S. Godden, F. Pẽna Mosca, E. Royster, B. Crooker, P. Raynor, and K. JanniUniversity of Minnesota

Management of Recycled Manure Solids Bedding on Midwest Dairy Farms. Part 1 –

Relationship between Processing Method and Bedding Bacteria Counts, Udder Health and Milk Production

Relationships between Bedding Bacteria Counts (BBC) and Udder Health

What do we know about bedding management and udder health?

• High bacteria levels in bedding are associated with increased mastitis risk

• Coliforms, Klebsiella spp., Staph spp.,Strep. & Strep-like spp. (SSLO)

(Patel et al., 2019; Rowe et al., 2019)

Manure solids(RMS)

New sand(NS)

Reclaimed sand(RS)

Shavings(ON)

Straw(ON)

Recycled manure solids (RMS) is highest risk bedding material for increased BBC and impaired udder health

(Wenz et al., 2007; Rowbotham and Ruegg, 2015, 2016; Patel et al., 2019; Esser et al., 2019)

Log1

0 cf

u/cc

Coliform Counts in Unused Bedding

MS ON RSNS

New Infection Rate (%)By Bedding Type

Patel et al., 2019

However…Not all herds using recycled manure solids

bedding have poor udder health(Patel et al., 2019; Rowe et al., 2019)

What’s theirsecret?

RMS Processing Systems

Pressed only Mechanical Drying700 °F at entry, 130 ° F at exit,

12-15 min to process

Rotating Drum Mixes solids with hot

air > 150 °F x 1d

Digestedthen pressed

(≥ 15 d retention)

Green Digested Composted Dried

Comparison of RMS Processing Systems(Patel et al., J. Dairy Sci. 2019)

Green12 systems(10 in MW)

Dried8 systems(2 in MW)

Drum Composted10 systems(2 in MW)

Digested3 systems

(all in MW)

Hot air drying systems had:- Dryer bedding (↑ DM%)- Lower clinical mastitis rate

HOWEVER very small sample size / very few systems in Midwest

Investigation of RMS Processing Methods on Midwest Dairy Farms

• Objectives. Describe associations between RMS processing method and:

• Bedding bacteria counts (BBC)• Udder health • Milk production

• Hypothesis: Herds with mechanically dried RMS would have lower BBC, better udder health and higher milk production than the other processing systems

Methods

• Cohort Study: Enroll RMS systems in MN/WI using:• Green • Digested• Drum composted • Mechanically dried

• Each herd visited twice: Aug. 2019 and Jan. 2020

• Study technicians collected:• DC305 backups• Herd management questionnaire• Bedding samples for aerobic culture (cfu/cc):

• Preprocessed, RTU and Used (from stalls)

Statistics

• Mixed effects linear regression (SAS v 9.4)

• Outcome variables:• BBC (log10, cfu/cc):

• Coliforms; Klebsiella; SSLO; Staph• DHIA SCC data for the test day preceding sample date:

• Avg LS; % infected; New IMI%; Chronics %• Clinical mastitis rate: % cows in last 30 day period• Avg 305ME (kg/cow) at last test

• Explanatory variables:• Processing: Green/Digested/Composted/Dried• Other covariates tested: season, breed, herd size, milking frequency, etc. • Herd = random effect• Critical P value ≤ 0.05 ; then adjusted for multiple contrasts

Results29 Free stall facilities: MN 8, WI 21

Green = 7 Digested = 6 Drum Composted = 4 Dried = 12

Herd Descriptive Stats

Avg (SD) RangeHerd size 1,771 (1,395) 235 – 5467305 ME (kg) 12,705 (1,371) 8,934 – 14,899Avg DIM 183 (11) 160-201Avg Parity 2.1 (0.2) 1.8 – 2.5Bed stalls (x/week) 3.6 (2.0) 0.7 – 7.0Scrape back of stalls (x/d) 2.7 (0.7) 0 - 3

Bacteria Counts in ‘Ready to Use’ Solids by Processing Method

0

1

2

3

4

5

6

7

Coliform Klebsiella SSLO Staph

Bedd

ing

Bact

eria

Cou

nt (l

og10

cfu

/cc)

Bedding Culture Bacteria Group

GreenDigestedCompostedDried

Coliform BBC lower in Driedand tended lower in Composted (vs Green)

Klebsiella BBC lower in Dried,Composted and Digested(vs Green)

SSLO lower in Composted and tended lower in Dried(vs Digested or Green)

Staph – no treatment effect,though numerically lowerin Dried RMS

Udder Health in Herds using Different RMS Processing Methods

0

5

10

15

20

25

30

Avg LS IMI (%) New IMI (%) Chronics (%) Clinicals (%/mos)

Udder Health Parameter

GreenDigestedCompostedDried

Herds using dried or composted RMShad (or tended to have) better udder health than Green or Digested solids:- Avg LS- IMI %- Chronics %

No processing effect for New IMI% or Clinicals%

No difference between… - Dried vs Composted - Green vs Digested

Milk Production in Herds using Different RMS Processing Methods

11,68912,517

12,75213,781

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

305

ME

(kg)

305 ME (kg)

GreenDigestedCompostedDried

a

a,b b,iia,b,i

a,b: Signifcant at P < 0.008i,ii: Significant at 0.008 ≤ P < 0.1

Herds using DriedRMS had higher production than Green RMS, andtended to havehigher productionthan Digested RMS.

Conclusions

• As compared to Green or Digested RMS systems, use of Mechanical Drying and Drum Composting was associated with:

• Reduced BBC for two or more groups of bacteria associated with increased mastitis risk

• Udder health was better, or tended to be better

• Milk production better, or tended to be better in herds using dried RMS

Implications for Midwest Producers using RMS

• Herds using MECHANICAL DRYERS or DRUM COMPOSTING may have better success achieving better udder health

Strengths, Limitations and Next Steps• Strengths:

• First study to compare 4 RMS processing methods in Midwest herds• Two seasons represented• Can generalize to large herds in MidWest & probably in NorthEast (not

West/Southern states)

• Limitations:• Small sample size, especially for Drum Composters• Cohort study: Controlled for potential confounders, but you never know

• Next questions: • How are Dryers or Drum Composters reducing BBC

• Heat? Drying effect? Effect on nutrient availability? - Part II of presentation• Economics?

Acknowledgements

Funding:

Technical Support:

Farms Students Lab for Udder Health

Thank you