Efficacy of ketamine hydrochloride administered as a basilar sesamoid nerve block in alleviating foot pain in horses caused by natural disease.

REASONS FOR PERFORMING STUDY: A local anaesthetic agent capable of temporarily resolving lameness after being administered perineurally would be helpful because rapid return of lameness would allow for other analgesic techniques to be performed within a short period of time. OBJECTIVES: To determine if a 3% solution of ketamine hydrochloride (HCl), administered around the palmar nerves at the level of the base of the proximal sesamoid bones, can improve naturally occurring lameness that can be improved or abolished with a basilar sesamoid nerve block performed using lidocaine HCl and to compare the change in gait produced using lidocaine to the change in gait produced using ketamine by using objective lameness assessment. STUDY DESIGN: Experimental trial using research horses with naturally occurring lameness. METHODS: Seven horses, chronically lame on a thoracic limb, were chosen for the study. A wireless, inertial, sensor-based, motion analysis system was used to evaluate lameness before and after administration of 2% lidocaine and later, before and after administration of 3% ketamine over the palmar digital nerves at the base of the proximal sesamoid bones (a basilar sesamoid nerve block) at 5 min intervals for 30 min. Lameness scores obtained before and after administration of lidocaine and ketamine HCl were compared using repeated measures analysis. RESULTS: Gait significantly improved after basilar sesamoid nerve blocks using 2% lidocaine, but gait did not significantly improve after performing the same nerve block using 3% ketamine HCl. CONCLUSIONS: Ketamine (3%) administered perineurally for regional anaesthesia of the digit does not desensitise the digit to the same extent as does lidocaine and thus 3% ketamine appears to have no value as a local anaesthetic agent for diagnostic regional anaesthesia.

Function of the ramus communicans of the medial and lateral palmar nerves of the horse.

REASONS FOR PERFORMING STUDY: The role of the communicating branch between the medial and lateral palmar nerves of horses (i.e. the ramus communicans) in conveying sensory impulses proximally should be determined to avoid errors in interpreting diagnostic anaesthesia of the palmar nerves. HYPOTHESIS: Sensory nerve fibres in the ramus communicans of horses pass proximally from the lateral palmar nerve to merge with the medial palmar nerve, but not vice versa. OBJECTIVE: To determine the direction of sensory impulses through the ramus communicans between lateral and medial palmar nerves. METHODS: Pain in a thoracic foot was created with set-screw pressure applied to either the medial or lateral aspect of the sole of each forelimb of 6 horses. The palmar nerve on the side of the sole in which pain was created was anaesthetised proximal to the ramus communicans with local anaesthetic. Lameness was evaluated objectively by using a wireless, inertial, sensor-based, motion analysis system (Lameness Locator). Lameness was also evaluated subjectively by using a graded scoring system. Local anaesthetic was then administered adjacent to the ramus communicans to determine the effect of anaesthesia of the ramus communicans on residual lameness. RESULTS: When pain originated from the medial or the lateral aspect of the sole, anaesthesia of the ipsilateral palmar nerve proximal to the ramus communicans did not entirely resolve lameness. Anaesthesia of the ramus communicans further attenuated or resolved lameness. CONCLUSIONS: Sensory fibres pass in both directions in the ramus communicans to connect the medial and lateral palmar nerves. POTENTIAL RELEVANCE: When administering a low palmar nerve block, both palmar nerves should be anaesthetised distal to the ramus communicans to avoid leaving nondesensitised sensory nerve fibres passing through this neural connection. Alternatively, local anaesthetic could also be deposited adjacent to the ramus communicans when anaesthetising the palmar nerves.

Pharmacokinetics of amikacin in plasma and selected body fluids of healthy horses after a single intravenous dose.

