Investigation of the safety and protective efficacy of an attenuated and marker M. bovis-BoHV-1 combined vaccine in bovines.

Bovine respiratory disease (BRD) is one of the most common diseases in the cattle industry worldwide; it is caused by multiple bacterial or viral coinfections, of which Mycoplasma bovis (M. bovis) and bovine herpesvirus type 1 (BoHV-1) are the most notable pathogens. Although live vaccines have demonstrated better efficacy against BRD induced by both pathogens, there are no combined live and marker vaccines. Therefore, we developed an attenuated and marker M. bovis-BoHV-1 combined vaccine based on the M. bovis HB150 and BoHV-1 gG-/tk- strain previously constructed in our lab and evaluated in rabbits. This study aimed to further evaluate its safety and protective efficacy in cattle using different antigen ratios. After immunization, all vaccinated cattle had a normal rectal temperature and mental status without respiratory symptoms. CD4+, CD8+, and CD19+ cells significantly increased in immunized cattle and induced higher humoral and cellular immune responses, and the expression of key cytokines such as IL-4, IL-12, TNF-α, and IFN-γ can be promoted after vaccination. The 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 BoHV-1 gG-/tk- combined strain elicited the most antibodies while significantly increasing IgG and cellular immunity after challenge. In conclusion, the M. bovis HB150 and BoHV-1 gG-/tk- combined strain was clinically safe and protective in calves; the mix of 1.0 × 108 CFU of M. bovis HB150 and 1.0 × 106 TCID50 BoHV-1 gG-/tk- strain was most promising due to its low amount of shedding and highest humoral and cellular immune responses compared with others. This study introduces an M. bovis-BoHV-1 combined vaccine for application in the cattle industry.

Modeling the effects of farming practices on bovine respiratory disease in a multi-batch cattle fattening farm.

Bovine Respiratory Disease (BRD) affects young bulls, causing animal welfare and health concerns as well as economical costs. BRD is caused by an array of viruses and bacteria and also by environmental and abiotic factors. How farming practices influence the spread of these causal pathogens remains unclear. Our goal was to assess the impact of zootechnical practices on the spread of three causal agents of BRD, namely the bovine respiratory syncytial virus (BRSV), Mannheimia haemolytica and Mycoplasma bovis. In that extent, we used an individual based stochastic mechanistic model monitoring risk factors, infectious processes, detection and treatment in a farm possibly featuring several batches simultaneously. The model was calibrated with three sets of parameters relative to each of the three pathogens using data extracted from literature. Separated batches were found to be more effective than a unique large one for reducing the spread of pathogens, especially for BRSV and M.bovis. Moreover, it was found that allocating high risk and low risk individuals into separated batches participated in reducing cumulative incidence, epidemic peaks and antimicrobial usage, especially for M. bovis. Theses findings rise interrogations on the optimal farming practices in order to limit BRD occurrence and pave the way to models featuring coinfections and collective treatments p { line-height: 115%; margin-bottom: 0.25 cm; background: transparent}a:link { color: #000080; text-decoration: underline}a.cjk:link { so-language: zxx}a.ctl:link { solanguage: zxx}.

Calves severely affected by bovine respiratory disease have reduced protection against histone toxicity and exhibit lower complement activity.

Bovine respiratory disease (BRD) remains the greatest challenge facing the beef industry. Calves affected by BRD can manifest illness ranging from subclinical infection to acute death. In pathologies similar to BRD, extracellular histones have been implicated as major contributors to lung tissue damage. Histones are basic proteins responsible for DNA organization in cell nuclei, however when released extracellularly during cell injury or via neutrophil activation they become cytotoxic. Cattle suffering severe cases of BRD demonstrate reduced capacity to protect against the cytotoxic effects of histones, however, the protective mechanism(s) of serum remain(s) unknown. Therefore, the objective was to identify components within serum that contribute to protection against histone toxicity. Serum proteins from animals considered protective (P; N = 4) and nonprotective (NP; N = 4) against the toxic effects of histones were precipitated by the addition and incubation of exogenous histones. Proteins that interact with histones from both groups were isolated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and identified via label free "shotgun" proteomics. Sixteen candidate proteins increased by ≥2-fold change in P vs. NP animals were identified, with several associated with the complement system. A subsequent study was conducted to evaluate complement system activity and serum protective capacity against exogenous histones in feedlot heifers. Serum samples were collected from 118 heifer calves (BW at arrival = 229 ±â€…2.4 kg) at feedlot arrival. Animals were retrospectively assigned to groups consisting of: calves not requiring treatment with antibiotics for BRD (CONT; N = 80), calves treated once (1TRT; N = 21), calves treated twice (2TRT; N = 5), calves treated thrice (3TRT; N = 3), or calves that died from BRD within 1 wk of entering the feedlot (DA; N = 9). Serum from DA animals was less protective than CONT (P = 0.0005) animals against histone toxicity. Complement activity of DA animals was reduced compared to CONT (P = 0.0044) animals. Additionally, the use of both assays as a ratio resulted in increased ability to detect DA animals. Results suggest that cattle predisposed to severe cases of respiratory disease may have impaired complement activity presumably contributing to reduced protective capacity against histone toxicity.

