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Dental changes are one of the main reasons for slaughtering sheep early before the end of their regular breeding period, resulting in increased costs due to the need to purchase new animals for the flock. Within this context, excessive dental wear and periodontal disease are key disorders affecting sheep teeth and bearing structures (West and Spence 2000). Periodontitis manifests as gingivitis, periodontal pocket formation, gingival recession, bleeding on probing, suppuration, food debris retention, teeth loosening and loss of teeth. Studies have reported similarities between oral microflora in sheep and human periodontitis (Frisken and others 1989, Ismaiel and others 1989, McCourtie and others 1990). Riggio and others (2013) demonstrated the prevalence of Mannheimia ruminalis and Moraxella caprae in sheep with broken mouth periodontitis. Among the microorganisms considered periodontopathogenic, those belonging to Socransky's red complex ( Porphyromonas gingivalis , Tannerella forsythia and Treponema denticola ) are of recognised importance in several forms of periodontitis in humans and a few other animal species (Hardham and others 2005, Booij-Vrieling and others 2010, Yamasaki and others 2012). In advanced cases of periodontitis, spirochaetes may comprise more than 50 per cent of the subgingival microflora (Chu and Holt 1994), enabling their adherence to skin cells and, consequently, …

Periodontal diseases are multifactorial infectious processes caused by complexes of microorganisms, with damage to health, production, and animal welfare. The aim of the present study was to evaluate the efficacy of virginiamycin in the prevention and control of two early forms of periodontal disease: gingivitis and necrotizing gingivitis. Ten weaned calves, aged four to six months, were permanently kept in a single lot under the same rotational grazing regime in a newly reformed area of Panicum maximum. Five of the calves were orally administered 340mg of virginiamycin (Virginiamycin Group) daily for a period of 18 weeks, while the remaining five calves (Control Group) remained under the same food management but did not receive virginiamycin. During this period, animals underwent 18 weekly evaluations regarding periodontal health, with monitoring and recording of clinical parameters of the eight deciduous incisor teeth on the labial and lingual faces. At approximately two-week intervals, nine collections of subgingival sulcus material from five sites of the four right incisor teeth of each animal were performed and subjected to microbiological evaluation using polymerase chain reaction with primers of 25 microorganisms considered potentially pathogenic. After 1440 periodontal clinical evaluations of incisor teeth of the 10 calves, a total of 395 episodes of gingivitis were recorded, of which 267 occurred in the Control Group and 128 in the Virginiamycin Group. Similarly, 89 episodes of necrotizing gingivitis were recorded; 58 in the Control Group and 31 in the Virginiamycin Group. Comparison of between-group means found significant differences for teeth with gingivitis and necrotizing gingivitis (t test; p