REASONS FOR PERFORMING STUDY: No studies have determined the pharmacokinetics of low-dose amikacin in the mature horse. OBJECTIVES: To determine if a single i.v. dose of amikacin (10 mg/kg bwt) will reach therapeutic concentrations in plasma, synovial, peritoneal and interstitial fluid of mature horses (n=6). METHODS: Drug concentrations of amikacin were measured across time in mature horses (n=6); plasma, synovial, peritoneal and interstitial fluid were collected after a single i.v. dose of amikacin (10 mg/kg bwt). RESULTS: The mean±s.d. of selected parameters were: extrapolated plasma concentration of amikacin at time zero 144±21.8 µg/ml; extrapolated plasma concentration for the elimination phase 67.8±7.44 µg/ml, area under the curve 139±34.0 µg*h/ml, elimination half-life 1.34±0.408 h, total body clearance 1.25±0.281 ml/min/kg bwt; and mean residence time (MRT) 1.81±0.561 h. At 24 h, the plasma concentration of amikacin for all horses was below the minimum detectable concentration for the assay. Selected parameters in synovial and peritoneal fluid were maximum concentration (Cmax) 19.7±7.14 µg/ml and 21.4±4.39 µg/ml and time to maximum concentration 65±12.2 min and 115±12.2 min, respectively. Amikacin in the interstitial fluid reached a mean peak concentration of 12.7±5.34 µg/ml and after 24 h the mean concentration was 3.31±1.69 µg/ml. Based on a minimal inhibitory concentration (MIC) of 4 µg/ml, the mean Cmax:MIC ratio was 16.9±1.80 in plasma, 4.95±1.78 in synovial fluid, 5.36±1.10 in peritoneal fluid and 3.18±1.33 in interstitial fluid. CONCLUSIONS: Amikacin dosed at 10 mg/kg bwt i.v. once a day in mature horses is anticipated to be effective for treatment of infection caused by most Gram-negative bacteria. POTENTIAL RELEVANCE: Low dose amikacin (10 mg/kg bwt) administered once a day in mature horses may be efficacious against susceptible microorganisms.

Efficacy of moxidectin against cyathostomins after long-term use in a large herd of draught horses with a high stocking density.

This study was undertaken to determine whether resistance to moxidectin had developed in a large herd of draught horses, maintained on a small acreage, which had been routinely treated with moxidectin for five years. Faeces were collected for egg counts immediately before moxidectin gel was administered orally, and seven, 30, 60 and 90 days later. The faecal egg counts were significantly reduced at seven and 30 days after treatment, but were not significantly different from pretreatment counts at 60 and 90 days after treatment. There was no evidence of resistance having developed.

Antimicrobial resistance and genotypic characterization of coagulase-negative staphylococci over the dry period.

Coagulase-negative staphylococci (CNS) have become the most frequently isolated organisms from bovine intramammary infections in recent years. While antimicrobial resistance (AR) is not considered a major problem among mastitis pathogens, concerns over emerging AR in general are increasing worldwide. Little information exists about the association between AR and one of the most common mastitis control measures, antibiotic dry cow therapy. The primary objective of the current study was to determine the prevalence of AR in CNS isolated before and after antimicrobial dry cow therapy. An additional objective was to genotypically characterize selected CNS isolates using pulsed-field gel electrophoresis (PFGE), to assess diversity and persistence of organisms over the dry period. Resistance against 10 antimicrobials was determined using a broth microdilution method and compared between CNS isolates collected at dry-off and at calving and from cows treated or not treated with intramammary antimicrobial products at dry-off (752 cows in total). Results suggested that increasing age of a cow and dry cow treatment when combined with high milk somatic cell count at dry-off and positive clinical mastitis history, were associated with increased AR to most beta-lactam antimicrobials and sulfadimethoxine. PFGE results suggested considerable diversity among the tested isolates as well as some clusters within cows and herds. PFGE would be useful in distinguishing between potentially persisting infections and cures and reinfections with different CNS strains.

Effects of analgesia of the digital flexor tendon sheath on pain originating in the sole, distal interphalangeal joint or navicular bursa of horses.