Bovine respiratory disease (BRD) remains the leading cause of feedlot calf sickness and death. In respiratory disease affecting humans and mice, major tissue damage is caused by release of histones. Histones are proteins found in the nucleus of cells that condense DNA, however, cells that become damaged release histones extracellularly. Research has shown that calves with severe cases of BRD are less able to protect against the toxic effects of histones residing outside of the cell. It is speculated that components within the blood may interact with histones and confer protection from histone toxicity. This study evaluated serum from protective and nonprotective cattle against histone toxicity and identified 16 proteins that were elevated in protective animals. Several proteins were associated with the complement system of the innate immune system. To evaluate immune complement activity and protective capacity against histone toxicity, serum was collected from heifers at feedlot arrival. Calves suffering from a severe case of BRD demonstrated reduced capacity to protect against histone toxicity. Complement activity of calves severely affected with BRD was reduced as well. Results suggest that cattle susceptible to severe cases of BRD may have impaired complement activity likely contributing to reduced protective capacity against histone toxicity.

Presence of co-infection between bovine leukemia virus and bovine herpesvirus 1 in herds vaccinated against bovine respiratory complex.

The aim of this study was molecular identification of bovine leukemia virus and possible co-infection with bovine respiratory disease complex (BRDC) viral agents in Mexican dairy herds. We collected 533 blood samples from cattle vaccinated against the BRDC virus in 9 states across Mexico. Peripheral blood leukocytes were removed and genetic material was extracted to detect bovine leukemia virus (BLV), bovine herpesvirus 1 (BoHV-1), bovine viral diarrhea virus (BVDV), bovine parainfluenza virus 3 (BPIV-3), and bovine respiratory syncytial virus (BRSV) infection using polymerase chain reaction. We identified high BLV infection rates in 270 cattle (50.65%). One hundred and thirty-three cows (24.95%) tested positive for BoHV-1, of which 65 samples were positive for both viruses (BoHV-1 and BLV) and 68 were only positive for BoHV-1. Only 4 samples tested positive for BPIV-3 and no sample was positive for BVDV or BRSV. Relative risk and odds ratio analyses did not identify that the presence of BLV infection favors BoHV-1 co-infection in vaccinated herds.

Le but de cette étude était l'identification moléculaire du virus de la leucémie bovine et une éventuelle co-infection par des agents viraux du complexe des maladies respiratoires bovines (BRDC) dans des troupeaux laitiers mexicains. Nous avons recueilli 533 échantillons de sang de bovins vaccinés contre le virus BRDC dans neuf états du Mexique. Les leucocytes du sang périphérique ont été prélevés et le matériel génétique a été extrait pour détecter le virus de la leucémie bovine (BLV), le virus de l'herpès bovin 1 (BoHV-1), le virus de la diarrhée virale bovine (BVDV), le virus parainfluenza bovin 3 (BPIV-3), et le virus respiratoire syncytial bovin (BRSV) par réaction d'amplification en chaîne par la polymérase. Nous avons identifié des taux élevés d'infection par le BLV chez 270 bovins (50,65 %). Cent trente-trois bovins (24,95 %) ont été testés positifs pour le BoHV-1, desquels 65 échantillons étaient positifs pour les deux virus (BoHV-1 et BLV) et 68 étaient uniquement positifs pour le BoHV-1. Seuls quatre échantillons ont été testés positifs pour le BPIV-3 et aucun échantillon n'a été positif pour le BVDV ou le BRSV. Les analyses du risque relatif et des rapports de cotes n'ont pas identifié que la présence d'une infection par le BLV favorise la co-infection par le BoHV-1 dans les troupeaux vaccinés.(Traduit par les auteurs).

