There is growing interest in the use of recycled manure as bedding for dairy cattle, particularly due to supply challenges with more conventional bedding materials. Researchers described the various bedding production processes already in use on farms, as well as the bacteriological and physicochemical characteristics of the bedding.
The researchers focused on the impact of these bedding materials on animal and worker health, as well as milk quality. They also assessed the impact of this bedding on hygiene, animal comfort, and udder health. Finally, they assessed the risks of transmission of various parasites and zoonotic pathogenic bacteria (i.e., those transmissible from animals to humans) such as Cryptosporidium, Salmonella spp., and Listeria monocytogenes.
As part of this project, 27 farms using recycled manure bedding were compared to 61 dairy farms using straw bedding. Various findings regarding the impacts of recycled manure bedding were identified, including:
- Methods for producing recycled manure bedding vary widely (with almost as many methods as there are users) and are often poorly standardized.
- Recycled manure bedding is believed to harbor a higher bacterial load at the start of use (and thus increase infection risk, for example regarding udder health) compared to well-managed straw bedding.
- The microbial populations in recycled manure bedding before use and at the end of use, after contamination by animal feces and urine, are virtually the same, suggesting a high degree of similarity to the microbial populations in bovine feces.
- Cows housed on recycled manure bedding had cleanliness scores similar to or higher than those housed on straw bedding, but clinical mastitis caused by Klebsiella pneumoniae was still 6 times more frequent on farms using recycled manure bedding.
- Three zoonotic agents—Salmonella spp., Listeria monocytogenes, and Cryptosporidium spp.—were found more frequently in recycled manure bedding samples than in straw.
- The egg counts of several parasites were maintained or even increased during the preparation of recycled manure bedding. This could pose a significant health risk to young animals under 6 months of age or to farm workers.
- Certain bacteria undesirable for cheese processing were isolated in milk from farms using recycled manure bedding, even after pasteurization. None of these bacteria caused over-acidification. However, they all showed good survival during cheddar production. This suggests that these proteolytic strains could be harmful during cheese ripening.
The results of this project provided a better understanding of the risks to animal and worker health, as well as the impacts on milk quality associated with the use of recycled manure bedding.
