Depletion of dexamethasone in cattle: Food safety study in dairy and beef cattle.

Dexamethasone is approved for cattle in Canada for several conditions, but no withdrawal times are currently provided on the approved labels. Recently, the list of Maximum Residues Limits for Veterinary Drugs in Foods in Canada was amended to include dexamethasone. The objectives of this study were to determine the residue depletion profile of dexamethasone after an extra-label dosage regimen in milk of healthy lactating dairy cattle (n = 18) and in edible tissues of healthy beef cattle (n = 16) and to suggest withdrawal intervals. Dexamethasone was administered intramuscularly at 0.05 mg/kg daily for 3 days. Milk samples were collected prior to treatment and every 12 h up to 96 h post-dose. Muscle, liver, kidney, and peri-renal fat tissues were collected from beef cattle at 3, 7, 11, or 15 days post-dose. Dexamethasone analysis was performed by liquid chromatography/mass spectrophotometry. Dexamethasone residues were detected in milk samples up to 36 h. Muscle and fat had no detectable dexamethasone residues while kidney and liver had detectable residues only on day 3 post-dose. A withdrawal interval of 48 h for milk in Canadian dairy cattle and 7 days for meat in Canadian beef cattle are suggested for the dexamethasone treatment regimen most commonly requested to CgFARAD™.

Characterisation of faecal microbiota in horses medicated with oral doxycycline hyclate.

BACKGROUND: Antimicrobial-associated diarrhoea is a common adverse effect of antimicrobial treatment in horses and has been reported following the administration of oral doxycycline. The administration of antimicrobials has also been associated with changes in the equine intestinal microbiota diversity yet has not been explored under doxycycline treatment. OBJECTIVES: To describe the dynamics of the faecal microbial diversity following a 5-day oral administration of doxycycline in healthy horses with Streptococcus zooepidemicus infected tissue chambers. STUDY DESIGN: Experimental prospective cohort study in a single horse group. METHODS: Seven healthy adult horses with S. zooepidemicus infected tissue chambers received oral doxycycline at 10 mg/kg q 12 h for 5-days following the tissue chamber inoculation. Faeces were collected prior to the tissue chamber inoculation and until 28-days post inoculation. Faecal microbiota was characterised by high throughput sequencing of the V4 region of the 16S rRNA gene on the Illumina MiSeq sequencing platform. Bioinformatic analysis was performed with Mothur and statistical analysis were conducted on R Studio. RESULTS: A significant decrease in alpha diversity, characterised by a decrease of richness and diversity, and a decrease in beta diversity, characterised by changes in relative abundance, occurred after initiation of and during the administration of doxycycline. A decrease in Verrucomicrobia and increase in Firmicutes:Bacteroidetes ratio occurred following the initiation of treatment, with a return to initial Firmicutes:Bacteroidetes ratio during the treatment. It took 23 days after discontinuing the treatment for the faecal microbiota to return close to the initial state. MAIN LIMITATIONS: Lack of control population within the study. CONCLUSIONS: Transitory intestinal dysbiosis occurs under oral administration of doxycycline in horses.

Pharmacokinetics and pharmacodynamics of doxycycline in a Streptococcusequi subsp. zooepidemicus infection model in horses.

The objectives of this study were to investigate the pharmacokinetics (PK), pharmacodynamics (PD), and the efficacy of oral administration of doxycycline (DXC) in horses with Streptococcus zooepidemicus tissue infections. Tissue chambers (TC) were implanted subcutaneously in the cervical region of 7 horses and inoculated with a single S. zooepidemicus isolate with a minimum inhibitory concentration (MIC) of 0.25 µg/ml, determined by agar dilution. Doxycycline hyclate (10 mg/kg, orally, q 12 h, for 5 days) mixed with poloxamer gel was started following inoculation. The TC fluid was sampled prior to and following inoculation for cytology analysis, quantitative culture, and DXC determination. Plasma DXC concentrations were measured over 48 h following the last dose of DXC administered. The mean plasma peak concentration (Cmax ) of DXC was 0.32 µg/ml, and concentrations above the MIC were only reached in 3 TC samples. In plasma, mean T > MIC was 2.4 h, mean Cmax /MIC was 1.30, and mean AUClast /MIC was 11.63 h. These PK/PD indices did not reach the suggested targets for DXC treatments of infections, and the TC abscessed in all horses. This is the first study to evaluate the recommended dose of DXC in horse in an infection model.