Evaluation of practices used to reduce the incidence of bovine respiratory disease in Australian feedlots (to November 2021).

Bovine respiratory disease (BRD) has been identified as the most significant infectious disease of feedlot cattle in eastern Australia.1 Bovine respiratory disease causes economic loss due to medication costs, mortalities, excessive feed inputs associated with increased time on feed, reduced sale prices and associated labour costs. Bovine respiratory disease is a complex multifactorial condition with multiple animal, environmental and management risk factors predisposing cattle to illness. A range of microorganisms are implicated in BRD with at least four viral and five bacterial species commonly involved individually or in combination. The viruses most commonly associated with BRD in Australia are bovine herpesvirus 1 (BHV1), bovine viral diarrhoea virus (BVDV or bovine pestivirus), bovine parainfluenza 3 virus (PI3) and bovine respiratory syncytial virus (BRSV). More recently, bovine coronavirus has been identified as a potential viral contributor to BRD in Australia.2 A number of bacterial species have also been recognised as important to the BRD complex; these include Mannheimia haemolytica, Pasteurella multocida, Histophilus somni, Trueperella pyogenes and Mycoplasma bovis. Although one or more of the pathogens listed above can be isolated from clinical cases of BRD, there is no evidence that infection alone causes serious illness. This indicates that, in addition to specific infectious agents, other factors are crucial for the development of BRD under field conditions. These can be categorised as environmental, animal and management risk factors. These risk factors are likely to exert their effects through multiple pathways including reductions in systemic and possibly local immunity. For example, stressors such as weaning, handling at saleyards, transport, dehydration, weather conditions, dietary changes, comingling and pen competition might reduce the effectiveness of the immune system. Reduced immunocompetence can allow opportunistic infection of the lower airways with potential pathogens leading to the development of BRD. The objective of this paper is to critically review the evidence for management practices aimed at reducing the incidence of BRD in Australian feedlot cattle. Predisposing factors (Table 1) largely beyond the control of most feedlots, such as weather and exposure to respiratory viruses, are discussed separately, but these factors can generate indirect prevention responses that are discussed under the preventative practices categories. The current practices are classified as either animal preparation practices (Table 2) or feedlot management practices (Table 3).

Modelling the effects of antimicrobial metaphylaxis and pen size on bovine respiratory disease in high and low risk fattening cattle.

Bovine respiratory disease (BRD) dramatically affects young calves, especially in fattening facilities, and is difficult to understand, anticipate and control due to the multiplicity of factors involved in the onset and impact of this disease. In this study we aimed to compare the impact of farming practices on BRD severity and on antimicrobial usage. We designed a stochastic individual-based mechanistic BRD model which incorporates not only the infectious process, but also clinical signs, detection methods and treatment protocols. We investigated twelve contrasted scenarios which reflect farming practices in various fattening systems, based on pen sizes, risk level, and individual treatment vs. collective treatment (metaphylaxis) before or during fattening. We calibrated model parameters from existing observation data or literature and compared scenario outputs regarding disease dynamics, severity and mortality. The comparison of the trade-off between cumulative BRD duration and number of antimicrobial doses highlighted the added value of risk reduction at pen formation even in small pens, and acknowledges the interest of collective treatments for high-risk pens, with a better efficacy of treatments triggered during fattening based on the number of detected cases.

How Forces of a Complex Adaptive System Affect Ability to Control Bovine Respiratory Disease in Feeder Cattle.

This chapter provides an introductory look into the practical application of the principals of systems thinking as a methodology to gain deeper understanding of the nature of bovine respiratory disease (BRD) in current North American beef production models. The "limits to success" archetype is used to explore the dynamic relationship between technological BRD mitigation improvements and the resultant adaptive changes made by the system. The chapter concludes, by using the tragedy of the common archetype, with an investigation into how the common shared resource of antimicrobials can be damaged and depleted over time.

Additive Bayesian network analysis of the relationship between bovine respiratory disease and management practices in dairy heifer calves at pre-weaning stage.

