Effects of Revalor-G®, R®algro, and Synovex-H® on the performance of stocker heifers grazing irrigated rye pasture

A 151-day field study was conducted to compare three anabolic implants for promoting weight gain in stocker heifers grazing center pivot-irrigated pastures of winter rye. Three hundred previously nonimplanted heifers averaging 421 lb were allotted to one of four treatments: 1) no implant-control (NC), 2) Ralgro® (RAL), 3) Revalor-G® (REV-G) and 4) Synovex-H® (SYN-H). Heifers were weighed at monthly intervals to evaluate the growth response curve of each implant type over time relative to controls. Only during the first 32-day period after implantation did heifers implanted with REV-G gain significantly faster (P<.05) than NC. All implant groups responded similarly (P>.05) during the next three monthly weigh periods. During the last period (day 124151), SYN-H heifers gained faster (P<.05) than all other treatments. Over the entire 151-day study, daily gains (lb/day) averaged as follows: NC, 1.50; RAL, 1.58; REV-G, 1.64; and SYN-H, 1.79. All implant types except RAL significantly improved gain (P<.05) compared to NC. Although no significant difference (P>.24) occurred between RAL and REV-G, SYN-H-implanted heifers. gained faster (P<.05) than the other implant groups over the 151-day grazing season.

Sincere appreciation is expressed to Great Plains Cattle, Pratt, Kansas for providing 1 cattle, facilities, and assistance, and to Hoeshst-Rouseel Vet for financial support.

Summary
A 151-day field study was conducted to compare three anabolic implants for promoting weight gain in stocker heifers grazing center pivot-irrigated pastures of winter rye.
The use of estrogenic implants to en-Three hundred previously nonimplanted hance the performance of grazing stockers heifers averaging 421 lb were allotted to one has been adopted widely by cattle producers.of four treatments: 1) no implant-control Revalor-G is a newly approved anabolic (NC), 2) Ralgro (RAL), 3) Revalor-G agent for grazing cattle containing trenbolone The 93-123) weigh periods.SYN-H heifers treatments were: 1) no implant-control (NC), gained significantly faster (P<.05) than heif-2) Ralgro (RAL), 3) Revalor-G (REV-G), ers in all other implant treatments between and 4) Synovex-H (SYN-H).For each of the days 124 and 151 and over the entire 151remaining weigh days (days 32, 60, 92, 123, day trial.and 151), heifers were gathered, placed in drylot, and fed hay and alfalfa/wheat mid-Figure 1 presents the cumulative growth dling (AWM) pellets for 1 day before individ-response of heifers to each implant type ual weights were obtained.
relative to nonimplanted controls over the All heifers grazed predominantly winter G and SYN-H-implanted heifers gained rye pasture during the 151-day trial.Heifers rapidly early in the study relative to the NC were assigned randomly to one of two rye treatment.However, the anabolic response pastures with center pivot irrigation.Equal from each implant was different over the pounds of live cattle were stocked per circle.
course of the study.For SYN-H, a sustained However, inclement winter weather and growth response was observed above the NC insufficient rye forage necessitated feeding treatment that did not vary much throughout supplemental alfalfa and AWM pellets in the 151-day experiment.This suggests that addition to either rye or alfalfa hay during a the payout response of SYN-H implants may 45-day period in December and January.
last at least 151 days.In contrast, the REV-Four heifers were removed because of health G implant demonstrated a classic "half-life" problems unrelated to implant treatment.
response relative to the NC treatment over Individual animal was the experimental unit the 151-day study.Finally, the response of for statistical analysis of weight gain data.
heifers implanted with RAL was initially very

Results and Discussion
Table 1 presents heifer daily gains by implant treatment and monthly weigh course of the 151-day study.Both the REVslow and never reached the growth trajectory demonstrated by the other two implants.

Figure 1 .
Figure 1.Cumulative Growth Responses of Heifers to Anabolic Implants Relative to Nonimplanted Controls during the Grazing Season.
b First = c,d,e Values in columns not sharing a common superscript are different (P<.05).