Tissue residue depletion of fenbendazole after oral administration in turkeys.

The objectives of this study were to determine tissue depletion of fenbendazole in turkeys and estimate a withdrawal interval (WDI). Forty-eight 9-week-old turkeys were fed fenbendazole at 30 mg/kg of feed for 7 consecutive days. Three hens and 3 toms were sacrificed every 2 days from 2 to 16 days post-treatment, and tissues were collected to determine fenbendazole sulfone (FBZ-SO2) concentrations using mass spectrometry. At all timepoints, FBZ-SO2 concentrations in liver and skin-adherent fat were above the limit of quantification (1 ppb), with higher concentrations than those in kidney and muscle. Two turkeys had detectable FBZ-SO2 concentrations in kidney at 16 days. No detectable FBZ-SO2 concentrations were found in muscle at 14 and 16 days. Fenbendazole residues depleted very slowly from the liver and a WDI of at least 39 days should be observed under the conditions of this study, in order to comply with Canadian regulatory agencies.

Déplétion du fenbendazole pour les résidus tissulaires après l'administration orale chez les dindons. Les objectifs de cette étude consistaient à déterminer la déplétion du fenbendazole dans les tissus chez les dindons et d'estimer un délai d'attente (DA). Du fenbendazole a été administré à quarante-huit dindons âgés de 9 semaines, à raison de 30 mg/kg d'aliments pendant 7 jours consécutifs. Trois dindes et 3 dindons ont été sacrifiés tous les deux jours pendant les jours 2 à 16 après le traitement et les tissus ont été prélevés pour déterminer les concentrations de fenbendazole sulfone (FBZ-SO2) en utilisant la spectrométrie de masse. À tous les moments de prélèvement, les concentrations de FBZ-SO2 dans le foie et le gras adhérent à la peau étaient supérieures à la limite de quantification (1 ppm), avec des concentrations supérieures à celles présentes dans les reins et les muscles. Deux dindes avaient des concentrations de FBZ-SO2 détectables dans les reins à 16 jours. Aucune concentration détectable de FBZ-SO2 n'a été trouvées dans les muscles à 14 et à 16 jours. Les résidus de fenbendazole se résorbaient très lentement du foie et un DA d'au moins 39 jours devrait être observé conformément aux conditions de cette étude afin de satisfaire aux exigences des agences réglementaires canadiennes.(Traduit par Isabelle Vallières).

Parasite control in Canadian companion animal shelters and a cost-comparison of anthelmintics.

Animal shelters have limited resources and must accommodate large numbers of animals at unpredictable intake rates. These dogs and cats are often parasitized, which can adversely affect the health of animals and expose shelter workers and adoptive owners to zoonoses. We analyzed survey responses from rural (n = 32) and urban (n = 50) companion animal shelters across Canada, and compared the wholesale cost of commercially available anthelmintics to identify cost-effective methods of managing parasites within shelters. Almost all shelters employed nematocides (98% to 99%), but cestocides and ectoparasiticides were used less frequently. Shelters identified cost as an important consideration in choosing to perform fecal diagnostic testing and administer anthelmintics, and this motivated many shelters to selectively perform testing (66%) or never to test (32%), and to use drugs extralabel (80%).

