Early Life Painful Procedures: Long-Term Consequences and Implications for Farm Animal Welfare

Abstract

Farm animals routinely undergo painful husbandry procedures early in life, including disbudding and castration in calves and goat kids, tail docking and castration in piglets and lambs, and beak trimming in chicks. In rodents, inflammatory events soon after birth, when physiological systems are developing and sensitive to perturbation, can profoundly alter phenotypic outcomes later in life. This review summarizes the current state of research on long-term phenotypic consequences of neonatal painful procedures in rodents and farm animals, and discusses the implications for farm animal welfare. Rodents exposed to early life inflammation show a hypo-/hyper-responsive profile to pain-, fear-, and anxiety-inducing stimuli, manifesting as an initial attenuation in responses that transitions into hyperresponsivity with increasing age or cumulative stress. Neonatal inflammation also predisposes rodents to cognitive, social, and reproductive deficits, and there is some evidence that adverse effects may be passed to offspring. The outcomes of neonatal inflammation are modulated by injury etiology, age at the time of injury and time of testing, sex, pain management, and rearing environment. Equivalent research examining long-term phenotypic consequences of early life painful procedures in farm animals is greatly lacking, despite obvious implications for welfare and performance. Improved understanding of how these procedures shape phenotypes will inform efforts to mitigate negative outcomes through reduction, replacement, and refinement of current practices.

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

“…Assessing pain in animals, is notoriously difficult and frequently under recognized or overlooked. ( Grace et al, 2010 ; Hutchinson and Terry, 2019 ; Williams, 2019 ; Adcock, 2021 ; Steagall et al, 2021 ; Tschoner, 2021 ). This difficulty is often attributed to livestock being prey species which hide behavioral evidence of pain to avoid predation ( Williams, 2019 ; Cohen and Beths, 2020 ; Steagall et al, 2021 ).…”

“…The transition from acute pain to chronic pain is not fully understood and there is significant variation in pain phenotype between individuals, owing to the complex multifaceted nature of pain. Dysregulation of the neuroimmune interface has been shown to be involved in pain chronification, particularly after priming of the immunocompetent CNS cells through prior injury or illness ( Grace et al, 2014 ; Moriarty et al, 2019 ; Adcock, 2021 ).…”

“…The implications of these findings in the context of the animal production sphere are significant, suggesting that a large proportion of livestock that have undergone various husbandry procedures at an early age may have increased pain sensitivity as adults. This could negatively affect their natural resilience and ability to respond to injury and disease ( Clark et al, 2014 ; Moriarty et al, 2019 ; Adcock and Tucker, 2020b ; Adcock, 2021 ). One study found that ewes tail docked at 3–4 days of age displayed significantly more pain-related behaviors during parturition at 24 months of age compared to undocked controls ( Clark et al, 2014 ).…”

“…In production animals, such as sheep, cattle, and pigs, the term chronic pain is used more broadly, often to describe pain persisting past the point of tissue healing or past the acute phase ( Kent et al, 1999 ; McCracken et al, 2010 ; McLennan, 2018 ; Williams, 2019 ; Herzberg et al, 2020a ; Adcock, 2021 ), with less focus on a specified time point. A well-recognized example of chronic pain in livestock is lameness caused by various pathogens and environmental factors including Dichelobacter nodosus causing footrot in sheep and osteoarthritis of infectious, traumatic, or degenerative origin ( Herzberg et al, 2020a ).…”

Limited Effects of Pain Control Treatments on Behaviour and Weight Gain of Pure and Crossbred Nellore Heifer Calves When Subjected to Hot-Iron Branding

“…These are usually carried out without any pain control treatment, such as anaesthetics, anti-inflammatory drugs, or analgesics [ 3 , 4 , 5 , 6 , 7 ]. These painful procedures usually result in traumatic experiences, generating stress and fear [ 8 , 9 , 10 ]. Therefore, there are negative consequences for animal welfare, which can lead to important changes in animal behaviour, compromising the human-animal relationship (HAR) [ 11 ].…”