REASON FOR PERFORMING STUDY: Specific analgesic techniques are required in diagnosis of lameness to isolate the exact origin of pain to the many structures of the foot that may be involved. OBJECTIVE: To determine if analgesia of the digital flexor tendon sheath (DFTS) results in anaesthesia of other portions of the foot, such as the sole, distal interphalangeal joint (DIPJ), or navicular bursa (NB). METHODS: Lameness caused by pain in the dorsal margin or heel region of the sole of the foot was induced in 18 horses by: using set-screws to create solar pressure (Trial 1: n = 5); or administering endotoxin intrasynovially into the DIPJ (Trial 2: n = 6) and NB (Trial 3: n = 7). The gait of each horse was evaluated by examining videotape recorded before and after creation of lameness and after administration of mepivacaine hydrochloride into the DFTS. RESULTS: Median lameness scores in Trial 1 at 10 min post injection of the DFTS were not significantly different from those before administration of local anaesthetic solution into the DFTS (P> or =0.05), but median lameness scores were reduced significantly at 20 min (P< or =0.05). In Trials 2 and 3, median lameness scores were not significantly different at observations made at 10 and 20 min post injection of the DFTS. CONCLUSIONS: Analgesia of the DFTS has little effect on lameness caused by pain originating in the sole, DIPJ or NB. POTENTIAL RELEVANCE: Improvement of lameness in horses after intrasynovial analgesia of the DFTS is probably caused by attenuation of pain within the structures contained in the DFTS.

Concentration of methylprednisolone in the centrodistal joint after administration of methylprednisolone acetate in the tarsometatarsal joint.

REASONS FOR PERFORMING STUDY: The centrodistal (CD) and tarsometatarsal (TMT) joints are often injected individually with a corticosteroid to resolve lameness caused by osteoarthritis (OA). There are no data available regarding diffusion of methylprednisolone (MP) from the TMT joint to the CD joint. HYPOTHESIS: A therapeutic concentration of MP diffuses into the CD joint after methylprednisolone acetate (MPA) is administered into the TMT joint. OBJECTIVE: To measure the concentration of MP in the CD joint after MPA was administered into the TMT joint. METHODS: MPA was administered into a TMT joint of 16 horses. At different times, the ipsilateral CD joint of these horses was injected with a small amount of saline and recovered saline was measured for concentration of MP using high performance liquid chromatography. RESULTS: Six hours after administration of MPA into the TMT joint, a therapeutic concentration of MP was found in all 10 CD joints sampled at this time. CONCLUSIONS: Horses with pain arising from the distal 2 joints of the hock can be treated by administering MPA into the TMT joint alone. POTENTIAL RELEVANCE: Administering MPA into the TMT joint only, to treat OA of the distal 2 hock joints, reduces the difficulties and risks associated with centesis of the CD joint.

Effect of anaesthesia of the palmar digital nerves on proximal interphalangeal joint pain in the horse.

REASONS FOR PERFORMING STUDY: Anaesthesia of the palmar digital nerves is claimed to attenuate lameness in some horses that are lame because of pain in the proximal interphalangeal (PIP) joint. OBJECTIVE: To determine the response of horses with pain in the PIP joint to anaesthesia of the palmar digital nerves. METHODS: Horses were video recorded trotting before and after induction of pain in the PIP joint and 10 mins after anaesthesia of the palmar digital nerves. The palmar digital nerves were anaesthetised 3 times at different sites, and the video recorded gaits were scored subjectively. RESULTS: The median lameness score of gaits after administration of 2% mepivacaine 1 cm proximal to the cartilages of the foot was not significantly different from the median lameness score before anaesthesia of the palmar digital nerves (P > or = 0.05), although that of 1 of 6 horses improved markedly. The median lameness score was significantly (P < or = 0.05) improved after mepivacaine was administered 2 and 3 cm proximal to the cartilages of the foot. CONCLUSIONS: The PIP joint is unlikely to be anaesthetised when the palmar digital nerves are anaesthetised at the proximal margin of the cartilages of the foot. POTENTIAL RELEVANCE: Pain within the PIP joint cannot be excluded as a cause of lameness when lameness is attenuated by anaesthesia of the palmar digital nerves at any site proximal to the proximal margin of the cartilages of the foot.

