The sickness response in steers with induced bovine respiratory disease before and after treatment with a non-steroidal anti-inflammatory drug

The welfare of ill and injured feedlot cattle: a review of the literature and implications for managing feedlot hospital and chronic pens

By definition, ill and injured animals are on the negative valence of animal welfare. For beef cattle kept in feedlot settings, advances in cattle health management have resulted in a greater understanding and prevention of illness and injury. However, the management of cattle once they become ill and injured is an understudied area, and there are gaps in knowledge that could inform evidence-based decision-making and strengthen welfare for this population. The aim of this review is to provide a comprehensive overview of the acquired knowledge regarding ill and injured feedlot cattle welfare, focusing on existing knowledge gaps and implications for hospital and chronic pen management and welfare assurance. Ill and injured feedlot cattle consist of acutely impaired animals with short-term health conditions that resolve with treatment and chronically impaired animals with long-term health conditions that may be difficult to treat. A literature search identified 110 articles that mentioned welfare and ill and injured feedlot cattle, but the population of interest in most of these articles was healthy cattle, not ill and injured cattle. Articles about managing ill and injured cattle in specialized hospital (n = 12) or chronic (n = 2) pens were even more sparse. Results from this literature search will be used to outline the understanding of acutely and chronically ill and injured feedlot cattle, including common dispositions and welfare considerations, behavior during convalescence, and strategies for identifying and managing ill and injured cattle. Finally, by working through specific ailments common in commercial feedlot environments, we illustrate how the Five Domains Model can be used to explore feelings and experiences and subsequent welfare state of individual ill or injured feedlot cattle. Using this approach and our knowledge of current industry practices, we identify relevant animal-based outcomes and critical research questions to strengthen knowledge in this area. A better understanding of this overlooked topic will inform future research and the development of evidence-based guidelines to help producers care for this vulnerable population.

Strategies for Bovine Respiratory Disease (BRD) Diagnosis and Prognosis: A Comprehensive Overview

Despite significant advances in vaccination strategies and antibiotic therapy, bovine respiratory disease (BRD) continues to be the leading disease affecting the global cattle industry. The etiology of BRD is complex, often involving multiple microbial agents, which lead to intricate interactions between the host immune system and pathogens during various beef production stages. These interactions present environmental, social, and geographical challenges. Accurate diagnosis is essential for effective disease management. Nevertheless, correct identification of BRD cases remains a daunting challenge for animal health technicians in feedlots. In response to current regulations, there is a growing interest in refining clinical diagnoses of BRD to curb the overuse of antimicrobials. This shift marks a pivotal first step toward establishing a structured diagnostic framework for this disease. This review article provides an update on recent developments and future perspectives in clinical diagnostics and prognostic techniques for BRD, assessing their benefits and limitations. The methods discussed include the evaluation of clinical signs and animal behavior, biomarker analysis, molecular diagnostics, ultrasound imaging, and prognostic modeling. While some techniques show promise as standalone diagnostics, it is likely that a multifaceted approach-leveraging a combination of these methods-will yield the most accurate diagnosis of BRD.

Effects of feed energy density, daily milking frequency, and a single injection of cabergoline on behavior and welfare in dairy cows at dry-off

