Selective Dry Cow TherapyWhen is it appropriate?
Pamela Ruegg, DVM, MPVM
Michigan State University
E. Lansing, MI
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
Mastitis Remains the Most Costly Disease of Dairy Cattle
• Mastitis is the most common disease of dairy cows– About 20 - 35% of cows have subclinical mastitis
– About 25 – 40% develop a clinical case each lactation
• Overall loss to US dairy industry of about $200 USD per cow per year
• Mastitis reduces– Yield
– Reproductive performance
– Value of milk to processor
– Final product quality
– Ability to sell milk
Almost all US Dairy Farms Use DCT
• Standard mastitis control
program
– >80% of US herds treat 100%
• most farmers treat most cows
– 93% of cows receive DCT
• Blanket dry cow therapy
programs developed in 1970’s
– >50% of cows had infected
quarters
• Today fewer cows are infected
– Re-examination of use of
antibiotics on dairy farms
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60%
70%
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90%
100%
None 1-33% 34-66% 67-99% 100%
Proportion of Herds Using Dry Cow Therapy: USDA NAHMS
2002 2007 2014
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
Dry Cow Treatment is About 20-40% of ALL Antibiotics Used on large WI farms (DDD/adult cow/yr) – 2017 data
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DD
D/c
ow
per
yea
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Farms
Treatment of mastitis
Dry cow treatment
Treatment of other diseases for adult cows
J. Leite de Campos, A. Steinberger, N. Safdar, J. Shutske, A. Sethi, G. Suen and P. Ruegg, 2020
Research Evidence from J Dairy Sci.
“…recent reports reflect growing interest in selective approach…”
“…concern as to possible selection for heightened resistance…”
“..preference for selective dry cow therapy and teat dipping in the Scandinavian countries may reflect their general lower incidence of intramammary infection.”
1983
ObjectiveTo review use and economic imparct of
Selective Dry Dry Cow Treatment
Control of Contagious Pathogens has Been Effective
• The prevalence of Staph aureus
& Strep agalactiae has steadily
decreased
– Adoption of 5 point plan
– Dry cow treatment
• Environmental pathogens now
cause most mastitis
– Many mild clinical cases
• Bulk tank SCC in US has dropped
to < 200,000 cells/mL
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50%
1994 1995 1996 1997 1998 1999 2000 2001
Pro
po
rtio
n o
f is
ola
tes
Year
Isolation of Bacteria from >77,000 Milk Samples, WI, USA
Staph aureus Strep agalactiae
Makovec & Ruegg, 2003. J Dairy Sci
Cows That Remain Infected Across Dry Period Pay a Big Price
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None 1 2 3
Milk
Yie
ld (
lb)
Number of High SCC Quarters 3-8 days Postpartum
First Test Milk Yield by Number of High SCC ¼ s
Quarter SCC data from 215 Holstein cows Compared SCC at dry off, early
lactation & first DHIA test
Percent of quarters with SCC >200,000 3-8 days postpartum 20% of 2nd lactation
59% of 3rd lactation
83% of 4+ lactation
Milk Yield was strongly associated with SCC during first week postpartum
Pantoja & Ruegg, Preventive Veterinary Medicine 2010
Cows With Chronic Infections Across Lactations Produce Less Milk
• Quarter SCC data from 215 Holstein cows– Compared DHIA SCC at last test and &
first DHIA test
• 1st monthly Milk Yield was decreased 20 lb/cow/day for – Cows with SCC >200,000 cells/ml at both
last test and 1st test
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Chronic New Infections Healthy
Milk
at
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b/d
ay)
Milk Yield at 1st DHIA Test (lb/day)
Pantoja, Hulland & Ruegg, Prev. Vet Med 2009
Early Lactation SCC & Risk of Clinical Mastitis: Research in France
1.0
1.5
2.0R
isk
Initial Test SCC (x 1000)
Risk of First Case of Clinical Mastitis
• French study evaluated influence of first test SCC on risk of clinical mastitis– Rupp & Bouchard, Livestock Prod. Sci. 2000
• First test SCC was 5-35 days in milk
• Looked at herds with low somatic cell counts
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
Conception Rate Decreases as Mastitis Progresses from Subclinical to Clinical
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Healthy SM during BRPCM during BRP Chronic CM
Od
ds
of
Pre
gnan
cy
Pre
gnan
cies
per
AI
Fuenzalida, Fricke & Ruegg, JDS 2015
Purpose of Dry Cow Therapy is to Reduce Risk of Mastitis
• Therapeutic
– Cure cows with subclinical infected
quarters at dry off
– Can we identify healthy cows
that don’t need treatment?
• Preventive
– Prevent new infections during high
risk period
– Can we use non-antibiotic tools
to protect these animals?
