AVAILABILITY OF PHOSPHORUS FROM TRICALCIUM-PHOSPHATE TO LACTATING AGENTS

During two periods of 3 weeks each, lactating goats were fed diets bas ed on NaOH-treated straw and concentrates which did nor cover their ne t requirements for phosphorus (P). Concentrates were supplied accordin g to the individual milk yield. In the concentrate used in period 2, 1 g P/kg was supplied by tricalcium phosphate. Balance periods were per formed during the last seven days of each period. Concentration of ino rganic phosphate in blood plasma was determined. The P balance was neg ative in both period 1 and period 2. Therefore, the availability of P from tricalcium-phosphate can be calculated. Phosphorus excretions wit h milk, faeces and urine were nor influenced by the supplementation of P in period 2. However, dry matter and, as a consequence, inevitable losses of P were lower in period 2 when compared with period 1. Availa bility of P from tricalcium-phosphate was 65 %. Concentration of inorg anic phosphate increased continuously from 0.2-0.47 mmol/l during peri od 2.