Objective—To evaluate and analyze data from controlled studies on the effectiveness of vaccinating cattle with commercially available viral antigen vaccines for mitigation of the effects of bovine respiratory disease complex (BRDC).
Design—Systematic review and meta-analysis.
Sample—31 studies comprising 88 trials.
Procedures—Studies that reported the effectiveness of commercially available bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV), and parainfluenza type 3 virus (PI3) vaccines for protection of cattle against BRDC or its components were included in the analysis. Studies or trials were categorized as natural exposure or experimental challenge and were further divided by the viral antigen evaluated and vaccine type (modified-live virus [MLV] or inactivated vaccine). Meta-analysis was performed; summary Mantel-Haenszel risk ratios were determined, and Forest plots were generated.
Results—In natural exposure trials, beef calves vaccinated with various antigen combinations had a significantly lower BRDC morbidity risk than did nonvaccinated control calves. In trials evaluating BHV-1 and MLV BVDV vaccines in experimental challenge models, vaccinated calves had a lower BRDC morbidity risk than did control calves; however, in experimental challenge trials evaluating MLV BRSV and PI3 vaccines, no significant difference in morbidity or mortality risk was found between vaccinated and control calves.
Conclusions and Clinical Relevance—Estimating clinical efficacy from results of experimental challenge studies requires caution because these models differ substantially from those involving natural exposure. The literature provides data but does not provide sufficiently strong evidence to guide definitive recommendations for determining which virus components are necessary to include in a vaccination program for prevention or mitigation of BRDC in cattle.
Objective—To determine the relationship between rectal temperature at first treatment for bovine respiratory disease complex (BRDC) in feedlot calves and the probability of not finishing the production cycle.
Design—Retrospective data analysis.
Animals—344,982 calves identified as having BRDC from 19 US feedlots from 2000 to 2009.
Procedures—For each calf, data for rectal temperature at initial treatment for BRDC and various performance and outcome variables were analyzed. A binary variable was created to identify calves that did not finish (DNF) the production cycle (died or culled prior to cohort slaughter). A mixed general linear model and receiver operating characteristic curve were created to evaluate associations of rectal temperature, number of days in the feedlot at time of BRDC diagnosis, body weight, quarter of year at feedlot arrival, sex, and all 2-way interactions with rectal temperature with the probability that calves DNF.
Results—27,495 of 344,982 (7.97%) calves DNF. Mean rectal temperature at first treatment for BRDC was 40.0°C (104°F). As rectal temperature increased, the probability that a calf DNF increased; however, that relationship was not linear and was influenced by quarter of year at feedlot arrival, sex, and number of days in the feedlot at time of BRDC diagnosis. Area under the receiver operating characteristic curve for correct identification of a calf that DNF was 0.646.
Conclusions and Clinical Relevance—Rectal temperature of feedlot calves at first treatment for BRDC had limited value as a prognostic indicator of whether those calves would finish the production cycle.
Objective—To determine effects of ambient temperature, relative humidity, wind speed, relative barometric pressure, and temperature-humidity index (THI) on nasal submucosal and rectal temperatures in cattle during extreme summer conditions.
Animals—20 black crossbred beef heifers (mean body weight, 217.8 kg).
Procedures—Nasal submucosal and rectal temperatures were monitored every 2 hours for 24 hours on 3 nonconsecutive days when ambient temperature was forecasted to exceed 32.2°C. Ambient temperature, relative humidity, wind speed, and relative barometric pressure were continuously monitored at a remote weather station located at the research facility. The THI was calculated and used in the livestock weather safety index (LWSI). Relationships between nasal submucosal or rectal temperature and weather variables were evaluated.
Results—Nasal submucosal and rectal temperatures were related to all weather variables monitored. A positive relationship was determined for ambient temperature and THI with both nasal submucosal and rectal temperatures. A negative relationship was evident for nasal submucosal and rectal temperature with relative humidity, wind speed, and relative barometric pressure. Nasal submucosal and rectal temperatures increased with increasing severity of LWSI category.
Conclusions and Clinical Relevance—Effects of environmental conditions on thermoregulation in calves exposed to extreme heat were detected. The positive relationship between nasal submucosal temperature and ambient temperature and THI raised concerns about the efficacy of intranasal administration of temperature-sensitive modified-live virus vaccines during periods of extreme heat. Environmental conditions must be considered when rectal temperature is used as a diagnostic tool for identifying morbid cattle.