Drying off dairy cows may challenge animal welfare due to high milk yields. A total of 111 loose-housed Holstein cows yielding >15 kg/d of milk were included in a 2 × 2 × 2 factorial design during dry-off to investigate the effects of reduced feeding level (normal vs. reduced energy density), reduced milking frequency (twice vs. once daily), and administration of a dopamine agonist (saline i.m. injection vs. cabergoline i.m. injection) on behavior in the home pen. During the 7 d before dry-off, cows were fed and milked according to 1 of the 4 feeding level and milking frequency combinations. Within 3 h after the last milking, cows were injected i.m. with 5 mL of either saline or a dopamine agonist (5.6 mg of cabergoline; Velactis, Ceva Santé Animale, Libourne, France; labeled for use only with abrupt dry-off, i.e., no preceding reduction in feeding level or milking frequency before last milking). Cows' behavior during d -1, 0, and +1 relative to the last milking was recorded via video and leg-attached sensors. Cows on the reduced energy density diet spent more time feeding and showed more attempts to feed from other cows' bins on d -1. Throughout the period of observations, cows on the reduced diet spent a lower percentage of lying time with their head raised, a higher percentage of lying time with their legs bent, and less time standing in a vigilant posture than did cows on the normal lactation diet. Reducing the daily milking frequency from 2 to 1 did not result in any clear behavioral signs of discomfort. On d 0, cows injected with cabergoline lay down longer but had their head raised for a shorter percentage of time while lying, compared with cows injected with saline. Cows injected with cabergoline also spent less time feeding than cows injected with saline on d 0, and reduced the time spent drinking from d -1 to d 0. Finally, fewer cabergoline-injected cows used the brush for self-grooming, and, among cows that did use the brush, the cows injected with cabergoline reduced the time spent using the brush from d -1 to d 0. In conclusion, cows injected with cabergoline showed several behavioral changes compared with control cows injected with saline. The behavioral changes shown by cows injected with cabergoline may be indicative of malaise during the first 24 h after injection, raising concern for animal welfare. No behavioral evidence for reduced udder pain in cows injected with cabergoline compared with control cows injected with saline was found. Drying off by reducing the energy density of the diet caused behavioral changes indicative of hunger before dry-off, whereas reducing the milking frequency had no clear effects on behavior.

Feeding behavior and activity levels are associated with recovery status in dairy calves treated with antimicrobials for Bovine Respiratory Disease

Calves with Bovine Respiratory Disease (BRD) have different feeding behavior and activity levels prior to BRD diagnosis when compared to healthy calves, but it is unknown if calves who relapse from their initial BRD diagnosis are behaviorally different from calves who recover. Using precision technologies, we aimed to identify associations of feeding behavior and activity with recovery status in dairy calves (recovered or relapsed) over the 10 days after first antimicrobial treatment for BRD. Dairy calves were health scored daily for a BRD bout (using a standard respiratory scoring system and lung ultrasonography) and received antimicrobial therapy (enrofloxacin) on day 0 of initial BRD diagnosis; 10–14 days later, recovery status was scored as either recovered or relapsed (n = 19 each). Feeding behaviors and activity were monitored using automated feeders and pedometers. Over the 10 days post-treatment, recovered calves showed improvements in starter intake and were generally more active, while relapsed calves showed sickness behaviors, including depressed feed intake, and longer lying times. These results suggest there is a new potential for precision technology devices on farms in evaluating recovery status of dairy calves that are recently treated for BRD; there is opportunity to automatically identify relapsing calves before re-emergence of clinical disease.

Assessment of diagnostic accuracy of biomarkers to assess lung consolidation in calves with induced bacterial pneumonia using receiver operating characteristic curves

Bovine respiratory disease (BRD) is the most economically significant disease for cattle producers in the U.S. Cattle with advanced lung lesions at harvest have reduced average daily gain, yield grades, and carcass quality outcomes. The identification of biomarkers and clinical signs that accurately predict lung lesions could benefit livestock producers in determining a BRD prognosis. Receiver operating characteristic (ROC) curves are graphical plots that illustrate the diagnostic ability of a biomarker or clinical sign. Previously we used the area under the ROC curve (AUC) to identify cortisol, hair cortisol, and infrared thermography imaging as having acceptable (AUC > 0.7) diagnostic accuracy for detecting pain in cattle. Herein, we used ROC curves to assess the sensitivity and specificity of biomarkers and clinical signs associated with lung lesions after experimentally induced BRD. We hypothesized pain biomarkers and clinical signs assessed at specific time points after induction of BRD could be used to predict lung consolidation at necropsy. Lung consolidation of > 10% was retrospectively assigned at necropsy as a true positive indicator of BRD. Calves with a score of < 10% were considered negative for BRD. The biomarkers and clinical signs analyzed were serum cortisol; infrared thermography (IRT); mechanical nociceptive threshold (MNT); substance P; kinematic gait analysis; a visual analog scale (VAS); clinical illness score (CIS); computerized lung score (CLS); average activity levels; prostaglandin E2 metabolite (PGEM); serum amyloid A; and rectal temperature. A total of 5,122 biomarkers and clinical signs were collected from 26 calves, of which 18 were inoculated with M. haemolytica. All statistics were performed using JMP Pro 14.0. Results comparing calves with significant lung lesions to those without yielded the best diagnostic accuracy (AUC > 0.75) for right front stride length at 0 h; gait velocity at 32 h; VAS, CIS, average activity and rumination levels, step count, and rectal temperature, all at 48 h; PGEM at 72 h; gait distance at 120 h; cortisol at 168 h; and IRT, right front force and serum amyloid A, all at 192 h. These results show ROC analysis can be a useful indicator of the predictive value of pain biomarkers and clinical signs in cattle with induced bacterial pneumonia. AUC values for VAS score, average activity levels, step count, and rectal temperature seemed to yield good diagnostic accuracy (AUC > 0.75) at multiple time points, while MNT values, substance P concentrations, and CLS did not (all AUC values < 0.75).

