattle were characterized for their inhibitory, adhesive, and immunomodulatory properties. In total, 6 strains were identified as having the best properties for use as intranasal therapeutics to inhibit M. haemolytica If successful in vivo, these strains offer an alternative to metaphylactic antimicrobial use in feedlot cattle for mitigating BRD.

Development of an aerosolized Mannheimia haemolytica experimental pneumonia model in clean-catch colostrum-deprived calves.

Mannheimia haemolytica is an important cause of bovine respiratory disease (BRD). BRD is usually a multifactorial disease with host factors and viral infections influencing pathogenesis. Previous studies that have attempted to experimentally induce pneumonia using aerosolized M. haemolytica alone have produced inconsistent results, yet an aerosol model would be useful to study the details of early infection and to investigate the role of innate defences in pathogenesis. The objective of these studies was to develop and characterize an aerosolized M. haemolytica disease model. In an initial study, conventionally raised calves with higher levels of antibody against M. haemolytica leukotoxin developed acute respiratory distress and diffuse alveolar damage, but did not develop bronchopneumonia, following challenge with M. haemolytica serotype 1. Clean-catch colostrum-deprived calves challenged with 1 × 1010 colony forming units of M. haemolytica serotype 1 consistently developed bronchopneumonia, with elevations in rectal temperature, serum haptoglobin, plasma fibrinogen, and blood neutrophils. Mannheimia haemolytica serotype 1 was consistently isolated from the nasal cavities and lungs of challenged calves. Despite distribution of aerosol and isolation of M. haemolytica in all lung lobes, gross lesions were mainly observed in the cranioventral area of lung. Gross and histologic lesions included neutrophilic bronchopneumonia and fibrinous pleuritis, with oat cells (necrotic neutrophils with streaming nuclei), and areas of coagulative necrosis, which are similar to lesions in naturally occurring BRD. Thus, challenge with M. haemolytica serotype 1 and use of clean-catch colostrum-deprived calves with low or absent antibody titres allowed development of an effective aerosol challenge model that induced typical clinical disease and lesions.

Effects of combined viral-bacterial challenge with or without supplementation of Saccharomyces cerevisiae boulardii strain CNCM I-1079 on immune upregulation and DMI in beef heifers.

Objectives were to determine whether live yeast (LY) supplementation would affect daily dry matter feed intake, body weight (BW), immune, and febrile responses to a viral-bacterial (VB) respiratory challenge. Crossbred heifers (N = 38, BW = 230 ± 16.4 kg) were allocated into a 2 × 2 factorial treatment arrangement: Factor 1 = roughage-based diet with or without LY (Saccharomyces cerevisiae boulardii CNCM I-1079, 62.5 g/hd/d), Factor 2 = VB, intranasal administration of bovine herpesvirus-1 (BHV-1, 2 ×108, PFU) on day 0 and endobronchial inoculation with Mannheimia haemolytica (5.4 × 1010, CFU) on day 3, or intranasal saline administration followed by inoculation with phosphate buffer solution (PBS). Heifers were fed their respective diets for 27 d prior to VB challenge on day 0. Heifers were housed by treatment and group-fed using electronic feedbunks. Thermo-boluses (Medria; Châteaubourg, FR) measured rumen temperature (RUT) at 5-min intervals and rectal temperature and whole blood samples were collected on days 0, 3 to 8, 10, 13, and 15. Data were analyzed using repeated measures in the mixed procedure of SAS with fixed effects of day, diet, inoculation, and their interactions. Animals fed LY exhibited a 16% increase (P = 0.02) in neutrophils relative to CON. Diet × inoculation × day interactions were detected for monocytes and haptoglobin. The VB-LY had the greatest (P < 0.05) concentration of monocytes on day 4, followed by VB-CON which was greater (P < 0.05) than PBS treatments. Haptoglobin concentration was greatest (P < 0.02) for VB-CON on day 5, followed by VB-LY which was greater (P < 0.05) than PBS. Heifers supplemented with LY had less (P < 0.05) haptoglobin production than CON. The VB challenge produced nasal lesions that increased (P < 0.01) with day, reaching a zenith on day 6 with 70% of the nares covered with plaques, and increased (P < 0.05) neutrophils on days 3 to 5. The VB challenge increased RUT (P < 0.05) days 2 to 7 and rectal temperature (P < 0.05) on days 0 and 3 to 6. The increased rectal temperature on day 0 was likely due to increased ambient temperature at time of challenge, as VB heifers were processed after the PBS heifers to avoid contamination. The VB challenge was effective at stimulating immune responses, and RUT was effective for measuring febrile responses. These results indicate that prior LY supplementation altered the leukogram in response to VB challenge, suggestive of increased innate immune response.

