Faraway Farm Alpacas is home to 18 alpacas. We treat the alpacas monthly with doramectin 1.0% (10 mg/ml) injectable. Using the manure from our alpacas, we propose a well-controlled study to: 1) determine maximum concentration of doramectin in alpaca manure after subcutaneous injection – these concentrations are determined from raw manure samples taken daily for 7 days and at 14 days after injection; 2) determine doramectin concentrations in turned and unturned piles of composted alpaca manure over the course of 6 months – samples are taken periodically from the composting piles; 3) compare temperature, and physical and chemical characteristics of composted alpaca manure between turned and unturned piles. The study will provide data to determine decay rates of doramectin in unturned and turned compost piles. It is expected that composting manure from alpacas that have been dewormed with doramectin decreases the concentration of doramectin in the resulting compost product and that the rate of decay will be greater for the optimally composted pile.
Most alpacas and llamas in eastern U.S. are treated with ivermectin (trade name Ivomec) or doramectin (Dectomax) via subcutaneous injection as part of a monthly regimen to prevent meningeal worm. Meningeal worm also known as deer worm is hosted by the white-tailed deer, and snails and slugs are intermediate hosts. When alpacas or llamas (or other unnatural hosts such as goats, elk or moose) ingest the infective larvae, migration through the body occurs. Migration to the central nervous system can cause muscle weakness, paralysis and death. No commercial vaccine is available therefore prevention is based on management principles such as reduction of exposure to deer, snails, etc., and with deworming every four weeks. Deworming every four weeks is efficacious in killing the infective larvae before the central nervous system is penetrated.
Doramectin and ivermectin are chemical formulations used to control external parasites such as ticks, flies, and worms. More specifically, they are macrocyclic lactones produced as fermentation products of soil microorganism and have been approved for subcutaneous injection. Veterinary studies have demonstrated that ivermectin can persist in manure and soil for months and that ivermectin can be excreted in manure in concentrations that can be highly toxic to organisms in the ecosystem
The 2012 U.S. Census of Agriculture reported 9,353 alpaca farms in the U.S. with 140,601 alpacas, and 15,296 llama farms with 76,086 llamas. The Alpaca Owners Association currently reports that there are 138,710 registered alpacas east of the Mississippi River. With most of these animals in the eastern U.S. being treated with doramectin or ivermectin, and evidence that these pharmaceuticals can be present in the animals’ manure, the fate of these medications in alpaca manure is of deep concern since they may pose environmental and health risks. In fact, without proper care, raw or improperly composted manure from these animals may contribute to agricultural pollution. With appropriate study, though, it can be determined when composted manure from de-wormed alpacas can be used without negative effect in the environment, whether on a farmer’s own fields or gardens, or sold as a compost product.
For the 2017 annual report, results were available from the first 28 days of data collection (see below). For this 2018 update, data were available for the proposed 6-month endpoint as well as for additional data collections at 12 and 18 months.
As part of our farm’s monthly regimen, 18 female and male alpacas were treated on May 31, 2017 with doramectin 1.0% (10 mg/ml) injectable. Recommended dosage is 1 cc/70 lb. administered via subcutaneous injection. Our alpaca weights ranged from 140 to 220 lbs. The day that the doramectin injection was given is considered Day 0. Baseline manure samples were collected the morning of Day 0 prior to doramectin injections. During the morning of Day 1 (1st day post injection), manure from the alpacas was collected and a sample was drawn. Half of the remaining manure then was placed on a pad that became the ‘turned’ pile and the remaining half was placed on a pad that become the ‘unturned’ pile. The same procedure was conducted on Days 2 to 7. On Days 14, 21, and 28 additional raw manure sample were taken. On Days 14, 21, 28, 56 (month 2), 112 (month 4), and 168 (month 6) samples were drawn independently from each of the turned and unturned piles. The turned pile was thoroughly mixed daily for the first week and weekly for the remainder of the study while the unturned pile was not mixed at all. Hay was added to the turned pile to provide a source of carbon and maximize decomposition (On-Farm Composting Handbook, 1992; Natural Resource, Agriculture, and Engineering Service [NRARES] Cooperative Extension). The piles were adjacent to one another so that they received the same amount of sunlight and rain. Drainage trenches surrounded each pile to prevent contamination between piles.
Grab samples were taken from 5 locations around the piles at varying depths to insure that samples were representative of all 18 alpacas. The grab samples were thoroughly mixed in a bucket. Samples then were drawn, placed in a sterile container, and frozen. On September 11, 2017, 33 frozen samples were overnighted to Dr. Daljit Vudathala, Senior Research Investigator, Pennsylvania Animal Diagnostic Laboratory System Toxicology Laboratory, University of Pennsylvania School of Veterinary Medicine, New Bolton Center, Kennett Square PA for analysis. The lab requires samples to be stored at -80°C (-112°F) to prevent any further degradation of doramectin so as to determine doramectin levels at the time of sample collection. The lab also assessed a negative control manure sample taken from alpacas at Tufts University School of Veterinary Medicine that had not been treated preventatively for meningeal worm. On December 12, 2017, the remaining frozen samples were overnighted to the Toxicology Lab.
