Objective--To describe the simple elimination kinetics of methyllycaconitine (MLA) and deltaline and evaluate the heart rate response in cattle following oral administration of larkspur. Animals--5 healthy Angus steers that were habituated to metabolism crates. Procedures--Tall larkspur (Delphinium barbeyi) in the early flowering stage was collected, dried, and ground. Each steer received a single dose of larkspur that was equivalent to 10.4 mg of MLA/kg and 11.0 mg of deltaline/kg via oral administration. Steers were housed in metabolism crates during a 96-hour period following larkspur administration; heart rate was monitored continuously, and blood samples were collected periodically for analysis of serum MLA and deltaline concentrations as well as assessment of pharmacokinetic parameters. Results--No overt clinical signs of poisoning developed in any steer during the experiment. Mean ± SE heart rate reached a maximum of 79.0 ± 5.0 beats/min at 17 hours after larkspur administration. Serum MLA concentration was correlated directly with heart rate. Mean times to maximal serum concentration of MLA and deltaline were 8.8 ± 1.2 hours and 5.0 ± 0.6 hours, respectively. Mean elimination half-life values for MLA and deltaline were 20.5 ± 4.1 hours and 8.2 ± 0.6 hours, respectively. Conclusions and Clinical Relevance--Following larkspur administration in 5 healthy steers, maximum serum concentrations of MLA and deltaline were detected within 10 hours, and changes in serum MLA concentration and heart rate were correlated. Results indicated that cattle that have consumed larkspur will eliminate 99% of MLA and deltaline from serum within 144 hours.

Objective--To determine whether larkspur-derived N-(methylsuccinimido) anthranoyllycoctonine (MSAL)-type alkaloids alter heart rate and electrically evoked electromyographic (eEMG) response of the external anal sphincter (EAS) in cattle and whether these effects can be reversed by acetylcholinesterase inhibitors. Animals--12 beef heifers and 4 cows. Procedures--3 or 4 heifers were used in 1 or 2 of 7 dose-response experiments; heart rate and EAS eEMG response were assessed before and 24 hours after oral treatment with larkspur (doses equivalent to 0.5 to 15 mg of MSAL-type alkaloids/kg). In 3 subsequent experiments, 3 heifers (1 of which was replaced with another heifer in the control experiment) each received 10 mg of MSAL-type alkaloids/kg and were injected IV with physostigmine (0.04 mg/kg), neostigmine (0.04 mg/kg), or saline (0.9% NaCl) solution 24 hours later, prior to assessment. Additionally, EAS eEMG response was measured in 4 cows before and after epidural administration of 2% lidocaine hydrochloride. Results--Larkspur-treated heifers developed dose-related increases in heart rate and decreases in EAS eEMG response. Twenty-four hours after administration of MSAL-type alkaloids, neostigmine decreased heart rate but did not affect eEMG response, whereas physostigmine did not affect heart rate but caused a 2-fold increase in eEMG response. In cows, epidural anesthesia did not alter eEMG response, suggesting that transdermal stimulation of the EAS pudendal innervation did not occur. Conclusions and Clinical Relevance--In cattle, cardiac effects and muscle weakness or loss of EAS eEMG response induced by larkspur-derived MSAL-type alkaloids were reversed by neostigmine or physostigmine, respectively. Treatment with anticholinesterase inhibitors may alter the clinical effects of larkspur poisoning in cattle.

To evaluate economic effects and health and performance of the general cattle population after exposure to cattle persistently infected (PI) with bovine viral diarrhea virus (BVDV) in a feedlot. 21,743 high-risk calves from the southeastern United States. PI status was determined by use of an antigen-capture ELISA (ACE) and confirmed by use of a second ACE, reverse transcriptase-PCR assay of sera, immunohistochemical analysis, and virus isolation from sera. Groups with various amounts of exposure to BVDV PI cattle were used. After being placed in the feedlot, identified PI cattle were removed from 1 section, but PI cattle remained in another section of the feedlot. Exposure groups for cattle lots arriving without PI animals were determined by spatial association to cattle lots, with PI animals remaining or removed from the lot. 15,348 cattle maintained their exposure group. Performance outcomes improved slightly among the 5 exposure groups as the risk for exposure to BVDV PI cattle decreased. Health outcomes had an association with exposure risk that depended on the exposure group. Comparing cattle lots with direct exposure with those without direct exposure revealed significant improvements in all performance outcomes and in first relapse percentage and mortality percentage in the health outcomes. Economic analysis revealed that fatalities accounted for losses of $5.26/animal and performance losses were $88.26/animal. This study provided evidence that exposure of the general population of feedlot cattle to BVDV PI animals resulted in substantial costs attributable to negative effects on performance and increased fatalities.

To determine whether an anti-Salmonella bacterium is involved in control of pathogen load in persistently infected cattle herds. 24 Holstein calves experimentally infected and 39 Holstein cows naturally infected with Salmonella spp. An Escherichia coli (designated as P8E5) that possessed anti-Salmonella activity was isolated from Salmonella-negative bovine feces obtained from a herd with endemic Salmonella infection. In vitro analysis involved enumerating Salmonella enterica serovar Typhimurium coincubated with E coli P8E5. In vivo analysis involved coadministration of Salmonella spp and E coli P8E5 or an E coli control strain to neonatal Holstein calves. Fecal samples were collected on multiple days after inoculation, and quantitative PCR assay was performed by use of Salmonella-specific primers. E coli P8E5 reduced viability of Salmonella spp in vitro. Shedding of Salmonella organisms was diminished in calves administered E coli P8E5, whereas the control strain of E coli had no effect on shedding of Salmonella organisms. In this study, an E coli strain was identified that possessed bacteriocin-like activity and was able to decrease viability of Salmonella organisms in vitro and in vivo. Therefore, it is possible that this organism could be representative of native microbiota that dampen Salmonella spp in persistently infected cattle herds.