Pessimistic dairy calves are more vulnerable to pain-induced anhedonia

Animal affect, welfare and the Bayesian brain

According to the Bayesian brain hypothesis, the brain can be viewed as a predictive machine, such that predictions (or expectations) affect how sensory inputs are integrated. This means that in many cases, affective responses may depend more on the subject's perception of the experience (driven by expectations built on past experiences) rather than on the situation itself. Little research to date has applied this concept to affective states in animals. The aim of this paper is to explore how the Bayesian brain hypothesis can be used to understand the affective experiences of animals and to develop a basis for novel predictions regarding animal welfare. Drawing from the literature illustrating how predictive processes are important to human well-being, and are often impaired in affective disorders, we explore whether the Bayesian brain theories may help understanding animals' affective responses and whether deficits in predictive processes may lead to previously unconsidered welfare consequences. We conclude that considering animals as predictive entities can improve our understanding of their affective responses, with implications for basic research and for how to provide animals a better life.

Pain pathophysiology and pharmacology of cattle: how improved understanding can enhance pain prevention, mitigation, and welfare

Globally, humans rely on cattle for food production; however, there is rising societal concern surrounding the welfare of farm animals. From a young age, cattle raised for dairy and beef production experience pain caused by routine management procedures and common disease conditions. The fundamental mechanisms, nociceptive pathways, and central nervous system structures required for pain perception are highly conserved among mammalian species. However, there are limitations to a comparative approach to pain assessment due to interspecies differences in the expression of pain. The stoicism of prey species may impede pain identification and lead to the assumption that cattle lack pain sensitivity. This highlights the importance of establishing validated bovine-specific indicators of pain-a prerequisite for evidence-based pain assessment and mitigation. Our first objective is to provide an overview of pain pathophysiology to illustrate the importance of targeted analgesia in livestock medicine and the negative welfare outcomes associated with unmitigated pain. This is followed by a review of available analgesics, the regulations governing their use, and barriers to implementation of on-farm pain management. We then investigate the current research undertaken to evaluate the pain response in cattle-a critical aspect of the drug approval process. With an emphasis on emerging research in animal cognition and pain pathology, we conclude by discussing the significant influence that pain has on cattle welfare and areas where further research and modified practices are indicated.

Invited review: The effect of weaning practices on dairy calf performance, behavior, and health-A systematic review

The aim of this systematic review was to summarize the literature assessing the effects of weaning practices on performance, behavior, and health of dairy calves. Only published, peer-reviewed articles written in English and specifically assessing the effects of weaning treatments on dairy calves were eligible for inclusion. Studies had to include 2 or more treatment groups that addressed at least one of 4 interventions: weaning age (i.e., when milk was fully removed), weaning duration (i.e., number of days from start of milk reduction to when milk was fully removed), weaning criteria (e.g., age vs. intake), or alternative weaning methods (e.g., water dilution). Outcome measures could include starter intake, growth (BW or ADG), behaviors (5 specific sucking behaviors; play behavior; lying behavior; vocalizations; unrewarded visits to an automated milk feeder), and health (mortality rate, diarrhea, and respiratory illness). We conducted 3 targeted searches using Web of Science and PubMed. The articles underwent a 2-step screening process, resulting in a final sample of 44 studies. The majority of studies investigated weaning age (n = 22), followed by weaning duration (n = 13), weaning criteria (n = 9), and other weaning methods such as dilution, linear versus step-down milk reduction, or meal-based approaches (n = 6). There was consensus for positive effects (or at least no negative effects) on overall growth of calves weaned at later ages, over longer durations, based on starter intake, or weaned using step-down or meal-based milk removal approaches. This is despite reduced starter intake in calves weaned at later ages; most studies found improved starter intake in calves weaned over longer durations. Weaning based on starter intake had superior growth and feed intakes compared with calves weaned at a fixed earlier age. Few studies assessed interactive effects of weaning method and milk allowance. However, weaning after 8 wk appears to support superior weight gain, provided preweaning milk allowances are adequate (above 6 L/d). Weaning can lead to hunger-related behaviors and reduced welfare, yet only half of the studies assessed the effects of weaning method on calf behavior. Weaning at later ages can reduce signs of hunger (based on unrewarded visits to the milk feeder), but it is unclear if weaning over longer durations or weaning by starter intake reduces or prolongs hunger. There was little consensus among the few studies that measured oral behaviors of calves. Positive welfare indicators, such as play behavior, were rarely measured, yet are crucial to understanding the emotional states of calves during this potentially stressful diet transition. Health was rarely the primary objective of the study, with low sample sizes to conduct statistical comparisons. Overall, there remains significant knowledge gaps in our understanding of how best to wean calves. A successful weaning program must minimize signs of hunger while promoting high growth and feed intakes, so we encourage future work to include behavioral indicators of hunger and positive welfare to evaluate how weaning methods are experienced by the calf.

