WSU College of Veterinary Medicine senior paper highlights, October 2024

By Thomas LeClair (Advisor: Dr. Margaret Wild)

Summary: Lameness due to hoof diseases is a critical challenge faced by both domestic and wild ruminants, resulting in welfare concerns, production losses, and changes in population dynamics. Over the last fifty years, digital dermatitis diseases have emerged in several species as a significant new source of lameness, with novel diseases being well documented in cattle, sheep, and elk (Cervus canadensis). To date, no specific etiologic agent has been found for any of these diseases, though each is associated with a proliferation of spirochetes of the genus Treponema, along with other changes to the bacterial community. Research on bovine digital dermatitis (BDD) and contagious ovine digital dermatitis (CODD) has resulted in a variety of empiric preventative and treatment options, while research on treponeme-associated hoof disease (TAHD) provides insights on surveillance to complement management actions. Pathogen discovery research is ongoing for all three diseases, with recently developed molecular tools providing new insights on the bacterial species that may be involved in their progression. A deeper understanding of these diseases is crucial to enable better surveillance and treatment, ultimately allowing effective mitigation of their impact on both agriculture and the environment at large.

Conclusions: Treponemes have been associated with a variety of emerging hoof diseases in ruminant species. While they share a collection of treponemes, there is no definitive etiologic agent for any of these diseases and the relationship between the diseases is not fully understood. Recent research on BDD and CODD has largely focused on treatment and prevention, while research on TAHD has focused more on pathogen discovery and epidemiology. Significant opportunities exist for integration of the research between these diseases, particularly with the maturation and increasing accessibility of next generation sequencing technology. Given the presumed polymicrobial basis of each disease, techniques like shotgun metagenomics provide an opportunity to more completely understand the microbial communities of diseased hooves, and the ability to compare them to healthy hooves. More widespread adoption and reporting of the genomes of potential etiologic agents across these diseases will enable researchers to determine if there is a shared cause and can provide better information about the potential of cross-species infection. Building a broader understanding of the root causes and epidemiology of these diseases is a critical step in designing more effective treatments and management plans, which in turn promise significant benefits for animal welfare, food animal productivity, and ecosystem health.

By Brendon Charlton (Advisor: Dr. Salman Waqas)

Summary: Sheep are short-day breeders. The reproductive cycle is under the influence of melatonin, photoperiod and geographical location. Although, not discussed in this review, hormonal and non-hormonal methods to induce reproductive cyclicity for out-of-season breeding exist. This review discusses the differing techniques in superovulation protocols, oocyte pickup (OPU) and maturation which are a prerequisites for in-vitro fertilization to produce embryos. The increased demand for assisted reproductive techniques is described, followed by the selection criteria of ewes. Among many synchronization protocols in sheep, in breeding season hormonal treatment will be discussed. Laparoscopic OPU techniques will be discussed as well. There are two main types of laparoscopic OPU: 1) in vivo insemination and retrieval and 2) OPU from the ovary followed by oocyte maturation. The manuscript discusses the merits of OPU from the ovary. Oocyte maturation has many techniques that involve different medias to achieve the highest rates of fertilization compotent oocytes from immature oocytes. Thus, the aim of this review to discuss super ovulation, laparoscopic OPU and oocyte maturation in sheep.

Conclusions: Assisted reproduction in sheep has demonstrated to decrease the generation interval allowing faster development for trait selections. The techniques discussed in this review are a few of many that aid in this. Progestin-based superstimulation and estrus synchronization protocols are the most common and effective methods. The laparoscopic OPU is a common technique to retrieve the oocytes. The subsequent oocyte grading and maturation is the most pivotal step with the most variability in success rate. Grading oocytes helps get an estimate of the probability of survival, maturation, and embryo production potential. The best oocytes have high mitochondrial activity and an increased number of layers of granulosa cells surrounding them. Maturation has a base media of TCM1 199 that is supplemented with antioxidants to enhance IVM and IVF rates. In-vitro fertilization and embryo transfer are the next steps that are not discussed in this review.