OBJECTIVE To assess the use of 3-D accelerometers to evaluate behavioral changes in cattle experimentally infected with a low-virulent strain of bovine viral diarrhea virus (BVDV).
ANIMALS 20 beef steers (mean weight, 238 kg).
PROCEDURES Calves were allocated to a BVDV (n = 10) or control (10) group. On day 0, calves in the BVDV group were inoculated with a low-virulent strain of BVDV (4 × 106 TCID50, intranasally), and calves in the control group were sham inoculated with BVDV-free medium (4 mL; intranasally). An accelerometer was affixed to the right hind limb of each calf on day −7 to record activity (lying, walking, and standing) continuously until 35 days after inoculation. Baseline was defined as days −7 to −1. Blood samples were collected at predetermined times for CBC, serum biochemical analysis, virus isolation, and determination of anti-BVDV antibody titers.
RESULTS All calves in the BVDV group developed viremia and anti-BVDV antibodies but developed only subclinical or mild disease. Calves in the control group did not develop viremia or anti-BVDV antibodies. Mean time allocated to each activity did not differ significantly between the BVDV and control groups on any day except day 8, when calves in the BVDV group spent less time standing than the calves in the control group. Following inoculation, calves in both groups tended to spend more time lying and less time walking and standing than they did during baseline.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that behavioral data obtained by accelerometers could not distinguish calves subclinically infected with BVDV from healthy control calves. However, subtle changes in the behavior of the BVDV-infected calves were detected and warrant further investigation.
OBJECTIVE To determine the proportion of yearling beef bulls classified as satisfactory potential breeders when reevaluated after failing an initial breeding soundness evaluation (BSE) and identify any factors at initial BSE that predicted satisfactory performance at reevaluation.
DESIGN Retrospective observational study.
ANIMALS 2,064 beef bulls between 11 and 14 months of age at first BSE, evaluated from 2006 to 2014.
PROCEDURES For each bull, data on age (categorized by month), breed, and BSE findings were extracted from the medical records. Bulls were classified as satisfactory potential breeders if they met Society for Theriogenology standards at the initial BSE or up to 2 subsequent reevaluations. Generalized linear mixed models were generated to assess potential associations between certain variables at initial BSE and passing that evaluation or passing subsequent BSEs after initial failure.
RESULTS 1,921 of 2,064 (93.1%) yearling bulls passed 1 of up to 3 BSEs. The proportion of yearling bulls that were not classified as satisfactory during initial BSE but were later classified as satisfactory was 143 of 287 (49.8%). A significant interaction was identified between bull age and breed in the probability of passing the initial evaluation. No variable, including breed, age, scrotal circumference per day of age, and spermatozoa morphology at initial BSE, significantly predicted passing subsequent reevaluations after failing an initial BSE.
CONCLUSIONS AND CLINICAL RELEVANCE Age and breed information should be considered when deciding the age at which initial BSE should be scheduled for a yearling bull cohort.
OBJECTIVE To determine whether infrared thermographic images obtained the morning after overnight heat abatement could be used as the basis for diagnostic algorithms to predict subsequent heat stress events in feedlot cattle exposed to high ambient temperatures.
PROCEDURES Calves were housed in groups of 20 in 3 pens without any shade. During the 6 am and 3 pm hours on each of 10 days during a 14-day period when the daily ambient temperature was forecasted to be > 29.4°C, an investigator walked outside each pen and obtained profile digital thermal images of and assigned panting scores to calves near the periphery of the pen. Relationships between infrared thermographic data and panting scores were evaluated with artificial learning models.
RESULTS Afternoon panting score was positively associated with morning but not afternoon thermographic data (body surface temperature). Evaluation of multiple artificial learning models indicated that morning body surface temperature was not an accurate predictor of an afternoon heat stress event, and thermographic data were of little predictive benefit, compared with morning and forecasted weather conditions.
CONCLUSIONS AND CLINICAL RELEVANCE Results indicated infrared thermography was an objective method to monitor beef calves for heat stress in research settings. However, thermographic data obtained in the morning did not accurately predict which calves would develop heat stress later in the day. The use of infrared thermography as a diagnostic tool for monitoring heat stress in feedlot cattle requires further investigation.
