Influence of calcium and phosphorus ratio in diet, on endogenous losses and absorption of phosphorus by sheep

Abstract

Eighteen crossbred male sheep (mean weight 34.4 ± 3.1 kg) were used to study the effect of three Ca:P ratios (0.75:1.0; 1.5:1.0 e 3.0:1.0). Sheep were kept in metabolic crates and received diets containing Cynodon dactylon hay (650 g), cassava root meal (150 g), urea (15 g) and trace-mineralized salt. At the 22^nd day each animal received, through the jugular vein, an injection of 7.4 MBq of radiophosphorus (³²P). Blood, feces and urine samples were collected for 8 days. Total P excretion (83.92 mg/kg LW) and endogenous fecal P (51.36 mg/kg LW) were not significantly different (P>0.05). P absorbed and coefficient of absorption for the (0.75:1.0; 1.5:1.0 e 3.0:1.0) treatments were 49.2, 62.7 and 55.2 mg/kg LW, and 0.56, 0.70 and 0.63, with significant difference (P<0.05) between 1.5:1.0 and 0.75:1.0 for both parameters. Positive correlation was observed between P absorbed and endogenous fecal P (r=0.82, P<0.001). Ca:P ratio of 1.5:1 seems to be the most indicate as it enhanced better P absorption indices than Ca:P ratio of 0.75:1, and tended to be better than Ca:P ratio of 3:1.