About

Jennifer Halleran is an assistant professor at North Carolina State University College of Veterinary Medicine. She is originally from New Jersey and holds a B.S. in Animal Science and Microbiology from the University of Rhode Island. She earned her Doctor of Veterinary Medicine (DVM) degree from Colorado State University in 2014. Following her veterinary degree, she completed a ruminant health internship at North Carolina State University and a large animal internal medicine residency at Oklahoma State University. She became a diplomate of the American College of Veterinary Internal Medicine Large Animal in 2019. Subsequently, she completed a PhD in Infectious Disease at NC State University. Her research focuses on enteric bacteria and their antimicrobial resistance profiles in large animals, contributing to the understanding of infectious diseases and antimicrobial resistance in veterinary medicine.

Research topics

• Microbiology
• Medicine
• Pharmacology
• Internal medicine
• Biology
• Veterinary medicine
• Bioinformatics

Selected publications

• Four-site distal paravertebral blocks improve physiologic indicators of analgesia in the immediate postoperative period as opposed to a 3-site distal paravertebral block

  Journal of the American Veterinary Medical Association · 2025-08-01

  article

  Objective: To determine differences in surgical and postoperative analgesia between 3-site distal paravertebral (DPV) blocks and modified 4-site DPV blocks. Methods: 12 healthy dairy or dairy cross steers were randomized into 1 of 2 treatments, 3-site DPV block (3DPV) or 4-site DPV block (4DPV); 2 mg/kg of 2% lidocaine was administered at each site-lumbar vertebrae 1, 2, and 4 in the 3DPV group (6 mg/kg), and an additional injection at lumbar vertebrae 3 for the 4DPV group (8 mg/kg). Heart and respiratory rates, temperature, reaction scores, and surgical condition scores were collected. Postoperative pain scores and physiologic data were collected for 24 hours following surgery. An ordinal logistic mixed-effects model was used to compare surgical conditions, reaction scores, and pain scores. A linear mixed-effects model was used for normally distributed data. Results: The success rate of 3DPV blockade was 5 of 6 (83%), and that for 4DPV was 6 of 6 (100%). Only 11 steers were included in the data analysis due to the failed block. The 4DPV group had lower respiratory rates following the return to stall (32 ± 3 vs 44 ± 4 breaths/min; P < .019). Additionally, the 4DPV group had significantly lower heart rates immediately following the return to the stall (62 ± 8 vs 88 ± 9 beats/min; P < .036). No differences in pain scores or intraoperative conditions were identified. Conclusions: Adding an injection site at L3 in a DPV reduced postoperative heart rate and respiratory rate in steers following laparotomy. Clinical Relevance: Adding a fourth injection site at L3 decreases physiologic indicators of postoperative discomfort.

  PublisherDOI

• Investigating the Pharmacokinetics and Efficacy of Intramammary Ceftiofur Hydrochloride in Prevention of Udder Inflammation in Non‐Lactating Dairy Heifers

  Journal of Veterinary Pharmacology and Therapeutics · 2025-04-21 · 1 citations

  articleOpen access

  Mastitis is the most burdensome concern for the dairy cattle industry. Antimicrobials are often prophylactically administered to dairy cows at dry-off to reduce the risk of intramammary infection during the dry period and subsequent lactation. Mastitis incidence has increased in dairy heifers after calving, leading to extralabel drug use of various dry cow products, including intramammary ceftiofur hydrochloride. However, the pharmacokinetics and efficacy of this application have yet to be studied. This study aimed to compare the pharmacokinetics and efficacy following no treatment, a non-antimicrobial teat sealant, or a single dose of intramammary ceftiofur given at 21 or 14 days before expected calving. We hypothesized that milk collected following dosing would contain drug residues below the FDA tolerance of 100 ng/mL by calving, and heifers within the ceftiofur treatment groups would have lower somatic cell counts (SCCs) than heifers in the teat sealant and nontreatment control groups. Following treatment or no treatment of 24 prepartum heifers, milk samples were collected until 21 days after calving. Somatic cell counts and ceftiofur concentrations were assessed utilizing a cell counter and UPLC/MS detection, respectively. Ceftiofur administration did not significantly reduce SCCs compared to other groups by days 7, 14, or 21. For heifers treated 14 and 21 days prior to calving, milk had a maximum ceftiofur concentration of 8.14 ± 6.24 and 4.20 ± 5.07 ng/mL 48 h into lactation, respectively. The minimal ceftiofur concentrations in milk collected from these heifers indicate that administration of ceftiofur 14 or 21 days before calving is unlikely to lead to violative residues. However, it is essential that regional regulations regarding the use of ceftiofur are adhered to.