To evaluate the reticulorumen pH of beef feedlot steers throughout the feeding period and to assess the association between the respective durations that the reticulorumen pH was ≤ 5.6 (subacute ruminal acidosis) and ≤ 5.2 (acute ruminal acidosis) and liver abscess severity.
59 feedlot steers (mean body weight, 349.5 kg).
On day 0, each steer was orally administered an electronic bolus that monitored the reticulorumen pH every 10 minutes for 150 days. Steers were transitioned from a starter to intermediate ration on day 8 (transition 1) and from the intermediate to finish ration on day 19 (transition 2). The ration carbohydrate and megacalorie contents increased with each transition. During each transition, the lower megacalorie ration was fed at the 8:00 AM feeding and the higher megacalorie ration was fed at the 2:00 PM feeding for 3 days before the higher megacalorie ration was fed extensively. Steers were sent to slaughter after 182 days; each carcass was assessed for liver abscesses.
The diurnal reticulorumen pH pattern was characterized by a peak at 7:00 AM and nadir at 8:00 PM. The mean percentages of time that the reticulorumen pH was ≤ 5.6 and ≤ 5.2 were more than 10-fold greater during transition 1, compared with during transition 2, and were significantly greater for steers with extensive liver abscesses than for steers without extensive liver abscesses.
CONCLUSIONS AND CLINICAL RELEVANCE
Efforts to minimize the duration that the reticulorumen pH is ≤ 5.6 might mitigate liver abscess formation in feedlot cattle.
Objective—To determine the effect of transportation during periods of high ambient temperature on physiologic and behavioral indices of beef heifers.
Animals—20 heifers (mean body weight, 217.8 kg).
Procedures—Ten heifers were transported 518 km when the maximum ambient temperature was ≥ 32.2°C while the other 10 heifers served as untransported controls. Blood samples were collected from transported heifers at predetermined intervals during the transportation period. For all heifers, body weights, nasal and rectal temperatures, and behavioral indices were measured at predetermined intervals for 3 days after transportation. A week later, the entire process was repeated such that each group was transported twice and served as the control twice.
Results—Transported heifers spent more time near the hay feeder on the day of transportation, had lower nasal and rectal temperatures for 24 hours after transportation, and spent more time lying down for 2 days after transportation, compared with those indices for control heifers. Eight hours after transportation, the weight of transported heifers decreased 6%, whereas that of control heifers increased 0.6%. At 48 hours after initiation of transportation, weight, rectal temperature, and time spent at various pen locations did not differ between transported and control heifers. Cortisol concentrations were higher 4 hours after initiation of transportation, compared with those determined just prior to transportation.
Conclusions and Clinical Relevance—Results indicated transportation during periods of high ambient temperatures caused transient changes in physiologic and behavioral indices of beef heifers.
Objective—To characterize clinical and behavioral changes in calves following inoculation with Mycoplasma bovis and evaluate relationships between those changes and pulmonary disease.
Animals—22 healthy Holstein steers.
Procedures—20 calves were inoculated intranasally with < 108 CFU or > 109 CFU of M bovis. Calves were assigned a clinical illness score (CIS) on a scale of 1 through 4 twice daily on the basis of severity of cough, labored breathing, and lethargy. For each calf, distance traveled and time spent near the waterer, feed bunk, or shelter were determined via a remote location monitoring device. Calves were euthanized and necropsied 22 days after inoculation.
Results—13 calves became clinically ill after challenge inoculation; 3 calves were euthanized within 20 days. Among all calves, consolidation was evident in 0% to 79.9% of the lungs; extent of lung consolidation did not differ between the challenge dose groups. Distance traveled and percentages of time spent in proximity to the feed bunk and shelter were associated with CIS; calves with more severe disease traveled less distance and spent less time at the feed bunk and more time in the shelter. Distance traveled by calves was negatively associated with extent of lung consolidation (< or ≥ 10% of lungs affected); this effect was modified by trial day.
Conclusions and Clinical Relevance—Following inoculation with M bovis, calf behavior patterns were associated with both CIS and severity of pulmonary disease. Use of behavior monitoring systems may aid in recognition of respiratory tract disease in calves.