A viable option to sand, straw or shavings
In a Midwest study involving nearly 50,000 cows, recycled manure solids (RMS) proved more than adequate as a bedding source.
Less abrasive than sand on equipment and often more available than straw or shavings, properly managed RMS "appear to be a satisfactory bedding option for freestall dairy herds," says Marcia Endres, a University of Minnesota dairy specialist.
In fact, when properly managed, RMS appear to provide as much cow comfort as sand in some herds. "Lameness prevalence, even for farms using mattresses, was similar to what we have observed in herds with deep-bedded freestalls," Endres says.
But, she adds, "excellent cow preparation at milking time, sanitation of milking equipment, cow hygiene, adequate dry cow housing and bedding/stall management appeared to be critical in maintaining a low somatic cell count when using RMS for bedding and making it work."
Endres and graduate student Adam Husfeldt conducted the study on 38 Midwest farms, which ranged in size from 130 to 3,700 lactating cows. Average herd size was 1,300 cows, with 55% of herds in deep-bedded freestalls. The remainder was housed on mattresses overlain liberally with RMS.
Half of the herds had plug-flow anaerobic digesters and five used complete-mix digesters. Six herds were purchasing RMS from farms with anaerobic digesters; 13 were using raw, separated manure solids.
Dairy producers’ biggest concern with RMS is its potential effect on somatic cell counts (SCC), mastitis and milk quality. Endres and Husfeldt sampled RMS before it was placed in stalls and after.
Total bacteria counts in unused RMS averaged 4.2 million CFU/ml (colony-forming units per milliliter), and ranged from 325 to 23.4 million. Total bacteria counts in used bedding was three times higher, averaging 13.3 million CFU/ml, with a range of 25,100 to 73 million.
Yet SCC did not differ from the Midwest average of 290,000 cells/ml. "We found that yearly average bulk tank SCC [with RMS] was 275,000, with a range of 121,000 to 688,000," Endres says.
Eighteen percent of the RMS herds had SCC below 200,000, and 9% had more than 400,000. All of the herds were using pre- and postmilking teat dips, individual towels and routine dry cow therapy.
The incidence rates for clinical mastitis ranged from 49 to 66.3 cases per 100 cow years, though no association was found between deep-bedded stalls and mattresses. "These relatively high results for clinical mastitis incidence suggest that udder health may be compromised when using RMS as bedding," Endres says.
For cow comfort, lameness prevalence was lower in deep-bedded stalls. But the researchers note that even on RMS-bedded mattresses, lameness prevalence was almost as low as in deep-bedded stall barns. Hock lesions were also lower in the deep-bedded RMS herds compared to those on mattresses.
One concern, however, is that death due to injuries in cows bedded with RMS was nearly double that of cows on sand. That might be because floors are more slippery when cows are bedded with RMS. "It’s something farmers need to be aware of when moving cows," Endres says. "RMS may require grooving or treating floors differently."