Bovine respiratory disease complex (BRD) is a common disease in weaned dairy calves that incurs economic and welfare costs. This study was an extension of a randomized clinical trial in which a single injection of tulathromycin (TUL) or oxytetracycline (TET) was administered at first movement to group housing for the prevention of BRD in the 60 d following antimicrobial treatment (BRD60). Calves treated with TUL were 0.5 times [95% confidence interval (CI): 0.4 to 0.7] as likely to be treated for BRD60 as calves treated with TET. The objectives of the current study were to evaluate the long-term effects of BRD and antibiotic treatment on growth of heifers until breeding age, age at first calving, incidence of dystocia, milk production, and mortality before first calving and mortality before 120 d in milk. At entry to the breeding barn (382 d of age), calves that experienced BRD60 weighed 16.0±2.3 kg less than calves that did not. Survival to first calving was recorded for 98% (1,343/1,392) of the heifers on this trial. For TET and TUL heifers with BRD60, 63% (94/150) and 73% (64/88) survived to first lactation, respectively. For TET and TUL calves without BRD60, 84% (436/517) and 84% (494/588) survived to first lactation, respectively. The median age at first calving for heifers with and without BRD60 was 714 (95% CI: 705-723) and 702 (95% CI: 699-705) days, respectively. Heifers with BRD60 were 1.5 (95% CI: 1.1-2.2) times more likely to have a calving ease score ≥2 at their first calving compared with heifers without BRD60. The administration of TUL at movement to group housing may have a role in the prevention of BRD and in mitigating some of the long-term effects of this disease.
Bovine respiratory disease (BRD) is a major concern when raising replacement heifers because of the high incidence and long-term effects of this disease, such as decreased growth and increased time to first calving. The objective of this study was to determine the effect of tulathromycin (TUL) treatment at postweaning movement on the incidence of BRD in dairy replacement heifers. A total of 1,395 heifers were enrolled between November 2006 and June 2007 at a commercial heifer-raising facility. Calves were randomly assigned either to treatment with TUL or to a positive control group treated with oxytetracycline (TET). Calves treated with TUL were 0.5 times (95% CI: 0.4 to 0.7) less likely to be treated for BRD in the 60 d following enrollment than calves treated with TET. For calves that had no history of BRD in the pre-enrollment period, TET calves weighed 4.9+/-0.5kg less than TUL calves after 6 wk in group housing. If calves were treated for BRD in the pre-enrollment period, there was no treatment effect on growth. Calves with clinical BRD in the 60 d following movement weighed 7.9+/-0.6kg less than calves without BRD after 6 wk in group housing. Treatment with TUL at the time of movement to group housing had a beneficial effect on the health and performance through the prevention of BRD in dairy calves with no prior history of the disease. Moreover, BRD after movement to group housing after weaning had a significant effect on the growth of dairy calves.
Neonatal calf diarrhea (NCD) and bovine respiratory disease (BRD) are the 2 most prevalent diseases affecting the welfare and productivity of preweaned dairy calves in the United States. Early detection of these diseases improves both the probability of recovery and animal welfare. Group housing of preweaned calves is increasing in popularity and disease detection in a socially competitive environment can be challenging. One method of detecting disease is through the observation of key behaviors that occur during illness. Novel object and stationary human approach tests can be used to measure exploratory behavior, which is decreased during the expression of sickness behavior. The objectives of this study were (1) to determine associations between 4 categories of health status and the probability of calves approaching a novel object or stationary human, and (2) to determine the associations between rectal temperature and the probability of calves approaching. Holstein heifer calves (n = 75) in group housing were tested weekly for the first 6 wk of life for their willingness to approach a novel object (OBJ) or stationary human (SH). After the approach tests, calves were evaluated by research staff using a standardized health-scoring system. Treatment records were obtained from the farm to determine detection of BRD, NCD, and umbilical infections. Associations between probability of approach and BRD status were analyzed using a linear mixed model with a logit-transform (PROC GLIMMIX), controlling for calf as a random effect. All models controlled for week, pen, pen order, and test order. Calves with clinical signs of BRD on test day were 0.5 [95% confidence interval (CI) = 0.3-0.9] and 0.5 (95% CI = 0.3-0.9) times as likely to approach the OBJ and SH compared with healthy calves, respectively. Calves with a fever (rectal temperature ≥ 39.4°C) were 0.4 (95% CI = 0.2-0.8) and 0.4 (95% CI = 0.1-0.7) times as likely to approach the OBJ and SH compared with calves without fever, respectively. Calves that were recovering from NCD on test day, but were not showing clinical signs of NCD, were 0.4 (95% CI = 0.2-0.9) times as likely to approach SH, compared with healthy calves. These results suggest that approach tests may be useful for the identification of calves with clinical signs of BRD and calves with a fever in group housing.
Producers report bovine respiratory disease and neonatal calf diarrhea as the 2 most common diseases in preweaned calves, both of which can affect calf performance and welfare. Housing calves in groups during the preweaning period has increased in popularity and has the potential to improve calf welfare, but only if producers can detect and treat disease efficiently. A health-screening tool is needed that allows producers to identify suspect animals but minimize the time spent examining healthy animals. The objective of this study was to determine if disease in preweaned, group-housed dairy calves was associated with behavioral measures of illness. This cross-sectional study included the evaluation of preweaned, group-housed calves (n=206) on 4 farms in Wisconsin, United States. Farm visits included the scoring of key behaviors (abnormal posture when lying or standing, isolation from the group, lethargy, and 2 approach tests that tested the willingness of calves to approach a stationary person) that were hypothesized to be components of sickness behavior. Following the behavior scoring, calves underwent an individual health assessment for bovine respiratory disease, neonatal calf diarrhea, and umbilical infections. Each behavior category was scored as normal (0 points) or abnormal (1 point), and then categories were summed to obtain a total behavior score for each calf. Behavior scores ranged from 0 (normal) to 5 (severely abnormal). A total behavior score of 3 or greater was considered positive for disease. The outcome of a positive or negative test on the behavior score were analyzed using PROC LOGISTIC (SAS Institute Inc., Cary, NC) and the model controlled for calf age and farm. Bovine respiratory disease was significantly associated with a behavior score of 3 or greater. The use of a behavior score shows promise as a screening tool for disease in preweaned calves.
Tulathromycin-treated calves in this study had a lower incidence of diarrhea and otitis media versus control calves. Various diseases had negative effects on average daily gain. Mycoplasma bovis status was not associated with otitis media in calves.
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