Norgestomet- and oestradiol valerate-induced luteolysis is dependent upon the uterus.

Beef heifers were assigned to three groups: (1) untreated controls (n=4), (2) Syncro-Mate B(R) (SMB)-treated (n=5), and (3) hysterectomized and SMB-treated (n=4). SMB was administered 8 or 9 days after oestrus, approximately 30 days after hysterectomy. This study was conducted to determine if the uterus was necessary for SMB to induce luteolysis. SMB induced premature luteolysis as only 20% of the intact SMB-treated heifers had >/=0.75 ng/ml of progesterone 7 days after the time of SMB treatment, compared to all (100%) of the untreated heifers (p<0.05). By 9 days after the time of SMB treatment, 25% of the untreated heifers and none (0%) of the intact SMB-treated heifers had >/=0.75 ng/ml of progesterone; however, all (100%) of the hysterectomized SMB-treated heifers had >/=0.75 ng/ml of progesterone (p<0.05). Therefore, SMB-induced luteolysis required the involvement of the uterus. The luteolysin, prostaglandin F(2alpha), is probably the secretion from the uterus that mediates the SMB-induced luteolysis. SMB treatment, however, required 7-8 days to induce luteolysis.

Technical note: a technique for multiple liver biopsies in neonatal calves.

Our objective was to develop a rapid and safe liver biopsy technique that could be repeated on multiple occasions in individual neonatal calves. A pilot study was performed to verify the efficacy of sedation and restraint procedures and to evaluate different biopsy instruments. Following the pilot experiment, a biopsy trocar was fabricated and an experiment was conducted using this procedure. Liver biopsies were performed in neonatal calves on d 4, 9, 15, 21, and 28 of life to evaluate the effect of vitamin A intake on liver vitamin A concentrations. On these days, a single injection of ceftiofur sodium was administered i.m. 1 to 2 h prior to the procedure. Calves were lightly sedated with xylazine and placed on a surgical table in left-lateral recumbency. The right caudo-thoracic area was clipped and scrubbed with an iodophor agent. Following administration of a local anesthetic (lidocaine), a small incision was made in the skin between the 12th and 13th ribs approximately 15 cm from the dorsal midline. The biopsy trocar was inserted through the body wall and peritoneum and introduced into the liver parenchyma, and a liver sample was collected. Following the biopsy, the cutaneous incision was sutured and an antiseptic agent was applied to prevent infection. An i.m. injection of an analgesic was administered 1 h following the procedure to alleviate postsurgical discomfort. Most calves were able to stand within 2 h after the biopsy. The entire procedure, which could be performed by a single individual, usually required about 20 min from initial sedation until skin closure. Although liver samples of up to 500 mg were obtained, most samples weighed 75 to 150 mg (wet weight). A total of 156 liver biopsies were performed on 33 calves. Complications due to the biopsy procedure were observed in only two calves. Therefore, this procedure can be useful for studies designed to monitor changes in liver composition or enzyme activities over time.

Sedation with xylazine and lumbosacral epidural administration of lidocaine and xylazine for umbilical surgery in calves.

OBJECTIVE: To determine whether anesthesia consisting of sedation induced by intramuscular administration of xylazine hydrochloride and lumbosacral analgesia induced by epidural administration of lidocaine and xylazine is useful for umbilical surgery in neonatal calves. DESIGN: Prospective study. ANIMALS: 6 neonatal male dairy calves. PROCEDURE: Calves were sedated with xylazine (0.1 mg/kg [0.045 mg/lb] of body weight, i.m.), and 5 minutes later a 2% solution of lidocaine (0.18 to 0.24 ml/kg [0.08 to 0.11 ml/lb]) and xylazine (0.05 mg/kg [0.022 mg/lb]) were administered into the lumbosacral epidural space. Calves were positioned in dorsal recumbency, and the umbilical structures were resected. Local infusion of lidocaine, cranial to the umbilicus, was required in 5 of 6 calves to provide adequate analgesia. Xylazine sedation was reversed with tolazoline (1 mg/kg [0.45 mg/lb], i.v.). RESULTS: Calves maintained adequate cardiac output and oxygen delivery throughout the procedure but were hypotensive. Reversal of xylazine-induced sedation with tolazoline caused transient sinus bradycardia and sinus arrest, accompanied by severe systemic arterial hypotension. All calves regained a suckle reflex within 10 minutes and were able to stand within 90 minutes. CLINICAL IMPLICATIONS: Intramuscular administration of xylazine for sedation and epidural administration of lidocaine and xylazine for analgesia failed to provide satisfactory analgesia for umbilical resection without supplemental local infiltration of lidocaine. The anesthetic protocol is most useful when respiratory compromise or cost are concerns and the surgical procedure can be completed in < 1 hour. Caution should be exercised when tolazoline is administered intravenously to reverse xylazine-induced sedation in calves.

