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WSU ag senior paper highlights, summer 2023

Regenerative Agriculture: A veterinary guide to integrative control of GI parasites in pastured livestock

By Emily Love (Advisor: Dr. Jennifer Sexton)

Summary

Since the organic movement, other sustainable practices have also become widespread such as regenerative agriculture. The focus of regenerative agriculture is in improving soil health and resilience through grazing. Producers commonly avoid chemical inputs not just to their land, but also in management of their livestock. Since gastrointestinal nematodes are a significant concern in pastured animal production, but anthelmintics are not an option, management practices are the primary tool for reducing parasitism. The objective of this paper is to provide information for veterinarians working with producers utilizing non-chemotherapeutic parasite mitigation. A review of integrative parasite control in pastured animals will follow with a focus on enteric nematodes in temperate climates affecting sheep, goats, cattle, and swine. Strategies explored will include grazing systems, forage utilization, and herd management.

Conclusions

In conclusion, decades of research already validate several non-chemotherapeutic strategies for mitigation of nematode infections. Even for producers willing to use traditional anthelmintics, a veterinarian’s knowledge of integrative controls can help slow the development of resistant parasites. Comprehensive understanding of GIN ecology and epidemiology paired with rotational grazing management of diverse pastures can reduce livestock exposure and boost defenses. Use of specialized bioactive forages may increase host resistance and resilience during infection, and even potentially impair developing larvae. These may be benefitted by herd systems that include selective breeding and stock selection, administration of copper oxide wire particles, and nematophagous fungi. While not comprehensive, the present report highlights important options for addressing parasitism in pastured livestock. For additional resources about sustainable and regenerative agriculture, please see the provided resources below.

Lop, lop, snip, snip, sizzle. That’s gotta hurt! How are we doing managing pain in cattle

By Emily Violini (Advisor: Dr. John Wenz)

Summary

Commonly performed painful procedures in beef and dairy calves include the practice of disbudding, dehorning, castration, and branding. Reasons to perform these procedures include concerns for human health and safety, ensuring carcass value, legally binding animal identification, and managing herd dynamics. There are many ways to perform each procedure, each with its list of pros and cons. The sum of discussion is that the methods we use to brand, castrate, and dehorn/disbud our bovines are all painful in some way or form. Consensus statements from both the American Veterinary Medical Association (AVMA) and American Association of Bovine Practitioners (AABP) are that they should be performed at the earliest age possible and should be performed with adequate analgesia. Despite these recommendations, using analgesia for these procedures varies in compliance. Access to analgesia is limited to producers due to the lack of FDA approved drugs for the control of pain in food animals. There is currently only one drug with a label for the use of pain management in calves, and all other drugs are considered extra label drug use (ELDU). ELDU requires more veterinary oversight and the establishment of proper protocol to ensure the withdrawal times are followed. This is just one barrier to proper analgesia implementation, including cost, producer perceptions of pain, and the logistics/timing of drug administration. While the administration of adequate analgesia may seem to lie solely in the hands of producers, a review of the problem reveals a multifaceted issue that lies at the junction of government, veterinarian, and producer. As food animal veterinarians, we are compelled to utilize our knowledge and expertise to break down these barriers in order to ensure the welfare of our patients while maintaining a safe and secure food supply.

Conclusions

While the administration of adequate analgesia may seem to lie solely in the hands of producers, a review of the problem reveals a multifaceted issue that lies at the junction of government, veterinarian, and producer. Food animal veterinarians are compelled to utilize our knowledge and expertise to break down these barriers in order to ensure the welfare of our patients while maintaining a safe and secure food supply. The lack of economic incentives are a difficult barrier to the implementation of adequate analgesia for our patients, but the social benefits in the eyes of the consumer are invaluable. Methods for low-cost, effective analgesia exist and utilizing those should be the standard for all food animal veterinarians. By making analgesia a part of the standard of care an example can be set for producers, creating an industry that shows that it values animal welfare in all stages of life. Food animal veterinarians assume the duty as advocates for their patients, as well as ensuring safe and secure food supply.

