Abstract
Fifty-four Rambouillet (avg wt, 34.6 kg) wether lambs were used to determine the effects of zeranol of p and N excretion, animal performance, carcass characteristics, and bone characteristics. Lambs were blocked by sire, randomly allotted to pens of 3 to 4 in an open sided barn and assigned to either an implant (1) or non-implant (NI) treatment group . Lambs had ad libitum access to a high concentrate diet containing 38% TDN and 16% CP or 67 d. Lambs were fed for 21 d prior lo implanting. At 14 d intervals post implanting, pens were thoroughly cleaned and excreta allowed to accumulate for 2 d. Excreta was collected and analyzed for P and N content. Lambs were slaughtered on d 67 and carcass characteristics were determined. Phosphorus excretion expressed as a percentage of P intake for I vs NI treatment groups at 4, 28, 42, and 56 d post implanting was 55.7 vs 61.4% (P=.32) 45.4 vs 55.8% (P=.04)1 50.5 vs 53.5/'o (P = .67) and 78.9 vs 80.7% (P =-.85), respectively. This resulted in an increase (P<. 05) in P retention for 1 lambs (2.56 g/d vs 3.19 g/d) on d 28. The percentage difference appears to follow the pay-Out, curve of the zeranol implant. There was no effect (P> . 1O) of zeranol oil N excretion in this study. Implanted lambs had a 26.3% greater (P =.0009) ADG and 16.8% improvement (P=.02) in feed efficiency compared with NI lambs. implanting treatment did not affect carcass characteristics" however, implanted lambs did have thicker hides (P < . 0 1) and larger livers (P < 10). Bone breaking load was increased (P <.05) in I lambs compared to NI lambs. However, there were no other differences in physical characteristics of the metacarpal bones. Results of this study indicate that zeranol improved P utilization, feed efficiency, and ADG in feedlot lambs. Zeranol treatment also altered metacarpal bone characteristics and increased hide thickness and liver weights.
Niemann, Dawn Renee (1998). Mineral status, bone characterisitics, carcass characteristics, and performance of feedlot lambs implanted with zeranol. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1998 -THESIS -N54.