Proceedings of the Vertebrate Pest Conference

When a large animal dies on a farm or ranch, there are often few options for disposal. In California, there are limited legal options especially as rendering facilities have closed, and both regulatory burden and the number of predators on the landscape have increased. Livestock Mortality Composting could be a viable solution to address these challenges. Composting of mammalian tissue is legal in most states and recommended for on-farm disposal of livestock mortalities but is currently illegal in California. Instead, many ranches have opted to use “bone piles” to dispose of livestock mortalities. This option has been shown to attract large predators such as wolves, mountain lions, bears and others making it a hazard for livestock operations by increasing the likelihood of livestock-predator interactions. Removing these bone piles is the number one predator attractant removal recommended by Oregon Department of Fish and Wildlife. Mammalian tissue composting is also a viable option for waste from on-farm animal processing especially as this practice has become more popular in the last few years. After navigating the regulatory oversight of multiple local and state agencies, a livestock mortality composting site was approved for research at the Intermountain Research and Extension Center in Tulelake, California. This site has composted four adult cows and demonstrated the effectiveness and safety of this process. Pile temperature was taken at 18 and 36 inches from August 2020 to January 2022. After each additional mortality, the temperature reached over 131°F for at least 72 hours to kill potential pathogens. Trail cameras were deployed at the compost site and at three nearby bone piles to compare wildlife interactions. The bone piles received on average 390 and 292 visits from predators in year one and year two respectively compared to eight visits to the compost pile. A best management practices document has been written to provide an on-farm livestock mortality composting exemption that falls within current California composting laws. This exemption could be carried out at the local, regional, or state level, although permanent changes to this policy will most likely need a legislative change.