BACKGROUND: Nursery farms that accept nursing and growing pre-weaned heifer calves from private dairy farms must work to prevent bovine respiratory disease (BRD). Knowledge of the BRD-associated risk factors related to calf management and calves' condition will help to develop appropriate neonatal management practices at original farms and to identify calves at higher risk for BRD at nursery farms. In this study, the relationship between BRD and calf management practices (colostrum feeding, dam parity, serum total protein concentration at introduction (TP), body weight at introduction, introduction season, and daily average growth) was investigated using observational data from pre-weaned dairy calves introduced into a nursery farm in Hokkaido, Japan between 2014 and 2018 (n = 3185). Using additive Bayesian network (ABN) analysis, which is a multivariate statistical modelling approach, the direct and indirect associations between these factors were assessed. RESULTS: Colostrum feeding contributed to an increase in TP (correlation 1.02 [95 % CI, 0.94;1.10]), which was negatively associated with BRD directly (log odds ratio - 0.38 [- 0.46;-0.31]) and indirectly through increasing daily growth (correlation 0.12 [0.09;0.16]). Calves of multiparous dams had higher body weight at introduction (correlation 0.82 [0.74;0.89]), which indirectly reduced BRD risk through the increasing daily growth (correlation 0.17 [0.14;0.21]). Calves introduced during winter had the highest risk for BRD (log odds ratio 0.29 [0.15;0.44]), while those introduced in summer had the lowest risk (log odds ratio - 0.91 [- 1.06;-0.75]). The introduction season was also associated with BRD indirectly through dam parity, body weight at introduction, and daily growth. CONCLUSIONS: The following calf management practices are recommended for preventing BRD in pre-weaned calves at nursery farms: (1) encouraging colostrum feeding to neonatal calves at their original farms; and (2) identifying calves with higher BRD risk, i.e., those without feeding colostrum, born to primiparous cattle, with low body weight at introduction, and/or introduced in winter, and paying intensive attention to the calves for rapid detection of BRD. ABN analysis applied enabled us to understand the complex inter-relationships between BRD incidence and the risk factors, which will help to reduce BRD incidence and to rear healthy calves at nursery farms.

Minimizing the number of origins in batches of weaned calves to reduce their risks of developing bovine respiratory diseases.

Bovine respiratory diseases (BRD) are a major concern for the beef cattle industry, as beef calves overwhelmingly develop BRD symptoms during the first weeks after their arrival at fattening units. These cases occur after weaned calves from various cow-calf producers are grouped into batches to be sold to fatteners. Cross-contaminations between calves from different origins (potentially carrying different pathogens), together with increased stress because of the process of batch creation, can increase their risks of developing BRD symptoms. This study investigated whether reducing the number of different origins per batch is a strategy to reduce the risk of BRD cases. We developed an algorithm aimed at creating batches with as few origins as possible, while respecting constraints on the number and breed of the calves. We tested this algorithm on a dataset of 137,726 weaned calves grouped into 9701 batches by a French organization. We also computed an index assessing the risks of developing BRD because of the batch composition by considering four pathogens involved in the BRD system. While increasing the heterogeneity of batches in calf bodyweight, which is not expected to strongly impact the performance, our algorithm successfully decreased the average number of origins in the same batch and their risk index. Both this algorithm and the risk index can be used as part of decision tool to assess and possibly minimize BRD risk at batch creation, but they are generic enough to assess health risk for other production animals, and optimize the homogeneity of selected characteristics.

Components of a risk assessment tool for prevention and control of bovine respiratory disease in preweaned dairy calves.

Bovine respiratory disease (BRD) is the leading natural cause of death in US beef and dairy cattle, causing the annual loss of more than 1 million animals and financial losses in excess of $700 million. The multiple etiologies of BRD and its complex web of risk factors necessitate a herd-specific intervention plan for its prevention and control on dairies. Hence, a risk assessment is an important tool that producers and veterinarians can utilize for a comprehensive assessment of the management and host factors that predispose calves to BRD. The current study identifies the steps taken to develop the first BRD risk assessment tool and its components, namely the BRD risk factor questionnaire, the BRD scoring system, and a herd-specific BRD control and prevention plan. The risk factor questionnaire was designed to inquire on aspects of calf-rearing including management practices that affect calf health generally, and BRD specifically. The risk scores associated with each risk factor investigated in the questionnaire were estimated based on data from two observational studies. Producers can also estimate the prevalence of BRD in their calf herds using a smart phone or tablet application that facilitates selection of a true random sample of calves for scoring using the California BRD scoring system. Based on the risk factors identified, producers and herd veterinarians can then decide the management changes needed to mitigate the calf herd's risk for BRD. A follow-up risk assessment after a duration of time sufficient for exposure of a new cohort of calves to the management changes introduced in response to the risk assessment is recommended to monitor the prevalence of BRD.

