Disposal of Cattle Mortalities
|
Cattle mortalities need to be disposed of within forty-eight hours after death to control the spread of disease, prevent contamination of air or ground water and for the cattle producer to avoid the risk of prosecution. How best to dispose of dead cattle is an important question. After the advent of BSE in Canada, disposal through traditional channels such as rendering has become more expensive and in some cases less available. Alternatives for disposal of cattle mortalities, along with their pros and cons, are listed below. Because regulations differ across provinces, it would be wise to check local regulations before adopting a particular method. Be aware that legality of disposal is subject to interpretation by local authorities who may restrict the use of a particular method if too many complaints are received. |
|
On this page:
Key Points
|
Introduction
Rendering
When dead stock is removed from the farm for rendering, minimal effort is required and complete removal of the dead stock provides excellent on-farm disease control. Costs for rendering have increased after the advent of BSE as only hide and tallow products can now be marketed, but the meat and bone meal cannot. Contacts for the various renderers across Canada are listed under ‘Learn More’ at the bottom of this page.
| Pro | Con |
|---|---|
| Excellent on-farm disease control | May be costly to producers – depends on distance to plant |
| No residues or other aftermath - less scavenging/predation | Minimum weights for pickup often required |
| Easy - just call for pick up | Dead stock pickup not available everywhere |
| Hide and tallow recycled | Excessive time may elapse before pickup |
Burial
Planning is required for disposal by burial. Digging a 1 to 1.2 meter pit is necessary for disposal of cattle and may not be possible during winter months. In areas with a high water table, burial may not be allowed and 150 metre offsets of burial pits from ground and surface water sources are required. Sites prone to flooding or erosion are not suitable for burial pits.
Lime is frequently added to burial pits for odor control, but also limits microbial activity and degradation of carcasses in burial pits may be slow. Cattle carcasses buried with lime during the Foot and Mouth disease outbreak of 1952 have been discovered relatively intact. Controlled access to the pit is necessary to prevent predation of mortalities and accidental entry of livestock and people into the pit.
| Pro | Con |
|---|---|
| Permanent containment for disease outbreaks | Need to have sites ready for winter burial |
| May be good choice on a large land base with suitable soil, topography and access to a backhoe | Ground water contamination possible and odor of an open pit is a magnet for predators |
| Costly as multiple burial pits will be required | |
| Permanent tracking of sites is required |
Incineration
In Canada, incineration is currently used for disposal of cattle carcasses only at a limited number of research installations due to the expense and infrastructure required. Incineration requires extremely high temperatures ( > 800oC in chamber) and the appropriate equipment. This is the best option for disease control as carcasses are reduced to ash, with all infectious agents destroyed. The ash does require disposal and fuel costs for incineration of cattle are high. High temperature incineration should not be confused with burning. Burning is seldom legal and results in excessive air pollution and risks of disease transfer from carcass residues.
| Pro | Con |
|---|---|
| Superior disease control | Specialized and expensive equipment and fuel required |
| Mobile incinerators limit infrastructure costs | Time required may be impractical for multiple mortalities |
| Minimal air pollution/odors from high temperature incineration | Ash requires disposal |
| Less scavenging/predation | Extreme heat is on-farm hazard |
Natural Exposure
Natural disposal involves offering cattle carcasses to the local predator/scavenger population. Although this method is not legal in many jurisdictions, it is being used more frequently with the decline of rendering. Little labor is required, but the risk of disease transfer is high. Cysticercosis, which requires a canine intermediate host is now present in some locales and leads to beef carcasses condemned at slaughter due to tape-worm cysts in muscles. Naturally, a well-fed predator population tends to multiply and increased calf predation has also been reported.
| Pro | Con |
|---|---|
| Easy and inexpensive | Not legal in all areas |
| Increased populations of predators and increased potential for agro-tourism | Air, water and soil contamination |
| Increased populations of predators and increased predation of cattle | |
| No disease control |
Anaerobic Digestor (Biodigestor)
Anaerobic digestion is a process where microorganisms break down compostable material such as food waste, without the presence of oxygen. Biodigestors can be an opportunity to capture greenhouse gas production and provide a renewable energy source from products such as manure and deadstock. Access and transportation of deadstock to a biodigestor facility may be limited depending on your location. Centralized biodigestors will require additional treatments of biodigestor products to eliminate infectious prions (BSE) before land-spreading, which will increase costs.
| Pro | Con |
|---|---|
| Reduce odour and pathogen levels in manure | Not accessible in every province |
| Reduce greenhouse gas production from a farmstead | Infrastructure is expensive |
| Produce renewable energy | Maintaining the “recipe” for biogas production due to the various types of wastes used |
| Utilize food by-products and other organic materials sourced off-farm | Has to be used along with a prion control technology which increases costs of centralized facilities. |
| Improve the fertilizer value of the manure |
Thermal Hydrolysis
Thermal Hydrolysis (THD) uses a combination of high temperature (356°F) and high pressure (174 psi) to break tissue down to very small parts. Like biodigesters, THD can be used to produce renewable energy such as biogas from animal biproducts including deadstock. The technology also has the capacity to destroy the prions which are responsible for bovine spongiform encephalopathy (BSE).