Contrôle des parasites dans les refuges pour animaux de compagnie du Canada et comparaison des coûts des anthelminthiques. Les refuges pour animaux possèdent des ressources limitées et doivent héberger un grand nombre d'animaux à des taux d'accueil imprévisibles. Des produits antiparasitaires sont souvent administrés à ces chiens et chats, ce qui peut influencer négativement la santé des animaux et exposer les travailleurs et les propriétaires adoptifs aux zoonoses. Nous avons analysé les réponses à un sondage provenant de refuges pour animaux de compagnie en région rurale (n = 32) et urbaine (n = 50) à l'échelle du Canada et nous avons comparé le coût de gros des anthelminthiques disponibles dans le commerce pour identifier des méthodes économiques de gérer les parasites dans les refuges. Presque tous les refuges employaient des nématicides (98 % à 99 %), mais les cestocides et les ectoparasiticides étaient utilisés moins fréquemment. Les refuges ont identifié le coût comme une considération importante lors des décisions relatives aux analyses des fèces et à l'administration des anthelminthiques et cette situation a motivé beaucoup de refuges à réaliser des analyses de manière sélective (66 %) ou de ne jamais effectuer d'analyses (32 %) et d'utiliser des médicaments en dérogation des directives de l'étiquette (80 %).(Traduit par Isabelle Vallières).

Pharmacokinetics and pharmacodynamics of a constant rate infusion of fentanyl (5 µg/kg/h) in awake cats.

OBJECTIVE: To evaluate the pharmacokinetics and thermal and mechanical antinociceptive effects of a fentanyl constant rate infusion (CRI) in conscious cats. ANIMALS: 8 healthy adult cats. PROCEDURES: At a ≥ 14-day interval, 7 cats received a loading dose (LD) of fentanyl (5 µg/kg, IV [administered at 0 hours]) followed by fentanyl infusion (5 µg/kg/h, IV) for 2 hours or similar administrations of equivalent volumes of 0.9% saline (NaCl) solution. One cat received only the fentanyl treatment. For both treatments, sedation and adverse events were evaluated and mechanical threshold (MT) and thermal threshold (TT) testing was performed prior to (baseline) and at predetermined times up to 26 hours after LD administration; plasma fentanyl concentrations were determined at similar times when the cats received fentanyl. RESULTS: Fentanyl induced mild sedation during the infusion. The only adverse effect associated with fentanyl LD administration was profuse salivation (1 cat). Saline solution administration did not significantly change MT or TT over time. For the duration of the CRI, MT and TT differed significantly between treatments, except for TT 1 hour after LD administration. For the fentanyl treatment, MT and TT were significantly higher than baseline at 0.25 to 0.75 hours and at 0.25 to 1 hour, respectively. During the fentanyl CRI, mean ± SD plasma fentanyl concentration decreased from 4.41 ± 1.86 ng/mL to 2.99 ± 1.28 ng/mL and was correlated with antinociception; plasma concentrations < 1.33 ± 0.30 ng/mL were not associated with antinociception. CONCLUSIONS AND CLINICAL RELEVANCE: Fentanyl CRI (5 µg/kg/h) induced mechanical and thermal antinociception in cats.

The rabbit as an infection model for equine proliferative enteropathy.

The objective of this study was to demonstrate the susceptibility of rabbits to Lawsonia intracellularis obtained from a case of clinical equine proliferative enteropathy (EPE). This is a preliminary step toward developing a rabbit infection model for studying pathogenesis and therapy of EPE in horses. Nine does were equally assigned to 3 groups. Animals in 2 groups (Group 1 and Group 2) were orally inoculated with different doses of cell-cultured L. intracellularis. Controls (Group 3) were sham-inoculated. Feces and blood were collected before the rabbits were infected and at 7, 14, and 21 days post-infection (DPI). Serum immunoglobulin G (IgG) titers were measured using an immunoperoxidase monolayer assay (IPMA) and fecal samples were analyzed with quantitative polymerase chain reaction (qPCR). A doe from each group was euthanized at 7, 14, and 21 DPI for collection and evaluation of intestinal samples. Tissues were stained by routine hematoxylin and eosin (H&E) method and immunohistochemistry (IHC) with L. intracellularis-specific mouse monoclonal antibody. At 14 DPI, serologic responses were detected in both infected groups, which maintained high titers through to 21 DPI. Lawsonia intracellularis DNA was detected in the feces of Group 2 on 7 DPI and in both infected groups on 14 DPI. Gross lesions were apparent in Group 1 and Group 2 on 14 DPI. Immunohistochemistry confirmed L. intracellularis antigen within cells of rabbits in Group 1 and Group 2 on 7, 14, and 21 DPI. No lesions, serologic response, shedding, or IHC labeling were found in Group 3 rabbits. This study describes an EPE rabbit model that simulates natural infection, as typical lesions, immune response, and fecal shedding were present.

