BackgroundDehorning is a common practice involving calves on dairy operations in the United States. However, less than 20% of producers report using analgesics or anesthetics during dehorning. Administration of a systemic analgesic drug at the time of dehorning may be attractive to dairy producers since cornual nerve blocks require 10 – 15 min to take effect and only provide pain relief for a few hours. The primary objectives of this trial were to (1) describe the compartmental pharmacokinetics of meloxicam in calves after IV administration at 0.5 mg/kg and (2) to determine the effect of meloxicam (n = 6) or placebo (n = 6) treatment on serum cortisol response, plasma substance P (SP) concentrations, heart rate (HR), activity and weight gain in calves after scoop dehorning and thermocautery without local anesthesia.ResultsPlasma meloxicam concentrations were detectable for 50 h post-administration and fit a 2-compartment model with a rapid distribution phase (mean T½α = 0.22 ± 0.087 h) and a slower elimination phase (mean T½β = 21.86 ± 3.03 h). Dehorning caused a significant increase in serum cortisol concentrations and HR (P < 0.05). HR was significantly lower in the meloxicam-treated calves compared with placebo-treated calves at 8 h (P = 0.039) and 10 h (P = 0.044) after dehorning. Mean plasma SP concentrations were lower in meloxicam treated calves (71.36 ± 20.84 pg/mL) compared with control calves (114.70 ± 20.84 pg/mL) (P = 0.038). Furthermore, the change in plasma SP from baseline was inversely proportional to corresponding plasma meloxicam concentrations (P = 0.008). The effect of dehorning on lying behavior was less significant in meloxicam-treated calves (p = 0.40) compared to the placebo-treated calves (P < 0.01). Calves receiving meloxicam prior to dehorning gained on average 1.05 ± 0.13 kg bodyweight/day over 10 days post-dehorning compared with 0.40 ± 0.25 kg bodyweight/day in the placebo-treated calves (p = 0.042).ConclusionsTo our knowledge, this is the first published report examining the effects of meloxicam without local anesthesia on SP, activity and performance of calves post-dehorning. These findings suggest that administration of meloxicam alone immediately prior to dehorning does not mitigate signs of acute distress but may have long term physiological, behavior and performance effects.

SAL administered PO through drinking water decreased cortisol concentrations and reduced the decrease in ADG associated with castration and dehorning in calves.

Insufficient diagnostic sensitivity and specificity coupled with the potential for cross-reactivity among closely related Anaplasma species has made the accurate determination of infection status problematic. A method for the development of simplex and duplex real-time quantitative reverse transcriptase PCR (qRT-PCR) assays for the detection of A. marginale and A. phagocytophilum 16S rRNA in plasma-free bovine peripheral blood samples is described. The duplex assay was able to detect as few as 100 copies of 16S rRNA of both A. marginale and A. phagocytophilum in the same reaction. The ratio of 16S rRNA to 16S DNA copies for A. marginale was determined to be 117.9:1 (95% confidence interval [95% CI], 100.7:1, 135.2:1). Therefore, the detection limit is the minimum infective unit of one A. marginale bacterium. The duplex assay detected nonequivalent molar ratios as high as 100-fold. Additionally, the duplex assay and a competitive enzyme-linked immunosorbent assay (cELISA) were used to screen 237 samples collected from herds in which anaplasmosis was endemic. When the cELISA was evaluated by the results of the qRT-PCR, its sensitivity and specificity for the detection of A. marginale infection were found to be 65.2% (95% CI, 55.3%, 75.1%) and 97.3% (95% CI, 94.7%, 99.9%), respectively. A. phagocytophilum infection was not detected in the samples analyzed. One-and two-way receiver operator characteristic curves were constructed in order to recommend the optimum negative cutoff value for the cELISA. Percentages of inhibition of 20 and 15.3% were recommended for the one-and two-way curves, respectively. In conclusion, the duplex real-time qRT-PCR assay is a highly sensitive and specific diagnostic tool for the accurate and precise detection of A. marginale and A. phagocytophilum infections in cattle.

Needle-free injection was superior to needle injection for the control of iatrogenic transmission of A marginale.

Chemosterilization is reported in cattle fed chlortetracycline hydrochloride (CTC) at dosages ranging from 1.1mg/kg for 120 days to 11 mg/kg for 30-60 days. The relationship between plasma CTC drug concentration and carrier clearance has not been described. Chronic carrier status was established in 21 steers with a Virginia isolate of Anaplasma marginale and confirmed by cELISA and an A. marginale-specific RT-PCR. Four negative, splenectomized steers served as active disease transmission sentinels. Steers were randomized to receive 4.4 mg/kg/day (LD); 11 mg/kg/day (MD); or 22 mg/kg/day (HD) of oral chlortetracycline; or placebo (CONTROL) for 80 days. The LD, MD and HD treatment groups consisted of 5 infected steers and 1 splenectomized steer; CONTROL group had six infected steers and 1 splenectomized steer. The daily treatments and ration were divided equally and fed twice daily. Blood samples were collected semi-weekly for determining plasma drug concentration by ultrahigh performance liquid chromatography-mass spectrometry/mass spectrometry method and assessment of disease status by both cELISA and RT-PCR. Mean (CV%) chlortetracycline plasma drug concentrations in the LD, MD, and HD groups were 85.3 (28%), 214.5 (32%) and 518.9 (40%)ng/mL during days 4 through 53 of treatment. A negative RT-PCR assay result was confirmed in all CTC-treated groups within 49 days of treatment; however, cELISA required an additional 49 to 88 days before similar results. Subinoculation of splenectomized steers confirmed chemosterilization. These results are important for influencing future chemosterilization strategies and impacting free trade policy among countries and regions of contrasting endemicity.