Abstract:
California is the largest agricultural producer in the United States and local dairy industry produces
21.5% of the national milk supply. There are 1470 dairies, 1789 million dairy cows and a total
annual milk production of 18 million metric tons. The amount of dead cows to be disposed of is
remarkable in intensive farming and it increases in periods of extreme weather events, such as
drought in California. Composting of bovine mortalities is prohibited in California as a means of
disposal of carcases, and can only be done under an emergency declaration. Composting is an
effective disposal method that can aid in carcase disposal, especially during an emergency. The
objective of this study was to use screened dairy manure solids (SDMS) as the composting
amendment for carcase decomposition. Our hypothesis was that temperatures would be sufficiently
high and of sufficient duration to destroy most bacteria within the carcases and that the
leachate from the carcases would penetrate less than one foot into the underlying soil. No significant
amounts of leachate were noted in the collection pipes buried beneath either soil type.
Total bacterial counts exceeded 1 106 CFU/ml in approximately 19% of the swab samples from
the sample collection pipes. The sandy soil had higher bacterial counts than the clay soil. Results
of these trials indicate that adult dairy cows can be successfully composted without significant
impact on the nearby surrounding environment. The basic hypotheses have been verified by the
simple and multiple regression and chi-square non-parametric test.
