Horses constantly face several challenges inherent to the domestic environment, and it is common for the expression of their natural behavior to be drastically limited. Environmental enrichment has been suggested as an alternative to improve the captive situation of domestic horses. Among the recently proposed enrichment strategies, olfactory stimulation has emerged as a method for improving several aspects related to animal behavior. Olfaction is a sensory modality that plays a significant role in the expression of equine behavior, and in recent years, studies have shown that olfactory stimulation can influence the physiological and behavioral parameters of horses. This review provides current information on the anatomical particularities of the equine olfactory system, presents the physiological mechanisms involved in the odor detection process, and demonstrates how stress can interfere with this process. Finally, the use of olfactory stimulation as an environmental enrichment for domestic horses (Equus ferus caballus) is explored. The need for new studies that answer pertinent questions related to this topic is discussed throughout the manuscript.

This study aimed to evaluate the effect of auditory stimuli on mares and geldings during social isolation and movement restriction, and their ability to promote the reduction of stress responses. The research was conducted with eight Pantaneiro horses, divided into Experiment I (4 mares) and Experiment II (4 geldings), both experiments were executed equally using a 4x4 Latin square design with experimental (classical, country and new age) and control (no music) treatments. Physiological parameters (heart rate, heart rate variability, respiratory rate, ocular temperature by infrared thermography, and surface temperature by infrared thermometer) and facial expressions (eye closure (AU143), blink (AU145), half blink (AU47), inner brow raiser (AU101), eye white increase (AD1), tongue show (AD19), nostril dilator (AD38), chewing (AD81), ears forward (EAD101), and ear rotator (EAD104)) were assessed throughout the 24 minutes that the animals remained in the restraining stock. In Experiment I, there was a reduction (p < 0.05) in heart rate during classical and country treatments and an increase (p < 0.05) in auricular and body temperatures during the classical treatment. Additionally, the frequencies of expressions of nostril dilator (AD38), ear rotator (EAD104), and half blink (AU47) were lower (p < 0.05). In Experiment II, there was an increase (p < 0.05) in ocular temperature during the country and control treatments, and a higher frequency (p < 0.05) of ears forward (EAD101) during the country treatment. Exposure to Beethoven’s 9th Symphony (classical genre) and Hank Williams Jr.’s “Ramblin’ In My Shoes” (country genre) reduced stress in mares. Geldings showed less pronounced responses to music genres, indicating a possible preference for Janet Marlow’s “Horsing Around” (new age genre). Music can be used as auditory enrichment for horses in the specific context of this study.

This study aimed to evaluate the ability of social noncontact environmental enrichment to facilitate social buffering and to characterize the emotional experience of horses subjected to restraint in stock by assessing physiological parameters and facial expressions. Pantaneiro horses (n = 11) were evaluated in a crossover design with two treatments: social noncontact enrichment during stock restraint and social isolation during stock restraint. Physiological parameters (heart rate, heart rate variability, respiratory rate, ocular temperature by infrared thermography, and auricular temperature by infrared thermometer) and facial expressions (EquiFACS) were assessed throughout the 24-minute restraint period. When horses were accompanied by a conspecific, heart rate, respiratory rate, and eye temperature were lower (p < 0.05) than when they were socially isolated. The frequency of facial expressions associated with stress responses, such as nostril dilator (AD38), inner brow raiser (AU101), upper eyelid raiser (AU5), eye white increase (AD1), ears forward (EAD101), and ears back (EAD104), was also lower (p < 0.05) in social noncontact enrichment compared to social isolation. The combined assessment of facial expressions and physiological parameters provides robust evidence that, during this intervention, the animals experience an emotional state characterized by high arousal and negative valence. In this context, social noncontact environmental enrichment can facilitate social buffering, leading to a reduction in stress indicators associated with high arousal and negative valence.

This study aimed to investigate factors associated with the welfare (lameness, body condition, and human-animal interaction) and economic value (sale price) of cull dairy cows sold at auctions in Panama. In an observational study, 5,734 cull cows were evaluated using publicly available YouTube videos from individual sales at the country's main auction facilities. The incidence of cows with low BCS and lameness was determined by visual scoring. Negative human-animal interactions were quantified based on the frequency of aggressive behaviors received by cows in the sales ring. The sale price was recorded in US dollars per kilogram of live weight (USD/kg). A total of 20.9% of the cows presented low BCS, 2.06% exhibited lameness, and 92.61% received aggressive interactions during the marketing process. The frequency of aggressive interactions was associated with genetic group, BCS, presence of lameness and horns, animal behavior, and auction location. Cows with lameness had a sale price 0.02 USD/kg lower compared with cows without lameness. Likewise, animals with a BCS ≤2 had a price 0.14 USD/kg lower than that of cows with a score >2. Additionally, cows classified as calm had a 0.04 USD/kg lower price than alert cows. Cull dairy cows sold at Panama auction have conditions that compromise their welfare, as demonstrated by the incidence of low BCS and high frequency of negative interactions during handling. Factors such as genetic group, body condition, cows' behavior, presence of lameness and horns, and auction location influenced the occurrence of negative interactions. Furthermore, thin cows, those with lameness, and those with calm behavior were economically evaluated less favorably, indicating an association between compromised welfare and the reduced market value of these animals.