Diacetoxyscirpenol (DAS) was given IV to pigs (0, 0.5, and 1.0 mg/kg of body weight), cattle (0 and 0.5 mg/kg), and dogs (0 and 0.5 mg/kg). Blood was collected and hemograms were done at 0.5-hour intervals for 8 hours. The animals were euthanatized at 8 hours after treatment, and bone marrow samples were taken and examined by light microscopy. Moderate to severe necrosis of bone marrow hematopoietic elements was found in animals given DAS. The sequential increase in the type and number of abnormal cells in the blood suggested a successive destruction of the hematopoietic elements. A marked left shift in the neutrophil population was found in animals given DAS. Metarubricytes and large platelets were found in the blood of animals given DAS. Lymphocytes were replaced with immature cells. Pathologic changes were most severe in the pigs given a dosage of 1.0 mg of DAS/kg. The order of species sensitivity to DAS was pigs greater than dogs much greater than cattle.

Concurrent bacteriologic culture of feces and agar gel immunodiffusion (AGID) testing was performed on all cows and bred heifers over 14 months old in 10 dairy herds during a 32-month period to determine the effectiveness of the AGID test for the detection of subclinical paratuberculosis. Herds were sampled 5 times and, when possible, culled animals were tested again at slaughter. During 5 herd-wide samplings, Mycobacterium paratuberculosis was isolated from 139 fecal specimens obtained from 109 cattle. Results of the AGID test were simultaneously positive 40 of 139 times (28.8%). Thirty-six of the 109 cattle (33.0%) determined to be infected had a positive AGID test result at some point during the 5 herd-wide samplings. When results of tests performed at time of slaughter were included, 117 cattle were identified as infected by culture methods; 55 of these (47.0%) were AGID test-positive at some point during the study. The upper limit of the maximal false-positive rate for the AGID test was 2.1%. On the basis of colony counts from cultures, subclinically infected cows shedding higher numbers of M paratuberculosis in the feces were more likely to have positive AGID test results (P less than 0.0001). In known infected cattle, neither the culture nor AGID test results were consistently positive on repeated testing. Of 48 official calfhood paratuberculosis vaccinates tested as adults, 3 had positive AGID test results and in 1 of these, M paratuberculosis was also isolated from the feces, indicating that the rate of false-positive AGID test results in calfhood vaccinates is low.

Twelve male cats were fed 2 diets that differed in the source of P. In diet 1 (1.4% P), 62.7% of P originated from poultry, meat, and fish meal, and the remainder from other organic ingredients of food. In diet 2 (1.6% P), 63.5% of P was derived from neutral monobasic/dibasic salts, and the remainder from other organic ingredients of the food. The P intake was nearly the same with both diets, but there was a significant (P less than 0.05) difference between diets in the percentage of ingested P that was excreted in the urine (14.7 +/- 5.3% for diet 1; 34.9 +/- 8.4% for diet 2), and in 6-day urinary P excretion (774 +/- 290 mg for diet 1; 2,004 +/- 556 mg for diet 2). The P concentrations in urine samples obtained by cystocentesis after cats ate were significantly (P less than 0.05) higher when cats were fed diet 2 than when those same cats were fed diet 1. Plasma P concentrations increased after ingestion of diet 2, but were unchanged after ingestion of diet 1. Seemingly, urinary excretion of P was markedly influenced by dietary composition. Diets with the same P content have potential for different biologic effects because of differences in availability of P.

The ability of pseudorabies virus (PRV) to infect and establish latency in pigs with passively acquired (maternal) antibody for PRV was tested by exposing such pigs to the virus and subsequently attempting to reactivate latent virus by administering large doses of dexamethasone. Pigs of each of 4 litters that had nursed gilts with relatively high (512, gilts 1 and 2), moderate (32, gilt 3), and no (less than 2, gilt 4) serum titers of virus-neutralizing (VN) antibodies for PRV were allotted to 3 treatment groups (A, B, C) when they were 2 weeks old. Group-A pigs were separated from littermates and dam and thereafter kept in isolation; group-B pigs were experimentally exposed oronasally to PRV and 1 hour later returned to their dam; group-C pigs were kept with their dam and potentially exposed to PRV by contact with littermates of group B. Sera obtained from pigs at selected intervals until they were 17 weeks old were tested for VN activity and for precipitating activity for radiolabeled viral proteins. All group-A pigs remained clinically normal throughout the experiment. Depending on the initial amount of passively acquired antibody, little or no serum VN or precipitating activity remained by the time these pigs were 17 weeks old. Group-B and -C pigs, with relatively high amounts of passively acquired antibody when exposed to PRV, also remained clinically normal. However, most became latently infected as subsequently evidenced by either dexamethasone-induced or noninduced virus reactivation. Noninduced reactivation may have been initiated by weaning the pigs when they were about 8 weeks old. Group-B and -C pigs with no or moderate amounts of passively acquired antibody when exposed to PRV, had severe clinical signs. These pigs either died or recovered but remained stunted in growth. Virus was reactivated in all of the recovered pigs by treatment with dexamethasone. Quantitative and qualitative changes in serum precipitating activity, especially for viral proteins of relatively low molecular weight (less than 46,000), were a more consistent indication of virus reactivation than were either increased VN titers or virus isolation. Results with litters 1 and 2 clearly indicate that latent infection of young pigs with highly virulent PRV can develop in the absence of clinical signs.