Cold therapy and pain relief after hot-iron disbudding in dairy calves

Even when pain control is implemented, calves may experience pain for days after hot-iron disbudding. Whether calves seek pain relief post-disbudding offers a novel approach to assessing pain in these animals. By employing an approach-aversion paradigm, we explored the ability of cold therapy to provide immediate pain relief in disbudded calves. Calves were habituated to the manual placement of a cool or ambient pack on their forehead for a short duration simultaneous to milk reward consumption, prior to disbudding. Calves were then disbudded under local anaesthesia (procaine) and analgesia (meloxicam), and responses to the packs were observed over subsequent days. Individual calves were consistently exposed to either cool or ambient packs in different halves of a two-sided experimental pen, allowing for the testing of approach-aversion and conditioned place preference. We found calves approached milk rewards quicker and maintained contact for longer when receiving cold therapy compared to the ambient control. However, calves did not display any conditioned preference for the pen where they received the cool pack. These results add to the growing evidence of lasting pain following disbudding procedures and suggests that cold therapy provides some form of pain relief post-disbudding. Future studies should seek other ways to use cold therapy post-disbudding to reduce aversiveness and human involvement.

Exploring the effect of pain on response to reward loss in calves

Negative emotional states are known to interact, potentially aggravating one another. In this study, we used a well validated paradigm (successive negative contrast, SNC) to determine if pain from a common procedure (disbudding) influences responses to a reward downshift. Holstein calves (n = 30) were trained to approach a 0.5 L milk reward. Latency to approach, number of vocalisations and pressure applied on the bottle were recorded during training. To assess how pain affected responses to reward downshift, calves were randomly assigned to one of three treatments before the downshift. Two groups were disbudded and provided the 'gold standard' of pain mitigation: intraoperative local anesthesia and analgesia. One of these disbudded groups was then provided supplemental analgesic before testing. The third group was sham disbudded. All calves were then subjected to the reward downshift by reducing the milk reward to just 0.1 L. Interactions were detected between test session and daily trials on pressure applied for the Disbudded group (estimate ± SEM: 0.08 ± 0.05), and on vocalisations for the Sham (0.3 ± 0.1) and Disbudding + Analgesia (0.4 ± 0.1) groups. Our results indicate that SNC is a promising paradigm for measuring negative affect in calves and suggests that pain potentially affects the response to a reward downshift.

Graduate Student Literature Review: Role of pain mitigation on the welfare of dairy calves undergoing disbudding

This review synthesizes research findings on the pain and welfare of dairy calves undergoing disbudding procedures. We describe disbudding practices in North America as well as the use and perceptions of pain control for these procedures. Governing bodies across Canada and the United States, including each country's veterinary medical association and nationwide initiatives such as proAction and Farmers Assuring Responsible Management (FARM), recommend or require the use of a local anesthetic, a nonsteroidal anti-inflammatory drug (NSAID), and a sedative for disbudding procedures. Although the use of pain relief for disbudding has increased over the past decade or so, some in the dairy industry still do not believe that pain control for disbudding is necessary. As a painful procedure, disbudding has numerous welfare impacts on the calf both during and following the procedure that can be categorized under all 3 principles of animal welfare: natural living, biological functioning, and affective state. The use of pain control for disbudding; namely, a local anesthetic and NSAID, can improve welfare outcomes such as procedure-induced pain behavior, cortisol concentrations, mechanical nociceptive threshold, emotional states, and so on, compared with no pain control for the procedure. Although extensive research exists on pain control practices for disbudding, this review identified further gaps in knowledge and areas for future research. Mechanical nociceptive threshold can be evaluated around the disbudding wounds and is a reliable test in older calves; however, this outcome in very young calves after caustic paste disbudding has been reported to be inconclusive compared with that in older calves. As well, research evaluating xylazine sedation for disbudding has reported both potentially positive and negative results that are difficult to interpret or base suggestions on for the use of this drug. Finally, wounds caused by disbudding take a long time to heal (up to 13 wk) and have increased sensitivity for the entire healing process. Therefore, future research should aim to (1) determine accurate behavioral tests for calves under 1 wk of age undergoing disbudding to better understand their experience, (2) further attempt to understand the effects of xylazine sedation for disbudding and potential impacts of providing this medication, and (3) determine more ways to reduce the healing time and pain experienced by the calf after disbudding procedures.