Characterizing the literature surrounding transportation of young dairy calves: A scoping review

Transportation is a stressful event for cattle, as it may involve various handling practices, commingling, deprivation of food and water, and fluctuating temperatures. Calves are particularly susceptible to these stressors because their physiological and immune systems are still developing. There has been no formal synthesis of the scientific literature evaluating the effect of transportation on young dairy calf health and performance; the aim of this scoping review is to describe and characterize this body of work. We targeted both descriptive and analytic studies examining transport of calves, including listing how the effect of transport has been evaluated. Eight databases were searched for relevant articles with eligible studies being primary research articles investigating transportation of calves of either sex who were younger than 60 d of age or weighed less than 100 kg. Two reviewers independently screened the title and abstracts of 6,859 articles with 361 potentially relevant articles screened at full text. Of these, 46 were relevant and had data extracted. Articles reporting study location were conducted in the United States (n = 5), Australia (n = 3), Japan (n = 3), and New Zealand (n = 3). Common transport-related variables evaluated included time in transit (n = 13), distance of transportation (n = 8), vehicle-related factors (n = 8), and age at time of transportation (n = 4). Outcome measures varied greatly, including blood parameters (n = 28), health assessments (n = 20), weight (n = 17), behavioral metrics (n = 14), mortality (n = 7), feed intake following transportation (n = 4), salivary cortisol concentrations (n = 3), morbidity (n = 3), and isolation of Salmonella Dublin in fecal samples (n = 2). Outcome parameters were measured during transport or ranged from immediately after to one year following transportation. As the transport-related risk factors and outcomes measured assessed varied widely between studies, future quantitative synthesis (e.g., meta-analysis) in this area may be limited. Several knowledge gaps were identified, including methods to prepare calves for transportation, such as improving nutrition, administering medication, or transporting calves at an older age or weight. Further research could also focus on consistent and clear reporting of key items related to study conduct and analysis, as well as the development of a core outcome set for calf transport studies.

Towards a Positive Welfare Protocol for Cattle: A Critical Review of Indicators and Suggestion of How We Might Proceed

Current animal welfare protocols focus on demonstrating the absence (or at least low levels) of indicators of poor welfare, potentially creating a mismatch between what is expected by society (an assurance of good animal welfare) and what is actually being delivered (an assurance of the absence of welfare problems). This paper explores how far we have come, and what work still needs to be done, if we are to develop a protocol for use on commercial dairy farms where the aim is to demonstrate the presence of positive welfare. Following conceptual considerations around a perceived “ideal” protocol, we propose that a future protocol should be constructed (i) of animal-based measures, (ii) of indicators of affective state, and (iii) be structured according to indicators of short-term emotion, medium-term moods and long-term cumulative assessment of negative and positive experiences of an animal's life until now (in contrast to the current focus on indicators that represent different domains/criteria of welfare). These three conditions imposed the overall structure within which we selected our indicators. The paper includes a critical review of the literature on potential indicators of positive affective states in cattle. Based on evidence about the validity and reliability of the different indicators, we select ear position, play, allogrooming, brush use and QBA as candidate indicators that we suggest could form a prototype positive welfare protocol. We emphasise that this prototype protocol has not been tested in practice and so it is perhaps not the protocol itself that is the main outcome of this paper, but the process of trying to develop it. In a final section of this paper, we reflect on some of the lessons learnt from this exercise and speculate on future perspectives. For example, while we consider we have moved towards a prototype positive welfare protocol for short-term affective states, future research energy should be directed towards valid indicators for the medium and long-term.