Impact of bovine respiratory disease in U.S. beef cattle.

Bovine respiratory disease (BRD) is one of the most common and costly diseases of beef cattle. Much research has been conducted to understand prevention, treatment, and economic impacts of this syndrome. Impacts from BRD occur in multiple phases of the beef industry including both pre- and post-weaned calves. This disease causes negative impacts due to production losses, treatment costs, and cattle mortality. The large scope of BRD impacts merits further research on effective prevention and intervention technologies to limit deleterious impacts to the cattle industry.

Longitudinal effects of enrofloxacin or tulathromycin use in preweaned calves at high risk of bovine respiratory disease on the shedding of antimicrobial-resistant fecal Escherichia coli.

The objective of this study was to longitudinally quantify Escherichia coli resistant to ciprofloxacin and ceftriaxone in calves treated with enrofloxacin or tulathromycin for the control of bovine respiratory disease (BRD). Dairy calves 2 to 3 wk of age not presenting clinical signs of pneumonia and at high risk of developing BRD were randomly enrolled in 1 of 3 groups receiving the following treatments: (1) single label dose of enrofloxacin (ENR); (2) single label dose of tulathromycin (TUL); or (3) no antimicrobial treatment (control, CTL). Fecal samples were collected immediately before administration of treatment and at d 2, 4, 7, 14, 21, 28, 56, and 112 d after beginning treatment. Samples were used for qualification of E. coli using a selective hydrophobic grid membrane filter (HGMF) master grid. The ENR group had a significantly higher proportion of E. coli resistant to ciprofloxacin compared with CTL and TUL at time points 2, 4, and 7. At time point 28, a significantly higher proportion of E. coli resistant to ciprofloxacin was observed only compared with CTL. The TUL group had a significantly higher proportion of E. coli resistant to ciprofloxacin compared with CTL at time points 2, 4, and 7. None of the treatment groups resulted in a significantly higher proportion of E. coli isolates resistant to ceftriaxone. Our study identified that treatment of calves at high risk of developing BRB with either enrofloxacin or tulathromycin resulted in a consistently higher proportion of ciprofloxacin-resistant E. coli in fecal samples.

Bovine Respiratory Disease Vaccination: What Is the Effect of Timing?

Vaccination is the act of administering a vaccine, whereas immunization may occur if appropriate time is allowed for a competent host immune system to respond to the antigen contained in a vaccine. Timing is critical to ensure bovine respiratory disease (BRD) vaccine safety, efficacy, and efficiency. The current review provides temporal considerations of BRD vaccination within the North American beef production system with focus on vaccination timing in high-risk, newly received beef stocker and feedlot cattle.

Bovine Respiratory Disease Vaccination Against Viral Pathogens: Modified-Live Versus Inactivated Antigen Vaccines, Intranasal Versus Parenteral, What Is the Evidence?

Vaccination of cattle against viral respiratory pathogens to minimize losses associated with bovine respiratory disease (BRD) is a common practice among producers and veterinarians. Three different calf populations in which BRD is most prevalent (recently weaned beef calves, preweaning beef calves, and young dairy calves) are the principal focus of morbidity and mortality prevention through vaccination; however, the evidence of vaccination efficacy is inconsistent in the literature. This review addresses the evidence of efficacy of vaccination in the prevention or reduction of naturally occurring and experimentally induced BRD in each calf group.

The Effect of Market Forces on Bovine Respiratory Disease.

Bovine respiratory disease (BRD) is a persistent negative economic impact on beef and dairy industries and the inability to show any progress in controlling BRD is a source of increasing frustration among animal health professionals and the industry. The complex economic structure of the cattle industry leads to market failures in which cow-calf producers do not have sufficient economic incentive to invest in improved BRD control. This leads to higher costs for stocker and feedlot sectors. An industry-wide comprehensive effort is needed to coordinate and motivate enhanced BRD control focusing on producing healthy calves with less morbidity rather than treatment.