The Neuroimmune Interface and Chronic Pain Through the Lens of Production Animals

Communication between the central nervous system (CNS) and the immune system has gained much attention for its fundamental role in the development of chronic and pathological pain in humans and rodent models. Following peripheral nerve injury, neuroimmune signaling within the CNS plays an important role in the pathophysiological changes in pain sensitivity that lead to chronic pain. In production animals, routine husbandry procedures such as tail docking and castration, often involve some degree of inflammation and peripheral nerve injury and consequently may lead to chronic pain. Our understanding of chronic pain in animals is limited by the difficulty in measuring this pathological pain state. In light of this, we have reviewed the current understanding of chronic pain in production animals. We discuss our ability to measure pain and the implications this has on animal welfare and production outcomes. Further research into the neuroimmune interface in production animals will improve our fundamental understanding of chronic pain and better inform human clinical pain management and animal husbandry practices and interventions.

Postpartum Stressors Cause a Reduction in Mechanical Brush Use in Dairy Cows

Dairy cows are often subjected to multiple post-partum stressors but how these stressors impact cows' affective states remain poorly understood. Negative affective states are often associated with reduced expression of low-resilience behaviors, so we explored whether cows would reduce their use of a brush after calving. Before calving, cows were offered the opportunity to use a mechanical brush once a week for 10 min. In Experiment 1, we explored whether cows reduced their use of a mechanical brush after parturition (compared to prepartum values) when subjected to the myriad of stressors typically experienced by cows at this time. In Experiment 2, we assessed the effect of cow-calf separation. Results from Experiment 1 showed that cows displayed a reduced brush use following parturition compared to the week before calving. In Experiment 2, we showed that cows given more time to bond with their calf, and who were separated more recently from their calf, showed a more pronounced reduction in brush use. Cows provided part-time contact with their calf for 29 days also reduced their brush use when they were permanently separated from their calf on day 30 after calving. These results suggest that cows experienced anhedonia and point to new directions for research on dairy cow affective states.

What is pain: Are cognitive and social features core components?

Pain is a universal experience, but it has been challenging to adequately define. The revised definition of pain recently published by the International Association for the Study of Pain addressed important shortcomings of the previous version; however, it remains narrow in its focus on sensory and emotional features of pain, failing to capture the substantial roles of cognitive and social core components of the experience and their importance to advances in pain management. This paper reviews evidence and theoretical models for the significant role social and cognitive factors play in pain experience and we argue that without explicit recognition of these core components in the definition, significant nuances are lost at a cost to understanding and clinical management of pain. A focus on sensory and emotional features perpetuates biomedical interventions and research, whereas recognition of cognitive and social features supports a multidimensional model of pain, advances in interdisciplinary care, and the benefits of cognitive behavioral therapy and self‐management interventions. We also explore the six Key Notes that accompany the new definition of pain, discuss their application to the understanding of pain in childhood, and, in doing so, further explore social and cognitive implications. Considerations are also described for assessment and treatment of pain in pediatric populations.

Captivity-Induced Depression in Animals

Concern over the welfare of captive animals is growing. Captivity is often associated with frequent exposure to stressors, which may be the source of persistent negative affective states. We argue that captivity may lead to depressive-like states and call for more research on this topic.