Incomplete linear tibial fractures in two horses.

Incomplete linear tibial fractures were identified in two horses with the aid of scintigraphy. Both horses were treated successfully by strict stall confinement, and both returned to normal athletic activity. Scintigraphy can be used to facilitate the generally difficult diagnosis of incomplete tibial fractures.

Peripheral detachment of the medial meniscus with injury to the medial collateral ligament in 50 cattle.

In 50 cattle the periphery of the medial meniscus had separated from the joint capsule and medial collateral ligament. The meniscus was hypermobile when varus and valgus stress were applied to the stifle joint, and concurrent injury to the collateral ligament allowed the medial side of the stifle joint to gape. Separation of the medial collateral ligament from the joint capsule and medial meniscus was seen at arthrotomy in 34 animals. In addition to signs of stifle injury, the affected cattle tended to abduct the leg and bear weight on the medial claw.

Surgical repair of peripheral detachment of the medial meniscus in 34 cattle.

A detachment of the periphery of the medial meniscus from the joint capsule and medial collateral ligament in 34 cattle was repaired by securing the meniscus to the joint capsule with vertical mattress sutures during arthrotomy. Of 28 cattle with follow-up reports, 20 had recovered satisfactorily by their owners' evaluations; 17 were either not lame or slightly lame after the operation and three were moderately lame. Three of four cattle without follow-up reports were either not lame or slightly lame when discharged from the hospital.

The quantitative effect of metoclopramide on abomasal and duodenal myoelectric activity of goats.

Electromyographic (EMG) recordings of the abomasal corpus, pyloric antrum and proximal duodenum were made from six goats for 2 h periods before and after administration of 0.5 mg/kg metoclopramide intravenously or intramuscularly. Analog EMG signal was transformed via a computer program to digital data. The percentage change in electrical activity was determined by comparing the electrical activity following administration of IV or IM metoclopramide with the electrical activity of the control periods for the abomasal corpus, pyloric antrum and proximal duodenum. Metoclopramide caused a significant, time-dependent increase in duodenal electrical activity following either route of administration. This increase in duodenal electrical activity coincided with peak plasma levels of metoclopramide until its decline below 100 ng/ml in plasma. There was a significant biphasic increase in electrical activity of the abomasal corpus and pyloric antrum following IM administration of metoclopramide. The first phase lasted approximately 5 min and was followed by a longer period (approximately 20 min) of diminished electrical activity. A second phase of increased electrical activity occurred approximately 40-60 min after initial IM injection of metoclopramide. It is uncertain whether this increase was drug-mediated or endogenously-triggered. Similar increases in corpus and antral electrical activity were present following IV metoclopramide administration, though early increases were not statistically significant. Overall, the percentage changes in electrical activity correlated well with predicted peak plasma levels of metoclopramide only in the duodenum. This correlation was limited to approximately 5 min after IV and 15 min after IM metoclopramide administration.

Electromyography of the reticulum, abomasum and duodenum in dairy cows with left displacement of the abomasum.