Cette étude visait à démontrer la susceptibilité des lapins à Lawsonia intracellularis obtenu d'un cas clinique d'entéropathie proliférative équine (EPE). Ceci est une étape préliminaire dans le développement d'un modèle d'infection chez le lapin pour étudier la pathogénie et le traitement de l'EPE chez les chevaux. Neuf lapines ont été assignées également à 3 groupes. Les animaux dans deux groupes (Groupe 1 et Groupe 2) ont été inoculés oralement avec différentes doses de L. intracellularis cultivés sur cellules. Les témoins (Groupe 3) étaient faussement inoculés. Des fèces et du sang ont été prélevés avant que les lapins soient infectés et aux jours 7, 14 et 21 post-infection (DPI). Les titres sériques d'immunoglobulines G (IgG) ont été mesurés par une épreuve d'immunoperoxydase en monocouche (IPMA) et les échantillons de fèces ont été analysés par réaction quantitative d'amplification en chaîne par la polymérase (qPCR). Une lapine de chaque groupe a été euthanasiée 7, 14 et 21 DPI pour prélèvement et évaluation d'échantillons intestinaux. Les tissus étaient colorés à l'aide d'hématoxyline et éosine (H&E) et en immunohistochime (IHC) avec un anticorps monoclonal de souris spécifique à L. intracellularis. Au jour 14 post-infection, une réponse sérologique a été détectée chez les animaux des deux groupes infectés, et des titres élevés ont été maintenus jusqu'à 21 DPI. De l'ADN de L. intracellularis fut détecté dans les fèces du Groupe 2 au jour 7 PI et dans les 2 groupes infectés au jour 14 PI. Des lésions macroscopiques étaient apparentes dans le Groupe 1 et le Groupe 2 au jour 14 PI. L'immunohistochime a confirmé la présence d'antigène de L. intracellularis à l'intérieur des cellules de lapins dans les Groupes 1 et 2 aux jours 7, 14 et 21 PI. Aucune lésion, réponse sérologique, excrétion, ou marquage en IHC n'ont été trouvés chez les lapins du Groupe 3. La présente étude décrit un modèle lapin d'EPE qui imite l'infection naturelle, étant donné la présence de lésions typiques, de réponse immunitaire et d'excrétion fécale.(Traduit par Docteur Serge Messier).

Species-specificity of equine and porcine Lawsonia intracellularis isolates in laboratory animals.

Lawsonia intracellularis infection causes proliferative enteropathy (PE) in many mammalian species, with porcine and equine proliferative enteropathy (PPE and EPE) known worldwide. Hamsters are a well-published animal model for PPE infection studies in pigs. There is no laboratory animal model for EPE infection studies and it is not known whether there is species-specificity for equine or porcine isolates of L. intracellularis in animal models. The objective of this study was to determine whether it is possible to generate typical EPE lesions in hamsters after inoculation with an equine strain of L. intracellularis (EPE strain) and whether it is comparatively possible to generate PPE lesions in rabbits after inoculation with a porcine strain of L. intracellularis (PPE strain). In 2 separate trials, 4-week-old and 3-week-old weanling golden Syrian hamsters were challenged with EPE strains and compared to uninfected (both trials) and PPE-infected controls (Trial 2 only). Concurrently, 6 female New Zealand white juvenile rabbits were infected with PPE strain and observed concomitantly to 8 similar rabbits infected with EPE strain for a different experiment. Hamsters and rabbits were observed for 21 to 24 days post-infection (DPI), depending on the experiment. Neither infected species developed clinical signs. The presence of disease was assessed with diagnostic techniques classically used for pigs and horses: immune-peroxidase monolayer assay on sera; quantitative polymerase chain reaction (qPCR) detection of molecular DNA in feces; and hematoxylin and eosin (H&E) stain and immunohistochemistry (IHC) on intestinal tissues. Our results showed that EPE-challenged hamsters do not develop infection when compared with PPE controls (IHC, P = 0.009; qPCR, P = 0.0003). Conversely, PPE-challenged rabbits do not develop typical intestinal lesions in comparison to EPE-challenged rabbits, with serological response at 14 DPI being significantly lower (P = 0.0023). In conclusion, PPE and EPE strains appear to have different host-specificities for hamsters and rabbits, respectively.