Effects of Mannheimia haemolytica challenge with or without supplementation of Saccharomyces cerevisiae boulardii strain CNCM I-1079 on immune upregulation and behavior in beef steers.

Objectives of this experiment were to examine the effects of live yeast (LY) supplementation on immunological, physiological, and behavioral responses in steers experimentally challenged with Mannheimia haemolytica (MH). Thirty-six crossbred Angus steers (BW = 352 ± 23 kg) seronegative for MH were allocated within a 2 × 2 factorial arrangement: Factor 1 = roughage-based diet with LY (Saccharomyces cerevisiae boulardii CNCM I-1079, 25 g·per steer daily) or negative control (CON). Factor 2 = bronchoselective endoscopic inoculation with MH or phosphate buffer solution (PBS). Steers were fed their respective diets for 28 d prior to MH challenge on day 0. Reticulo-rumen temperature (RUT; ThermoBolus, Medria) was measured continuously at 5-min intervals and rectal temperature on days -4, 0, 1, 2, 3, 5, 7, 10, and 14 relative to MH inoculation. Compared with PBS-treated steers, the steers inoculated with MH had increased (P < 0.05) RUT from 2 to 24 h, reaching a zenith (>41 °C) 9 to 11 h post-MH challenge, whereas rectal temperature was increased (P < 0.04) in MH-inoculated steers on day 1 post-MH challenge. Supplementation with LY increased (P < 0.05) rectal temperature on days 0, 7, and 10, relative to CON steers. There were inoculation x day interactions (P < 0.01) for lymphocyte, neutrophil, leukocyte, and haptoglobin concentrations. Steers challenged with MH had increased (P < 0.05) neutrophil concentration from days 1 to 3, leukocyte concentration on days 1 and 2 and haptoglobin concentration on days 1 to 5 post-MH challenge compared with PBS-treated steers. Steers supplemented with LY exhibited increased (P < 0.02) cortisol throughout the study compared with the CON treatment. Following inoculation, MH-challenged steers exhibited reduced (P < 0.05) DMI, eating rate, frequency, and duration of bunk visit (BV) events compared with PBS-treated steers. Results from this study demonstrate that the experimental challenge model effectively stimulated acute-immune responses and behavioral changes that are synonymous with naturally occurring bovine respiratory disease (BRD). However, supplementation with LY minimally altered the impact of the MH challenge on physiological and behavioral responses in this study. Continuously measured RUT was more sensitive at detecting febrile responses to MH challenge than rectal temperature. These results serve to guide future research on behavioral and physiological alterations exhibited during a BRD infection.

Multidrug resistant Mannheimia haemolytica isolated from high-risk beef stocker cattle after antimicrobial metaphylaxis and treatment for bovine respiratory disease.

