99 Interrupting the composting process for equine carcass skeleton recovery

Abstract

Proper disposal of equine carcasses continues to be a challenge for equine owners. Recently, composting has been of interest for post-mortem disposal due to pathogen and parasite reduction, and economic concerns associated with traditional burial. Additionally, many educators lack appropriate resources to teach equine skeletal structure due to cost and availability. Study objectives were to 1) determine if in-ground composting can reach over 48.8°C needed for pathogen and parasite destruction and 2) develop methodology to successfully recover full skeletons. Two carcasses (C1 and C2, respectively) were placed in identically constructed pits 1.8–2.4m deep, with 0.6–0.9m of wood pine shavings under the carcass, a layer of metal wire, carcass, followed by 1.2–1.5m of wood shavings on top. A probe thermometer was used to monitor temperature 0.9m down from the pile surface, and weather data including rainfall was collected daily. For C2 only, additional data loggers were placed under the carcass at the rib cage, on top of the animal at the hock, and inside the animal's body cavity. Descriptive statistics were calculated using the means procedure in SAS, where data are expressed as mean ± SD. Carcasses 1 and 2 composted for 187.5 ± 36 d, where excavation time was determined by a plateau in pile temperature, and ambient temperatures ranged from 14.3 ± 9.3°C for C1 and 20.9 ± 6.2°C for C2. Rainfall amounts duringthese periods ranged from 4.2 ± 10.5mm for C1 and 3.3 ± 8.1mm for C2. Midway through the composting process, when temperatures either declined or were failing to increase, the top of the pile was scraped without disrupting the carcass, to increase airflow and provide oxygenation to the carcass below as is customary within composting procedures. Piles were scraped at 92 d for C1 and 85 d for C2. Within the first 107 d of composting, probe temperatures were numerically similar for both carcasses (C1 = 46.6 ± 6.3°C, C2 = 41.4 ± 3.6°C). Data loggers placed on carcass 2 recorded an average of 29.6 ± 0.8°C (min = 20.6°C, max = 31.0°C) under the rib cage, 35.5 ± 2.0°C (min = 20.6°C, max = 37.6°C) on the hock, and 32.4 ± 1.8°C (min = 28.5°C, max = 36.5°C) inside the body cavity. Once carcasses were excavated, bones were immediately washed, and subsequently soaked in an equal part mixture of 3% hydrogen peroxide, 10% ammonium hydroxide, water, and clear dish detergent until grease residues were no longer emitted from bones. Results indicate that ideal temperatures for pathogen and parasite destruction were not always reached within compost piles; however, in-ground composting did prove as an efficient means to obtain teaching skeletons at a low cost ($3,500 per skeleton).