Ionophores.

Ionophores are a class of polyether antibiotics that are commonly used as anticoccidial agents and growth promotants in ruminant diets. Ionophores transport ions across lipid membranes and down concentration gradients, which results in mitochondrial destruction, reduced cellular energy production, and ultimately cell death. Cardiomyocytes are the primary target in equine patients when exposed to toxic concentrations and the clinical disease syndrome is related to myocardial damage. Animals can survive acute exposures but can have permanent heart damage that may result in acute death at future time points. Animals that survive a poisoning incident may live productive breeding lives, but physical performance can be greatly impacted. Animals with myocardial damage are at risk of sudden death and pose a risk to riders.

Blue Green Algae.

Blue green algae cyanotoxins have become increasingly more prevalent due to environmental, industrial, and agricultural changes that promote their growth into harmful algal blooms. Animals are usually exposed via water used for drinking or bathing, though specific cases related to equines are very limited. The toxic dose for horses has not been determined, and currently only experimental data in other animals can be relied upon to aid in case interpretation and treatment. Treatment is mostly limited to supportive care, and preventative control methods to limit exposures are more likely to aid in animal health until more research has been performed.

Presumptive hepatogenous photosensitization in beef cattle winter grazing a cover crop containing Brassica spp. turnips.

Over a period of ~2 wk, 5 adult beef cows developed severe necrotizing skin lesions on the face and neck shortly after being moved to a field with a cover crop of Brassica spp. turnips. We describe here the clinical signs, hematology, and serum chemistry results, as well as gross and histopathologic findings, from this outbreak. We made a presumptive diagnosis of Brassica-associated liver disease (BALD) based on the similarities in the history and diagnostic findings observed with previously reported cases of BALD from elsewhere in the world. BALD has not been reported previously in cattle in North America, to our knowledge, despite the increasing usage of cover crops to improve soil conditions and provide forage for livestock. After the presumptive diagnosis of BALD was made, the cattle were removed from the turnip field and no additional cases were noted by the producer. BALD is well known in other parts of the world, and veterinarians and diagnosticians should be aware of this condition given that the usage of cover crops is likely to continue to increase.

Pharmacokinetics, Milk Residues, and Toxicological Evaluation of a Single High Dose of Meloxicam Administered at 30 mg/kg per os to Lactating Dairy Cattle.

Adverse effects associated with overdose of NSAIDs are rarely reported in cattle, and the risk level is unknown. If high doses of NSAIDs can be safely administered to cattle, this may provide a longer duration of analgesia than using current doses where repeated administration is not practical. Meloxicam was administered to 5 mid-lactation Holstein dairy cows orally at 30 mg/kg, which is 30 times higher than the recommended 1 mg/kg oral dose. Plasma and milk meloxicam concentrations were determined using high-pressure liquid chromatography with mass spectroscopy (HPLC-MS). Pharmacokinetic analysis was performed by using noncompartmental analysis. The geometric mean maximum plasma concentration (Cmax) was 91.06 µg/mL at 19.71 h (Tmax), and the terminal elimination half-life (T1/2) was 13.79 h. The geometric mean maximum milk concentration was 33.43 µg/mL at 23.74 h, with a terminal elimination half-life of 12.23 h. A thorough investigation into the potential adverse effects of a meloxicam overdose was performed, with no significant abnormalities reported. The cows were humanely euthanized at 10 d after the treatment, and no gross or histologic lesions were identified. As expected, significantly higher plasma and milk concentrations were attained after the administration of 30 mg/kg meloxicam with similar half-lives to previously published reports. However, no identifiable adverse effects were observed with a drug dose 30 times greater than the industry uses within 10 days of treatment. More research is needed to determine the tissue withdrawal period, safety, and efficacy of meloxicam after a dose of this magnitude in dairy cattle.

Mineral-salt supplementation to ameliorate larkspur poisoning in cattle.

Larkspurs (Delphinium spp.) are native forbs that are poisonous to cattle and cost livestock producers millions of dollars in losses each year. Macro and micro minerals are required for normal functioning of essentially all metabolic processes in ruminants. The role that mineral status may play in larkspur poisoning in cattle is not clear. In this study, we seek to determine the effects a mineral-salt supplement, commonly used by cattle producers, to potentially reduce cattle losses to larkspur. The ability of mineral-salt supplementation to alter susceptibility to larkspur toxicosis was evaluated in a pen study. Animals supplemented with mineral-salt were found to be less susceptible to larkspur poisoning than the non-supplemented animals. A separate group of animals were then grazed on larkspur infested rangelands. One group was supplemented with a mineral-salt mix and the other group did not receive any mineral-salt. Supplementing cattle with the mineral-salt mix did not alter larkspur consumption (P > 0.05). However, overall larkspur consumption was low and averaged 3 ± 1.0% and 2 ± 1.1% for cattle supplemented with mineral and non-supplemented, respectively. Serum was collected from animals once a week during the grazing study. Average and maximum serum concentrations of toxic larkspur alkaloids were numerically higher in mineral-salt supplemented cattle compared with the non-supplemented animals. Results from the pen study suggest that a good mineral supplementation program will provide a protective effect for animals grazing in larkspur-infested ranges. The mineral-salt supplemented steers, in the grazing study, were not observed to consume less larkspur than the non-supplemented animals; however, the mineral-salt supplemented animals had higher concentrations of larkspur alkaloids in their serum indicating they may be able to tolerate higher larkspur consumption. The data also indicate that mineral-salt supplementation must be continuous throughout the time the animals are grazing these rangelands as the positive effects can be lost within 30 d post supplementation.

Larkspurs (Delphinium spp.) are native forbs poisonous to cattle and cost livestock producers millions of dollars in losses each year. The role mineral status may play in larkspur poisoning in cattle is unclear. The ability of mineral-salt supplementation to alter susceptibility to larkspur toxicosis was evaluated in a pen and grazing study. In the pen study, animals supplemented with mineral-salt were found to be less susceptible to larkspur poisoning than non-supplemented animals. A separate group of animals grazed on larkspur infested rangelands. One group was supplemented with a mineral-salt mix and the other group did not receive any mineral-salt. Supplementing cattle with the mineral-salt mix did not alter larkspur consumption of grazing cattle. However, overall larkspur consumption was low. Results from the pen study suggest that a good mineral supplementation program will provide a protective effect for animals grazing in larkspur-infested ranges. The mineral-salt supplemented steers, in the grazing study, had higher concentrations of larkspur alkaloids in their blood serum indicating they may be able to tolerate higher larkspur consumption. The data also indicate that mineral-salt supplementation must be continuous throughout the time the animals are grazing as the positive effects can be lost within 30 days after supplementation.