Antimicrobial resistance (AMR) in bacterial respiratory pathogens in high-risk stocker cattle has been poorly characterized. The objective of this study was to describe the prevalence of multidrug resistant (MDR; resistance to > 3 antimicrobial classes) respiratory pathogens in 50 conventionally managed stocker cattle over 21 days after arrival. Cattle received tildipirosin metaphylaxis on day 0 and were eligible to receive up to 3 additional antimicrobials for bovine respiratory disease (BRD): florfenicol, ceftiofur and enrofloxacin. Nasopharyngeal swabs were collected on days 0, 7, 14, and 21 for bacterial culture and antimicrobial susceptibility testing using disc diffusion and broth microdilution. Mannheimia haemolytica was isolated from 5 of 48, 27 of 50, 44 of 50, and 40 of 50 cattle on days 0, 7, 14, and 21, respectively. One of 5, 27 of 27, 43 of 44, and 40 of 40 M. haemolytica were MDR on days 0, 7, 14, and 21, respectively. Pasteurella multocida was isolated from 6 of 48 cattle on day 0 and none were MDR; no other pathogens were isolated. Twenty-four cattle required at least one BRD treatment; M. haemolytica was isolated before treatment from 13 of 24 cattle; all were MDR. One hundred-eighteen M. haemolytica isolates were subjected to pulsed-field gel electrophoresis (PFGE); multiple genotypes were identified. Whole genome sequencing of 33 isolates revealed 14 known AMR genes. Multidrug resistant M. haemolytica can be highly prevalent and genetically diverse in stocker cattle; additional research is necessary to determine factors that influence prevalence and the impact on cattle health.

Treatment history and antimicrobial susceptibility results for Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni isolates from bovine respiratory disease cases submitted to the Iowa State University Veterinary Diagnostic Laboratory from 2013 to 2015.

Bovine respiratory disease is the most costly disease facing the cattle industry. Increasing resistance to antimicrobial treatment has been presented as a significant contributing factor, often through summarized susceptibility testing data. We assessed the relationship between previous antimicrobial treatment and antimicrobial susceptibility results from isolates of Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni cultured from bovine respiratory cases submitted to the Iowa State University Veterinary Diagnostic Laboratory from 2013 to 2015. Antimicrobial susceptibility data from 1,251 bacterial isolates were included for analysis. More bacterial isolates from cattle that received antimicrobial treatment showed resistance compared to isolates from untreated cattle, and the percentage of resistant isolates increased as the number of antimicrobial treatments increased. Resistance to enrofloxacin, spectinomycin, tilmicosin, and tulathromycin was present in >75% of M. haemolytica isolates from cattle that had received 3 or more antimicrobial treatments; resistance to each of those 4 antimicrobials was present in ≤10% of M. haemolytica isolates from untreated cattle. Similar but less dramatic trends were apparent for isolates of P. multocida and H. somni. The percentage of multi-drug resistant bacterial isolates also increased with the number of treatments. Results of our study suggest that previous antimicrobial treatment may have a profound effect on antimicrobial susceptibility testing. Summarized susceptibility results from diagnostic laboratories should not be used to make generalized statements regarding trends in antimicrobial resistance without providing context regarding antimicrobial treatment history.

A vapour phase assay for evaluating the antimicrobial activities of essential oils against bovine respiratory bacterial pathogens.

The objectives of this study were to develop a new assay for the evaluation of the antimicrobial activities of essential oils (EOs) in vapour phase and to demonstrate the antimicrobial activities of commercial EOs against BRPs. To achieve the first objective, a microtube cap containing 100 µl of EO was embedded in an agar plate. An agar plug (diameter 13 mm) inoculated with a bacterial suspension containing108  CFU per ml was then placed over the cap and incubated at 37°C for 24 h. Subsequently, bacteria were recovered from the agar plug by immersion in 5 ml of broth for 10 min, followed by vortexing for 30 s, and the broths were then plated for enumeration. To demonstrate the usefulness of the assay, nine commercial EOs derived from the following specific plants: ajowan, carrot seed, cinnamon leaf, citronella, fennel, ginger grass, lavender, rosemary and thyme were first evaluated for their vapour phase antimicrobial activities against Mannheimia haemolytica serotype 1. Selected EOs were further tested against Pasteurella multocida and Histophilus somni. The EOs of ajowan, thyme and cinnamon leaf completely or partially inhibited BRPs growth. This new assay provided reproducible results on the vapour phase antimicrobial activities of EOs against BRPs. These results support further study of EOs as a potential mitigation strategy against BRPs. SIGNIFICANCE AND IMPACT OF THE STUDY: In this study, we present a new vapour phase assay for evaluating the antimicrobial activities of essential oils (EO) against bovine respiratory pathogens (BRPs). Using this assay, we identified EOs, such as ajowan, thyme and cinnamon leaf, that can effectively inhibit growth of the BRPs Mannheimia haemolytica serotype 1, Pasteurella multocida and Histophilus somni. This is the first study to demonstrate the vapour phase antimicrobial activity of EOs against BRPs.

