Ample bedding in stalls can optimize cow comfort, reduce hock lesions and lameness, and increase cow longevity (Tucker and Weary, 2004). The great price increase seen in other more traditional bedding sources has resulted in recycled manure solids (RMS) becoming increasingly common on dairy farms.
Recycled manure solids are obtained by mechanical separation of manure removed from dairy cows’ housing systems. Their low cost of recovery, together with high on‐site availability, has allowed for their use as an alternative bedding source. However, RMS can favor the growth of environmental bacteria (i.e., Klebsiella) compared to other materials commonly used as bedding (new or recycled sand and wood shavings; Godden et al., 2008). This article examines several recent experiments using RMS as a source of bedding for dairy cows.
Composition of recycled manure solids
The composition and bacterial counts of RMS from 38 Midwest dairy farms are shown in Tables 1 and 2 (Husfeldt et al., 2012). Of these farms, 25 obtained RMS from manure processed in anaerobic digesters (dRMS), whereas the remaining 13 dairies separated RMS from fresh manure. Of the dairies working with fresh manure, four treated the RMS in a compost drum (cRMS) for 18 to 24 hours, whereas the other nine farms used them “fresh” (fRMS).
The compost drum uses a horizontal rotary drum to mix, aerate, and move the material. Air is supplied through the discharge end in the opposite direction of the material being moved by incorporating air as the mass tumbles. Composting proceeds rapidly, aided by the supply of oxygen to the decomposing material as it tumbles during the drum rotation. The average moisture content for both fRMS and dRMS was close to 72%, whereas that of cRMS was 60.3%. Although moisture dropped once RMS were distributed in the stalls, cRMS continued to have lower moisture content (41.3%) compared to both dRMS (55.9%) and fRMS (57.2%). The RMS with higher moisture content favored microbial growth, with the most frequent bacterial groups encountered being environmental Streptococcus and Bacillus species.
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