A survey to detect Streptococcus suis serotype 2 in 1,716 weaned pigs was done in Quebec. Forty-nine sow herds were included in this survey: in 26 herds, S suis serotype 2 had been isolated during the preceding 12 months and in 23 herds (control), the organism had not been detected during a previous study. Swab specimens of the nasal cavity and tonsils of pigs were obtained for bacteriological culture, and S suis serotype 2 was easily detected by the use of brain-heart infusion agar containing a Streptococcus-selective supplement and 5% goat antiserum raised against S suis serotype 2. After measurement of the diameter of the precipitation zone of 539 isolates, a slide agglutination test was performed to identify the S suis serot ype 2 isolates. The mean precipitation zone diameter obtained for group S suis serotype 2 was larger (P less than 0.001) than that for the group designated as "others." With slide agglutination test results as reference and on the basis of discriminant analysis to simulate detection of S suis serotype 2, 93.1% of all isolates were correctly classified, using the precipitation zone diameter as unique classification criterion. Relative specificity was 94.5% and relative sensitivity was 88.7%. Use of the precipitation zone diameter on a quantitative basis led to the proposal of a simple and reliable technique to screen swine herds for S suis serotype 2 in weaned pigs. Nasal and tonsillar swab specimens were obtained and analyzed concurrently for S suis serotype 2. The organism was found in both sites in only 20.4% of 103 carrier pigs. Nasal and tonsillar specimens yielded 55.3 and 65%, respectively, of all S suis serotype 2 isolates. Statistically significant difference was not observed between the numbers of S suis serotype 2 isolated from each site. Both sites permitted the recovery of S suis serotype 2 isolates; it was advantageous to use nasal and tonsillar swab specimens to determine the most reliable evaluation of S suis serotype-2 carrier status in weaned pigs.

Colostral volume and IgG and IgM concentrations were determined in 6 multiparous mares at foaling and then every 2 hours from 16 to 20 hours after parturition. Serum IgG and IgM concentrations at foaling also were determined in each mare. The rate of mammary secretion was 292 +/- 26 ml/h (range, 202 to 389 ml/h), and the colostral volume was 5.1 +/- 0.5 L (range, 3.2 to 7.0 L). The colostral IgG and IgM contents were 440 +/- 106 g (range, 199 to 855 g) and 3.1 +/- 0.9 g (range, 0.7 g to 7.1 g), respectively. There was no significant correlation between serum and initial colostral IgG and IgM concentration or between serum and total colostral IgG or IgM values. The colostral IgG and IgM concentrations at foaling correlated well with the total colostral IgG and IgM contents, respectively. The initial 250 ml of colostrum contained 10 +/- 1.4% (range, 6.0 to 13.9%) and 6 +/- 1.0% (range, 2.4 to 8.5%) of the total IgG and IgM contents, respectively, and the initial 500 ml of colostrum contained 20 +/- 2.7% (range 12.0 to 27.1%) and 14 +/- 1.2% (8.2 to 17%) of the total colostral IgG and IgM contents, respectively.