EFFICACY AND SAFETY OF BAN HUANG ORAL LIQUID FOR TREATING BOVINE RESPIRATORY DISEASES.

BACKGROUND: Ban Huang oral liquid was developed as a veterinary compound preparation by the Lanzhou Institute of Husbandry and Pharmaceutical Sciences of the Chinese Academy of Agricultural Sciences (CAAS). The purpose of this study was to determine whether the oral liquid preparation of traditional Chinese medicine, Ban Huang, is safe and effective for treating respiratory diseases in cattle. MATERIALS AND METHODS: Acute oral toxicity experiments were conducted in Wistar rats and Kunming mice via oral administration. The minimum inhibitory concentration of the drug against Mycoplasma bovis in vitro with the double dilution method was 500 mg/mL, indicating good sensitivity. The results of laboratory pathogen testing, analysis of clinical symptoms, and analysis of pathological anatomy were combined to diagnose bovine respiratory diseases in 147 Simmental cattle caused by mixed infections of M. bovis, bovine respiratory syncytial virus, bovine parainfluenza virus type 3, and Mannheimia haemolytica. These cattle were randomly divided into three groups: drug treatment group 1 (treated via Tilmicosin injection), drug treatment group 2 (treated with Shuang Huang Lian oral liquid combined with Tilmicosin injection), and drug treatment group 3 (treated with Ban Huang oral liquid combined with Tilmicosin injection). Treatment effects were observed within 7 days. RESULTS: The results showed no toxicity and a maximum tolerated dose greater than 20 g/kg BW. For the 87 cattle in drug-treatment group, the cure rate was 90.80%, whereas the response rate was 94.25%. The cure rate of drug treatment group was increased by 14.13% in comparison with that of drug control group 1 and by 7.47% in comparison with that of drug control group 2 (both P < 0.05). CONCLUSION: This study demonstrates that Ban Huang oral liquid is a safe and effective treatment for bovine respiratory diseases, especially for mixed infection caused by M. bovis, bacteria, and viruses.

Effect of copper, manganese, and zinc supplementation on the performance, clinical signs, and mineral status of calves following exposure to bovine viral diarrhea virus type 1b and subsequent infection.

Research has indicated that trace mineral (TM) supplementation may alter immune function and reduce morbidity associated with bovine respiratory disease. The objective of this experiment was to determine the influence of dietary Cu, Mn, and Zn supplementation on the performance, clinical signs, and TM balance of calves following a bovine viral diarrhea virus (BVDV) and (MH) combination respiratory pathogen challenge. Steers ( = 16; 225 ± 20 kg BW) from a single ranch were processed, weaned, and randomly pairwise assigned to either the TM-supplemented (MIN) or the control (CON) experimental treatments. The MIN calves received an additional 150 mg of Cu, 130 mg of Mn, and 320 mg of Zn daily and the CON calves received the basal diet with no additional Cu, Mn, or Zn supplementation. The basal diet contained sufficient Mn and Zn but inadequate Cu based on published nutrient requirements. After 46 d on the experimental treatments, all calves were naturally exposed to a heifer persistently infected with BVDV type 1b for 4 d and then subsequently intratracheally challenged with MH. Data were analyzed using the GLIMMIX procedure of SAS with sampling time serving as a repeated measure and calf serving as the experimental unit. The respiratory challenge was validated via increased BVDV type 1b antibody concentrations, MH whole cell and leukotoxin antibody concentrations, rectal temperatures (TEMP), and subjective clinical severity scores (CS). Calf performance ( ≥ 0.48) was not affected by TM supplementation. Mineral supplementation also did not impact the CS or TEMP of calves ( ≥ 0.53). There was a treatment × time ( < 0.001) interaction observed for liver Cu concentrations. The concentrations of Cu, Mn, Zn, and Fe within the liver; Cu, Mn, and Zn within the muscle; and Cu, Zn, and Fe within the serum were all impacted by time ( ≤ 0.03). Calves receiving the MIN treatment had greater ( < 0.01) liver Cu and Mn concentrations compared with CON calves. In contrast, serum Cu and Fe concentrations were increased ( ≤ 0.05) in CON calves compared with MIN calves. Mineral supplementation did not impact TM concentrations within the muscle ( ≥ 0.38). The supplementation of Cu, Mn, and Zn can improve the Cu and Mn status within the liver and serum of calves in response to a BVDV and MH challenge. When Cu is supplemented to calves receiving a marginally Cu-deficient diet, Cu status within the body is significantly improved.

