Ralgro vs Synovex 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:

• Compare an initial Synovex-S to an initial and re-implant Ralgro
• Compare a complete mineral to a high Selenium trace mineral salt

In this paper the implant phase will be discussed. A companion paper will contain the results of the mineral supplementation 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 (36 mg per dose), 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. 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.

Results - There was no significant difference in cattle growth by implant treatment to either day 81 or for the entire trial (P>.15) (table 1). However, over the 132-day trial Ralgro cattle outgained Synovex-S cattle by .16 pounds per day. With a larger number of cattle in the study this could well have been a significant difference. There was no significant interaction between the mineral treatments and the implant treatments. 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. Steers gained quite well during the study with overall gains averaging 242 pounds (ADG=1.84 pounds).

Conclusions - There was a nonsignificant trend for steers to gain faster with an initial and reimplant Ralgro vs an initial Synovex-S implant. This could be interpreted that it took two doses of Ralgro administered 81 days apart to provide growth promotion similar to a single Synovex-S. Heavy steers can respond well to implants during the stocker phase.

Table 1. Initial and Re-implant Ralgro vs Initial Synovex-S for Stocker Steers

Item	Initial and Reimplant Ralgro	Initial Synovex-S
81-day Average Daily Gain, lb	2.34	2.09
132-day Average Daily Gain, lb	1.93	1.77

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