Submitted to: Proceedings of the American Society of Agricultural and Biological Engineers International (ASABE)
Publication Type: Proceedings
Publication Acceptance Date: 3/1/2002
Publication Date: 3/11/2002
Citation: Niemann, D.R., George, D.R., Greene, L.W., Cole, N.A., McCollum, F.T., Chirase, N.K. 2002. Phosphorus excretion from ruminants implanted with estrogenic growth implants. In: Proceedings of the American Society of Agricultural and Biological Engineers (ASABE) Meeting, March 11-13, 2002, Fort Worth, Texas. p.579-594.
Technical Abstract: When collected, most beef cattle feedyard manure has a nitrogen:phosphorus ratio of about 2:1. Unfortunately, most plants prefer a N:P ratio of about 5:1. If the amount of P in the manure could be decreased, feedyard manure would be a more acceptable and valuable fertilizer for farmers. One way to decrease P in the manure is to retain more of the dietary P in the animal. To that end, these studies were conducted to determine the effect of estrogenic growth implants on P excretion and retention of sheep (a model for cattle) and cattle in concentrated animal feeding operations (CAFO). In experiment 1, lambs were either implanted with 12 mg zeranol (Ralgro) or not implanted. From d 0 to 42, 53.7% of consumed P was excreted, and from d 42 to 56, 79.8% of consumed P was excreted. During the first 28 d, sheep implanted with zeranol retained more P and excreted less P than nonimplanted sheep. Experiment 2 was conducted to determine P excretion from cattle previously implanted when grazing pasture. Steers were implanted with no implant, 20 mg estradiol + 200 mg progesterone or 8 mg estradiol + 40 mg trenbolone acetate and grazed for 179 d. During the feeding period, cattle consumed 21.5 g of P per head daily and 11.0 g/d of the consumed P accumulated on the pen surface. Implant strategy before entering the CAFO did not affect (P > 0.10) the efficiency of P utilization in the CAFO. These results indicate that the use of estrogenic implants will decreased P excretion for a short period of time; however, implanting during the grazing period will not affect P excretion in the feedlot.