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 distributed 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 fertilized 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 during the afternoon-night grazing (5 p.m. to 7 a.m.). LW was measured every 21 days and blood samples were taken to determine the mineral composition in blood serum using a hierarchical model where the effects of treatment, sampling month and animal within the treatment were controlled. Significant differences (P<0.01) in live weight (602.58, 628.66 and 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) between 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 encountered. This experimental reflects an improvement when Ca and P were supplemented to growing animals.