Earlier this year, in Hong Kong, several racehorses were euthanized due to severe injuries, poor prognosis that could not be saved during races (Lees, 2025; Lees, 2025). Though such decisions followed veterinary protocols, images of black cover erected mid-track and horses collapsed under pain quickly flooded social media, triggering public outrage about ethics. Critics condemned the horse racing industry for profits” and called for abolition. Others, however, defended the decision, advocating that euthanasia in such cases minimize pain, serving as the best choice considering the horses’ life quality.
These thoughts expose the deeper ethical debate of the well-being and moral status of animals. While advocates for animal rights hold that animals have inviolable moral rights, animal interests emphasize that sentience, such as the capacity to suffer, demands equal consideration. Animal rights theory often collapses when faced with the complex realities of legal system and social relationships (Duckler, 2007). Therefore, I argue for interest only, because rights fail to address the differences in animal species and perceptions. I will argue for the nuanced complexity of interest, the reality about economic and experimental animals based on sentience, and varying animal needs in Section 1, 2, and 3, respectively.
The Nuanced Complexity of Interest in Animal Ethics beyond Animal Rights
Facing the discussion of whether non-human animals deserve moral protection, philosophers have proposed varying criteria to define which animals morally matter, and how to treat them properly. Tom Regan, one of the most influential figures in animal ethics, asserts the animal rights theory. His theory was built on the idea of moral rights and the threshold of being a “subject-of-a-life:” animals who possess “belief”, “desire”, “perception”, “memory”, “a sense of future”, and “emotional life.” In fact, these beings ought to be granted rights equivalent to those of humans, and thus should never be treated as a means to an end, being used for benefiting humans or other animals (Regan, 1983). This includes abolishing all forms of animal agriculture, experimentation, and hunting.
However, Regan’s criterion about the “subject-of-a-life” introduces serious ambiguities—which one/ones among episodic memory, reasoning, or planning, etc. serve as the criteria for judgement. Research on domestic mammals such as cows and horses, reveals evidence of emotional complexity, ability to understand cues, and stable social relationships (Marino & Allen, 2017; Proops et al., 2013), yet questions remain about whether they possess a future-oriented self-concept. For instance, horses display anticipation behaviors and memory of past handlers (D’Ingeo et al., 2019), but there appears to be no evidence showing that they fully understand the concept standing for the ultimate future: death (Mendonça et al., 2020). Whether this can be translated to “desires” and “sense of future” in Regan’s framework is unclear. This set such animals in the grey area between bonds. To be specific, these animals, despite exhibiting signs of sentience and cognition, failed to enter a certain ethical zone within the rights framework, either they qualify for full protection and respect or none. Thus, I believe that the definition of being “subject-of-a-life” in animal rights is vague, which undermines the complexity of animals and risks reintroducing speciesism.
This is where interest theory presents a more nuanced framework since it recognizes that animals occupy a range of cognitive capacities, and moral obligations should scale accordingly. An interest, according to Singer (2011), is any stake an animal has in its own flourishing: the desire to avoid pain, experience comfort, to socialize, or to engage in natural behaviors. Hence, they are grounded in observable behavior and physiological response. Thus, a cow’s preference for gentle handling, or a pig’s engagement with environmental enrichment, are ethically significant even if we cannot prove they have desire or sense of future. Interests warrant moral consideration for animals without the relying on requirement of advanced cognitive ability.
Yet, Regan’s theory does not provide tools to assess their vastly different needs and levels of sentience, which means that they require varying moral treatment. For example, the moral obligations we owe to an octopus, an intelligent, emotionally responsive cognitive animal, differ fundamentally from those owed to a fruit fly, a basic sensory animal, despite both being under the kingdom of Animalia. The growing body of ethological research supports this spectrum approach. Recent studies defend the sentience of not only mammals and birds but also fishes (Balcombe 2017), cephalopods (Mather 2020), crustaceans (Crump et al. 2022), and even some arthropods (Mikhalevich and Powell 2020). Considering the scientific and ethical richness of the interests framework, I believe that the interest theory is more complex and adaptive since it can grow alongside evidence, while rights theory remains locked in rigid binaries.
Furthermore, sentience-based interest theory finds support beyond utilitarian circles. Korsgaard (1996), writing from a Kantian perspective, emphasizes that “it is a pain to be in pain. And that is not a trivial fact”. When we witness an animal in pain, we perceive a moral reason, an immediate demand for action. This perceptual grounding makes interest-based ethics more attuned to how moral decisions are actually made: not through cognitive thresholds, but through empathetic recognition. As Singer (1993) argues, “Any being that has an interest in not suffering deserves to have that interest taken into account”.
Unlike rights theory, which demands that animals be like us in specific capacities, such as cognitions and intelligence, to qualify for concern, interest theory begins from the fact that they are different from humans, and their variability can still be taken into consideration.
Economic Animals and Experimental Animals
Many animals central to human society, such as racehorses, dairy herds, and pets, are products of human design, serving the economic interests of humans. These animals are not merely “used” by humans; their continued existence depends on structured market systems that provide them with great care. Hence, they paradoxically often live longer, healthier lives. Racehorses, for instance, receive veterinary treatment, structured nutrition, and highly regulated stable conditions, whereas almost all horse species do not have the ability to survive in nature. If we adhere strictly to rightsbased approach that any use of animals as instruments is prohibited (Regan, 1983), then an ethical paradox exist: the so-called protected resulted in removing the system for them to survive. An interest-based approach, by contrast, acknowledges the complexity of real world animal species, including both wild and domesticated ones. It can work within economic systems to improve welfare, ensuring these animals not only survive but also live well under human stewardship.