Common diseases in backyard flocks: Laying hens

By Paloma Beyer (Advisor: Dr. Marcie Logsdon)

Summary

More and more families across the United States are deciding to raise their flock of birds for egg production. The experience level of these bird raisers varies, from the experienced small farmers to families that have never been around livestock. Compared to the commercial industry, producer expectations, goals, and biosecurity levels differ in a backyard flock. The human-animal bond varies among different flocks. Some have a mixed view of their chickens as pets and livestock, while many others see them more as pets that also provide eggs. Most common diseases these birds may face are related to improper management or biosecurity.

Conclusions

The common thread among all these diseases is that prevention strategies are better than treatment, which typically entails good biosecurity, cleanliness, and management. Unfortunately, there is a wide range of biosecurity, management, and sanitation practices among backyard poultry owners. And they are not typically seeking out veterinary professionals for preventative care advice before their chickens become ill. Chickens are a vital part of the food animal industry, and backyard flocks are at risk of becoming a reservoir of disease that can potentially affect the commercial industry. Therefore, veterinary professionals need to be well informed and better prepared to communicate with owners of backyard chickens.

Differential gene expression in peripheral leukocytes of pre-weaned Holstein heifer calves with respiratory disease

By Lily Elder (Advisor: Dr. Craig McConnel)

Summary

Bovine respiratory disease (BRD) is a leading cause of calf morbidity and mortality, and prevalence remains high despite current management practices. Differential gene expression (DGE) provides detailed insight into individual immune responses and can illuminate enriched pathways and biomarkers that contribute to disease susceptibility and outcomes. The aims of this study were to investigate differences in peripheral leukocyte gene expression in Holstein preweaned heifer calves 1) with and without BRD, and 2) across weeks of age. Calves were enrolled for this short-term longitudinal study on two commercial dairies in Washington State. Calves were assessed every two weeks throughout the pre-weaning period using clinical respiratory scoring (CRS) and thoracic ultrasonography (TUS), and blood samples were collected. Calves were selected that were either healthy (n = 10) or had BRD diagnosed by CRS (n = 7), TUS (n = 6), or both (n = 6) in weeks 5 or 7 of life). Three consecutive time point samples were analyzed for each BRD calf consisting of PRE, ONSET, and POST samples. Nineteen genes of interest were selected based on previous gene expression studies in cattle: ALOX15, BPI, CATHL6, CXCL8, DHX58, GZMB, HPGD, IFNG, IL17D, IL1R2, ISG15, LCN2, LIF, MX1, OAS2, PGLYRP1, S100A8, SELP, and TNF. Comparisons were made between age and disease time point matched BRD and healthy calves as well as between calf weeks of age. No DGE was observed between diseased and healthy calves; however, DGE was observed between calf weeks of age regardless of disease state. Developmental differences in leukocyte gene expression, phenotype, and functionality make pre-weaned calves immunologically distinct from mature cattle, and early life shifts in calf leukocyte populations likely contribute to the age-related gene expression differences we observed. Age overshadows disease impacts to influence gene expression in young calves, and immune development progresses upon a common trajectory regardless of disease during the preweaning period.

Conclusions

Nineteen genes that are candidate biomarkers of inflammatory disease in postweaned and adult cattle were not differentially expressed in pre-weaned Holstein heifer calves with BRD. However, differential expression was observed relative to calf age between three and nine weeks of life. Factors related to age and immune system development overshadow disease impacts to influence gene expression patterns in young calves, and immune development progresses upon a common trajectory during the preweaning period regardless of respiratory disease. https://doi.org/10.1371/journal.pone.0285876

Regulatory involvement throughout highly pathogenic Avian Influenza outbreak

By Claire Stein (Advisor: Dr. Craig McConnel)