By Caden Colombik (Advisor: Ramanathan Kasimanickam)

Summary: The bovine breeding soundness examination (BSE) is extensively discussed in veterinary literature describing bovine reproduction, theriogenology, and production medicine. A reliable and economic strategy used to screen bulls before their sale or use, it is widely applied to a variety of breeds found throughout different environments all around the world. Though bulls represent only roughly 5% of a herd, they account for over 90% of the herd’s genetics and have a weighted impact on many facets of a production system including breeding percentage, calving interval, and weaning weight. Bulls determined to be fertile through BSEs not only significantly improve production, but also have a significant positive economic impact on the cattle operation.

Conclusions: The breeding soundness examination has a vast effect on both the production and profitability of cow-calf operations by improving the bioeconomic variables of production. It is a low-cost management tool and is an important technological alternative that has proven to benefit beef cattle production. When used correctly, this reproductive assessment positively impacts various aspects of cow-calf operations, including total production, ultimately increasing the overall revenue of the production system.

By Jace Enwards (Advisor: Dr. Craig McConnel)

Summary: Infectious bovine keratoconjunctivitis (IBK), also known as bovine pinkeye, is a disease in cattle that causes significant morbidity and economic loss to the beef and dairy industries. It is one of the most significant eye diseases in cattle and is a problem worldwide. IBK is primarily associated with Moraxella bovis, but recent research has found that it may also be associated with other organisms, such as Moraxella bovoculi and Mycoplasma spp. Additionally, environmental factors such as UV light and face flies have been associated with IBK, indicating that it is likely a multifactorial disease. IBK primarily affects the bovine cornea and causes signs that are similar to other diseases like foreign body ulceration, Chlamydiosis, and infectious bovine rhinotracheitis-associated keratoconjunctivitis. The primary focus of recent research includes vaccination and prevention of IBK. Although vaccination attempts have been successful in laboratories, few studies have found efficacy of vaccinations in the field. Treatment of IBK is relatively easy, and many options have been found that have proven to be efficacious. The primary issues and more recent research areas include vaccination and prevention of IBK. Vaccination attempts have been successful in laboratories, but few studies have found efficacy of vaccinations in the field.

Conclusions: Infectious bovine keratoconjunctivitis (IBK) is an economically significant and extremely common disease in both the beef and dairy industries. IBK has historically been used as a blanket term for ocular disease in cattle, but only recently have definitions been proposed to help define the disease and limit the misdiagnoses caused by using IBK as a blanket term. IBK is primarily considered to be caused by Moraxella bovis, but associations with Moraxella bovoculi and Mycoplasma spp. suggest that IBK is likely a multifactorial disease. Further, the fact that field trials for M. bovis vaccines often fail to show efficacy when efficacy is shown in laboratory studies may also suggest a multifactorial disease that is far more complex than we thought. IBK research has come a long way since the disease was first described, but there are still multiple areas that need further research. Primarily, further research into the true etiology of IBK needs to be investigated to grasp a better understanding of not only how the disease works but what it is. A deeper understanding of the disease will help us create vaccinations that are effective in the field with naturally occurring IBK and will help us increase the accuracy of treatment. Simply understanding the disease and its factors will also help optimize lab-based studies. Also, further research needs to be done on different treatment and prevention modalities that may be efficacious, including bacteriophage therapy. Still, these cannot be effectively researched without a proper understanding of the disease itself.

By Natalie Klinker (Advisor: Dr. Babiche Heil)

Summary: Each domesticated mammal has a unique estrus cycle and a unique mechanism of maternal recognition of pregnancy. Species reproductive cyclicity can be divided based on frequency and timing throughout the year. The three major types of reproductive cyclicity are monoestrous, polyestrous, and seasonally polyestrous. The seasonally polyestrous species are based on photoperiod. The estrous cycle has two major phases, the follicular phase, and the luteal phase. During the follicular phase, follicles are the dominant structure, and estradiol is the dominant hormone. During the luteal phase, luteal tissue is present with progesterone being the dominant hormone. Further, sufficient circulating levels of progesterone is required for maintenance of pregnancy. When no pregnancy is detected by the dam during diestrus, prostaglandin is released causing luteolysis and subsequent decrease in progesterone production, allowing for a new follicular phase to start. To allow pregnancy to succeed, maternal recognition of pregnancy is essential, to prevent a rise in prostaglandin and a subsequent drop in progesterone.

