Growth Responses of 1- to 40-Day-Old Calves to Three Levels of Steer-oid® Implant

Abstract

A field trial was conducted to compare growth responses of 1- to 40-day-old calves to three levels of STEER-oid® implant. A full dose of STEER-oid® consists of 8 pellets and contains 200mg progesterone, U.S.P., and 20mg estradiol benzoate, U.S.P. Calves implanted with 1/4 dose (n=35), 1/2 dose (n=30) and a full dose (n=31) were compared with a control group (n=30) receiving no implant. Calves were implanted on October 31, 1984, and December 18, 1984, to meet age restrictions. Mean age at the end of the study was 209 days. Variation in average daily gain (ADG) and final weight (FWT) due to initial weight, initial age, age of dam, sex, sire breed (Charolais vs. Simmental), dam group [Zebu cross (ZX) vs. British and Continental cross (BCX)], implant date and dosage was evaluated. Initial weight and initial age influenced (P<.05) both ADG and FWT. Age of dam, sex and sire breed did not influence ADG or FWT. Calves from ZX dams had higher (P<.05) ADG and FWT (.74 and 189.8 kg, respectively) than calves from BCX dams (.68 and 177.8 kg, respectively). Calves implanted December 18 had higher (P<.05) ADG and FWT (.77 and 198.7 kg, respectively) than calves implanted October 31 (.64 and 168.9 kg, respectively). Average daily gain and FWT of calves receiving 1/4 dose (.75 and 191.6 kg, respectively) and 1/2 dose (.73 and 188.3 kg, respectively) were higher (P<.05) than ADG and FWT of the control group (.67 and 175.9 kg, respectively). Calves receiving a full dose did not differ from the control group. These results indicate that improvements in gains of young calves were achieved with doses lower than those levels of STEER-oid® usedin calves heavier than 180kg.