title: The primary-secondary rumen contraction and gas expulsion in sheep (Ovis aries).
abstract: 1. Sheep rumens were insufflated with nitrogen to 5, 10, 15 and 20 cm HOH pressure and sustained at each pressure for 5 min. 2. Measurements included rumen motility, reticulorumen myoelectrical activity, eructation frequency and volume, and changes in tracheal pressure. 3. Associated with elevated intrarumen pressure was a previously unreported type of rumen contraction on which gas expulsion occurred, the primary-secondary contraction. 4. Gas expulsion volume was similar on primary-secondary and secondary contractions. 5. The maximum rumen contraction rate per min was 4-5 for secondaries and 1-2 for primary-secondaries. 6. Irrespective of the sustained initial pressure, resting intrarumen pressure was reached within 5 min.
mesh_terms: D000818:Animals; D004576:Electromyography; D005740:Gases; D005769:Gastrointestinal Motility; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology; D011312:Pressure; D012417:Rumen / Q000502:physiology*; D012756:Sheep / Q000502:physiology*; D014132:Trachea / Q000502:physiology
chemical_list: D005740:Gases