Maternal recognition of pregnancy is species specific: The ruminant blastocyst secretes interferon-tau which is responsible for blocking the synthesis of oxytocin receptors so that oxytocin cannot synthesize prostaglandin. The swine blastocyst secretes estradiol which in turn does not allow prostaglandin to reach high enough levels in circulation. The equine embryo makes extensive contact with the endometrial surface to block prostaglandin function. In felines and canines, there is likely not a specific signal required for maternal recognition of pregnancy given that they have a long period of diestrus which exceeds the length of gestation.

Conclusions: Maintenance of pregnancy is heavily dependent on high levels of circulating progesterone, which the corpus luteum is responsible for secreting. To maintain pregnancy, PGF2α secreted by the endometrium, must be blocked or kept at low circulating level to prevent luteolysis of the corpus luteum. Each species has differences in their estrous cycle and has different mechanisms of maternal recognition of pregnancy. The elongated ruminant blastocyst secretes protein called interferon tau which is responsible for the maternal recognition of pregnancy mechanism. INF-t is specific to ovine (o-INFt) and bovine (b-INFt). INF-t has multiple critical roles including inhibiting the production of oxytocin and aiding in nourishment of the conceptus. Swine are similar to ruminants in that the maternal recognition of pregnancy mechanisms relies on the conceptus for secretion of a substance. The sow’s conceptus secretes estradiol which effectively re-routes PGF2α secreted from the endometrium away from the submucosal capillaries and towards the uterine lumen not allowing PGF2α to reach high enough concentrations in the circulation to cause luteolysis. The mare is unique in the aspect that the embryo does not remain in one location. For the proposed equine maternal recognition of pregnancy mechanism to occur, the conceptus must make extensive contact with the endometrial surface. The equine embryo migrates through the uterine body and each uterine horn due to myometrial contractions. Contact with the endometrial surface prevents the endometrium from producing PGF2α. Canine and feline mechanisms of maternal recognition of pregnancy are alike in the aspect that neither species has a known purposed mechanism. Given that both canine and felines have a long diestrus period and a short gestational length, it is likely that there the lifespan of the corpus luteum responsible for progesterone production is nearly the same as the lifespan of the corpus luteum in the diestrus phase.

By Jessica Johnson (Advisor: Dr. Caio Figueiredo)

Summary: Freemartinism, a condition observed in female calves born from a heterogeneous twin pregnancy, has provided critical insights into reproductive biology and genetics. Early research by Frank Rattray Lillie and Ray Owen revealed that shared placental blood and masculinizing hormones from the male twin have a strong correlation with the presence of XX/XY chimerism and reproductive abnormalities in affected females. This phenomenon involves the interplay of the sex-determining Y gene, which dictates male sexual differentiation, as well as masculine hormonal disruptions that interfere with the normal development of the female reproductive tract. Economically, freemartins pose a challenge for dairy operations, as they are non-productive animals and acquire costs due to their inability to produce milk or viable offspring. Raising a freemartin to first breeding involves substantial costs, and their eventual sale as beef at lower market prices compounds financial losses. Strategies such as using sexed semen to prevent the occurrence of freemartins represent a proactive but costly approach. Future research into blood chimerism holds promise for advancing medical treatments in human medicine, such as in organ transplant recipients, by potentially reducing the need for lifelong immunosuppressive therapy. However, ethical considerations and potential risks must be carefully evaluated. Continued research and technological advancements have been essential for improving the management of freemartinism and exploring its broader applications in science and medicine.

Conclusions: Studying freemartinism has significantly advanced the understanding of reproductive biology and genetics, shedding light on the complex mechanisms underlying this phenomenon. Frank Rattray Lillie’s and Ray Owen’s observations which proposed that shared sex hormones between twin calves masculinize female fetuses and placental blood anastomoses and natural chimerism, have been instrumental in explaining the cause of freemartinism. These early findings revealed how the interplay of male hormones and genetic factors lead to the development of XX/XY blood chimeric animals with various reproductive tract abnormalities.

The genetic and hormonal basis of freemartinism involves the SRY gene, crucial for male sexual differentiation. In freemartins, the presence of male hormones like testosterone and AMH, shared through the placental blood supply, disrupts the normal development of the female reproductive tract. This disruption results in a range of reproductive anomalies, from mildly affected to severely masculinized tracts, ultimately compromising fertility and reproductive function.