Sulfadiazine (SDZ)/trimethoprim (TMP; 30 mg of SDZ/TMP/kg of body weight) was given IV to the same 6 male calves at 1, 7, and 42 days of age and to 2 additional calves at 7 days of age. Serum concentrations of SDZ and TMP were best represented by a 2-compartment open model, but in 42-day-old calves, CSF concentrations of both drugs were best represented by a 1-compartment open model with first-order input. Between 1 and 42 days of age, the elimination half-life (t1/2(beta)) of SDZ decreased from 5.7 to 3.6 hours, and total body clearance (CLtot) increased from 1.43 to 1.88 ml/min/kg; the area under the curve (AUCo leads to x) decreased from 291.5 to 225.4 mg/L.h. The distribution coefficient (Vd(area)/kg of body weight) decreased with age, changing from 0.72 to 0.59 L/kg, between 1 and 42 days of age. Therapeutic concentrations of SDZ in serum (greater than 2 micrograms/ml) were maintained for 24 hours in 1-day-old calves and for about 15 hours in 7- and 42-day-old calves. The elimination rate of TMP increased about 9-fold; t1/2(beta) was 8.4, 2.1, and 0.9 hours, respectively, at 1, 7, and 42 days of age. Other values also reflected an increase in TMP elimination rate with age: CLtot increased from 2.8 to 12 to 28.9 ml/min/kg, k13 increased from 0.336 to 0.654 to 1.664/h and AUC(0 to infinity) decreased from 32.8 to 7.9 to 3.1 mg/L/h, respectively. Therapeutic concentrations (greater than 0.1 microgram/ml) were maintained for 15 hours, 8 hours, and about 6 hours in 1-, 7-, and 42-day-old calves, respectively. Penetration of SDZ and TMP into the CSF in 42-day-old calves was substantial; ratios of AUC(CSF)/AUCserum were 0.60 and 0.69, respectively. Therapeutic concentrations of drugs in CSF were maintained if serum concentrations were above therapeutic concentrations; elimination rates of both drugs from the CSF equaled those of serum. Sulfadiazine was excreted mainly unchanged; the percentage of dose excreted unchanged in 24 hours increased from 22.1 to 47.8 to 50.8% in 1-, 7-, and 42-day-old calves, respectively, paralleling the increase in CLtot. Trimethoprim was extensively biotransformed; the percentage of dose excreted unchanged in the urine in 24 hours decreased from 12.8 to 8.7 to 3.5%. Sulfadiazine and TMP were concentrated in the urine, and therapeutic concentrations of both drugs in urine were maintained for greater than 24 hours in calves of all ages.

Five Collies sensitive to toxic effects of ivermectin and 7 nonsensitive Collies were given 100 microgram of ivermectin/kg of body weight, PO. Blood samples were collected from each dog before treatment; at posttreatment hours 1, 2, 3.5, 5, and 8; and at posttreatment days 1, 2, 4, 7, 14, and 21. Each sample was assayed for ivermectin concentration, and statistical analyses were performed on the resulting plasma concentration data to determine differences in absorption and clearance of drugs between the 2 groups. Variables measured were area under the curve (using the trapezoidal rule), peak plasma concentration, and the time to peak concentration. Differences between sensitive and nonsensitive Collies for variables analyzed were not significant (P greater than 0.05).

Continous electromyographic recordings of pharyngeal muscle activity were made in 5 clinically normal control dogs and in 7 dogs 3 years after partial denervation of the pharyngeal muscles. Electromyographic recordings were made of the sequence of actions of each muscle and of the combined muscle activity, at rest and during swallowing of food. During 30-second periods, the recordings were digitalized and stored on diskette for further analysis. All control dogs had a distinct pattern of muscle activity during swallowing, the onset being in a constant order (hyopharyngeal, thyropharyngeal, and cricopharyngeal) and bilaterally synchronous. While eating, each dog had about 5 to 12 short periods of synchronous activity in each muscle, between the swallowing actions. During the resting period, there were longer periods of activity, which were synchronous with respiration. In each denervated dog, there were normal and irregular swallowing actions. Swallowing activity was recognized, but the sequence of hyopharyngeal, thyropharyngeal, and cricopharyngeal muscle activity was irregular and different from that in control dogs. Partial denervation of the pharyngeal muscles does not seriously impair motor activity of the muscles, but does alter the sequence of activity in the pharyngeal muscles during swallowing.

Ceftazidime pharmacokinetic values were studied in unweaned calves given the antibiotic alone or in combination with probenecid. Ceftazidime was administered IV to 9 calves at a dosage of 10 mg/kg of body weight and IM (10 mg/kg) to 8 calves, to 7 calves (10 mg/kg plus probenecid [40 mg/kg]), and to 9 calves (10 mg/kg plus probenecid [80 mg/kg]). Serum concentration-vs-time data were analyzed, using noncompartmental methods based on statistical moment theory. The data for IV ceftazidime administration also were fitted by use of a linear, open 2-compartment model. The mean (+/- SD) terminal half-life was 138.7 +/- 23.6 minutes and 126.3 +/- 10.5 minutes after IV and IM administrations, respectively. The mean residence time was 167.3 +/- 21.1 minutes and 201.4 +/- 16.8 minutes after IV and IM administrations, respectively. Coadministration of probenecid did not affect the terminal half-life or mean residence time values. The total body clearance was 1.75 +/- 0.26 ml/min/kg, and the volume of distribution at steady state was 0.294 +/- 0.064 L/kg. The estimated mean absorption time was 34.1 minutes. There were no significant differences between the mean residence time calculated by statistical moment theory or by compartmental analysis, indicating central compartment output of ceftazidime. The 90% minimal inhibitory concentration values of ceftazidime determined for Escherichia coli, Salmonella spp, Pasteurella multocida, and P haemolytica isolates ranged from less than 0.01 to 0.1 microgram/microliter.