  PublisherOA PDFDOI

• Pharmacokinetics of Intravenous and Transdermal Flunixin Meglumine in Wool and Hair Sheep ( <i>Ovis aries</i> )

  Journal of Veterinary Pharmacology and Therapeutics · 2025-08-01

  articleOpen access

  The objective of the study was to evaluate the pharmacokinetics of flunixin meglumine of intravenous (IV) and transdermal (TD) flunixin meglumine administration on different coat types (wool vs. hair) in 12 healthy sheep. Polled dorset (wool) sheep (n = 6) and katahdin (hair) sheep (n = 6) received 2.2 mg/kg IV and 3.3 mg/kg TD with a 10-day washout period between treatments. Plasma samples were obtained for 96 h following both IV and TD administration, respectively. Flunixin concentrations were quantified by use of high-performance liquid chromatography with mass spectrometry, and PK parameters were derived using different modeling techniques. A population non-linear mixed effect model showed that coat type has a significant effect on the absorption rate following TD administration. The mean bioavailability of TD flunixin was not significantly different (48.76% ± 17.49% and 36.61% ± 4.33%; p = 0.093) in wool and hair sheep, respectively. Maximum plasma concentrations following TD administration were higher in wool sheep (1.57 μg/mL; range, 0.6-3.41 μg/mL) compared to hair sheep (0.57 μg/mL; range, 0.36-0.83 μg/mL). The PK results provide further support for clinical studies to examine the efficacy of TD flunixin in different breeds of sheep.

  PublisherOA PDFDOI

• Pharmacokinetics of Orally Administered Phenazopyridine in Goats With Obstructive Urolithiasis

  Journal of Veterinary Internal Medicine · 2025-06-26

  articleOpen accessSenior authorCorresponding

  BACKGROUND: Phenazopyridine is used for ancillary pain management in the treatment of goats with obstructive urolithiasis. However, there are no published studies on the pharmacokinetics, safety, or efficacy of phenazopyridine in goats. HYPOTHESIS/OBJECTIVES: Determine the pharmacokinetic parameters of phenazopyridine after oral administration in goats with obstructive urolithiasis after tube cystostomy surgery. ANIMALS: Six male goats, ages 3 months to 4 years. METHODS: Prospective, observational study. Goats presenting to a veterinary institution diagnosed with obstructive urolithiasis underwent a tube cystostomy surgery. After surgery, phenazopyridine (4 mg/kg PO q12h) was administered. Plasma and urine samples were collected at predetermined intervals, and the concentration of phenazopyridine and clinically relevant metabolites was determined using ultra high-performance liquid chromatography with mass spectrometry. The pharmacokinetic parameters were determined using non-compartmental analysis. RESULTS: ), and area under the curve (AUC) were 0.5 h (0.22-1.57 h), 263.4 ng/mL (137.35-1047.88 ng/mL), and 0.69 h*ng/mL (0.10-2.99 h*ng/mL), respectively for phenazopyridine. The concentration of phenazopyridine in urine samples was below the limit of assay detection (1.5 ng/mL) in all but one sample. CONCLUSIONS AND CLINICAL IMPORTANCE: Phenazopyridine was rapidly eliminated from plasma and did not concentrate at detectable levels in the urine after oral administration.

  PublisherOA PDFDOI

• Pharmacokinetics of Ampicillin Trihydrate in Plasma, Interstitial, and Peritoneal Fluid Following Intraperitoneal or Intramuscular Administration in Steers at the Beginning of a Standing Flank Laparotomy

  Journal of Veterinary Pharmacology and Therapeutics · 2025-09-04

  articleOpen access

  Prophylactic and perioperative use of antibiotics is common prior to abdominal surgery in cattle for minimizing the risk of postoperative infections. Yet, there is little information on drug concentrations at sites of potential infections following surgical procedures. The objective of this study was to compare the concentrations in the plasma, peritoneal fluid, and interstitial fluid of ampicillin trihydrate in cattle. In a randomized design, ampicillin trihydrate, a β-lactam antibiotic, was administered to 12 healthy Holstein-Friesian steers intraoperatively via intraperitoneal (IP; n = 6) or intramuscular (IM; n = 6) injection in the cervical neck muscles at 11 mg/kg for both groups. For IP administration, ampicillin trihydrate was deposited into the abdominal cavity following an incision in the right paralumbar fossa. Steers in the IM group were administered ampicillin prior to surgical closure. Peritoneal fluid and interstitial fluid were collected using ultrafiltration probes. IP administration achieved higher concentrations in peritoneal fluid as compared to IM administration. Maximum plasma concentrations were significantly higher following IP administration (3.11 ± 2.5 μg/mL; p < 0.004) compared to the IM group (0.05 ± 10.9 μg/mL). Despite high peritoneal fluid concentrations of ampicillin, the variability in critical pharmacokinetic parameters following IP administration raises concerns about its therapeutic reliability. The correlation between intraperitoneal drug concentrations and clinical efficacy warrants further investigation.