Economically, freemartins present a challenge for dairy operations. These non-productive animals lead to financial loss due to their inability to produce milk or viable offspring. The cost of raising a heifer to first lactation becomes a sunk cost if the animal is found to be infertile. Additionally, the culling of freemartins and their sale for beef at lower market prices further exacerbates these losses due to a net negative income on the individual. Strategies such as using sexed semen to prevent the birth of freemartins represent a proactive, albeit more expensive, approach to managing this issue, highlighting the ongoing challenge of balancing operational costs with herd productivity.

Future research into blood chimerism and its potential applications beyond reproduction and dairy operations offers promising avenues for scientific and medical progression. For instance, the possibility of inducing chimerism in organ transplant recipients could revolutionize treatment options by omitting the need for long-term immunosuppressive therapies. However, this approach raises ethical considerations and risks, such as the potential transmission of genetic diseases from donor to recipient. As our understanding of freemartinism continues to evolve and technological innovations advance, both dairy farmers and researchers will benefit from improved strategies to mitigate the economic impacts of freemartins while exploring novel applications of chimerism in broader scientific context.

By Andrew Myer (Advisor: Dr. Ramanathan Kasimanickam)

Summary: Artificial insemination of sheep has vastly increased in popularity as preserved semen has become more readily available. Laparoscopic artificial insemination is considered the gold standard method of artificial insemination in sheep due to low conception rates associated with other methods. Although Laparoscopic artificial insemination involves a higher start-up cost compared to other techniques, it is an economically feasible option. With the continual development of new equipment, techniques, and semen preservation technologies, producers can diversify the genetics of their herd without buying expensive studs that can be aggressive and costly to maintain. When laparoscopic artificial insemination is paired with the correct estrous synchronization protocol, producers can see a higher lambs per ewe ratio, and higher quality lambs that can potentially bring a higher profit margin. Comparative economic analyses were performed to examine the potential benefits of using laparoscopic artificial insemination over trans-cervical artificial insemination. Laparoscopic artificial insemination can offer higher profit margins and higher lambing rates to producers while being a profitable service a veterinary practice can offer to clients.

Conclusions: LAI is a proven method of artificial insemination that offers many benefits over TCAI. There is a modest investment in equipment required, but there is very little overhead costs associated with offering this service. If a practitioner has a sufficient clientele base, most costs associated with equipment can be covered in one breeding season. There are many factors affecting the success of artificial insemination in sheep. Some of these factors include semen quality, semen storage, overall fertility levels, animal management, scheduling, producer compliance, season, and many other factors. It is important to note that many factors can be partially controlled, and risks mitigated. The economic benefits of LAI are clear and should be effectively communicated to potential clients. Offering LAI procedures can add value to veterinary practice and to a producer’s herd.

By Aimee Thompson (Advisor: Dr. Kerry Rood)

Summary: Worldwide there are shortages of veterinarians that serve in rural areas, with an increasing number of animals forgoing veterinary care due to lack of access. In the United States, there are widespread areas that are considered “veterinary deserts”, impacting large and small animals alike. Lack of veterinary care is associated with increased incidence of zoonotic or emerging diseases, misuse of antimicrobials resulting in increased resistance, decreased food safety, making this an extremely important One Health topic. In this paper, I aim to evaluate the implications of lack of rural veterinary care on veterinarians, clients, and patients. From a veterinarian standpoint, factors that influence veterinarians to serve in rural areas (background, exposure to rural) and factors that push veterinarians to more urban areas (emergency duty, salary etc.) will be examined. Client health in response to their animal’s wellbeing is rarely evaluated, but is an important factor to consider, as it directly aligns with the One Health concept. Client health is directly impacted by pet ownership, both positively and negatively in cases of illness. Finally, animal survival in the face of serious illness or trauma when in isolated “veterinary deserts” has largely not been researched. This is in direct opposition of human research into survival outcomes, which has been demonstrated to be directly correlated with proximity to definitive health care. Lack of rural veterinary care plays a direct role on the health and survival of animals. In this paper, I aim to evaluate the existing literature on the implications of lack of veterinary care in rural areas on the veterinarians, factors that influence veterinarians to practice in these areas, client wellbeing, and the implications on animal health.