The effects of local anaesthetic solution in the navicular bursa of horses with lameness caused by distal interphalangeal joint pain.

REASONS FOR PERFORMING STUDY: Analgesia of the palmar digital (PD) nerves has been demonstrated to cause analgesia of the distal interphalangeal (DIP) joint as well as the sole. Because the PD nerves lie in close proximity to the navicular bursa, we suspected that that analgesia of the navicular bursa would anaesthetise the PD nerves, which would result in analgesia of the DIP joint. OBJECTIVES: To determine the response of horses with pain in the DIP joint to instillation of local anaesthetic solution into the navicular bursa. METHODS: Lameness was induced in 6 horses by creating painful synovitis in the DIP joint of one forefoot by administering endotoxin into the joint. Horses were videorecorded while trotting, before and after induction of lameness, at three 10 min intervals after instilling 3.5 ml local anaesthetic solution into the navicular bursa and, finally, after instilling 6 ml solution into the DIP joint. Lameness scores were assigned by grading the videorecorded gaits subjectively. RESULTS: At the 10 and -20 min observations, median lameness scores were not significantly different from those before administration of local anaesthetic solution into the navicular bursa (P > or = 0.05), although lameness scores of 3 of 6 horses improved during this period, and the 20 min observation scores tended toward significance (P = 0.07). At the 30 min observation, and after analgesia of the DIP joint, median lameness scores were significantly improved (P < or = 0.05). CONCLUSIONS: These results indicate that pain arising from the DIP joint can probably be excluded as a cause of lameness, when lameness is attenuated within 10 mins by analgesia of the navicular bursa. POTENTIAL RELEVANCE: Pain arising from the DIP joint cannot be excluded as a cause of lameness when lameness is attenuated after 20 mins after analgesia of the navicular bursa.

Quantitative detection of Chlamydia spp. by fluorescent PCR in the LightCycler.

Quantitative detection of intracellular bacteria of the genus Chlamydia by the standard cell culture method is cumbersome and operator dependent. As an alternative, we adapted hot-start PCR to the glass capillary quantitative PCR format of the LightCycler. The optimized PCR was consistently more efficient than commercially available pre-assembled PCRs. Detection by quantitative PCR of as few as single copies of DNA of Chlamydia spp. was accomplished by SYBR Green fluorescence of the dsDNA product and by fluorescence resonance energy transfer (FRET) hybridization probes. The PCRs were 15-fold more sensitive than the cell culture quantitative assay of C. psittaci B577 infectious stock. The number of chlamydial genomes detected by C. psittaci B577 FRET PCR correlated well with cell culture determination of inclusion forming units (IFUs) (r = 0.96, P < 0.0008). When infected tissue samples were analyzed by cell culture and PCR, the correlation coefficient between IFUs and chlamydial genomes was higher with C. psittaci B577 FRET PCR (r = 0.90, P < 0.0004) than with Chlamydia omp1 SYBR Green PCR (r = 0.85, P < 0.002).

Role of rpoS in acid resistance and fecal shedding of Escherichia coli O157:H7.

Acid resistance (AR) is important to survival of Escherichia coli O157:H7 in acidic foods and may play a role during passage through the bovine host. In this study, we examined the role in AR of the rpoS-encoded global stress response regulator sigma(S) and its effect on shedding of E. coli O157:H7 in mice and calves. When assayed for each of the three AR systems identified in E. coli, an rpoS mutant (rpoS::pRR10) of E. coli O157:H7 lacked the glucose-repressed system and possessed reduced levels of both the arginine- and glutamate-dependent AR systems. After administration of the rpoS mutant and the wild-type strain (ATCC 43895) to ICR mice at doses ranging from 10(1) to 10(4) CFU, we found the wild-type strain in feces of mice given lower doses (10(2) versus 10(3) CFU) and at a greater frequency (80% versus 13%) than the mutant strain. The reduction in passage of the rpoS mutant was due to decreased AR, as administration of the mutant in 0.05 M phosphate buffer facilitated passage and increased the frequency of recovery in feces from 27 to 67% at a dose of 10(4) CFU. Enumeration of E. coli O157:H7 in feces from calves inoculated with an equal mixture of the wild-type strain and the rpoS mutant demonstrated shedding of the mutant to be 10- to 100-fold lower than wild-type numbers. This difference in shedding between the wild-type strain and the rpoS mutant was statistically significant (P