Pharmacokinetic/pharmacodynamic integration and modelling of amoxicillin for the calf pathogens Mannheimia haemolytica and Pasteurella multocida.

The antimicrobial properties of amoxicillin were determined for the bovine respiratory tract pathogens, Mannheima haemolytica and Pasteurella multocida. Minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) and time-kill curves were established. Pharmacokinetic (PK)/pharmacodynamic (PD) modelling of the time-kill data, based on the sigmoidal Emax equation, generated parameters for three levels of efficacy, namely bacteriostatic, bactericidal (3log10 reduction) and 4log10 reduction in bacterial counts. For these levels, mean AUC(0-24 h) /MIC serum values for M. haemolytica were 29.1, 57.3 and 71.5 h, respectively, and corresponding values for P. multocida were 28.1, 44.9 and 59.5 h. Amoxicillin PK was determined in calf serum, inflamed (exudate) and noninflamed (transudate) tissue cage fluids, after intramuscular administration of a depot formulation at a dosage of 15 mg/kg. Mean residence times were 16.5 (serum), 29.6 (exudate) and 29.0 h (transudate). Based on serum MICs, integration of in vivo PK and in vitro PD data established maximum concentration (Cmax )/MIC ratios of 13.9:1 and 25.2:1, area under concentration-time curve (AUC0-∞ )/MIC ratios of 179 and 325 h and T>MIC of 40.3 and 57.6 h for P. multocida and M. haemolytica, respectively. Monte Carlo simulations for a 90% target attainment rate predicted single dose to achieve bacteriostatic and bactericidal actions over 48 h of 17.7 and 28.3 mg/kg (M. haemolytica) and 17.7 and 34.9 mg/kg (P. multocida).

Anti-inflammatory effects of retinoids and carotenoid derivatives on caspase-3-dependent apoptosis and efferocytosis of bovine neutrophils.

OBJECTIVE: To evaluate immunomodulatory properties of all-trans retinoic acid and a fully oxidized ß-carotene dietary product in calves with Mannheimia haemolytica-induced pneumonia. ANIMALS: Twenty-five 6- to 10-week-old male Holstein calves for experimental inoculations and three 8- to 30-week-old Angus heifers for blood donations. PROCEDURES: In vitro, neutrophils and monocyte-derived macrophages isolated from blood of healthy Angus heifers were treated with all-trans retinoic acid (1 µM) or fully oxidized ß-carotene (8.3 µg/mL) for various times and assessed for markers of cellular death, antimicrobial function, and production of proinflammatory leukotriene B4. Following 28 days of dietary supplementation with fully oxidized ß-carotene, Holstein calves were experimentally inoculated with M haemolytica. Bronchoalveolar lavage fluid was collected at 3 and 24 hours after challenge inoculation and analyzed for markers of apoptosis. RESULTS: In vitro, all-trans retinoic acid and fully oxidized ß-carotene induced cell-selective, caspase-3-dependent apoptosis in neutrophils, which subsequently enhanced efferocytosis in macrophages. Conversely, neither treatment altered phorbol 12-myristate 13-acetate-induced oxidative burst, phagocytosis of nonopsonized zymosan (complement or antibody independent), or M haemolytica-induced leukotriene B4 production in bovine neutrophils. In vivo, fully oxidized ß-carotene enhanced leukocyte apoptosis in bronchoalveolar lavage fluid as well as subsequent efferocytosis by macrophages without altering numbers of circulating leukocytes. CONCLUSIONS AND CLINICAL RELEVANCE: Neutrophil apoptosis and subsequent efferocytosis by macrophages are key mechanisms in the resolution of inflammation. Findings for the present study indicated that all-trans retinoic acid and fully oxidized ß-carotene could be novel nutraceutical strategies that may confer anti-inflammatory benefits for cattle with respiratory tract disease.