Stationary brush use in naive dairy heifers

Weaned dairy heifers are often housed in environments with few appropriate outlets for grooming or oral manipulation. Our objective was to characterize brush use by naive heifers, including patterns over time. In phase 1, groups of 4 heifers (n = 13 groups, 146.4 ± 9.1 d old, mean ± standard deviation; SD) were introduced to a bedded pack pen with 4 wall-mounted brushes (25.4 × 6.0 cm with 3.8-cm-long bristles). On d 1, 2, and 6 of exposure, continuous video recordings were used to observe 2 focal heifers per group for brush use (oral manipulation, grooming, and the sum of total brush use; all averaged at the group level). Latency to use a brush upon entering the pen was 3.4 ± 4.9 min (mean ± SD; range: 0.1 to 17.8 min among individuals). Heifers used the brushes for oral manipulation (39.7 ± 17.5% of brush use, mean ± SD) and grooming (60.3 ± 17.5%), primarily of their heads (89.9 ± 5.4% of grooming). In phase 2, heifers were moved in pairs (n = 13 pairs/treatment) to freestall pens either with (brush treatment) or without (control) brushes mounted inside the stalls for the first 5 d of phase 2 (d 8-12 of the study); on the last day (d 13 of the study), brushes were provided in both treatments. On d 8 (brush treatment) and 13 (both treatments), one focal heifer/pen was recorded for the same behaviors as in phase 1. Linear mixed models were used to evaluate brush use patterns across days (phase 1: d 1, 2, and 6; phase 2 brush treatment: d 8 vs. 13) and between treatments on d 13. In phase 1, brush use was greatest on d 1 [45.9 min; 95% confidence interval (CI): 33.2-63.3 min, back-transformed from natural-log values], decreased on d 2 (25.0 min, 95% CI: 18.4-34.0 min), but then remained steady until d 6 (21.0 min, 95% CI: 15.4-28.5 min); the initial reduction in total brush use was due to changes in grooming, but oral manipulation remained relatively static. In phase 2, heifers in the brush treatment showed similar usage on d 8 versus d 13 (3.8 vs. 3.7 min, 95% CI: 1.9-6.8 vs. 1.9-6.5 min). Compared with heifers with continuous brush access on d 8-12, those in the control treatment showed more brush use on d 13, both for oral manipulation (6.6 vs. 2.5 min, 95% CI: 3.8-11.1 vs. 1.3-4.5 min) and grooming (3.5 vs. 1.2 min, 95% CI: 1.9-5.7 vs. 0.5-2.3 min). Our study is the first to characterize stationary brush use in weaned dairy heifers. We conclude that, despite lacking previous experience, heifers use brushes for both grooming and oral manipulation.

Changes in social and feeding behaviors, activity, and salivary serum amyloid A in cows with subclinical mastitis