Pharmacokinetics of ibuprofen after intravenous and oral administration and assessment of safety of administration to healthy foals.

OBJECTIVE: To determine pharmacokinetics of ibuprofen in healthy foals and to determine clinical effects after oral administration for 6 days. ANIMALS: 7 healthy 5- to 10-week-old foals. PROCEDURE: Serum concentrations of ibuprofen were measured after IV and oral (nasogastric tube) administration at dosages of 10 and 25 mg/kg of body weight. Foals were given ibuprofen (25 mg/kg, PO, q 8 h) as a paste for 6 days. Serum and urine were obtained before and after the 6-day period. RESULTS: Half-life of elimination (Kel t1/2) of IV-administered ibuprofen (ie, 10 and 25 mg/kg), was 79 and 108 minutes, maximal serum concentration (C(MAX)) was 82 and 160 microg/ml, and clearance was 0.003 and 0.002 L/kg/min, respectively. At the higher dosage, clearance was significantly lower and C(MAX) was significantly higher. Ibuprofen given via nasogastric tube resulted in Kel t1/2 of 81 and 100 minutes and C(MAX) of 22 and 52 microg/ml for 10 and 25 mg/kg, respectively. The absorption half-life was 13 minutes, and bioavailability ranged from 71 to 100%. Foals remained healthy during oral administration of ibuprofen. Serum urea nitrogen, creatinine, and L-iditol dehydrogenase values increased significantly, and gamma-glutamyltransferase (GGT) activity and osmolality decreased, but all measurements remained within reference ranges. Urine GGT activity doubled. Necropsy did not reveal gross or histologic renal lesions attributable to ibuprofen. Acute gastric ulcers were evident in 1 foal, although clinical signs of ulcers were not observed. CONCLUSIONS AND CLINICAL RELEVANCE: Ibuprofen can be given safely to healthy foals at dosages < or = 25 mg/kg every 8 hours for up to 6 days.

Stereospecific pharmacokinetics of free and protein-bound ketoprofen in serum and synovial fluid of horses after intravenous and intramuscular administration.

OBJECTIVE: To determine intravascular and intrasynovial pharmacokinetics of the R and S enantiomers of ketoprofen after i.v. and i.m. administration to horses. ANIMALS: 6 healthy adult mares. PROCEDURE: Horses were weighed and ketoprofen (2.2 mg/kg of body weight) was administered i.v. Blood and synovial fluid samples were obtained and analyzed for concentrations of the R and S enantiomers by means of a modified reverse-phase stereospecific high-pressure liquid chromatographic method. Three weeks later, the procedure was repeated, except that ketoprofen was given IM. Protein binding of ketoprofen enantiomers was determined by means of ultrafiltration. Nonlinear least squares methods were used to calculate pharmacokinetic parameters. RESULTS: Data obtained after i.v. administration best fit an open, two-compartment model. Mean +/- SD S-to-R serum concentration ratios after i.v. and i.m. administration were 1.36 +/- 0.214 and 1.34 +/- 0.245, respectively. Intrasynovial concentrations of the R and S enantiomers of ketoprofen could be measured for only the first 3 hours after i.v. administration; concentrations were less than the limit of quantification by 4 hours after i.v. administration and at all times after i.m. administration. Extent of protein binding of the R enantiomer was not significantly different from extent of protein binding of the S enantiomer; extent of protein binding did not appear to be concentration dependent. Mean free S-to-free R serum concentration ratios, adjusted for protein binding, after i.v. and i.m. administration were 1.58 and 1.56, respectively. CONCLUSIONS: The R and S enantiomers of ketoprofen are rapidly absorbed and eliminated, have low volumes of distribution, and are highly protein bound.