L'infection par Lawsonia intracellularis provoque une entéropathie proliférative chez de nombreuses espèces de mammifères; celle des porcins (EPP) et des équidés (EEP) sont connues mondialement. Les hamsters sont un modèle animal bien connu pour l'étude de l'EPP. Il n'existe pas de modèle animal de laboratoire pour étudier l'EEP, et on ne sait pas s'il y a spécificité d'espèce pour les isolats équins ou porcins de L. intracellularis dans des modèles animaux. L'objectif de la présente étude était de déterminer s'il est possible de générer des lésions typiques d'EEP chez les hamsters après inoculation d'une souche équine de L. intracellularis (souche EEP) et s'il est également possible de générer des lésions d'EPP chez des lapins après inoculation d'une souche porcine de L. intracellularis (souche EPP). Dans 2 essais séparés, des hamsters dorés syriens sevrés âgés de 4 semaines et de 3 semaines ont été inoculés avec des souches EEP, et ont été comparés à des témoins non infectés (les deux essais) et à des témoins infectés avec EPP (essai 2 seulement). Parallèlement, 6 jeunes lapines Nouvelle-Zélande ont été infectées par la souche EEP et observées de façon concomitante à 8 lapins similaires infectés par la souche EPP pour une expérience différente. Les hamsters et les lapins ont été observés pendant 21 à 24 jours après l'infection (JAI), en fonction de l'expérience. Aucune des espèces infectées n'a développé de signes cliniques. La présence de maladie a été évaluée par des techniques classiques de diagnostic utilisées pour les porcs et les chevaux : l'essai par immuno-peroxydase sur monocouche pour les sérums; la détection par réaction d'amplification en chaîne par la polymérase quantitative (qPCR) de l'ADN moléculaire dans les selles; la coloration hématoxyline-éosine et l'immunohistochimie (IHC) sur des tissus intestinaux. Nos résultats ont montré que les hamsters inoculés avec EEP ne développent pas d'infection comparativement aux EPP témoins (IHC P = 0,009; qPCR P = 0,0003). À l'inverse, les lapins inoculés avec EPP ne développent pas des lésions intestinales typiques comparativement aux lapins inoculés avec EEP, avec une réponse sérologique à 14 JAI significativement plus faible (P = 0,0023). En conclusion, les souches d'EPP et d'EEP semblent avoir des spécificités d'hôte différentes chez les hamsters et les lapins, respectivement.(Traduit par Dr. J.M. Dhillon).

Synchrotron X-ray fluorescence microscopy of gallium in bladder tissue following gallium maltolate administration during urinary tract infection.

A mouse model of cystitis caused by uropathogenic Escherichia coli was used to study the distribution of gallium in bladder tissue following oral administration of gallium maltolate during urinary tract infection. The median concentration of gallium in homogenized bladder tissue from infected mice was 1.93 µg/g after daily administration of gallium maltolate for 5 days. Synchrotron X-ray fluorescence imaging and X-ray absorption spectroscopy of bladder sections confirmed that gallium arrived at the transitional epithelium, a potential site of uropathogenic E. coli infection. Gallium and iron were similarly but not identically distributed in the tissues, suggesting that at least some distribution mechanisms are not common between the two elements. The results of this study indicate that gallium maltolate may be a suitable candidate for further development as a novel antimicrobial therapy for urinary tract infections caused by uropathogenic E. coli.

A retrospective diagnostic laboratory survey of antimicrobial resistance in fecal Escherichia coli isolated from spring calves in western Canada.

