1University of California 1004 E. Holton Rd., El Centro CA, 92243 U.S.A.
2Instituto de Investigaciones en Ciencias Veterinarias Universidad Autónoma de Baja California Obregón y Julián Carrillo S/N, 21100, Mexicali, Baja California, México
3Facultad de Medicina veterinaria y Zootecnia Universidad Autónoma de Tamaulipas Apartado Postal 263. Carretera Cd. Victoria-Cd. Mante km 6.5 Cd. Victoria, Tam. 87000, México
*E-mail: razinn@ucdavis.edu
Ninety-six Holstein steer calves (120.7±5.3 kg) were used to evaluate the influence of dietary phosphorus level (0.27, 0.31, 0.35 and 0.39%, DMB) on growth-performance during the initial 105 d on feed. Dicalcium phosphate was the source of supplemental phosphorus. All diets were formulated to contain 0.85% calcium (DMB). Dietary phosphorus level did not affect (P>.10) DMI or body size measurements. However, increasing dietary phosphorus level increased ADG (linear component, P <.05), gain efficiency (quadratic component, P <.05) and dietary NE (quadratic component, P <.05). It is concluded that during the initial growing period ADG, gain efficiency and dietary NE are optimal at a dietary phosphorus level of 0.35%, 15% lower than current NRC recommendations.
Requirement, phosphorus, Holstein, growth, feedlot