Health and growth of veal calves provided a fatty acid supplement and a dry teat.

Veal calves are at a high risk of disease early in life, which can lead to poor growth. Research is needed to determine interventions that can reduce disease and promote the growth of veal calves. The aim of this study was to determine the effects of fatty acid supplementation and the provision of a dry teat on the incidence of bovine respiratory disease (BRD), navel inflammation, and diarrhea, as well as calf growth. Upon arrival to a commercial veal facility (d 0), 240 Holstein bull calves from 2 cohorts were randomly assigned to 4 treatments using a 2 × 2 factorial arrangement (n = 60/treatment): (1) milk replacer (MR) without fatty acid supplementation and without access to a dry teat (control), (2) MR with fatty acid supplementation (NeoTec5g, Provimi, Brookville, OH) and without access to a dry teat (FAS), (3) MR without fatty acid supplementation and with access to a dry teat (TT), or (4) MR with fatty acid supplementation and with access to a dry teat (FAS+TT). Calves were housed in individual pens from 0 to 9 wk and then paired by treatment at wk 9. Milk replacer was fed twice daily using a step-up program. Fatty acid supplement was added to milk replacer at a feeding rate of 0.5 g/kg of body weight per head per day for the FAS and FAS+TT groups. Health exams were conducted twice weekly for 6 wk to diagnose BRD, navel inflammation, and diarrhea. Body weight, body condition score (BCS), and structural measurements were recorded at wk 0, 5, and 10. Average daily gain (ADG) was calculated for wk 1 to 5, wk 5 to 10, and wk 1 to 10. Health data were analyzed using logistic regression and are reported as relative risk. Body weight, BCS, and structural measurements were analyzed using repeated-measures ANOVA, and ADG was analyzed using a generalized linear model. There was no effect of FAS, TT, or their interaction on body weight or BCS. There was no effect of FAS on ADG wk 1 to 5, wk 5 to 10, or wk 1 to 10. There was a tendency for TT to decrease ADG from wk 1 to 5 but not from wk 5 to 10 or wk 1 to 10. There was a tendency for the interaction of FAS and TT to decrease ADG for wk 1 to 5 but not for wk 5 to 10 and wk 1 to 10. There was no effect of FAS, TT, or their interaction on the risk of BRD, diarrhea, or navel inflammation. We saw no effect of our interventions on calf health or growth. More research is needed to determine whether other factors, such as failure of passive transfer, poor ventilation, barren housing, and low milk allowance in the first few weeks after arrival, may have affected the efficacy of our interventions.

Field trial to evaluate the effect of an intranasal respiratory vaccine protocol on bovine respiratory disease incidence and growth in a commercial calf rearing unit.

BACKGROUND: Bovine respiratory disease (BRD) continues to be great challenge in calf rearing units. The urgent need to decrease the use of antibiotics and increase animal welfare in beef production has forced us to introduce new preventive methods. Vaccinations could contribute to the solution, but the high incidence of BRD already at an early age has made it difficult to introduce suitable vaccination programs. Challenge studies have shown promising results in 3-14 day old calves vaccinated with intranasal BRD vaccine, but very few field trials are available to assess the efficacy of the intranasal vaccines in field conditions. We evaluated the effect of one dose of commercial intranasal vaccination on calf mortality, daily gain, and treatment incidence for BRD in one calf rearing unit. In total, 497 calves (mean age 19 days) were included in our study, 247 of which were vaccinated at the time of arrival to the unit and 250 served as negative controls (unvaccinated). Vaccinated and unvaccinated calves were situated in separate compartments until weaning. Daily gain, treatment incidence, and mortality were recorded until the calves were transported to the finishing unit, which averaged 154.5 days from arrival. RESULTS: Average daily gain over the complete study period was 1151.9 g/day (SD 137.9) for the vaccinated calves and 1139.5 g/day (SD 135.9) for the unvaccinated calves. Intranasal vaccination combined with older arrival age (17 days or older) resulted in a higher daily gain (47.8 g/day) compared with unvaccinated calves (coef. 0.0478, p = 0.003). This association was not recorded in calves that were younger than 17 days upon arrival. Intranasal vaccination was not significantly associated either with mortality (OR 0.976, p = 0.968) or treatment incidence for BRD (OR 1.341, p = 0.120). In total, six vaccinated calves (2.43%) and six unvaccinated calves (2.40%) died during the study period. CONCLUSIONS: Vaccinating arriving calves with intranasal vaccine in the calf rearing unit did not decrease the mortality or treatment incidence for BRD, but it significantly improved the weight gain in calves transported to the unit at the age of 17 days or older.