Diagnostic laboratory data on antimicrobial susceptibility of Escherichia coli isolated from feces of spring calves were evaluated retrospectively for the 5-year period from 1999 to 2003. The antimicrobials to which resistance was most prevalent were tetracycline, ampicillin, and trimethoprim/sulphamethoxazole. Resistance to 3 or more antimicrobials was found in 52.5% [95% confidence interval (CI): 47.9 to 56.6] of the E. coli isolates. Incomplete records reduced the usefulness of the diagnostic laboratory data for surveillance. Standardized patient information submitted by veterinary clinics would increase the value of this data for surveillance.

Pharmacokinetics of intravenous tramadol in dogs.

The purpose of this study was to determine the pharmacokinetics of tramadol and the active metabolite mono-O-desmethyltramadol (M1) in 6 healthy male mixed breed dogs following intravenous injection of tramadol at 3 different dose levels. Verification of the metabolism to the active metabolite M1, to which most of the analgesic activity of this agent is attributed to, was a primary goal. Quantification of the parent compound and the M1 metabolite was performed using gas chromatography. Pharmacodynamic evaluations were performed at the time of patient sampling and included assessment of sedation, and evaluation for depression of heart and respiratory rates. This study confirmed that while these dogs were able to produce the active M1 metabolite following intravenous administration of tramadol, the M1 concentrations were lower than previously reported in research beagles. Adverse effects were minimal, with mild dose-related sedation in all dogs and nausea in 1 dog. Analgesia was not documented with the method of assessment used in this study. Tramadol may be useful in canine patients, but additional studies in the canine population are required to more accurately determine the effective clinical use of the drug in dogs and quantification of M1 concentrations in a wider population of patients.

Bacterial isolates from equine infections in western Canada (1998-2003).

All bacterial samples of equine origin submitted to the diagnostic laboratory at the Western College of Veterinary Medicine from January 1998 to December 2003 from either "in-clinic" or Field Service cases were accessed (1323 submissions). The most common bacterial isolates from specific presenting signs were identified, along with their in vitro antimicrobial susceptibility patterns. The most common site from which significant bacterial isolates were recovered was the respiratory tract, followed by wounds. Streptococcus zooepidemicus was the most common isolate from most infections, followed by Escherichia coli. Antimicrobial resistance was not common in the isolates and acquired antimicrobial resistance to multiple drugs was rare. The results are compared with previous published studies from other institutions and used to suggest appropriate antimicrobial treatments for equine infections in western Canada.

A survey of antimicrobial use during bovine abdominal surgery by western Canadian veterinarians.

Members of the Western Canadian Association of Bovine Practitioners were surveyed regarding their use of antimicrobials in bovine abdominal surgery. Perioperative antimicrobials were used in 100% of abdominal surgeries by 96 of 98 respondents. Although postoperative administration was the most common perioperative period for antimicrobial use, intraoperative intraperitoneal use was reported by more than half of the veterinarians surveyed. Procaine penicillin G and oxytetracycline were the most commonly administered perioperative antimicrobials.

Antimicrobial resistance and prevalence of canine uropathogens at the Western College of Veterinary Medicine Veterinary Teaching Hospital, 2002-2007.

Between January 2002 and June 2007, uropathogens were isolated from 473 of 1557 canine urine samples submitted to Prairie Diagnostic Services from the Western College of Veterinary Medicine Veterinary Teaching Hospital. Culture and susceptibility results were analyzed, retrospectively, to estimate the prevalence of common bacterial uropathogens in dogs with urinary tract infections and to identify changes in antimicrobial resistance. The most common pathogens identified were Escherichia coli, Staphylococcus intermedius, Enterococcus spp., and Proteus spp. Antimicrobial resistance increased during the study period, particularly among recurrent E. coli isolates. Using the formula to help select rational antimicrobial therapy (FRAT), bacterial isolates were most likely to be susceptible to gentamicin, fluoroquinolones, amoxicillin-clavulanic acid, and groups 4 and 5 (third generation) cephalosporins.

Ivermectin use and resulting milk residues on 4 Canadian dairy herds.

The Canadian gFARAD was contacted for milk withdrawal recommendations after multiple cases of topical ivermectin use in lactating dairy cows. The following 4 cases included pertinent milk residue information and illustrate the challenges faced by producers, veterinarians, and regulatory authorities when ivermectin use occurs in dairy cows.