  PublisherOA PDFDOI

• Impact of florfenicol dosing regimen on the phenotypic and genotypic resistance of enteric bacteria in steers

  Scientific Reports · 2024-02-28 · 4 citations

  articleOpen access1st authorCorresponding

  The food animal sector's use of antimicrobials is heavily critiqued for its role in allowing resistance to develop against critically important antimicrobials in human health. The WHO recommends using lower tier antimicrobials such as florfenicol for disease treatment. The primary objective of this study was to assess the differences in resistance profiles of enteric microbes following administration of florfenicol to steers using both FDA-approved dosing regimens and two different detection methods. Our hypothesis was that we would identify an increased prevalence of resistance in the steers administered the repeated, lower dose of florfenicol; additionally, we hypothesized resistance profiles would be similar between both detection methods. Twelve steers were administered either two intramuscular (20 mg/kg q 48 h; n = 6) or a single subcutaneous dose (40 mg/kg, n = 6). Fecal samples were collected for 38 days, and E. coli and Enterococcus were isolated and tested for resistance. Fecal samples were submitted for metagenomic sequencing analysis. Metagenomics revealed genes conferring resistance to aminoglycosides as the most abundant drug class. Most multidrug resistance genes contained phenicols. The genotypic and phenotypic patterns of resistance were not similar between drug classes. Observed increases in resistant isolates and relative abundance of resistance genes peaked after drug administration and returned to baseline by the end of the sampling period. The use of a "lower tier" antimicrobial, such as florfenicol, may cause an increased amount of resistance to critically important antimicrobials for a brief period, but these changes largely resolve by the end of the drug withdrawal period.

  PublisherOA PDFDOI

• Validation of a reference interval for symmetric dimethylarginine in healthy goats and its comparison to values in goats with obstructive urolithiasis

  Journal of Veterinary Internal Medicine · 2024-08-17 · 1 citations

  articleOpen accessSenior author

  BACKGROUND: Symmetric dimethylarginine (SDMA), a sensitive biomarker for detecting renal injury, has not been characterized in goats. Obstructive urolithiasis (OU) is the most common urinary tract disease in male small ruminants. HYPOTHESIS/OBJECTIVE: Establish an SDMA reference interval (RI) in healthy adult goats and describe SDMA concentrations in goats with OU. We hypothesize that the SDMA RI in healthy adult goats will be similar to that of other adult veterinary species and that SDMA can be utilized to assess the renal function of goats experiencing OU. ANIMALS: Fifty-five healthy adult male and female goats from a university herd were enrolled for SDMA RI development. Twenty male and female goats from a university herd were enrolled for validation of the SDMA RI established. Thirteen male goats diagnosed with OU were enrolled. METHODS: Clinical trial. Serum samples for all animals enrolled were collected and analyzed for SDMA using an immunoassay (IDEXX Laboratories, Inc); goats with OU had additional blood work analyzed (PCV, total solids, and serum biochemistry). Symmetric dimethylarginine and other values in goats with OU were analyzed and compared at specific time points. RESULTS: The SDMA RI for healthy, adult goats is 8.03 μg/dL (90% CI 4.81-11.04) to 25.93 μg/dL (90% CI 22.88-28.97). There was no correlation identified between serum creatinine and SDMA in goats with OU. CONCLUSIONS AND CLINICAL IMPORTANCE: The SDMA RI for adult goats is higher than in other adult large animal species. Use of SDMA in goats with OU is not useful in assessing their renal function.