Economics of respiratory disease in dairy replacement heifers.

Bovine respiratory disease (BRD) is a frequent disease concern in dairy cattle and is most commonly diagnosed in young dairy heifers. The impact of BRD is highly variable, depending on the accuracy and completeness of detection, effectiveness of treatment, and on-farm culling practices. Consequences include decreased rate of weight gain, a higher culling risk either as heifers or as cows, delayed age at first service, delayed age at first calving, and in some cases, lower future milk production. In this data set of 104,100 dairy replacement heifers from across the USA, 36.6% had one or more cases diagnosed within the first 120 days of age with the highest risk of new cases occurring prior to weaning. Comparison of the raising cost for heifers with BRD and those without a recorded history of BRD resulted in an estimated cost per incident case occurring in the first 120 days of age of $252 or $282, depending upon whether anticipated future milk production differences were considered or not. Current market conditions contributed to a cost estimate that is significantly higher than previously published estimates, driven in part by the losses associated with selective culling of a subset of heifers that experienced BRD.

Economic considerations of enhanced BRD control.

Cattle producers and animal health professionals are increasingly frustrated by the inability to reduce the impacts of bovine respiratory disease (BRD). Improved BRD control is difficult due to the complex nature of the disease; the complexity of cattle industry structure and function; and the imbalance of economic incentives for enhanced BRD control. Success in improving BRD control will depend on an industry-wide comprehensive effort to address lifetime animal health issues as well as correcting or offsetting imbalances in economic benefits and costs for enhanced animal health management across cattle production sectors.

Management factors associated with bovine respiratory disease in preweaned calves on California dairies: The BRD 100 study.

The objective of this cross-sectional study was to determine how management practices on California dairies may be associated with bovine respiratory disease (BRD) in preweaned calves. A convenience sample of 100 dairies throughout California, providing a study population of 4,636 calves, were visited between May 2014 and April 2016. During each farm visit, in-person interviews with the herd manager or calf caretaker were conducted to collect information about herd demographics, maternity pen, colostrum and calf management, herd vaccinations, and dust abatement. A random sample of preweaned calves was identified and evaluated for the presence of BRD using a standardized tool. A survey-adjusted generalized linear mixed model with a logit link function was fitted with calf as the unit of analysis and dairy as the random effect. Mean study herd size (±SE) was 1,718 (±189.9) cows. Survey-adjusted estimates of breed types in the sample were 81.6% (±0.6) Holstein, 13.1% (±0.4) Jersey, and 5.3% (±0.5) crossbred or other purebred breeds, and calf sex proportions were 73.8% (±1.0) female and 26.2% (±1.0) male. Overall survey-adjusted BRD prevalence in the study herds was 6.91% (±0.69). Housing factors positively associated with BRD were metal hutches compared with wood hutches [odds ratio (OR) = 11.19; 95% confidence interval (CI) = 2.80-44.78], calf-to-calf contact in calves >75 d of age (OR = 9.95, 95% CI = 1.50-65.86), feeding Holstein calves <2.84 L of milk or replacer per day (OR = 7.16, 95% CI = 1.23-41.68), and lagoon water used for flushing manure under hutches compared with no flush (OR = 12.06, 95% CI = 1.93-75.47). Providing extra shade over hutches (OR = 0.08; 95% CI = 0.02-0.37), feeding calves at least 90% saleable milk (OR = 0.27, 95% CI = 0.13-0.54) or pasteurized milk (OR = 0.10; 95% CI = 0.03-0.36), and feeding >5.68 L of milk or replacer per day to Jersey calves (OR = 0.04; 95% CI = 0.01-0.28) were negatively associated with BRD. Our study identified management practices on California dairies with variability and that may contribute to differences in BRD prevalence, which will be incorporated into a risk-assessment tool to control and prevent BRD in preweaned dairy calves.