Associations between feed and water antimicrobial use in farrow-to-finish swine herds and antimicrobial resistance of fecal Escherichia coli from grow-finish pigs.

Escherichia coli (n = 1439), isolated from the feces of apparently healthy grow-finish pigs in 20 herds, were tested for susceptibility to 16 antimicrobials. Logistic regression models were developed for each resistance that was observed in more than 5% of the isolates. Each production phase's (suckling, nursery, grow-finish pigs or sows) antimicrobial exposure rate, through feed or water, was considered as a risk factor. Management variables were evaluated as potential confounders. Six resistance outcomes were associated with an antimicrobial use risk factor and four included exposures of pigs outside the grow-finish phase. In the case of sulfamethoxazole, the odds of resistance increased 2.3 times for every 100,000 pig-days of nursery pig exposure to sulfonamides. Thus, swine producers and veterinarians must be aware that antimicrobial use in pigs distant from market could have food safety repercussions. Five resistance outcomes were associated with exposure to an unrelated antimicrobial class. Most notably, the odds of sulfamethoxazole and chloramphenicol resistance were each six times higher in herds reporting high (more than 500/1,000 pig-days) grow-finish pig, macrolide exposure compared to herds with no macrolide use in grow-finish pigs. Therefore, the potential for co-selection should be considered in antimicrobial use decisions. This study emphasizes the importance of judicious antimicrobial use in pork production.

The effects of feeding and fasting on gastrointestinal sounds in adult horses.

The effect of changes in feed intake on auscultatable gastrointestinal sounds has not been systematically studied. Disagreement also is present in the literature about variation in sounds according to the quadrant of auscultation. Gastrointestinal sounds were recorded over the center of the left dorsal, left ventral, right ventral, and right dorsal quadrants and over the middle of the right abdominal flank. During 24 hours (n = 4) or 48 hours (n = 5) of fasting, there was a reduction in the intensity of gastrointestinal sounds as assessed by analysis of sound recordings. There was also a reduction in the number of mixing-like and propulsive-like sounds heard by 2 blinded observers. After refeeding, there was a marked increase in sound. Sound intensity varied among abdominal quadrants, but blinded observers did not notice significant differences in the number of mixing-like sounds. The left dorsal quadrant was quieter than others during fasting and refeeding. The right ventral quadrant appeared to be least affected by fasting, and sounds were louder over the right ventral and right middle quadrants than over the others. The blinded observers' perceptions of sound correlated poorly with one another and with objective measures of sound intensity. This experiment demonstrates the effectiveness of computerized analysis of abdominal sound in detecting a reduction in the intensity of gastrointestinal sounds during fasting and their return during refeeding. The left dorsal quadrant was quieter than other quadrants, likely because of its position over the small colon. There was considerable observer variation in the number of intestinal sounds heard.

Geriatric pharmacology.

When faced with the geriatric dog or cat, the practitioner should consider the following: 1. Avoid using any drugs at all unless there are definite therapeutic indications. If the patient has some degree of renal insufficiency, try to select drugs that are hepatically metabolized and excreted in bile rather than eliminated by the kidneys (eg, doxycycline, tolfenamic acid). If hepatic insufficiency is present, select drugs that do not undergo metabolism before renal excretion (eg, penicillins, cephalosporins). 2. If therapeutic drug monitoring is available, tailor the drug dosage regimen to that specific patient (eg, phenobarbital, digoxin, amino-glycosides). 3. If therapeutic drug monitoring is unavailable, determine if there are clinically proven adjusted dosage regimens for specific drugs. The package insert on human pharmaceutics often gives guidelines for adjusting dosages in geriatric patients. 4. If the drug has not been sufficiently studied to have dosage adjustment recommendations, determine if there is sufficient information about its kinetics to estimate the proper drug dose in a geriatric patient. Some general guidelines for commonly used drugs in geriatric veterinary patients are provided in Table 1. In general, if the Vd changes in your patient, change the dose. If the elimination half-life changes, change the dosing interval. 5. Carefully monitor treated patients for signs of efficacy and toxicity.