The aim of this study was to identify detailed changes in behavior, and in salivary serum amyloid A (SAA), associated with subclinical mastitis. This included standard sickness behaviors, such as decreased activity, feeding and drinking (here labeled "core maintenance" behaviors), and less well-studied social, grooming, and exploratory behaviors (here labeled "luxury" behaviors). Luxury behaviors are biologically predicted to change at lower levels of mastitis infection and are, therefore, particularly relevant to detecting subclinical mastitis. Salivary serum amyloid A is a physiological marker of systemic inflammation, with levels in milk and serum already known to increase during subclinical mastitis. We investigated whether the same was true for SAA in cow saliva. Data were collected for 17 matched pairs of commercial barn-housed Holstein-Friesian cows. Each pair comprised a cow with subclinical mastitis (SCM) and a healthy control (CTRL), identified using somatic cell count (SCC; SCM: SCC >200 × 1,000 cells/mL; CTRL: SCC <100 × 1,000 cells/mL). SCM cows were selected for study ad hoc, at which point they were paired with a CTRL cow, based upon parity and calving date; consequently, the full data set was accrued over several months. Data were collected for each pair over 3 d: SCC (d 1), behavior (d 2), salivary SAA (d 3). All behaviors performed by the focal cows over a single 24-h period were coded retrospectively from video footage, and differences between the SCM and CTRL groups were investigated using the main data set and a subset of data corresponding to the hour immediately following morning food delivery. Saliva was collected using cotton swabs and analyzed for SAA using commercially available ELISA kits. We report, for the first time, that an increase in salivary SAA occurs during subclinical mastitis; SAA was higher in SCM cows and demonstrated a positive (weak) correlation with SCC. The behavioral comparisons revealed that SCM cows displayed reductions in activity (behavioral transitions and distance moved), social exploration, social reactivity (here: likelihood to be displaced following receipt of agonism), performance of social grooming and head butts, and the receipt of agonistic noncontact challenges. In addition, SCM cows received more head swipes, and spent a greater proportion of time lying with their head on their flank than CTRL cows. The SCM cows also displayed an altered feeding pattern; they spent a greater proportion of feeding time in direct contact with 2 conspecifics, and a lower proportion of feeding time at self-locking feed barriers, than CTRL cows. Behavioral measures were found to correlate, albeit loosely, with serum SAA in a direction consistent with predictions for sickness behavior. These included positive correlations with lying duration and the receipt of all agonistic behavior, and negative correlations with feeding, drinking, the performance of all social and all agonistic behavior, and social reactivity. We conclude that changes in salivary SAA, social behavior, and activity offer potential in the detection of subclinical mastitis and recommend further investigation to substantiate and refine our findings.

Construction of a conceptual framework for assessment of health-related quality of life in calves with respiratory disease

Bovine respiratory disease (BRD) is one of the most prevalent diseases affecting beef and dairy calves worldwide, with implications for lifetime productivity, antimicrobial use and animal welfare. Our objective was to construct a conceptual framework for assessment of health-related quality of life (HRQL) in calves with respiratory disease, based on indicators suitable for direct pen-side visual observation. Health-related quality of life measures aim to evaluate the subjective experience of the animal rather than any related pathology. A conceptual framework graphically represents the concepts to be measured and the potential relationships between them. A multistage, mixed method approach involving diverse data sources, collection methods and stakeholders was applied to promote comprehensiveness, understanding and validity of findings. A scoping review was conducted to identify, characterize and collate evidence of behavioural indicators of BRD. The indicators identified were mapped against the principal attributes of five prominent animal welfare assessment frameworks to appraise their correspondence with different characterizations of the dimensions of welfare. Forty-two semi-structured, individual, qualitative interviews with a purposeful sample of experienced veterinarians and stockpersons from UK, USA and Canada elicited in-depth descriptions of the visual observations of HRQL they make in diagnosing and assessing the response to treatment of calves with BRD. Verbatim interview transcripts were examined using inductive thematic analysis. Respondents provided insights and understanding of indicators of HRQL in BRD such as interaction with feed source, hair coat condition, specific characteristics of eye appearance, eye contact, rumen fill and stretching (pandiculation). In an on-farm pilot study to assess the value of potential HRQL behavioural indicators, there was a moderate positive correlation between behaviour and clinical scores (r_s = 0.59) across the 5 days preceding veterinary treatment for BRD. Interestingly, the behaviours evaluated were observed a median of 1.0 (interquartile range: 1.0-3.5) days before clinical indicators used in the scoring system. The proposed conceptual framework for assessment of HRQL features 23 putative indicators of HRQL distributed across two interrelated domains - clinical signs and behavioural expressions of emotional well-being. It has potential applications to inform the development of new HRQL measures such as structured questionnaires and automated sensor technologies.