Conclusions: Lack of rural veterinary care is a complex issue, that spans more than just the health of animals, it directly impacts the health of the clients, community, environment, and also the veterinary professionals. From a veterinarian standpoint, factors such as being raised in a rural background, having livestock experience, and developing an interest early on in life significantly increases the chance that a veterinarian will have interest in serving in rural veterinary areas. Conversely, aspects of rural practice that influence veterinarians to leave include emergency duty, time off, salary, family concerns, and practice atmosphere. Veterinarian well-being is also affected in rural areas, as veterinarians are less likely to have the support of other veterinary professionals causing veterinarians to become overworked leading to higher rates of stress and burnout. Veterinarians are also affected by the client’s financial situation, with many feeling that it limits their ability to provide desired medical care for their patients. This may lead to veterinarians experiencing emotional pain and guilt regarding the treatment of animals in their care.

From a client standpoint, there are multiple barriers they may face when seeking veterinary care for their animals. The most common barriers encountered include financial barriers, hours of operation, geographic location, transportation barriers, equipment for transportation barriers, cultural language issues, and veterinarian client communication. In rural communities geographic and transportation barriers are significant. It is a well-researched fact that poverty rates increase as distance from metropolitan centers increases, which makes financial barriers relevant in rural areas.

Companion animal ownership is known to play a positive role in human well-being, with benefits such as decreased cortisol levels, lower blood pressure, reduced loneliness, increased feelings of social support and mood elevation. Lack of access to veterinary care may lead to animals being surrendered or euthanized prematurely due to clients being unable to overcome barriers to veterinary care. Clients may often carry guilt, that they are unable to provide appropriate veterinary care for their animals.

The effects of losing a human loved one are greatly documented. With up to 95% of households considering their pets as loved ones, it can be argued that losing a pet can have some of the same negative effects as losing a human loved one. Owners who are unable to overcome barriers to veterinary care are significantly more likely to feel stress regarding their pet’s healthcare and experience more poor mental health days per month, than owners who do not face the same barriers. The presence of caregiver burden has been demonstrated in human – animal caregiving situations and is associated with increased levels of anxiety and depression.

Within the five freedoms of animals, the third point is an animal’s “freedom from pain, injury or disease by prevention or rapid diagnosis and treatment”. When barriers to veterinary care are faced, especially geographically, there is a lack of ability to seek rapid veterinary care for prevention, rapid diagnosis and treatment of animal ailments. This is in direct opposition of the third freedom of animals. As a veterinary profession, there is progress to be made in this area.

Lack of veterinary care represents a persistent one health issue, as poor animal health is directly correlated with the health of humans and the environment. Lack of veterinary care could lead to an increased risk of zoonotic and emerging diseases, animals forgoing preventative care, increasing antimicrobial resistance and lack of rapid treatment in the face of illness. Furthermore, 47 out of the 50 states have been identified as lacking enough veterinarians to meet the state’s food animal population, directly endangering the safety of the human food supply.

Animal health outcomes are directly influenced by the presence or lack of veterinary care services. When animal health programs are introduced into areas with geographic barriers, there are multiple positive health influences seen within the animals in that area. Although, survival outcomes of animals have not been evaluated in rural veterinary deserts, this topic has been extensively researched from the human side. It is widely known that survival of people significantly decreases if they are not able to receive care within an hour of life threatening injuries. With this information, it can be hypothesized that animal survival outcomes may be similar or possibly worse in similar situations, due to the fact that it often takes longer to recognize illness and that not all veterinary care can adequately handle life threatening animal emergencies.

Lack of veterinary care in rural areas is a persistent one health concern. Although there are steps being taken to try to recruit veterinarians into rural areas, we are still seeing detrimental effects of lack of care in these areas. As a veterinary profession, further research into this topic is much needed and needs to be addressed. Something as simple as doing outreach clinics within these rural areas could significantly improve the One Health status of these communities. As a 4th year veterinary student hailing from a severe rural veterinary shortage area, I have firsthand experience – both personal and observed – of the implications that lack of care has on the community, veterinarians, clients, and animals. In rural veterinary shortage areas, the consequences can be dire and also carry heavy emotional burden to those directly involved, therefore making this a pressing ethical issue within the veterinary field.