The objectives of this cohort study were to identify a cut point on a previously described 6-level ultrasound score (USS6) at which average daily gain (ADG) is affected and to determine whether there is any additional benefit of using a clinical respiratory score. Calves from a commercial herd in Ohio were enrolled at entry to an automated calf feeder barn at (mean ± standard deviation) 21 ± 6 d of age (n = 308). Calves that survived until 50 d (n = 233) were included in the analyses. Twice-weekly health exams included a clinical respiratory score (CRS), USS6 (0-5, based on lung mass involved), and body weight. For the CRS, the nose, eyes, ears, cough, and rectal temperature were assigned a score (0-3), and calves were considered positive (CRS+) when at least 2 areas scored ≥2. For analysis, USS6 and CRS status were based on a calf's first bovine respiratory disease event identified during the study period. The first multivariable linear model was fit to determine whether USS6 was associated with ADG and controlled for CRS. We detected no difference in ADG among calves with USS6 scores of 2, 3, 4, and 5. Based on this finding, we proposed a simplified 2-level ultrasound score (USS2; without lung consolidation or with lung consolidation ≥1 cm 2 ). A second multivariable model was fit to assess the association between USS2 and ADG; this model controlled for CRS, birth weight category, breed, and cohort. Calves with lung consolidation (n = 169) had lower ADG than calves without lung consolidation (n = 64; 0.73 vs. 0.85 kg/d, respectively). Calves that were CRS+ (n = 61) had lower ADG than calves that were CRS− (n = 172; 0.74 vs. 0.84 kg/d, respectively). Although CRS did not affect the relationship between USS2 and ADG, both CRS and USS2 are necessary to explain variation in ADG. We simplified USS6 and proposed USS2 based on how lung consolidation affected ADG. A simplified 2-level ultrasound score may be more practical for veterinarians to identify calves that may be at risk for poor growth. The effect on ADG was similar between calves with lung consolidation and calves identified as CRS+. Therefore, both thoracic ultrasonography and CRS should be used to identify calves with all types of respiratory disease that affect growth. However, this study represents calves in group housing from 21 to 50 d of age on 1 farm with high disease incidence. We encourage studies that investigate the effects of lung consolidation and CRS on ADG in different management systems.
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.
There are currently no clear guidelines in the US and some other countries regarding euthanasia decision making timelines for dairy cattle that become injured or ill to the extent that recovery is unlikely or impossible. Our study aimed to identify decision making criteria and the most common factors considered when making and carrying out euthanasia decisions. Dairy producers were recruited to participate in a mailed survey (Part I, 307 completed surveys were returned) or in one of three focus groups (Part II, 8–10 producers/group, n = 24). Part I (survey): Farm owners were most commonly responsible for on-farm euthanasia and most respondents would treat and monitor compromised cattle for a majority of 15 health conditions. Responses were highly variable; for example, 6.3% and 11.7% of respondents would never euthanize a non-ambulatory cow or calf, respectively. Part II (focus groups): Three main themes (animal, human, and farm operation) were identified from discussion which focused primarily on animal welfare (16% of the discussion) and human psychology (16%). Participants expressed a desire to eliminate animal suffering by euthanizing, alongside a wide range of emotional states. Development of specific standards for euthanasia is a critical next step and more research is needed to understand the human emotions surrounding euthanasia decision making.
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.
When dairy cattle become ill or injured to the extent that recovery is unlikely or impossible, on-farm euthanasia should be used as a tool to eliminate pain and suffering. Our study aimed to identify decision-making criteria and the most common factors considered by veterinarians when making and carrying out euthanasia decisions. Dairy cattle veterinarians were recruited to participate in an online survey (Part I, 61 surveys collected) or in one of three focus groups (Part II, 4–10 veterinarians/group, n = 22). Part I (survey): Surveyed veterinarians varied regarding health condition management and demonstrated a strong proclivity to treat compromised cattle, mirroring trends amongst dairy producers identified in previous research. Sixty percent of respondents indicated that most facilities for which they serve as the primary veterinarian have a written euthanasia protocol in place. Part II (focus groups): Three main themes about euthanasia decision-making (logistical, animal, and human) were identified from focus group discussions. Discussions focused primarily on logistical factors such as financial considerations and client/public perceptions. Development of specific standards for euthanasia, alongside interactive training programs for dairy veterinarians and producers are vital next steps to improving cattle welfare and consistency in euthanasia decision-making across the United States dairy industry.
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