Effects of varied dietary calcium and phosphorus on renal function of male Blue Duiker antelope

Abstract

Sixteen adult male Blue Duikers ( Cephalophus monticola bicolor) were fed a basal diet with four levels of Ca and P for 4 months. Pretrial, 24-h urine clearance was studied in each Duiker while they consumed the herd diet (1.38% Ca/0.66% P) (The Pennsylvania State University (PSU) formulation). Pretrial, 24-h urine clearance values revealed no differences ( P > 0.05) among treatment groups consuming the PSU diet. However, younger males did have higher serum P and lower serum and urine Ca concentrations ( P < 0.05). Posttrial renal function studies indicated age differences for [P] Plasma, [K] Urine, urine/plasma [K], and absolute excretion of K, which were higher in younger males, and free water clearance and tubular P excretion, which were highest in older males. Renal function was affected by the level of Ca and P in the diet. Glomerular filtration rate (GFR) and effective renal blood flow (ERBF) were lower ( P < 0.05), and fractional excretion (FE) of electrolytes and creatinine (Cr) were higher ( P < 0.05) in the T 3 group (0.8% Ca/0.4% P), indicating possible onset of renal dysfunction in these Duikers. Clearance of creatinine ( C Cr) was negatively correlated with [Cr] Plasma, suggesting tubular secretion of Cr increased during decreased renal function. Endogenous C Cr was not an accurate approximation of GFR, as determined by clearance of inulin ( C In, in Blue Duiker under varying nutritional conditions. FE of all electrolytes, as calculated by C In, regressed against the FE calculated from C Cr, indicated a poor correlation except for P. This suggests that FE P as measured by C Cr may be a useful index of early renal dysfunction in Blue Duiker. It appears that Blue Duiker have the ability to maximize P retention that may be available in limited quantity in the wild. The Ca/P ratio of 0.5:0.4% in the ration appears to be best suited for adult males.