Effects of hay-feeding on acid/base balance,renal sodium excretion,aldosterone and vasopressin secretion in the goat

Effects of 30 min intense hay-feeding on acid/base and sodium homeostasis were studied in semi-starved goats during hyper- and euhydration. Parallel analyses of carotid and jugular blood samples revealed that feeding induced metabolic acidosis, which to some extent was subjected to respiratory compensation. The acidosis was accompanied by renal sodium retention and urinary acidification persisting for 2–3 h. The sodium retention was succeeded by an increase in renal Na excretion above the initial level. This natriuresis was most accentuated during hyperhydration. Blood samples taken for hormone assays during euhydration revealed a 15% increase in haematocrit and a significant rise in plasma aldosterone at termination of feeding. Inhibition of the water diuresis in hyperhydrated animals, and moderate increases in renal arginine vasopressin (AVP) excretion and plasma AVP were inconsistent effects of feeding. It is concluded, that simply jugular vein blood provides reliable information on the acid/base status of goats, but that the feeding schedule has to be considered in all experiments where small ruminants are used to investigate the integrated control of acid/base and sodium homeostasis.