Pharmacokinetic-pharmacodynamic integration and modelling of florfenicol in calves.

Florfenicol was administered subcutaneously to 10 calves at a dose of 40 mg/kg. Pharmacokinetic-pharmacodynamic (PK-PD) integration and modelling of the data were undertaken using a tissue cage model, which allowed comparison of microbial growth inhibition profiles in three fluids, serum, exudate and transudate. Terminal half-lives were relatively long, so that florfenicol concentrations were well maintained in all three fluids. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration were determined in vitro for six strains each of the calf pneumonia pathogens, Mannhemia haemolytica and Pasteurella multocida. An PK-PD integration for three serum indices provided mean values for P. multocida and M. haemolytica, respectively, of 12.6 and 10.4 for Cmax /MIC, 183 and 152 h for AUC0-24 h /MIC and 78 and 76 h for T>MIC. Average florfenicol concentrations in serum exceeded 4 × MIC and 1.5 × MIC for the periods 0-24 and 48-72 h, respectively. Ex vivo growth inhibition curves for M. haemolytica and P. multocida demonstrated a rapid (with 8 h of exposure) and marked (6 log10 reduction in bacterial count or greater) killing response, suggesting a concentration-dependent killing action. During 24-h incubation periods, inhibition of growth to a bacteriostatic level or greater was maintained in serum samples collected up to 96 h and in transudate and exudate samples harvested up to 120 h. Based on the sigmoidal Emax relationship, PK-PD modelling of the ex vivo time-kill data provided AUC0-24 h /MIC serum values for three levels of growth inhibition, bacteriostatic, bactericidal and 4 log10 decrease in bacterial count; mean values were, respectively, 8.2, 26.6 and 39.0 h for M. haemolytica and 7.6, 18.1 and 25.0 h for P. multocida. Similar values were obtained for transudate and exudate. Based on pharmacokinetic and PK-PD modelled data obtained in this study and scientific literature values for MIC distributions, Monte Carlo simulations over 100 000 trials were undertaken to predict once daily dosages of florfenicol required to provide 50% and 90% target attainment rates for three levels of growth inhibition, namely, bacteriostasis, bactericidal action and 4 log10 reduction in bacterial count.

A study on ovine pneumonic pasteurellosis: isolation and identification of Pasteurellae and their antibiogram susceptibility pattern in Haramaya District, Eastern Hararghe, Ethiopia.

BACKGROUND: Sheep constitute the second major component of livestock in Ethiopia. However, efficient utilization of this potential resource is hampered by combination of health problems, poor management and feed shortage. Haramaya district is one of the remote settings in Ethiopia where information about the livestock disease is not well documented. Hence this study was conducted to determine the causative agents and their antimicrobial susceptibility pattern of bacterial Pasteurella isolates among pneumonic ovine in Haramaya district, Eastern Hararghe, Ethiopia. RESULTS: Out of 256 samples examined, Pasteurella was isolated in 64 (25%), of which 38 (59.4%) were from lungs and 26 (40.6%) were from nasal cavities. 87.5% of the isolates were Mannheimia haemolytica and 12.5% were Pasteurella multocida. All of the isolates from the lungs were Mannheimia haemolytica whereas 69% of the isolates from nasals cavities were Mannheimia haemolytica. Age and body temperature were significantly associated with Pasteurella isolates from clinic (P < 0.05). Despite diverse in the site of origins, the isolates exhibited uniformity in sensitivity to a majority of the antibacterial agents. The most effective drug was Cholramphenicol (100%) followed by Sulfamethoxazole (89.1%) and Tetracycline (84.4%). Both species were completely resistant to Gentamycin and Vancomycin. CONCLUSION: Mannheimia haemolytica is the most common cause of ovine pneumonic pasteurellosis in the study area. The isolates were susceptible to limited antimicrobial agents. Therefore, the antimicrobial susceptibility test should be conducted before treatment, except for critical cases.