Summary

Avian Influenza (AI) is a viral infection that circulates among wild birds. The United States Department of Agriculture (USDA) considers the disease a Foreign Animal Disease when it becomes recognized in domestic poultry as a highly pathogenic strain, causing mortality in greater than 75% of poultry. The virus is spread across migratory flyways by wild birds, increasing infections across both wild and domestic bird populations. A presumptive or confirmed positive sample among domestic birds must be reported to the appropriate animal health authority, the State Veterinarian. The facility becomes an infected premises by definition of a confirmed positive result and is dealt with according to USDA guidelines. Guidelines include quarantine, rapid depopulation, cleaning/disinfecting (or 120-day fallow), and surveillance. The effort to contain the virus and prevent further spread is coordinated between the State and USDA. Strict biosecurity is the most effective method to avoid exposing poultry to the virus. Biosecurity practices include both structural boundaries and operational protocols such as footbaths and handwashing. Vaccination is rarely used as a method to prevent illness in poultry, as there is not yet an effective way to determine between infected and vaccinated birds. Many United States trade partners that import poultry or poultry products typically require poultry to be unvaccinated for this reason. Avian Influenza outbreak in domestic flocks has a range of impacts, including possible zoonoses, threat to wildlife, and major US trade markets.

Conclusions

The impact of Avian Influenza is extensive. It has potential to impact global trade, market prices, commercial business, and human, avian, and wildlife health. Due to this, domestic poultry with symptoms of Avian Influenza warrant a thorough investigation, which is far beyond the scope of an individual clinician. State and Federal agricultural agencies have the highest authorities during a disease investigation, and it is their responsibility to control the disease for the sake of trade and health. It is also the responsibility of these agencies to prevent the entrance of a Foreign Animal Disease into the US. HPAI is preventable with enhanced biosecurity practices. Measures such as development of an effective DIVA (Differentiate Infected from Vaccinated Animals) vaccine may be necessary in the future as AI becomes more endemic.

Comparative diagnoses of respiratory disease in preweaned dairy calves using sequential thoracic ultrasonography and clinical respiratory scoring

By Holly Hinnant (Advisor: Dr. Craig McConnel)

Summary

Bovine respiratory disease (BRD) has serious impacts on dairy production and animal welfare. It is most commonly diagnosed based on clinical respiratory signs (CRS), but, in recent years, thoracic ultrasonography (TUS) has emerged as a diagnostic with improved sensitivity and specificity. In this study, 60 calves on two farms were followed from the 2nd week of life through the 12th week of life and assessed on a weekly basis for lung consolidation on ultrasound and CRS. Data points were then grouped based on progression of disease seen on TUS and alignment with CRS was assessed. Receiver operator curves and area under the curves were combined with Cohen’s kappa, sensitivity, and specificity to assess alignment of CRS against TUS consolidation. This study aimed to look at the dynamics of lung consolidation seen with TUS and alignment with CRS on a week-by-week basis. Furthermore, it aimed to assess how severity of lung consolidation impacts CRS alignment. Results showed that CRS aligned best with TUS lesions that were considered lobar (TUS score ≥3, lesion >1cm wide and full lobar thickness) and were at the onset of consolidation (first week seeing consolidation). There was an acceptable level of discrimination for this comparison (AUC=0.76), and fair agreement (kappa=0.28) with a sensitivity of 39% and specificity of 93%. Alignment dropped slightly with addition of less severe consolidation (TUS score=2, consolidation >1cm wide but not full lobar thickness) to acceptable discrimination (AUC=0.71), fair agreement (kappa=0.27), sensitivity of 30% and specificity of 94%. Overall, CRS showed fair agreement and acceptable discrimination at best, though this alignment decreased as consolidation became chronic or recovered. This indicates that CRS may not be an accurate representation of the true amount of BRD present in pre-weaned dairy heifers.

Conclusions

The major finding of this study was that the best alignment between CRS and TUS was at onset of lobar consolidation determined by TUS (AUC=0.76, kappa=0.28, Se=39%, Sp=3%). Even though this is the best alignment found in the study it is still only acceptable discrimination per the AUC and fair alignment per the kappa, indicating that CRS does not provide a representative snapshot of BRD in a population. Additionally, this study found that there was a slight decrease in alignment when lobular consolidation (TUS=2) was included in the diseased population (AUC=0.71, kappa=0.27, Se= 0.30, Sp=0.94).