Ractopamine and Other Growth-Promoting Compounds in Beef Cattle Operations: Fate and Transport in Feedlot Pens and Adjacent Environments

Abstract

The current study represents a comprehensive investigation of the occurrence and fates of trenbolone acetate (TBA) and metabolites 17α-trenbolone (17α-TBOH), 17β-TBOH, and trendione (TBO); melengesterol acetate (MGA); and the less commonly studied β-andrenergic agonist ractopamine (RAC) in two 8 month cattle feeding trials and simulated rainfall runoff experiments. Cattle were administered TBA, MGA, or RAC, and their residues were measured in fresh feces, pen floor material, and simulated rainfall runoff from pen floor surfaces and manure-amended pasture. Concentrations of RAC ranged from 3600 ng g–1, dry weight (dw), in pen floor to 58 000 ng g–1 in fresh feces and were, on average, observed at 3–4 orders of magnitude greater than those of TBA and MGA. RAC persisted in pen floors (manure t 1/2 = 18–49 days), and contamination of adjacent sites was observed, likely via transport of windblown particulates. Concentrations in runoff water from pen floors extrapolated to larger-scale commercial feedlots revealed that a single rainfall event could result in mobilization of gram quantities of RAC. This is the first report of RAC occurrence and fate in cattle feedlot environments, and will help understand the risks posed by this chemical and inform appropriate manure-management practices.

Productivity-Enhancing Technologies. Can Consumer Choices Affect the Environmental Footprint of Beef?

“…In the US, RC has been detected in airborne particulate matter (4700 ng/g) in the feed yard and also in water bodies (271 ng/L) near the feed yard [81]. The transport of RC in water bodies and the feed yard is possible, as a recent study by Challis et al [82] in Canada confirmed that by feeding RC to feedlot cattle for 42 days, RC was still detected in the pen floor feces during (13 days; 3600 ng/g) and post feeding (37 days; 681 ng/g) such that run-off manure from pen floors and pasture contained RC at concentrations of 6300 and 2100 ng/L, respectively. The authors also showed that catch basins near commercial feedlots in Lethbridge, Canada, can contain RC at concentrations of 4000 to 27,000 ng/L in water and 234 to 1506 ng/g in sediment [82].…”

“…The transport of RC in water bodies and the feed yard is possible, as a recent study by Challis et al [82] in Canada confirmed that by feeding RC to feedlot cattle for 42 days, RC was still detected in the pen floor feces during (13 days; 3600 ng/g) and post feeding (37 days; 681 ng/g) such that run-off manure from pen floors and pasture contained RC at concentrations of 6300 and 2100 ng/L, respectively. The authors also showed that catch basins near commercial feedlots in Lethbridge, Canada, can contain RC at concentrations of 4000 to 27,000 ng/L in water and 234 to 1506 ng/g in sediment [82]. Groundwater adjacent to cattle operations in Nebraska was also found to contain MON at concentrations ranging from 20 to 2080 ng/L, and the metabolites of steroidal hormones (i.e., estrone, testosterone, 4-androstenedione, and androsterone) ranging from 40 to 390 ng/L, and [83].…”

“…However, endogenous hormones and their metabolites (e.g., testosterone, 4-androstenedione, 17β-estradiol, estrone, progesterone, and 17α-hydroxyprogesterone) have been detected after 100 days in manure from cattle that did and did not receive TBA, E, Z, or MGA in the US [99]. Similarly, in Canada, due to the fast degradation rate of TBA, its metabolites (17α-trenbolone and 17β-trenbolone), and MGA, these PETs were below the detection limit in manure of treated cattle, but the βAA and RC persisted in manure from the pen floor due to its slow rate of degradation (half-lives of 18 to 49 days [82]). Researchers have shown that composting and stockpiling cattle manure can reduce endogenous hormones in manure.…”

“…Composting has also been proven in Canada to dissipate the antibiotic, tylosin, in excreted manure of beef cattle by 85% [100]. This suggests that composting as a means of handling cattle manure could also potentially reduce other PET residues in manure, including RC, which can persist in the pen floor for up to 39 days [82]. Thus, the effect of compositing on RC residue in manure requires further exploration.…”

Mechanism evolution and prediction of carbamazepine sorption by mangrove plant residue–derived biochars

“…The widespread use of pharmaceuticals for human and animal health management has increased substantially in recent decades (Challis et al., 2021; Kibuye et al., 2019). Carbamazepine (CBZ) is a typical antiepileptic drug widely used for the treatment of epilepsy, acute mania, and emotional disturbance.…”