Role of rumen and saliva in the homeostatic response to rehydration in cattle.
It has been shown recently that the circulation created by the continuous secretion of voluminous amounts of saliva rich in Na+ to the large store of fluid sequestered in the rumen and its reabsorption from the gut is an integral part of water and Na+ homeostasis in cattle. The role of this system in water and Na+ restitution following acute dehydration and rapid rehydration was studied. Cattle were able to withstand dehydration of 18% of their initial mass and to replenish their water losses in one drinking. The water imbibed was first retained in the rumen and slowly released. Rapid expansion (or dilution) of their blood as a result of large influxes of hypotonic water from the rumen was prevented by a parallel increase in the secretion of hypotonic saliva. The accelerated saliva secretion refluxed back to the rumen almost half of the water absorbed. Saliva electrolyte concentration varied simultaneously with an increase or decrease in saliva flow. Na+, HCO3-, HPO3-, and pH were inversely related to saliva flow rate while Cl and K+ were positively related. It seems that visceral afferent response was involved in activation of salivary flow rate.
Silanikove
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Migal-Galilee Technological Centre, Kiryat Shmona, Israel.
D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000503:physiopathology*; D003681:Dehydration / Q000503:physiopathology / Q000662:veterinary*; D004326:Drinking; D005260:Female; D005440:Fluid Therapy; D006706:Homeostasis; D012417:Rumen / Q000502:physiology*; D012463:Saliva / Q000378:metabolism*; D012636:Secretory Rate; D012964:Sodium / Q000378:metabolism; D014882:Water-Electrolyte Balance
D012964:Sodium