Hyperactivated Sperm Motility: Are Equine Sperm Different?

A recent study has suggested a central role for hyperactivated sperm motility in successful equine in vitro fertilization, as the highest apparent fertilization rates reported yet were obtained using exogenous stimulation of hyperactivated motility in sperm that had been incubated for capacitation. Hyperactivated motility has been studied intensively in other species, but little data are available in this area in the horse. Hyperactivated motility is associated with an influx of calcium from the extracellular space, and in other species this occurs because of an increase in intracellular pH during capacitation. Influx of calcium seems to trigger changes in flagellar function through calcium–calmodulin–calmodulin kinase-related effects on dynein function, but the exact mechanisms resulting in hyperactivated motility are still unclear. We have been exploring the physiology of hyperactivated motility in stallion spermatozoa and have found many of the mechanisms present in other species to be in place in the stallion. Further research is needed to determine why stallion spermatozoa seem to fail to undergo hyperactivation in response to capacitating environments that support this activity in other species.     

Needs Assessment: What Are the Barriers to Use of Equine Genetic Testing?

Genetic testing offers precise and accurate data to horse owners concerning their horse’s health and offers potential economic value increases of foal crops via genome-assisted selection. Despite availability of at least 96 commercially available markers, fewer than 20 are commonly used. This project seeks to identify the barriers to the incorporation of genomic tools in diverse equine operations. Based on studies examining public opinion of human medical testing, we expected that lack of genetic education and few industry requirements for testing may contribute to neutral or negative opinions regarding genomic tools for horses. We developed a 20 total question survey to capture demographic information such as facility size, type, and primary breed, as well as horse owner familiarity, use, and outlook regarding equine genetic testing. Question types included multiple choice, Likert-type scale, and open-ended response. Recruitment through county extension agents and breed organizations supplied a broad sampling of the Florida horse industry. Responses were collected from February through May 2019. Data showed that 25% of horse owners had genetically tested their horses (n = 60). Of these consumers, 80% rated the quality of their experience as “excellent” or “good” (n = 15). There was a significant positive association between genetic education and likelihood to genetically test. Most respondents (65%) were interested in receiving information regarding genetic testing. Study participants preferred to find materials on genetic testing through Web-based articles and veterinarians. Results of this study will provide researchers with critical knowledge of their audience’s needs and a roadmap to tailor future educational resources.     

Equine glaucoma: Where are we now?

The following article discusses the pathophysiology, clinical signs, diagnosis, medical treatment and surgical management of glaucoma in the horse.     

Current Knowledge of Equine Water Treadmill Exercise: What Can We Learn From Human and Canine Studies?

Equine water treadmills (WTs) are increasingly being found in research and therapy centers and private competition yards. However, the programs incorporating WT exercise for training and rehabilitation of horses are mainly based on anecdotal evidence due to the lack of scientific evidence available. This review aims to evaluate what is currently known about WT exercise for horses drawing on what is known from human and canine investigations. Studies of WT exercise have demonstrated that water depth, temperature, and speed have a significant effect on physiological responses in humans. The physiological studies in horses show many similarities to human responses with much evidence demonstrating that WT exercise is an aerobic form of exercise which does not appear to induce improvement in aerobic capacity when used within training programs. Equine and canine studies have shown that water depth can have a significant effect on the biomechanical responses to WT exercise, but little is known about the effect of different speeds at the various water depths. Key areas we would recommend for future research are as follows: how combinations of water depth and speed alter equine biomechanics compared to overland exercise, determination of long-term benefits of WT exercise, and how to use WT for rehabilitation for horses with specific injury.     

Equine eosinophilic keratitis: An emergent ocular condition?

Eosinophilic keratitis (EK) is considered an immune mediated disorder associated with an underlying type I or IV hypersensitivity reaction to parasitic or environment allergens. It is believed that the persistency of inflammatory mediators and recruitment of eosinophils into the conjunctival tissue have detrimental effects on the corneal surface. Epithelial cells are consequently damaged, particularly by eosinophilic toxic proteins, which determine the lack of epithelial healing and plaque formation. Although some clinical signs are common to other corneal diseases, the location of the lesion, presence of corneal plaques and time of the year, may help practitioners to identify EK. Topical therapy with steroids or immune-modulators seems to be the most effective treatment in small, localised lesions while large epithelial defects will benefit from a thorough debridement and/or early keratectomy, before secondary microbial infection may occur.     

Equine insect bite hypersensitivity: what do we know?

Insect bite hypersensitivity (IBH) is an allergic dermatitis of the horse caused by bites of insects of the genus Culicoides and is currently the best characterized allergic disease of horses. This article reviews knowledge of the immunopathogenesis of IBH, with a particular focus on the causative allergens. Whereas so far hardly any research has been done on the role of antigen presenting cells in the pathogenesis of IBH, recent studies suggest that IBH is characterized by an imbalance between a T helper 2 (Th2) and regulatory T cell (T(reg)) immune response, as shown both locally in the skin and with stimulated peripheral blood mononuclear cells. Various studies have shown IBH to be associated with IgE-mediated reactions against salivary antigens from Culicoides spp. However, until recently, the causative allergens had not been characterized at the molecular level. A major advance has now been made, as 11 Culicoides salivary gland proteins have been identified as relevant allergens for IBH. Currently, there is no satisfactory treatment of IBH. Characterization of the main allergens for IBH and understanding what mechanisms induce a healthy or allergic immune response towards these allergens may help to develop new treatment strategies, such as immunotherapy.