Machine Learning Algorithms to Classify and Quantify Multiple Behaviours in Dairy Calves Using a Sensor: Moving beyond Classification in Precision Livestock

Previous research has shown that sensors monitoring lying behaviours and feeding can detect early signs of ill health in calves. There is evidence to suggest that monitoring change in a single behaviour might not be enough for disease prediction. In calves, multiple behaviours such as locomotor play, self-grooming, feeding and activity whilst lying are likely to be informative. However, these behaviours can occur rarely in the real world, which means simply counting behaviours based on the prediction of a classifier can lead to overestimation. Here, we equipped thirteen pre-weaned dairy calves with collar-mounted sensors and monitored their behaviour with video cameras. Behavioural observations were recorded and merged with sensor signals. Features were calculated for 1-10-s windows and an AdaBoost ensemble learning algorithm implemented to classify behaviours. Finally, we developed an adjusted count quantification algorithm to predict the prevalence of locomotor play behaviour on a test dataset with low true prevalence (0.27%). Our algorithm identified locomotor play (99.73% accuracy), self-grooming (98.18% accuracy), ruminating (94.47% accuracy), non-nutritive suckling (94.96% accuracy), nutritive suckling (96.44% accuracy), active lying (90.38% accuracy) and non-active lying (90.38% accuracy). Our results detail recommended sampling frequencies, feature selection and window size. The quantification estimates of locomotor play behaviour were highly correlated with the true prevalence (0.97; p < 0.001) with a total overestimation of 18.97%. This study is the first to implement machine learning approaches for multi-class behaviour identification as well as behaviour quantification in calves. This has potential to contribute towards new insights to evaluate the health and welfare in calves by use of wearable sensors.

Symposium review: Precision technologies for dairy calves and management applications

There is an increasing interest in using precision dairy technologies (PDT) to monitor real-time animal behavior and physiology in livestock systems around the world. Although PDT in adult cattle is extensively reviewed, PDT use for the management of preweaned dairy calves has not been reviewed. We systematically reviewed research on the use and application of precision technologies in calves. Accelerometers have the potential to be used to monitor lying behavior, step activity, and rumination, which are useful to detect changes in behavior that may be indicative of disease, responses to painful procedures, or positive welfare behaviors such as play. Automated calf feeding systems can control delivery of nutritional plans to individualize feeding and weaning of calves; changes in feeding behaviors (such as milk intake, drinking speed, and unrewarded visits) may also be used to identify early onset of disease. The PDT devices also measure physiological and physical attributes in dairy calves. For instance, temperature monitoring devices such as infrared thermography, ruminal boluses, and implanted microchips have been assessed in calves, but no herd management-based commercial system is available. Many other PDT are in development with potential to be used in dairy calf management, such as image and acoustic-based monitoring, real-time location, and use of enrichment items for monitoring positive emotional states. We conclude that PDT have great potential for application in dairy calf management, enabling precise behavioral and physiological monitoring, targeted feeding programs, and identification of calves with poor health or behavioral impairments. We strongly encourage further development and validation of commercially available technologies for on-farm application of the monitoring of dairy calf welfare, performance, and health.

The effects of pretransportation or arrival meloxicam administration to calves entering the feedlot on morbidity, biomarkers, performance, and carcass characteristics

The objective of this trial was to investigate the effects of using meloxicam as a pretransport or on arrival therapeutic on disease outcomes of bovine respiratory disease (BRD), biomarker outcomes associated with BRD, performance characteristics over the first 42 d on feed, and carcass traits at harvest in cross bred beef cattle. Multisourced, crossbred steer calves (n = 168) consisting of mainly British and British-Continental breeds were purchased from an auction market in central Missouri. Calves were processed prior to transportation and again upon feedlot arrival. Animals were randomized to 3 separate treatments: pretransport meloxicam (PMEL), arrival meloxicam (AMEL), and a control group receiving inactive excipient (CONT). Dosing at 1 mg/kg on weighted averaged administered per os. Animals were weighed and blood was collected pre- and post-transport. Haptoglobin (Hp)-matrix metaloproteinase (MMP)-9 complex, cortisol, and substance P were quantified. Weights were taken again at 42 d and at harvest. Clinical signs of BRD were monitored using indicators of depression, appetite, respiration, and temperature that qualified the animals for treatment. Harvest parameters were collected using a standardized United States Department of Agriculture grading system for quality grade and yield grade. Meloxicam did not have a significant effect on BRD morbidity over the course of the study and there was no significant effect on performance characteristics at 42 d (P > 0.10). Of the calves that did succumb to BRD, no significant differences were found in severity of disease (P > 0.10). Concentrations of substance P and Hp- MMP-9, were increased on arrival (P ≤ 0.05) however no significant treatment effect or interaction were found between AMEL, PMEL, CONT, or across different levels of biomarkers (P > 0.10). Meloxicam use prior to or on arrival does not mitigate disease or improve performance during the feeding period.

