Date of Award
Master of Science
J.C. Waller, R.R. Shrode
The data used in this study were collected from calves born at the University of Tennessee Highland Rim Experiment Station (HRES) near Springfield, Tennessee. The treatments involved various intervals at which calves were implanted with 36 mg zeranol at each implanting. The treatment groups were: 1) a control group of calves that were never implanted, 2) a group implanted at weaning only, 3) a group implanted at birth and weaning only, 4) a group implanted at birth and re-implanted at 90-day intervals thereafter until they were slaughtered.
This study was replicated over 7 trials, a trial using calves born in the spring of the year or calves born in the fall of the year. The experiment was a 2 x 4 factorial arrangement of treatments replicated in time. Responses to various frequencies of zeranol implant treatments were evaluated as increased gain during the various periods as compared to gain of non-implanted control calves. The response periods were: 1) birth to weaning, 2) weaning to first post-weaning weight, 3) post-weaning to slaughter, and 4) birth to slaughter.
During the pre-weaning response period, calves that received implants every 90 days performed significantly better than did control calves. Post-weaning performance indicated that gains of calves implanted at birth and at weaning and calves implanted every 90 days were not significantly different. However, both groups gained significantly more than did the control group. Re-implanting throughout life was evaluated. Gains of calves implanted at birth and at weaning and calves Implanted every 90 days were not significantly different, but were significantly greater than gains of calves implanted at weaning only and gains of control calves. Gains of calves implanted at weaning only and gains of control calves were not significantly different.
Swabe, Larry Allen, "Effect of frequency of pre-weaning zeranol implants on pre-weaning and post-weaning performance. " Master's Thesis, University of Tennessee, 1986.