The effect of pseudorabies (Aujeszky''s) virus infection on young mature boars and boar fertility.

This study was designed to determine the effects of experimental inoculation with pseudorabies virus on the reproductive tracts of young adult boars. Pseudorabies virus was inoculated intranasally into 12 boars and intrapreputially into four boars. All animals seroconverted after nasal or preputial inoculation. Semen abnormalities were observed 21 days postinoculation with partial recovery by 50 days postinoculation. Virus was isolated from the preputial sheath of two intrapreputially inoculated boars 12 days postinoculation. It was concluded that pseudorabies virus infection can be established via preputial inoculation and that decreased spermatogenesis and infertility can result.     

Modification of standard freezing media to limit capacitation and maximise motility of frozen-thawed equine spermatozoa

OBJECTIVE: To investigate cryopreservation-induced capacitation-like changes in equine spermatozoa frozen in three different media using chlortetracycline (CTC) fluorescence staining analysis. PROCEDURE: Semen collected from three stallions was diluted in one of three centrifugation media and, after centrifugation and removal of supernatant, extended in corresponding freezing media containing additional egg yolk, glycerol, lactose and Equex paste. The semen was frozen in 5 mL straws and the spermatozoa assessed for motility and membrane quality after thawing. RESULTS: Following centrifugation, spermatozoa diluted with modified Kenney's Centrifugation Medium (MKCM) displayed a higher percentage of (normal) F pattern (94.3%) compared with spermatozoa in Kenney's Centrifugation Medium (KCM) (84.9%) and Glucose-EDTA Centrifugation Medium (GECM) (85.2%). Conversely, the percentage of spermatozoa displaying the (capacitated) B pattern was higher in the KCM (14.1%) and GECM (13.8%) than in the MKCM (5.0%). Following freezing-thawing, there were lower percentages of spermatozoa displaying the AR (acrosome reacted) pattern in modified Kenney's Freezing Medium (MKFM) (45.6%) compared with Kenney's Freezing Medium (KFM) (61.4%) and lactose-EDTA Freezing Medium (LEFM) (61.1%). There was a correspondingly higher percentage of spermatozoa displaying the B pattern in MKFM (52.3%) compared with KFM (37.9%) and LEFM (38.6%). There was no significant difference between the freezing media in the percentage of spermatozoa displaying the F pattern. The percentage of progressively motile spermatozoa was also influenced by the type of freezing medium (P < 0.001). Post-thaw percentages of progressively motile spermatozoa, frozen in MKFM, KFM, and LEFM, were 31.4, 25.8 and 23.3%, respectively. CONCLUSION: MKFM was the preferred medium for cryopreservation of equine spermatozoa due to its superior protection against changes in motility and membrane quality compared with the other freezing media studied.     

Mycoplasma gallinarum infection in commercial layers and onset of fatty liver hemorrhagic syndrome

Fatty liver hemorrhagic syndrome (FLHS) was observed in each of three trials in which commercial layers were utilized to determine the effect of Mycoplasma gallinarum (MGn) on egg and eggshell quality parameters and egg production. In each of three trials, FLHS occurred 31-54 days later in MGn-inoculated hens as compared with the Mycoplasma-clean (control) hens. In trials 1 and 2, no therapeutic intervention was initiated to ameliorate FLHS. In trial 3, therapeutic intervention was instituted and consisted of the addition of 1 pound of choline chloride/ton of feed. Total mortality recorded throughout the duration of each trial and attributable to FLHS was not significantly different between the control and the MGn-inoculated treatment. However, FLHS-associated mortality in each of the three trials was numerically greater for the control treatment.     

Full pedigree quantitative trait locus analysis in commercial pigs using variance components

In commercial livestock populations, QTL detection methods often use existing half-sib family structures and ignore additional relationships within and between families. We reanalyzed the data from a large QTL confirmation experiment with 10 pig lines and 10 chromosome regions using identity-by-descent (IBD) scores and variance component analyses. The IBD scores were obtained using a Monte Carlo Markov Chain method, as implemented in the LOKI software, and were used to model a putative QTL in a mixed animal model. The analyses revealed 61 QTL at a nominal 5% level (out of 650 tests). Twenty-seven QTL mapped to areas where QTL have been reported, and eight of these exceeded the threshold to claim confirmed linkage (P < 0.01). Forty-two of the putative QTL were detected previously using half-sib analyses, whereas 46 QTL previously identified by half-sib analyses could not be confirmed using the variance component approach. Some of the differences could be traced back to the underlying assumptions between the two methods. Using a deterministic approach to estimate IBD scores on a subset of the data gave very similar results to LOKI. We have demonstrated the feasibility of applying variance component QTL analysis to a large amount of data, equivalent to a genome scan. In many situations, the deterministic IBD approach offers a fast alternative to LOKI.     

