The Importance of Animal Welfare Science in Animal Research and One Health

Abstract

Animal welfare has been a concern in many societies for decades now. For example, Ruth Harrison published her impactful book, Animal Machines, in 1964, which described the housing and management conditions of farm animals at the time and highlighted the welfare issues observed [1]. There are different definitions of animal welfare in published literature, but in general they relate to the experience of the animal from external (e.g., housing) and internal (e.g., hormone) factors, which are integrated to form the animal's current state or welfare status [2]. Focus has often been on minimizing negative experiences, such as the Five Freedoms framework, which states that animals should have freedom from thirst, hunger, and malnutrition; freedom from discomfort; freedom from pain, injury, and disease; freedom from fear and distress; and freedom to express normal behavior [3]. However, more recently this has been expanded to also include promotion of positive animal welfare, where animals do not just have reduced suffering but also have opportunities to have positive or rewarding experiences [4]. The resultant effects of housing and management on mental state are now often incorporated in animal welfare frameworks [5]. Additionally, animal welfare can be considered on a continuum throughout the animal's life, with the goal that animals should at least experience ‘a life worth living’ overall, and we should strive to provide them ‘a good life’ [6].

Subjective states and mental experiences of animals are key to animal welfare. However, it is not possible to measure the subjective experiences of others directly [7]. This is where animal welfare science is essential. Animal welfare science uses indicators from multiple scientific disciplines, including animal behavior, stress and neurophysiology, animal science, immunology, psychology, and veterinary science [2]. For example, behavioral motivation testing, where an animal works/overcomes a cost for access to an important resource, and home pen behavior were collected alongside samples of blood, brain, and gut tissues to assess the effects of feed restriction in broiler breeder females [8]. These results showed physiological indicators of hunger, such as increased agouti-related protein (AGRP) [9], and behavioral indicators of hunger, such as paying an increased cost (working harder) to access an area to search for food and increased home pen activity in the feed-restricted birds [10]. This leads to the conclusion that feed-restricted broiler breeders are hungry, and this negatively impacts their welfare.

These multidisciplinary approaches to assessing animal welfare can be potentially time-consuming and costly. However, after our fundamental understanding is established, measures can be focused on the more important indicators, and ongoing research is validating more practical welfare assessment protocols for specific species that minimize the time and cost while still providing valuable information on an animal's welfare state [11]. Therefore, using animal welfare science to assess (at least some aspects of) animal welfare in our research subjects is feasible. However, why is considering animal welfare in animal research and One Health important?

Animals housed and managed in ways that negatively affect their welfare can exhibit abnormal or stereotypic behavior, have increased stress, reduced learning capabilities, and more [12]. Therefore, using animals that are ‘abnormal’ in research will affect the study results, contributing to poor reproducibility, and may negatively affect other animals or human subjects based on recommendations from unreliable results [13]. Additionally, for more applied research, poor welfare can also affect production measures and, therefore, profitability in commercial settings. For example, using cubicle housing for dairy cows can lead to high levels of foot issues, which is a welfare issue for the cows [14], but it also impacts the profitability of the system [15]. Dairy cow foot health can be improved by a number of management strategies, such as providing increased bedding material, decreasing stocking density, and additional foot trimming [16]. This not only improves the welfare of the cows, but it also reduces economic losses for the producers. Similarly, broiler chickens kept at high stocking densities and with poor-quality bedding can develop lesions on their feet and hocks. This is painful for the birds, but it also reduces profits for the carcasses and chicken ‘paws’ when sold [17].

Animal welfare is an essential part of the One Health framework, with animal and human health and the environment being interconnected [18]. This is especially relevant to farmed animals, with the safety of the food chain and the incidence of foodborne diseases being influenced by animal welfare [19]. Additionally, other factors that affect animal welfare, such as high stocking densities, can increase the risk of emerging infectious disease that could spread to humans [20]. Increasing human populations and the development of land not only destroy established ecosystems but also bring wildlife or feral animals into closer contact with humans, causing stress and disrupting survival for the animals and exposing both wild/feral and domestic animals (and humans) to greater disease risks [21]. Methods to control displaced animals can often bring humans into even closer contact with the animals (e.g., trapping and transport) while simultaneously exposing the animals to novel and stressful conditions that negatively impact welfare [22]. Additionally, land animal farming contributes significantly to global greenhouse gas emissions (GHG), estimated at 12%–20% [23]. There are many proposed strategies to mitigate or minimize these emissions, but none are straightforward, and they may conflict with other One Health issues [24]. For example, ‘sustainable intensification’ suggests maximizing the efficiency and production of farmed animals as a means to reduce emissions [25]. However, this would lead to increased crowding of animals in enclosed spaces, decreasing animal welfare and increasing the risk of emerging infectious diseases [20]. It may also lead to a decrease in animal product prices, which impacts the economic sustainability of farming and could lead to even more animals being farmed in a given time, increasing the number of animals exposed to poor welfare and removing the benefit of decreasing GHG emissions [26]. These are only a few examples of how animals, humans, and the environment are interconnected, but the link between them is clear and demonstrates that including consideration of the welfare of animals is needed to ensure human and environmental health in the future. This special issue on One Health further demonstrates the importance of animals and our treatment and management of them in this framework.

In conclusion, animal welfare science is important not only in improving the lives of animals but also important in the collection of good-quality research data, improving economic gains in production, and being an integral part of human and environmental health. Therefore, consideration of how we house and manage animals needs to be made in both research and practical settings to achieve One Health goals in the future.

Laura M. Dixon: conceptualization, writing – original draft, writing – review and editing.

The author declares no conflicts of interest.