Comparison among the effects of oral, intraperitoneal and intravenous fluid-loading on kidney function and drinking in goats.

The effects of hyperhydration, induced by oral loading via a stomach tube (41 of 0.9% NaCl within 2-3 min), intra-peritoneal and intra-jugular infusions (41 of 0.9% NaCl solution at a rate of 21 hr-1) in normally hydrated goats, on fluid retention, plasma expansion, kidney function and drinking response were compared. Higher fluid retention (67 and 65% vs. 40% at 3 hr after the termination of the infusion, P < 0.01), attenuated diuretic (P < 0.01) and natriuretic (P < 0.01) responses and lower expansion of plasma volume (P < 0.05) were recorded in the orally and intra-peritoneally treated goats in comparison with the intra-jugularly treated animals. Portal expansion apparently induces acceleration of saliva secretion which recycles water to the gut. Recycling of water to the gut reduced excessive expansion of plasma fluid and load on the kidney. Retention of water in the rumen satiated the urge to drink in the orally and intra-peritoneally treated goats for at least 24 hr. The intra-jugularly treated goats consumed a significant amount of water (1l), which was approximately half of their normal requirement. Under arid conditions, these responses are appropriate to the animals' regular exposure to severe dehydration and rapid rehydration.