The role of the kidney in nitrogen conservation in sheep

Creatinine and inulin clearance at the different nitrogen and energy intake in sheep

1. Renal creatinine and inulin clearances were compared between sheep fed (a) high nitrogen and high energy diet; (b) low nitrogen and high energy diet and (c) low nitrogen and low energy diet. 2. Inulin clearance was significantly lower in sheep on both low nitrogen diets vs the group with high nitrogen intake. Differences were not ascertained between the groups on low nitrogen diets. 3. No significant differences were found in the creatinine clearance. The creatinine inulin clearance ratio was higher when animals were fed low nitrogen diets, vs the group on a high nitrogen diet. 4. Results suggest that the endogenous creatinine is not suitable for the GFR measurement in sheep under the different conditions of nutrition.

Renal excretion of urea in response to changes in nitrogen intake in desert (black Bedouin) and non-desert (Swiss Saanen) goats

Renal responses were compared between desert (black Bedouin) and non-desert (Swiss Saanen) goats fed Lucerne hay ad. lib., Lucerne hay restricted to 65% of the ad. lib. consumption and wheat straw. Reduced feeding in both breeds resulted in proportional reduction in glomerular filtration rate (GFR) and the amount of urea excreted with no change in the percentage of urea reabsorbed. In both breeds appreciably less urea was filtered at the glomerulus when a low-nitrogen diet was fed compared with a high nitrogen diet and the percentage of filtered urea reabsorbed increased from about 55 to about 90%. In both breeds the reduction in GFR is quantitatively more important than the increase in the percentage of filtered urea reabsorbed in regard to renal urea conservation. The results indicate no qualitative differences between desert and non-desert breeds of goat. The advantages of the Bedouin over the Saanen goats is related to the lower GFR values in the Bedouin goat and mainly their ability to reduce its GFR much more than the Saanen goats in response to lower nitrogen intake.