Minerals for Stocker Steers
Livestock Update, March 1997
Mark L. Wahlberg, Bill R. McKinnon, W. Terry Swecker
A stocker trial was conducted during 1996 with two objectives in mind:
In this paper the mineral supplementation phase will be discussed. A companion paper will contain the results of the implant phase.
Procedures - Thirty-two yearling steers (average weight 667 pounds) were used in a grazing trial at the Glade Spring Experiment Station. Steers were blocked by weight and put into 4 groups to which treatments were randomly assigned in a 2X2 factorial design. Treatments were 1) Initial Synovex-S implant, 2) Initial and re-implant with Ralgro, 3)Supplemented with a complete commercial mineral and 4)Supplemented with High-Selenium trace mineral salt. Cattle receiving the two different mineral supplements were grazed in different pastures, and within each mineral group one-half of the steers received each implant treatment. Both mineral products were purchased locally from the same vendor. Composition of the supplements is shown in table 1. Steers were rotated between the pastures every 2 weeks to minimize pasture effects.
At the beginning of the trial (May 16) steers received their designated implant and all steers were weighed and received a dose of pour-on Ivomec. Blood samples were taken for mineral analysis. On June 20 (day 35) steers received a second treatment of pour-on Ivomec and were weighed again. On August 5 (day 81) steers were bled and the Ralgro group was re-implanted. The trial terminated on September 25 (day 132) when steers were weighed and bled. Forage was grab-sampled throughout each pasture on May 22, August 5, and September 25. Samples from each pasture on each sample date were composited and mineral content was determined. Mineral was available at all times in self-feeders. Amount of mineral put into feeders was recorded, and every 2 weeks amount remaining was determined so that intake for the group could be calculated.
Results - There was no significant difference in cattle growth by mineral treatment to either day 81 or for the entire trial (table 2). Steers gained quite well during the study with overall gains averaging 242 pounds (ADG=1.84 pounds) There was no difference due to mineral treatment in any of the blood mineral levels at the end of the trial. All blood minerals were at normal levels. The forage mineral levels did not change greatly from May through September (table 3). When compared to NRC requirements for minerals, the forage was deficient or marginal for only Calcium, Sodium, Zinc, Copper, and Selenium. Grazing pressure was adequate to keep the forage at a vegetative stage of growth, and the abundant rainfall enabled the grass to continue to grow. Intake was higher for the complete mineral ((table 4). The complete mineral cost more than the high-Se trace mineral salt (20.9 cents vs 13.9 cents per pound). Total cost of the mineral program for these steers was 2.6 times higher for the complete mineral.
Conclusions - Pasture provided adequate levels of most minerals for stocker steers in this study. Consequently, gains of cattle consuming a high-Se trace mineral salt were not different from those consuming a complete mineral. Mineral status of cattle receiving either mineral was normal. Cattle ate less of the trace mineral salt, and it was less expensive. Cattle provided with high-Se trace mineral salt gained the same as cattle consuming a complete mineral supplement, but at a lower cost.