Biovailability of ivermectin administered orally to dogs

The bioavailability of three formulations of ivermectin was determined following oral administration to dogs. The average peak plasma level (C _max) of ivermectin administered in the standard tablet formulation at 6 and 100 µg/kg of body weight was 2.97 and 44.31 ng/g, respectively. This suggest dose-dependent pharmacokinetics.C _max and total ivermectin bioavailability, as assessed from the area under the plasma curve (AUC), were similar between two tablet formulations of ivermectin administered at 100 µg/kg. Furthermore,C _max was similar following administration of radiolabelled ivermectin at 6 µg/kg in either a beef-based chewable formulation or in the standard tablet formulation.     

Common and stage-specific antigens of Theileria annulata.

Western blot analysis of Theileria annulata antigens was carried out using sera collected from cattle which had been immunised and challenged with either T. annulata sporozoites or schizont-infected cells. Three antigens between 71 and 73 kDa proved to be common to the three stages of parasite studied: sporozoites, schizonts and piroplasms. An antigen was found at 32 kDa which was specific to T. annulata piroplasms. Results were reproducible using sera from Morocco and the UK. At least one of the proteins at 71-73 kDa, but not that at 32 kDa were also recognised by sera from animals infected with Babesia species.     

Administration of porcine somatotropin by sustained-release implant: growth and endocrine responses in genetically lean and obese barrows and gilts.

Previous studies have documented the effectiveness of porcine somatotropin (pST) administered by daily injection in promoting lean tissue growth in lean and obese pigs and the influence of sex and genotype. The present study examined the accretive responses in pigs of different lines and sexes to a slow release formulation of pST (pST-SR). Implants that deliver 2.0 mg of pST/d were implanted in genetically lean and obese barrows and gilts at 65 +/- .7 kg BW (mean +/- SE). Pigs received no, one, or two implants (i.e., doses of 0, 2.0, and 4.0 mg of pST/d). Pigs (four per line x sex x dose) were housed individually and continuously supplied with fresh water and a 19% CP diet containing 1.08% lysine. Pigs were slaughtered on d 0 (four per line x sex) and at the end of the trial (approximately 42 d after implantation) for estimation of initial composition and calculation of accretion rates. Blood samples were collected at d 0, 7, 14, 28, and 42 to measure endocrine and metabolite responses to pST-SR. Sustained-release pST elevated (P < .05) circulating pST throughout the trial with peak concentrations at d 7. On d 7, serum pST concentrations in the pigs given 2.0 mg of pST-SR per day were 16-fold greater than those in control pigs, and in pigs given 4.0 mg of pST-SR per day pST concentrations were 33-fold greater than in controls. Elevated serum pST resulted in increased (P < .05) serum concentrations of insulin-like growth factor (IGF)-I, IGF-II, insulin, and glucose and in reduced (P < .05) concentrations of urea nitrogen and IGF binding protein (IGFBP)-2. Gain was not influenced by pST-SR dose; however, feed consumption was reduced (P < .05) and efficiency of gain was increased (P < .05). Accretion of all body components except cold carcass weight, cecum, and untrimmed Boston butt and ham were changed (P < .05) with pST-SR administration. Heart and stomach were the only components of the carcass and offal whose accretion was not affected by line or sex. Increases in accretion of carcass components (< 75%) induced by sustained-release pST were considerably less than those measured in the organs (liver, 157%; lungs, 748%). The pST-SR treatment resulted in elevated serum concentrations of pST and its mediators and improved efficiency and composition of gain.(ABSTRACT TRUNCATED AT 400 WORDS)     

Comparative virulence of NAD-dependent and NAD-independent Actinobacillus pleuropneumoniae strains.

The virulence of a NAD-independent Actinobacillus pleuropneumoniae serotype 2 strain and NAD-dependent serotype 2, 3 and 9 strains was compared under experimental conditions. Hysterectomy-derived piglets were inoculated endobronchially with 50-500 cfu of these strains. All 23 piglets inoculated with the NAD-dependent strains developed acute disease within 12 hours post inoculation. Twenty-two of these piglets died within 24 hours after the first clinical signs. Three of nine piglets inoculated with the NAD-independent strain did not develop clinical disease. In the other six piglets, disease signs were similar as in the piglets inoculated with the NAD-dependent strains. No differences in clinical disease were observed between colostrum deprived piglets and piglets that obtained colostrum from a SPF sow.     

Subcutaneously implanted tissue chambers — a pharmacokinetic study

The purpose of this study was to characterize the pharmacokinetics of a subcutaneously implanted tissue-chamber model. Thermoplastic tissue chambers were implanted in the paralumbar fossae of six steers. Starting 30 days after implantation, the distribution of intravenously administered antipyrine and phenylbutazone into the tissue chambers was studied. These pharmacokinetic experiments were repeated 10 days later to determine the effect of time after implantation on tissue-chamber distribution. Fifty days after implantation, tissue chambers were drained of transudate, refilled with sterile saline and the rate of influx of endogenous urea, creatinine and albumin was measured. Delayed diffusion of antipyrine and phenylbutazone into tissue chambers was well described using a compartmental model in which tissue-chamber fluid represented the third of three compartments arranged in series. The distribution of antipyrine into tissue chambers was greater than that of phenylbutazone; an observation which is well correlated with the high degree of protein binding of phenylbutazone. There was no effect of time on the penetration of the two agents. Rapid diffusion of urea and creatinine and extremely slow influx of albumin into chambers showed that these chambers formed true interstitial compartments.