  PublisherOA PDFDOI

• Continuous sampling of healthy and mastitic quarters of lactating cattle by ultrafiltration after intramammary ceftiofur hydrochloride administration

  Journal of Veterinary Internal Medicine · 2024-08-12 · 2 citations

  articleOpen access

  BACKGROUND: Pharmacological activity of intramammary drugs depends on adequate drug concentrations within the cistern, but sampling is often limited. Insight into the active drug concentration within the mammary cistern may assist in determining effective and appropriate therapeutic decisions for cows being treated for mastitis. OBJECTIVE: Evaluate the disposition of ceftiofur hydrochloride administered intramammary in diseased and nondiseased quarters. Whole milk and ultrafiltrate sampling techniques were compared. ANIMALS: Ten mature, late lactation Holstein (n = 9) and Jersey (n = 1) dairy cows (422-670 kg) with naturally occurring clinical mastitis, producing between 1.4 and 15.9 kg/day of milk. METHODS: Ultrafiltration probes were placed in both mastitic and healthy quarters. Each quarter was treated with 2 doses of 125 mg ceftiofur hydrochloride suspension, and whole milk and milk ultrafiltrate samples were collected. Ceftiofur concentrations in composite whole milk and milk ultrafiltrate were analyzed. RESULTS: The maximum concentration of ceftiofur was higher in ultrafiltrate samples, but no differences were identified in healthy or mastitic quarters. The use of ultrafiltration probes provides a novel technique for free drug concentrations within the mastitic and healthy bovine mammary gland. CONCLUSIONS AND CLINICAL IMPORTANCE: Significant inter- and intracow variability and lower daily milk weights may overestimate ceftiofur concentrations available within the cistern. The pharmacokinetic (PK) parameters reported in milk ultrafiltrate will help establish a link between the PK and the corresponding drug effect, potentially providing a meaningful rationale for the selection of a safe and effective dose in cows with mastitis.

  PublisherOA PDFDOI

• Pharmacokinetics of oral phenazopyridine in goats with obstructive urolithiasis

  Texas A&M University Libraries · 2024-05-08

  articleOpen accessSenior author

  Phenazopyridine, an azo dye and urinary bladder analgesic widely used in human medicine, is commonly used for ancil­lary pain management in the treatment of goats with obstruc­tive urolithiasis. Despite its common use in these patients, there are no published studies on the pharmacokinetic param­eters, safety, or efficacy of phenazopyridine in caprine patients. The aim of this study was to determine the pharmacokinetic pa­rameters of oral phenazopyridine administration in goats with obstructive urolithiasis following tube cystostomy surgery

  PublisherDOI

• Pharmacokinetics of pradofloxacin, florfenicol, and tulathromycin and response to treatment of steers experimentally infected with <i>Mannheimia hemolytica</i>

  Journal of Veterinary Internal Medicine · 2024-12-10 · 2 citations

  articleOpen access

  BACKGROUND: Bovine respiratory disease (BRD) is an economically important disease in the beef industry, and a major driver of therapeutic antibiotic use. Pharmacokinetic data of these drugs is relatively limited in diseased animals. HYPOTHESIS/OBJECTIVE: To determine the concentrations of pradofloxacin, florfenicol, and tulathromycin in the airways, plasma, and interstitial fluid (ISF) of steers with a clinically relevant model of bacterial respiratory disease. ANIMALS: Twenty-four Holstein and Holstein/Jersey cross steers ranging in age from 6 to 15 months. METHODS: A randomized, blinded clinical trial was performed. After transport stress, steers were inoculated with Mannheimia hemolytica to induce BRD. Upon onset of clinical disease, steers were treated with pradofloxacin, florfenicol or tulathromycin. Blood, ISF, and pulmonary epithelial lining fluid (PELF) samples were obtained for drug concentration determination. Clinical exams and thoracic ultrasound examinations were conducted daily. Animals were euthanized at the end of the study period to assess lung lesions. RESULTS: was 0.9 μg/mL (45.03%) and PELF penetration was 518.97% (56.59%). CONCLUSIONS AND CLINICAL IMPORTANCE: There are differences in penetration of the drugs into the ISF and PELF compared to one another and previous data from healthy steers demonstrating the effect of disease on the PK of these drugs.

  PublisherOA PDFDOI

Frequent coauthors

• Derek M. Foster

  North Carolina State University

  19 shared

• Megan E. Jacob

  North Carolina State University

  11 shared

• Ronald E. Baynes

  North Carolina State University

  10 shared

• Timo Prange

  North Central State College

  8 shared

• Hannah J. Sylvester

  North Carolina State University

  6 shared

• Mark G. Papich

  North Carolina State University

  6 shared

• Benjamin J. Callahan

  North Carolina State University

  5 shared

• Juliano Coelho da Silveira

  Universidade de São Paulo

  4 shared

Education

• Doctor of Veterinary Medicine, College of Veterinary Medicine

  Colorado State University

  2014

• B.S. in Animal Science and Microbiology, College of Environmental and Life Sciences

  University of Rhode Island

  2010