THE EFFECTS OF SPAYING AND ANABOLIC IMPLANTS ON THE AVERAGE DAILY WEIGHT-GAIN OF HEIFERS ON PASTURE

Two studies were carried out to determine the effects of spaying and i mplanting on the growth of heifers and compare Ralgro and Synovex-S fo r spayed heifers. In the first study, 121 crossbred heifers were rando mly allocated to four groups: intact and no implant; intact and proges terone and estradiol benzoate (Synovex-S); spayed and no implant; and spayed and Synovex-S. The average daily gain (ADG) and body weight (BW ) data were analyzed as a 2 X 2 factorial experiment with a pasture ef fect which was considered as a block. Based on ADG for days 0-120, the response to implanting was 17.6% for spayed heifers and 1.8% for inta ct heifers. In the second study, 31 spayed heifers implanted with zera nol (Ralgro) were compared with 30 spayed heifers implanted with Synov ex-S. The data were analyzed as a one-way analysis of variance. The AD G for spayed heifers on Ralgro did not differ significantly (p>0.05) f rom those implanted with Synovex-S over a period of 92 days, suggestin g that both implants produce similar growth responses.