The evolution of FEI dressage objectives offers a paradigmatic illustration of how interest ethics functions in such industries. Prior to 2004, Article 401.1 of the FEI (Fédération Equestre Internationale) dressage handbook defined the object of dressage as “harmonious development of the physique and ability of the horse,” implicitly emphasizing obedience. In 2004, however, the objective was revised to “the development of the horse into a happy athlete through harmonious education,” emphasizing the horse’s subjective welfare (The Chronicle of the Horse, 2005; Fédération Equestre Internationale, 2025). Indeed, the emphasis was on a horse who enjoys its work instead of simply obeying commands (The Chronicle of the Horse, 2005). Therefore, I argue that this change reflects interest-based reasoning. Human interests are no longer placed above those of animals, as reflected in Singer’s equal moral consideration. For example, dressage no longer allows the use of sharp spurs, which prioritize horse welfare and place animal’s interest at the center of the sport’s norm.
Meanwhile, the moral dilemma of using experimental animals in research remains one of the most contested areas in animal ethics. In practice, the selection of laboratory animals is rarely based purely on their capacity to suffer. Instead, factors such as cost-effectiveness, ease of handling, reproductive rate, and evolutionary similarity to humans are all taken into consideration (Bennett & Ringach, 2016). To deal with this, proponents of animal rights, such as Regan (1983), argue that the industry for experimental animals should be abolished. Yet, it fails to account for cases where animal experimentation is not purely for human purpose but aims to enhance animal welfare, which would be morally permissible.
Consider the innovation of FaySport bridle, which avoid essential facial neurons, muscles, and bones, leading to the improvement of comfort and behavior of horses. An extensive research into the anatomy of the horse’s head has been done to reach this (FaySport Bridle | PrESTEQ, n.d.). Similarly, there are also some groundbreaking treatments for nonhuman animals veterinary biomedical research, such as cancer immunotherapies for dogs (Dogs and Scientific Research, n.d.). Without these studies and animals, the advancement of horse and dog welfare in this context would not exist.
In contrast, the interest-based view permits animal experimentation under strict ethical conditions and costs-benefits analysis. Singer (1985) argues that experimentation on animals might, in some cases, cause less suffering than similar experiments on humans. Plus, experiments are only ethically acceptable if they offer significant human benefits, outweighing the animals’ pain, minimized suffering and have no alternatives—guided by equal consideration of interests. Still, it risks outweighing the value of humans to animals. Therefore, considering the multiple purposes of animal experiments, I propose that these experiments that have direct benefits to animals is morally permissible. In this case, the experiments, under the framework of interest, are no longer a form of pure exploitation of animals.
Interpreting Varying Needs Through Sensory Thinking
The rights-based approach values animals’ inherent worth by banning their use, but it risks becoming disconnected from reality. On the other hand, an interest-based ethical framework allows for a more perceptually grounded understanding of animals, which aligns with the practical realities of co-existence. Therefore, I propose that animal interests, especially when understood through the lens of sensory perception, offer a more effective and morally meaningful foundation for sharing the planet. Here, Temple Grandin’s theory and applications of sensory thinking is inspiring in how animal interest can transition from theory to practical improvement.
Grandin described herself as “sensory thinker” due to autism, meaning that she processes information primarily through images and physical sensations rather than language. She states that animals are also sensory beings who understand the world through visual, auditory, and tactile cues (Grandin, 2010). While most human beings perceive the world in an abstract way, animals are detail-oriented. In particular, when a ball appears, normal humans will think of the concept “yellow ball”, but animals will think about the super-specific visual category “things that are round, big, 30 centimeters in diameter, and probably yellow.” Such detailed observations make animals extremely sensitive to the environment they lived in and more vulnerable to environmental disruptions, leading to emotional stress when the conditions unfamiliar. As a result, she proposed that the right goal of animal welfare is to literally put oneself in the place where animals live and try to make animals in good emotions with the enriched environment (Grandin & Johnson, 2010).
Grandin’s theory equips us with conceptual tools towards differentiate moral duties across species and settings. For economic animals, such as dogs and horses, should not be confined to the same sensory environment. Instead, they require variation in stimuli and task to fulfill their perceptual and emotional needs. Experimental animals, subjected to invasive procedures like injections, experience additional stress that should be mitigated through acclimation, such as using mock trials with fake needles and positive reinforcement, to reduce fear. Any distressing items, such as collected blood samples, should be removed immediately to avoid triggering negative emotions.
By contrast, a wild animal’s primary interest might be non-interference, allowing it to live according to its natural behaviors. Infrastructure like roads or pipelines can introduce huge difference in these habitats, disrupting natural behaviors and inducing chronic stress. Zoo animals, while not truly wild, still deserve environments that mimic natural ones in complexity. The broader implication is that moral obligations must be responsive to species-specific needs, cognitive capacities, and modes of life. Unlike the purely “hands-off” approach proposed by animal rights theory, interests accommodate abundant moral responses. As Yeates (2011) notes, animal welfare is not about minimizing use but maximizing well-being within use. This requires understanding species-specific behaviors and affective cues, a goal that is best served by the animal interest theory.
In conclusion, a rigid animal rights approach risks oversimplifying the moral status of animals by ignoring the complexity of species, and such differences can be flexibly accommodated without the arbitrary definition like “subject-of-a-life” in the framework of interest. For many experimental or economic animals, living under under careful regulation may not be a torture but an enhancement of their whole welfare. Finally, the abundant needs across species are best understood through sensory thinking that is against the absolute prohibitions imposed by rights theory. Interest-based ethic guides us how to treat animals.
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