Step 1: Understanding the Concept:
Etiology of chronic recurrent bovine tympany: mechanical or functional impairment of the eructation reflex and ruminal motility pathways.
Step 2: Detailed Explanation:
Pathogenesis of Chronic Recurrent Bloat in ruminants:
1. A. Diaphragmatic Hernia (DH): Herniation of the reticulum through a tear in the diaphragm into the thoracic cavity leads to mechanical displacement of the cardia, adhesions, and persistent failure of the eructation reflex, producing chronic recurrent tympany.
2. D. Vagal Indigestion (Hoflund's Syndrome): Injury to the dorsal or ventral vagal nerve trunks impairs coordinated forestomach reticulo-ruminal motility and prevents normal opening of the cardia, causing classic chronic recurrent bloat and L-shaped ruminal distension.
3. (Legume bloat is acute frothy bloat; enteritis and rhinitis do not cause recurrent bloat).
Thus, recurrent bloat is characteristic of A and D only.
Step 3: Final Answer:
Hence, recurrent bloat is seen in A and D only, matching option (D).