Domestic cattle (Bos taurus taurus) are motivated to obtain forage and demonstrate contrafreeloading

Domestic cattle (Bos taurus taurus) are adapted to digest high-roughage diets, but in confinement they are commonly fed low-roughage, high-energy diets. This practice may leave cattle with an unfulfilled need to consume forage. A way to quantify motivation is to require animals to work to access a resource. Using this method, we evaluated cattle motivation to obtain forage when fed high- or low-roughage diets during and 30 d before the study. Individual heifers were fed Sudan grass (Sorghum × drummondii) hay (high roughage, n = 6) or a diet with 12% forage (as fed, low roughage, n = 6) in an open feed trough. In a second trough, 200 g/d of Sudan grass hay were fed behind a push gate, to which additional weight was added daily until heifers no longer pushed. We predicted heifers would push heavier weights, show a shorter latency, and spend more time pushing the gate when fed a low- vs. high-roughage diet. Indeed, heifers fed a low-roughage diet pushed the gate immediately after hay delivery (1.7 min) and much sooner than those fed a high-roughage diet (75.7 min). On the day before they no longer pushed the gate, latency for heifers in the low-roughage treatment remained only 3.2 min after hay delivery. The suddenness with which they ceased pushing the next day suggests they were unable to move heavier weights to express their motivation. This may explain why maximum weight pushed and time spent pushing the gate did not differ between treatments. The gate pushing by heifers with unrestricted hay access is the first demonstration by cattle of contrafreeloading: performing work to obtain a resource that is simultaneously available for free. In conclusion, consuming forage is important to cattle and is affected by both their primary diet and an internal motivation to work to obtain feed.

Technical note: Use of an automated grooming brush by heifers and potential for radiofrequency identification-based measurements of this behavior

Healthy cattle readily use grooming brushes but this behavior subsides when animals become ill. Tracking use of a brush may provide an opportunity for health monitoring, especially if the process could be automated. We assessed how healthy heifers groom themselves on a brush and hypothesized that radiofrequency identification (RFID) could be used to accurately and automatically record this behavior. Angus and Hereford heifers (n = 16) were fitted with 2 ultra-high-frequency RFID ear tags and monitored in groups of 8 while housed in a pen with an electronic brush, video cameras, and 4 RFID antennas. Each heifer was observed for a 6-h period using continuous video recordings, and brush contact was characterized in terms of anatomic region involved (head/neck, trunk, or posterior) and when not touching the brush but within 1 body length of it. The RFID data were collected for the same period and then processed such that intervals of up to 16 s with no detections but contained between 2 recordings were also considered positive (animal in brush proximity). Brush proximity (RFID) was regressed against brush contact duration (video) and the sensitivity and specificity for each individual heifer calculated. Across heifers, the majority of brush use involved the head/neck, although a few heifers demonstrated relatively large amounts of posterior contact, which contributed to false-negative readings when antennas failed to read the ear tags. Furthermore, for the majority of time that animals were near the brush, they were not in contact with it but rather standing or lying nearby, resulting in false-positive readings. It follows that the ability of the RFID system to accurately detect brush contact varied widely across individual heifers (sensitivity 0.54-1.0; specificity 0.59-0.98), with RFID generally overestimating the duration of brush proximity relative to actual time spent in brush contact. The implication is that RFID-based ear tag recording of brush proximity relative to continuous video observations of contact does not yield accurate results in certain heifers and therefore, as currently configured, is not a reliable representation of this type of grooming behavior.