Clinical Applications and Factors Involved in Validating Thermal Windows Used in Infrared Thermography in Cattle and River Buffalo to Assess Health and Productivity

Abstract

Infrared thermography (IRT) is a non-ionizing, non-invasive technique that permits evaluating the comfort levels of animals, a topic of concern due to the growing interest in determining the state of health and welfare of production animals. The operating principle of IRT is detecting the heat irradiated in anatomical regions characterized by a high density of near-surface blood vessels that can regulate temperature gain or loss from/to the environment by modifying blood flow. This is essential for understanding the various vascular thermoregulation mechanisms of different species, such as rodents and ruminants’ tails. The usefulness of ocular, nasal, and vulvar thermal windows in the orbital (regio orbitalis), nasal (regio nasalis), and urogenital (regio urogenitalis) regions, respectively, has been demonstrated in cattle. However, recent evidence for the river buffalo has detected discrepancies in the data gathered from distinct thermal regions in these large ruminants, suggesting a limited sensitivity and specificity when used with this species due to various factors: the presence of hair, ambient temperature, and anatomical features, such as skin thickness and variations in blood supplies to different regions. In this review, a literature search was conducted in Scopus, Web of Science, ScienceDirect, and PubMed, using keyword combinations that included “infrared thermography”, “water buffalo”, “river buffalo” “thermoregulation”, “microvascular changes”, “lacrimal caruncle”, “udder”, “mastitis”, and “nostril”. We discuss recent findings on four thermal windows—the orbital and nasal regions, mammary gland in the udder region (regio uberis), and vulvar in the urogenital region (regio urogenitalis)—to elucidate the factors that modulate and intervene in validating thermal windows and interpreting the information they provide, as it relates to the clinical usefulness of IRT for cattle (Bos) and the river buffalo (Bubalus bubalis).

Experimental Applications and Factors Involved in Validating Thermal Windows Using Infrared Thermography to Assess the Health and Thermostability of Laboratory Animals

“…IRT can detect temperature modifications in response to events that generate stress or pain or due to environmental influences [ 33 , 49 , 50 ]. Specific anatomical areas of the body, denominated thermal windows, have been identified with characteristics such as a high density of surface blood capillaries, arteriovenous anastomosis, and the absence of hair, which facilitates temperature loss or gain by changing the diameter of the blood vessels [ 51 , 52 ]. In laboratory animals, the body regions that comply with these conditions include the tail, ears, eyes, interscapular region with BAT, and the paws, as shown in Table 1.…”

“…Figure 5 illustrates the vascularization of the eye, especially two large arteries—the arteria supraorbitalis and angularis occuli—that are ramifications of the facial artery which supplies circulation to this region. One aspect that must be emphasized is that the arteria angularis occuli is innervated by the facial nerve [ 54 ], so that zone responds sensitively to the predominant autonomous tone during diverse stimuli that is applied to species such as large ruminants [ 51 ], dogs ( Canis lupus familiaris ) [ 67 ], and equines [ 68 ].…”

Transient Receptor Potential (TRP) and Thermoregulation in Animals: Structural Biology and Neurophysiological Aspects

“…This group consists of six units that are considered sensory mediators activated by endogenous ligands, heat, mechanical stimuli, and osmotic changes [ 43 ]. Of the six receptors included, TRPV1, TRPV2, TRPV3, and TRPV4 are called thermosensitive [ 44 ], while TRPV5 and TRPV6 are selective channels for Ca 2+ ions whose function is to maintain Ca 2+ homeostasis. TRPV are channels also involved in the transduction and activation of the nociceptive arch [ 45 ].…”

Current Advances in Assessment of Dog’s Emotions, Facial Expressions, and Their Use for Clinical Recognition of Pain

“…Further studies in dogs also require the development and implementation of techniques and tools currently applied in other species, such as artificial intelligence and computer vision systems for the recognition of pain gestures in humans and equines [ 158 ], or the automatic detection of Facial Units in sheep, a technique with up to 67% accuracy [ 52 ]. Likewise, cameras or visual sensors, global positioning systems (GPS), electrocardiography, electroencephalography [ 159 ], and infrared thermography [ 160 , 161 ] are alternatives to evaluate emotions and motor responses in dogs comprehensively. It is essential to consider that human perception of emotions can be subjective and that the anatomical characteristics of the dog [ 162 ] (e.g., the coat color, the shape of the ears, or the breed itself) can influence and affect the objectivity of facial expression recognition and must be discussed and analyzed before associating facial gestures with a particular emotion.…”