| Pro | Con |
|---|---|
| Complete pathogen destruction | Not accessible in every province, it is currently available in Lethbridge, AB |
| No groundwater contamination risk from disease | Infrastructure and energy required increases costs |
| Create clean, renewable biogas which can be converted to electricity or natural gas |
Composting
 Finished mortality compost. Very few residual bones remain. Photo credit: Dr. Kim Stanford, Alberta Agriculture and Forestry Composting is a naturally occurring process in which bacteria, fungi and other microorganisms convert organic material into a stabilized product called compost. Composting of livestock mortalities involves two phases. In the first phase, the animal carcasses are placed in a composting bin or on a windrow of straw. A bulking agent that is high in carbon, such as sawdust or straw, added to completely surround the carcasses. This heap is entirely covered with manure, which is full of microbes. Anaerobic microorganisms (those not requiring oxygen) work in the carcass to degrade it. The second phase involves regularly turning the pile and introducing air to feed aerobic microorganisms (those requiring oxygen), which degrade these materials produced by the first stage into odour-free carbon dioxide (CO2) and water (H2O). This stage causes the temperature of the compost pile to rise, which kills common viruses and other bacteria that may be present. Scientific composting was first developed for the poultry industry, but after the advent of BSE, composting of cattle mortalities in the Canadian climate was studied. Composting requires some time and effort, although costs for raw materials are minimal, disease control is good and the resulting compost can be used as a fertilizer or soil amendment. The initial construction of the compost pile is key to the eventual success of the composting process. A bad set up (too wet, too dry, no carbon source) is not easy to remedy. |
| Pro | Con |
|---|---|
| Inexpensive; uses materials available on farm | For intensive operations, there may not be sufficient land base |
| Good disease control | Compost requires management – monitoring temperatures and turning |
| Can build compost as required year round | More difficult in wet climates |
| Residual material used as fertilizer | Bones exposed at surface of pile do not degrade and may cause damage to spreading or harvesting |
| Less scavenging/predation | Compost manure containing cattle carcasses cannot legally be removed for spreading on rented or neighbours' land |
Essentials of composting: Moisture
A target of 50 to 60% moisture in the initial build is optimal. The cattle themselves are a source of moisture, but manure and sawdust used in compost should be subjected to a squeeze test, if dry matter values are not known. If it is possible to manually squeeze moisture from a sample, it is too wet. If the sample crumbles when squeezed, it is too dry. Optimal moisture is damp to the touch and forms a loose ball that would crumble if dropped to the ground. Once a compost pile is built, it is difficult to add moisture. Small piles with one or two carcasses dry out more readily and have a greater risk of getting too wet due to rain or snow falls. Generally, compost piles should be shaped so that water does not pool on the compost, unless the climate is very dry.
Essentials of composting: Air
The growth of aerobic bacteria is essential for composting. If the compost becomes too wet, air flow is restricted, anaerobic bacteria flourish and the compost will have a foul stench. If compost is properly aerated and heating, no objectionable odors will be present and predators will not scavenge from the compost piles.
If composting with manure, a manure-straw mix from a bedding pack makes an excellent compost amendment as the straw aids in compost aeration. If composting with sawdust, wood shavings or a larger particle size used in bedding are preferable to finer sawdust particles.
 Figure 1. Compost temperature at four locations in a single pile. Note more uniform heating after the compost was first turned. Source: Dr. Kim Stanford, Alberta Agriculture and Forestry |
Fortunately, turning the compost improves aeration as well as mixing and improving compost homogeneity. For cattle compost, turning 3 times at approximately 2 to 3 month intervals is generally sufficient to complete the composting process, provided the compost spent some weeks at 40 to 60oC.
Monitoring the temperature of the compost also provides guidance as to when compost should be turned. Commercial composting operations use specialized windrow turners, but for smaller-scale composting, a front-end loader is sufficient. Drop the compost from the maximum height of the bucket to promote aeration and fracture the bones.
Fresh manure or sawdust or matured compost should be used to cover the surface of the pile after turning as bones exposed to sun do not degrade. Manure is a better substrate than sawdust for bone degradation.
Essentials of composting: Nutrients
Compost requires sources of both carbon (C) and nitrogen (N). Ratios between 20:1 and 40:1 C:N are optimal. Straw and sawdust/shavings are excellent carbon sources. Manure contains lesser amounts of carbon, but the carbon and nitrogen in manure is readily available to compost microbes.
Laying cattle carcasses on a base of at least 18” (45 cm) straw or sawdust and heaping manure over the carcasses to a depth of at least 3.5’ (100 cm) will provide an appropriate C:N ratio. Soil cannot be used in place of manure due to a lack of nutrients. Turning the compost is also necessary to re-distribute nutrients and ensure more uniform heating and degradation of the mortalities.
Other composting considerations
 Initial lay out of carcasses on straw. Photo credit: Dr. Kim Stanford, Alberta Agriculture and Forestry A windrow layout, with carcasses in a single line, is the easiest to manage. Carcasses should be placed at least 18” (45 cm) from the edge of the pile to ensure adequate coverage and nutrients. Carcasses should also be at least 10” (25 cm) apart to promote air flow. Degradation of carcasses is impaired if they touch. Carcasses should be laid on their side as feet protruding from a carcass pile will not degrade. The windrow can be extended as new mortalities arrive and carcasses rapidly covered to prevent attracting scavengers to the pile.  Steam rises as compost is turned in the winter. Photo credit: Dr. Kim Stanford, Alberta Agriculture and Forestry Winter composting is possible and piles can be started at temperatures of -20oC or colder, provided that either the carcasses or the stockpiled manure is warm. Compost using sawdust without manure may be more difficult to make under winter conditions. |
Feedback
Feedback and questions on the content of this page are welcome. Please e-mail us at info [at] beefresearch [dot] ca.
Acknowledgements
Thanks to Dr. Kim Stanford, Alberta Agriculture and Forestry Beef Research Scientist for contributing her time and expertise to writing this page.
This topic was last revised on August 1, 2019 at 9:09 AM.
Related Topics
Related Blog Posts
- November 3, 2015: Methods of deadstock disposal to reduce predation: Webinar November 17
- November 15, 2013: How to dispose of cattle mortalities: new video
Fact Sheets
-
March 2013
Can composting destroy BSE prions?
View Web Page
View PDF
