title: [Investigation of the age-dependent development of brachygnathia inferior in the East Friesian milk sheep].
abstract: Shortness of the lower jaw (brachygnathia inferior, underbite) is a common anomaly in sheep. In order to study the age-dependent development of brachygnathia inferior, data of 73 East Friesian milk sheep from a breeding experiment over six generations were analysed. Data were recorded in regular intervals of four weeks from birth up to an age of at least 25 weeks. Brachygnathia inferior was determined by the distance between the edge of the central incisor of the lower jaw and the anterior surrounding of the upper jaw (DIFF-UK) using a measuring tape. Four main types of brachygnathia inferior were distinguished using means, standard deviations and maximum values of the individual animals.The thresholds were a maximum and mean DIFF-UK of 0.5 cm and a standard deviation of 0.266 cm. A total of 14 sheep (main types 3 and 4) showed an obvious brachygnathia inferior with mean DIFF-UK larger than 0.5 cm whereof ten animals showed a large variation of DIFF-UK values (standard deviation > 0.226 cm). Mean DIFF-UK values of 59 sheep were smaller than 0.5 cm (main types 1 and 2). One of these 59 animals had during the first four weeks of life DIFF-UK values of 1 cm and than decreasing values reaching zero within the next nine months (main type 2). Five of the 58 animals with main type 1 had a perfect occlusion of jaws, all with DIFF-UK values at zero during the whole recording period. Parents with severe or mild brachygnathia inferior had severely affected progeny. Selection of sheep for breeding with a perfect occlusion of jaws decreases the risk to pass on the hereditary disposition for brachygnathia inferior. An early inspection of potential breeding animals is advisable to detect all cases of brachygnathia inferior even if the underbite decreases in the first year of life.
authors.affiliation: Institut für Tierzucht und Vererbungsforschung, Stiftung Tierärztliche Hochschule, Hannover.
authors.forename: Ricarda
authors.initials: R
authors.lastname: Pielmeier
authors.forename: Andrea
authors.initials: A
authors.lastname: Kerkmann
authors.forename: Ottmar
authors.initials: O
authors.lastname: Distl
mesh_terms: D000367:Age Factors; D000818:Animals; D003612:Dairying; D005260:Female; D005858:Germany / Q000453:epidemiology; D007571:Jaw Diseases / Q000453:epidemiology / Q000662:veterinary*; D008297:Male; D008313:Malocclusion, Angle Class III / Q000453:epidemiology / Q000662:veterinary*; D012756:Sheep; D012757:Sheep Diseases / Q000453:epidemiology*; D034561:Sheep, Domestic