Metabolizable protein supply modulated the acute-phase response following vaccination of beef steers.

Our objective was to evaluate the effects of MP supply, through RUP supplementation, on the acute-phase response of beef steers following vaccination. On d 0, Brangus-crossbred steers (n = 24; 173 ± 31 kg; 175 ± 16 d of age) were randomly assigned to receive 1 of 3 isocaloric diets formulated to provide 85, 100, and 115% of the daily MP requirements of a beef steer gaining 0.66 kg of BW daily. Diets were limit-fed at 1.8% of BW (DM basis) and individually provided to steers once daily (0800 h) from d 0 to 29. Steers were weighed on d 0 and 29, following a 12-h period of feed and water withdrawal. On d 7, steers were vaccinated against Mannheimia haemolytica (OneShot, Pfizer), and blood samples were collected on d 0, 7, 8, 10, 14, 21, and 30. Plasma metabolites were analyzed as repeated measures using the MIXED procedure of SAS. Final BW and ADG were similar (P ≥ 0.50) among treatments (mean = 184 ± 9 kg and 0.5 ± 0.08 kg/d, respectively). Effects of time were detected (P < 0.01) for plasma concentrations of all acute-phase proteins, which peaked between d 7 to 14, returning to baseline concentrations by d 29. Treatment effects were not detected (P ≥ 0.19) for plasma concentrations of acid-soluble protein, albumin, fibrinogen, IGF-1 and serum amyloid-A. Plasma concentrations of total protein (TP) and plasma urea nitrogen (PUN) increased (P ≤ 0.05) with increasing supply of MP (87.1, 89.6, and 90.1 ± 1.09 mg TP/mL and 6.1, 8.3, and 10.3 ± 0.41 mg PUN/dL for 85, 100, and 115% MP steers, respectively). From d 10 to 29, steers provided 115% MP had less (P < 0.001) plasma concentrations of ceruloplasmin than steers fed 85 and 100% MP, which had similar plasma ceruloplasmin concentrations. On d 14, plasma concentrations of haptoglobin were greatest (P ≤ 0.06) for steers fed 115% MP, intermediate for 100% MP, and least for 85% MP (0.98, 0.71 and 0.44 ± 0.099 mg/mL, respectively). On d 10, plasma concentrations of creatinine were greater (P = 0.01) for steers fed 115 vs. 85% MP, and intermediate for steers fed 100% MP (1.63, 1.28, and 1.50 ± 0.099 mg/dL, respectively). Thus, steers provided increasing metabolizable protein had greater plasma concentrations of haptoglobin, creatinine, total protein and PUN following vaccination against M. haemolytica.

Colostrum from cattle immunized with a vaccine based on iron regulated proteins of Mannheimia haemolytica confers partial protection.

Passive protection afforded by colostrum from cattle vaccinated prepartum with an inactivated combination vaccine against viral pathogens and Mannheimia haemolytica (M. haemolytica) was evaluated against an experimental M. haemolytica challenge. Newborn calves were either fed colostrum from vaccinated dams or control colostrum. At approximately 3 weeks of age 24 calves were experimentally infected with M. haemolytica. Animals of both groups displayed clinical signs of respiratory disease and lung damage. The survival rate was considerably higher in calves which received colostrum from vaccinated cows. Colonies consistent with M. haemolytica were recovered in large numbers from all animals, but the geometric mean recovery was more than ten-times lower in the vaccinate colostrum fed animals. It can be concluded that maternal antibodies partly protected the calves against a severe M. haemolytica challenge.