3-methylindole induces transient olfactory mucosal injury in ponies

Response to 3-methylindole (3MI) varies among species. Mice recover from 3MI-induced bronchiolar epithelial injury but sustain persistent olfactory mucosal injury with scarring and epithelial metaplasia. In contrast, 3MI induces obliterative bronchiolitis in horses and ponies, but olfactory mucosal injury has not been reported. To evaluate the effect of 3MI on equine olfactory mucosa, ponies were dosed orally with 100 mg 3MI/kg (n = 9) or corn oil vehicle (n = 6). All ponies treated with 3MI developed obliterative bronchiolitis with mild olfactory injury. By 3 days after 3MI dosing, olfactory epithelium appeared disorganized with decreased and uneven surface height and scalloping of the basement membrane zone. Epithelial cells of Bowman's glands were hypertrophic. Proliferation of olfactory epithelium and Bowman's glands was supported by an increased mitotic index and positive immunohistochemical staining for proliferating cell nuclear antigen as compared with controls. The activity of 11beta-hydroxysteroid dehydrogenase, an olfactory mucosal cytosolic enzyme localized to sustentacular and Bowman's glandular epithelial cells, was concurrently decreased. By 9 days postdosing, olfactory mucosal lesions had lessened. Results indicate that 3MI transiently injures equine olfactory mucosa without the extensive necrosis, scarring, or metaplasia seen in murine olfactory mucosa or in equine bronchiolar epithelium.     

Effects of a P2Y(12) receptor antagonist on the response of equine platelets to ADP. Comparison with human platelets

Horses show susceptibility to platelet-related disorders. Equine platelets differ from human platelets in some of their responses, so information available about human platelets must be validated in the horse. Aggregation of platelets by ADP involves both P2Y(1) and P2Y(12) receptors on the platelet surface. We have compared the effect of the P2Y(12) antagonist, AR-C67085, on equine and human platelets in vitro using turbidimetric aggregometry to measure the rate and final extent of aggregation. Aggregation profiles, concentration-response curves and pA(2) values show that the rate of aggregation of equine platelets is much more susceptible to inhibition by AR-C67085 than that of human platelets. This species difference may reflect differences in the relative numbers of P2Y(1) and P2Y(12) receptors, or in intracellular signalling pathways, but will need to be considered by equine clinicians before using P2Y(12) antagonists in the treatment of thrombotic conditions.     

Issues associated with the application to veterinarians of a mailed questionnaire regarding lower respiratory-tract disease in racehorses

This study evaluated a questionnaire investigating the attitudes and behaviours of veterinarians regarding the cause, diagnosis and treatment of lower respiratory-tract disease in racehorses. The questionnaire was sent to all non-student members (648) of the Australian Equine Veterinary Association: two mailings and a single telephone contact (each separated by four weeks). Subsequent phases were only administered to those who had not responded to earlier phases. In total, 467 (72.1%) of the 648 mailed questionnaires were returned. Of these, 354 were usable. The remaining 113 respondents gave various reasons for not completing the questionnaire; the most common (68%) was that horses were not a component of their practice. Those respondents working primarily with horses required fewer phases to return the questionnaire. Although deviating from previously described questionnaire designs, the described protocol provided a reasonable response rate.     

Dose selection of selamectin for efficacy against adult fleas (Ctenocephalides felis felis) on dogs and cats

Selamectin, a novel avermectin, was evaluated in two controlled studies (one in Beagles, one in domestic shorthaired cats) to determine an appropriate topical dose for efficacy against adult Ctenocephalides felis felis (C. felis) fleas on dogs and cats for 1 month. For each study, animals were allocated randomly to four treatments. One treatment consisted of the inert formulation ingredients (vehicle) administered as a negative control, and the other three treatments consisted of a single topical dosage of 3, 6, or 9mgkg(-1) of selamectin. In each study, selamectin was administered as a topical dose applied to the skin in a single spot at the base of the neck in front of the scapulae. Dogs and cats were infested with 100 viable unfed C. felis (50 males and 50 females) on days 4, 11, 18, and 27. Seventy-two hours (+/-2h) after each infestation, on days 7, 14, 21, and 30, a comb count to determine the number of viable fleas present on each animal was performed. Efficacy of selamectin on day 30 was used to select an appropriate dose. For dogs and cats, percentage reductions in geometric mean flea comb counts for the three selamectin treatments ranged from 94. 6 to 100% on days 7, 14, and 21, compared with the negative-control treatment. On day 30, reductions in flea comb counts were 81.5, 94.7, and 90.8% for dogs, and 79.8, 98.0, and 96.2% for cats treated with selamectin at 3, 6, or 9mgkg(-1), respectively. For day 30 flea comb counts for dogs and cats, analysis of variance showed that the three selamectin treatments resulted in significantly (P< or =0.05) lower counts than did the negative-control treatment. For dogs and cats, geometric mean flea counts for selamectin administered at a dosage of 3mgkg(-1) were significantly (P< or =0.05) higher than those for the 6 and 9mgkg(-1) treatment dosages combined. There were no significant differences in flea counts between the 6 and 9mgkg(-1) treatments. This analysis was confirmed by linear-plateau modeling. Thus, the optimal dose of selamectin for efficacy against adult fleas for both dogs and cats, as estimated by the turning point (plateau) in the dose response curve, was 6mgkg(-1).