Fontes de fósforo em suplementos para bovinos de corte em pastagem de Cynodon nlemfuensis Vanderyst

Abstract

This trial was carried out on Duas Fontes Farm, located in the city of Cruzeiro do Sul, northwest of Paraná and in the Feed Analyses and Animal Nutrition Laboratory of Maringá State University, during 2007, from January, 10th to November, 20th. The objective was to evaluate the use of three phosphorus sources in mineral supplements for cattle in grazing pasture (Cynodon nlemfuensis Vanderyst) comparing with dicalcium phosphate considering performance and physiological parameters of animals. In this period, forage quality and production were also evaluated. Treatments were distributed in a completely randomized design. Thirty-two crossbred steers (Bos indicus x Bos taurus) with 347 kg of initial body weight were used. The animals were allocated to four treatments corresponding to mineral supplements with different supplemental phosphorus sources: 1) Dicalcium phosphate (DP); 2) Supertriple phosphate (SP); 3) Monoammonium phosphate (MP) and 4) Araxa rock phosphate (ARP). The body weight gain per hectare (BW/ha) was influenced (P?0.05) by periods, with a significant reduction in the last period, as a result of quality and forage production reduction. Average daily gain (ADG) was not influenced (P>0.05) by treatments, and gains were 0.67; 0.65; 0.63 and 0.56 kg/d for DP, SP, MP and ARP, respectively. The consumption of mineral supplement was highest (P?0.05) for SP with consumption of 68 g/animal/d, while the mixtures containing DP and MP did not differ with consumptions of 56.6 and 43.2 g/animal/d, respectively. Mineral supplement containing ARP showed consumption of 33.4 g/animal/d and was inferior (P?0.05) to SP and DP. Plasma osteocalcin was similar among treatments (47.67 ng/mL). Supplemental phosphorus sources did not differ (P>0.05) and they were efficient in maintaining appropriate levels of serum phosphorus, with an average of 7.03 mg/100 mL.