LEVELS OF CALCIUM AND PHOSPHORUS SUPPLEMENTATION TO GRAZING HEIFERS

The effect of calcium and phosphorus supplementation to heifers until they entered AI was evaluated. 45 heifers with an average LW of 252 kg and 15 months of age were used in a completely randomized design dist ributed in three treatments: A) control, B) 10 g/animal/day and C) 30 g/animal/day of dicalcium phosphate, respectively. The animals grazed common guinea grass (Panicum maximum) without irrigation and fertilize d with 100 kg N/ha/year. The animals grazed together in groups of 7 ha divided in 8 paddocks. The stocking rate was 6.4 animals/ha and durin g the afternoon-night grazing (5 p.m. to 7 a.m.). LW was measured ever y 21 days and blood samples were taken to determine the mineral compos ition in blood serum using a hierarchical model where the effects of t reatment, sampling month and animal within the treatment were controll ed. Significant differences (P<0.01) in live weight (602.58, 628.66 an d 758.33 for A, B and C, respectively) in favour of the highest level of supplementation were found, Differences in Na in blood (P<0.01) bet ween the level of 30 g of supplement/day and the remaining two and in P(P < 0.001) between the supplemented groups and the control were enco untered. This experimental reflects an improvement when Ca and P were supplemented to growing animals.