Evaluation of analgesia induced by epidural administration of medetomidine to cows.

OBJECTIVE: To evaluate analgesic effects after epidural administration of medetomidine to cows, compared with effects of lidocaine hydrochloride and 0.9% NaCl solution. ANIMALS: 6 adult beef cows. PROCEDURE: 3 treatments were administered to each cow, with a 1-week interval between subsequent treatments. Treatments consisted of 5 ml of physiologic saline (0.9% NaCl) solution; 0.2 mg of lidocaine/kg of body weight, not to exceed 100 mg (5 ml); and 15 micrograms of medetomidine/kg, diluted with 0.9% NaCl solution to provide a volume of 5 ml. Epidural injections were given in the first or second coccygeal space. Heart rate, respiratory rate, and arterial blood pressure values were recorded before injection, 5 and 10 minutes after injection, and at 10-minute intervals thereafter. Onset and duration of analgesia, sedation, and ataxia were recorded. A repeated-measures ANOVA was used to detect differences between treatments. RESULTS: Epidural administration of 0.9% NaCl solution did not induce analgesia. Lidocaine induced analgesia within 5 to 20 minutes, which lasted 10 to 115 minutes (mean +/- SD, 43.3 +/- 37.2 minutes). Heart rate decreased during lidocaine-induced analgesia. Heart and respiratory rates decreased, but blood pressure remained unchanged, after medetomidine administration. Medetomidine induced analgesia within 5 to 10 minutes, which lasted 412 +/- 156 minutes. Mild to moderate sedation and moderate ataxia were observed. Two cows became recumbent, but were easily coaxed to stand. Medetomidine-induced salivation and increased frequency of urination were observed in all cows. CONCLUSIONS AND CLINICAL RELEVANCE: Epidural administration of medetomidine induced prolonged analgesia that was suitable for perineal surgery, postoperative analgesia, and relief of continuous straining.

Sedative effects of medetomidine and its reversal by atipamezole in llamas.

OBJECTIVE: To determine a dose of medetomidine that will induce sedation in llamas, to assess effects of medetomidine sedation on arterial blood gas variables, and to determine efficacy of atipamezole in reversing medetomidine-induced sedation. DESIGN: Prospective, randomized clinical trial. ANIMALS: 15 clinically normal adult llamas. PROCEDURE: 9 llamas received various doses of medetomidine (0.01, 0.02, or 0.03 mg/kg [0.005, 0.009, or 0.014 mg/lb] of body weight, i.m.). Heart and respiratory rates and sedative effects were recorded. Using the lowest dose that induced deep sedation, 6 different llamas were used to assess effects of medetomidine on arterial blood gas variables. These same 6 llamas were later given atipamezole (0.125 mg/kg [0.057 mg/lb], i.v.) 30 minutes after medetomidine injection. Heart and respiratory rates, sedative effects, and time from atipamezole injection to standing were recorded. RESULTS: Sedation began 6.67 +/- 1.15 minutes (mean +/- SD) after medetomidine administration (0.03 mg/kg, i.m.). Arterial blood gas variables measured 30 and 60 minutes after injection were not different from baseline. Llamas that did not receive atipamezole remained recumbent for 91.50 +/- 24.68 minutes. After atipamezole administration, llamas were able to stand in 5.80 +/- 3.27 minutes. CLINICAL IMPLICATIONS: Medetomidine induced light to deep sedation in a dose-dependent manner in clinically normal llamas. A dose of 0.03 mg/kg induced deep sedation with a short period of analgesia. Atipamezole rapidly reversed effects of medetomidine, and llamas recovered quickly and were soon able to stand.

Use of synthetic antigens improves detection by enzyme-linked immunosorbent assay of antibodies against abortigenic Chlamydia psittaci in ruminants.