Electromyographic (EMG) recordings of the reticulum, abomasal corpus, pyloric antrum and duodenum of six dairy cows with left displacement of the abomasum (LDA) were made in order to substantiate abomasal atony as a prerequisite to abomasal displacement. EMG recordings were made when LDA was present as well as when absent. Mean values were determined in five of six cows for the maximum peak or amplitude, mean peak values, peak-to-peak interval and count of the electrical response activity (ERA) for each 15 min segment of the waveform recordings. Segments containing phase III migrating myoelectric activity were not analysed. LDA positive periods were compared to LDA negative periods in each cow. The 6 h period (transition period) prior to the diagnosis of LDA was analysed separately. Paired t-tests were applied to group values with statistical significance established at the P = 0.05 level. There was a significant decrease in the ERA count during the LDA positive periods in the abomasal corpus (-1.40% to -7.88%, P = 0.0217) and in the pyloric antrum (-2.05% to -11.98%, P = 0.0430). A corresponding significant increase occurred in the peak-to-peak interval. During the transition period spike activity in the duodenum increased 0.5% to 48.31% (P = 0.0474) and the peak-to-peak interval was significantly decreased. No extended periods of atony were observed in the abomasum during this study.

Pharmacokinetics of metoclopramide in goats.

The pharmacokinetics of a parenteral formulation of metoclopramide (monochloride monohydrate) were determined following single intravenous (i.v.) and intramuscular (i.m.) 0.5-mg/kg doses to two groups of 4 goats in a crossover design. Mean serum concentrations of metoclopramide following i.v. administration of 0.5 mg/kg declined rapidly from a peak of 277.5 ng/ml at 3 min post-dosing to 25 ng/ml at 90 min. Serum concentrations were not detectable by 120 min after drug administration. The curve of serum concentrations vs. time was characteristic of a two-compartment open model. Mean parameters from analysis of the individual i.v. data gave a biological half-life of 0.62 h and a volume of distribution of the central compartment of 1.34 l/kg. Serum concentrations of metoclopramide following i.m. administration of 0.5 mg/kg rose rapidly to a peak of 160.9 ng/ml at 15 min post-dosing and then declined in parallel with the elimination phase of the i.v. study. These data were best described by a two-compartment open model with first-order absorption. The mean biological half-life was 1.04 h. There were no adverse reactions associated with metoclopramide at the 0.5-mg/kg dose administered by either route.

The steady-state pharmacokinetics and bioequivalence of carprofen administered orally and subcutaneously in dogs.

Eighteen male Beagle dogs were randomized to oral (p.o.) or subcutaneous (s.c.) carprofen administration in a two-sequence, two-period crossover design with a 10-day washout between periods. Twenty-five milligrams of carprofen was administered p.o. or s.c. every 12 h for 7 days. Plasma concentrations of carprofen collected after the first and last treatments were determined by high-performance liquid chromatography. Carprofen concentration data were natural log transformed and geometric means were calculated for maximum plasma concentration (Cmax) and area under the plasma concentration-time curve (AUC0--12) following the first dose and Cmax and AUC0--12 following administration of the last dose. Formulations were considered bioequivalent if the 90% confidence interval (CI) of the mean difference for each variable between formulations were within -20% and 25% of the oral formulation. The mean Cmax and AUC0--12 were 16.9 microg/mL and 73.1 microg. h/mL, respectively, following a single oral dose and 8.0 microg/mL and 64.3 microg x h/mL, respectively, following a single s.c. injection. The 90% CI for Cmax (-56.8 to -48.7%) was outside of the bioequivalence criteria whereas the 90% CI for AUC0--12 (-16.3 to -7.5%) was within the bioequivalence criteria. At steady-state, the mean Cmax and AUC0--12 were 18.7 microg/mL and 101.9 microg x h/mL, respectively, following p.o. administration and 14.7 microg/mL and 111.0 microg x h/mL, respectively, following s.c. injection. The 90% CI was outside the bioequivalence criteria for Cmax (-30.8 to -10.8) but within the bioequivalence criteria for AUC0--12 (2.3-15.9%). The results of this study indicate that peak plasma concentrations of carprofen differ when administered p.o. and s.c., but that total drug exposure following a single dose and at steady-state are bioequivalent.