In addition to the samples to be assessed for doramectin, a baseline sample of manure was sent to Agro-One, Ithaca, NY to be analyzed for components such as pH, nitrogen, carbon, phosphorous, potassium, and carbon:nitrogen ratio. Four months later, composted manure samples were taken from the turned and unturned piles and sent to Agro-One for the same component analyses that were performed for the baseline sample.
The location of the manure piles insured that they could get full sun all day. Each pile was placed on hard soil and was surrounded by an untreated wood and wire mesh frame 8’ wide by 8’ long and 4’ high. Pile temperatures were measured daily with a Reotemp Compost Thermometer Model No. 3LPU9, 36″ x 1/4″ diameter stem, ½” NPT mount, with a 0 to 200F range. Amount of sunlight and rain, ambient temperatures and other weather data were collected daily with a Davis 6250 Weather Station with a Davis 6450 Solar Radiation Sensor.
Raw manure samples were collected prior to doramectin injection (baseline) and at days 1 to 7, 14, 21, 28. Turned and unturned compost pile samples were collected at days 1 to 7, 14, 21, 28, 56, 112, 168 (6 months), 168 (12 months), and 504 (18 months). Samples were stored at -80 deg C (-112 deg F) and sent to the University of Pennsylvania Toxicology Lab in batches for analysis.
The first month of data for raw manure, and for turned and unturned compost pile doramectin concentrations are displayed in Figure 1. Figure-110 Doramectin raw manure levels increased until day 3 (565 ppb) and then decreased and were still detectable at day 28 (87.1 ppb). Curve estimation regression models were used described the curvilinear relationship between time and doramectin raw manure levels. An S-curve function best fit the raw manure data from baseline to day 28, R2 = .29, with a trend-level p = .087. From peak concentration at day 3 to day 28, an exponential decay function significantly fit, R2 = .88, p = .001.
Inspection of the first month of compost pile doramectin levels in Figure 1 reveals that for the turned pile doramectin level peaked at day 14 while the unturned pile doramectin had peaks at days 4 and 14. Of the 10 sample collections in the first 28 days of the study, doramectin levels for the turned pile were lower than the unturned pile for 8 (80%) of the collections. Data for the total 15 doramectin samples from day 1 through 18 months for both compost piles are displayed in Figure 2. Figure-212 For the 8 data points from peak levels at day 14 and through 18 months, curve estimation regression indicated that S-curve functions best fit the turned pile data, R2 = .73, p = .007, and the unturned pile data, R2 = .81, p = .002. With doramectin levels after the 1st month demonstrating linearity for the turned (R2 = .71, p = .036) and unturned piles (R2 = .54, p = .098), t tests for independent samples were conducted to assess differences in doramectin levels between turned and unturned piles. For the 6 data points from month 1 to month 18, the mean doramectin concentration for the turned pile (M = 101.87, sd = 20.52) was significantly lower than for the unturned pile (M = 161.00, sd = 26.75), p = .002.
Component analyses revealed differences from baseline and between the turned and unturned piles. For example, a key index of the composting process is the C:N ratio, the ratio of the weight of carbon (C) to that of total nitrogen (N) in an organic material. The C:N ratio decreases during the composting process, with the ratio of finished compost typically close to 10:1, or 10. Our baseline sample raw manure C:N ratio = 18.65. At 135 days (4.8 months) post baseline, the unturned pile C:N = 15.56, while the turned pile C:N = 11.42. The turned compost looked and felt like it was ready as a soil amendment.
A paired-sample t test indicated that mean compost pile temperatures (°F) were statistically significantly higher for the turned pile (M = 95.09, sd = 19.57) than the unturned pile (M = 86.68, sd = 13.51), p < .001. The peak temperature for the turned pile was 124 °F and was 110 °F for the unturned pile.
We proposed a well-controlled study to: 1) determine maximum concentration of doramectin in alpaca manure after subcutaneous injection: initial results are reported above; 2) determine doramectin concentrations in turned and unturned piles of composted alpaca manure over the course of 6 months: initial results for the 1st month are reported above; 3) compare temperature, and physical and chemical characteristics of composted alpaca manure between turned and unturned piles: C to N ratio and initial temperature results are reported above. It was expected that composting manure from alpacas that have been dewormed with doramectin decreases the concentration of doramectin in the resulting compost product and that the rate of decay will be greater for the optimally composted pile. Initial results support these expectations but more results are forthcoming.
Education & Outreach Activities and Participation Summary
-Environmental Defense Fund economists toured project as part of their annual meeting (October 2017).
-NYC Watershed Agricultural Council members have toured farm and project multiple times to educate other farmers.
-Westchester Counter HS Science and Education Fair 2017-18: Our high school intern has been invited to speak at WESEF based on an abstract of our study’s preliminary findings; our intern was awarded the WESEF Conservation Award based on our research proposal.
-Study results will be presented to an East of Hudson NYC Watershed Agricultural Council Committee meeting in early 2019.
-A manuscript will be submitted to a relevant peer-reviewed scientific journal in early 2019.
Environmental risks of veterinary medicines; optimal composting techniques
Our preliminary results provide support for doramectin being used as a long-acting GI antiparasitic; farmers and educators are recommending that raw manure of alpacas treated with dormectin not be used as a soil amendment; turning composted manure piles and adding sources of carbon optimize doramectin degradation and enhance the composting process.