Synthetic peptide antigens were prepared for use in enzyme-linked immunosorbent assays (ELISAs) to detect serum antibodies against abortigenic strains of Chlamydia psittaci in livestock. Peptide antigens were identified with C. psittaci B577-immune sera by solid-phase scanning of overlapping octapeptides of variable domains (VDs) of the major outer membrane protein of C. psittaci serovar 1 (omp1 type C. psittaci B577). Two VD 4 regions and one VD 2 region were strongly reactive with all C. psittaci B577 antisera. Peptides encompassing these regions were synthesized with biotin and a serine-glycine-serine-glycine spacer at the N terminus and were attached to streptavidin-coated microtiter plates. In direct ELISAs with these plates, the synthetic peptides reacted with C. psittaci B577 antisera, but not with sera from specific-pathogen-free animals. Serum specimens from 40 sheep and 40 cattle, obtained from herds with abortion problems, were screened for antibodies by these C. psittaci B577 peptide ELISAs and an ELISA with recombinant, genus-specific Chlamydia lipopolysaccharide (LPS) antigen. Results from these newly developed ELISAs were compared to those from the reference C. psittaci B577 elementary body (EB) ELISA and the Chlamydia complement fixation test (CFT). The C. psittaci B577 peptide ELISAs, the LPS ELISA, and the EB ELISA correctly identified the presence or absence of antibodies against chlamydiae in all sheep and bovine sera. The Chlamydia CFT, which is the most widely accepted serodiagnostic method for chlamydial infections in animals, correctly identified the presence or absence of antibodies against chlamydiae in only 78 and 4.9% of sheep and bovine sera, respectively. These results suggest that the C. psittaci B577-peptide and Chlamydia LPS ELISAs are superior for the serodiagnosis of ruminant infections with abortigenic chlamydiae, since they are more sensitive than the CFT, they are easy to standardize, and they use readily available synthetic antigens instead of organism-derived CFT antigen.

Clinical and clinicopathologic effects of large doses of raw linseed oil as compared to mineral oil in healthy horses.

The clinical and clinicopathologic effects of raw linseed oil and mineral oil were compared. In a crossover experimental design trial, 6 horses were given either raw linseed oil (2.5 mL/kg body weight) or mineral oil (10 mL/kg body weight), twice, 12 hours apart. Two weeks later, the horses received the opposite treatment. All horses given mineral oil or linseed oil developed nonformed feces by 24 hours of the first administration of oil. Horses treated with mineral oil had formed feces at 48 hours; horses treated with linseed oil developed normally formed feces at 96 to 108 hours. All horses treated with linseed oil had signs of depression and anorexia, and 3 had signs of mild colic. These signs were not observed in horses treated with mineral oil. Concentrations of serum glucose and bilirubin were significantly higher in horses treated with linseed oil when compared with horses treated with mineral oil.

Pharmacokinetics of caffeine in lactating dairy cows.

Because caffeine is metabolized by the hepatic P-450 cytochrome oxidase system, clearance of caffeine is an excellent quantitative test of hepatic function in human beings. It is currently used in much the same way that creatinine clearance is used to assess renal function. Caffeine clearance was measured in lactating dairy cows initially to determine the suitability of caffeine clearance as an indicator of hepatic function in cattle. Pharmacokinetic variables of caffeine were studied in 6 adult lactating dairy cows after i.v. administration of a single dose of caffeine sodium benzoate (2 mg of caffeine/kg of body weight). Caffeine concentration was analyzed by use of an automated enzyme immunoassay. The lower limit of detection of the assay for caffeine in serum was 0.079 micrograms/ml. Serum caffeine concentration-time curves best fit an open two-compartment pharmacokinetic model. Harmonic mean elimination half-life was 3.8 (range, 2.6 to 6.9) hours, and total clearance was 0.118 (range, 0.090 to 0.197) L/kg/h. Milk caffeine concentration was similar to serum concentration 1.5 to 24 hours after caffeine administration. Adverse effects were not observed in cows given caffeine.