Therapeutic Function
• SCC >200,000 cells/ml = evidence of mastitis
• SCC does not increase with DIM unless the cow
becomes infected
• Many herds have >30% of cows with subclinical
infections
• Treatment of these infections is best
performed at dry off
• Increased efficacy
• Reduced risk of drug residues
• More economical – no milk discard
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250
% o
f C
ow
s w
ith
SC
C >
20
0,0
00
cel
ls/m
L
Days in Milk
Prevalence of Subclinical IMI1 WI Dairy Farm with BTSCC 160,000
cells/mL
Lact 1 Lact 2 Lact 3
Preventive Function
• Keratin Plug is Primary
Defense against IMI
• Delayed formation of keratin plug
• Open teats were found:– 40% (2 weeks)
– 30% (4 weeks)
– 24% (6 weeks)
• Dingwell et al., 2003
• High production delayed formation of keratin plug
– 50% of cows that produced >46 lbs. on day of dry off
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
Selective DCT Means Use ofAntibiotics &/OR Sealants
• Purpose
– Use antibiotics only to cows that have evidence of current intramammary
infection
• Selective dry cow programs
– use IMM antibiotics only to treat cows infected at dry off
– Use internal or external teat sealants to prevent new infections
• Selective dry cow programs are NOT simply stopping use of DCT
Which test is Best?
• There is no perfect test
–All tests have error
• Which error means
more to your herd?
–Fail to treat infected
cows?
• This error is more common
with use of culturing
–Treat healthy cows?• This error is more common
with non-culture based
selection
• Cows with increased
SCC have evidence
of ongoing infection
– Using SCC history will
maximize treatment
• The false negative
rate with culture is
about 40%
–Fail to treat infected ¼
Pantoja et al., 2009, Prev. Vet. Med 90:43
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
Methods for Identifying Cows with Active Infections
• Review history of cow
– Previous cases of clinical
mastitis
– Monthly SCC history
• Perform individual quarter
tests such as
– CMT or SCC
• Culture quarters
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
What Does Research Show about Use of Selective Dry Cow Therapy?
Evaluation of Selective DCT - Ohio
• Enrolled 723 cows from 4 OH herds– BTSCC from 162 to 340
• SCC & CM history in last 90 ddetermined eligibility– Eligible (low SCC)
•
Large Herd Effects Were Noted
• Overall..– No effect on milk yield
was noted
– SCC was 16% greater in eligible quarters that did not get DCT
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Milk Yield SCCMilk
Yie
ld (k
g) o
r SCC
(log
uni
ts)
Interactions with HerdDiff. Between DCT & NoDCT
Herd 1
Herd 2
Herd 3
Herd 4
P = 0.12
P = 0.12
Conclusion of authors“…in some herds Blanket DCT was beneficial..while in other herds, no DCT had no detrimental impact…”
Rajala-Schultz et al., 2011 JDR 78:489
Evaluation of Selective DCT- Dutch
• Enrolled 1657 cows from 97 Dutch herds
• SCC at last DHI test determined eligibility– 1st lact:
Evaluation of Selective DCT
• Increased SCC at dry off – was not associated with being
culture +– Increased risk of CM in next
lactation 1.8x
• 36% of low SCC cows had high SCC ¼
• Strep uberis was primary major pathogen
Scherpenzeel et al., 2014 S97:3606
Conclusion of authorsUse of Selective DCT resulted in large decrease in AB but increased mastitis
Evaluation of Selective DCT- Canada
• Enrolled 729 cows from 16 herds in PEI & Quebec– BTSCC < 250,000
• Cow eligibility–
Evaluation of Selective DCT- Canada
• Characteristics of cows & herds–Median SCC of enrolled
cows• 36,000 to 39,000
cells/mL
–Incidence of Clinical Mastitis in 1st 120 d• 7.7%
Blanket DCT Selective DCT
IMI - parallel 15.3% 15.8%
CM 120 d 9.1% 8.0%
SCC – 180 d 3.95 3.97
SCC – 180 d 51,935 52,984
Milk – 180 d 86.1 lb 85.9 lb
Cameron et al., 2014 JDS 97:270 & 2014 JDS 97:2427
Results of Selective DCT Trial – No Sig. Effects
Conclusion of authorsUse of Selective DCT Based on
Petrifilm did not affect milk quality or yield
Selection Using Cow HistoryVasquez et al., 2017
• Single herd with BTSCC of 201,000
• Used history to select cows eligible for selective DCT– SCC
Selection Using SCC HistoryMcParland et al., 2019
• 3 Research herds in Ireland
• Selected cows based on SCC and clinical mastitis history–
Intramammary Use of AB has NOT been Associated with Increased Resistance of Mastitis Pathogens
• Use of IMM antibiotics is a lower risk route– Large dose
– Short duration
– No known commensal microbiota in mammary gland itself• Teat canal?
• Recent study demonstrated NO effect of IMM AB on resistance– Increased risk with systemic therapy
What Can We Conclude?
• Recent research indicates that: –Selective DCT when randomly applied• Decreases antibiotic usage
• Increases mastitis
–Selective DCT when carefully applied in selected herds• Can decrease antibiotic usage
without increasing mastitis
• No evidence to date that:–Use of blanket DCT increases
antimicrobial resistance
–Use of selective DCT reduces development of antimicrobial resistance
What does Dry Cow Therapy Cost?200 cow Dairy
• Costs (per cow)– Orbeseal - $10.45
– SpectramastDC - $18.35
– Lockout - $9.30
– Tomorrow - $11.30
• 200 cows * 85%
– 170 cows dried off
• Assumption is
selective DCT
reduces antibiotic
usage by 50% $0
$1,000
$2,000
$3,000
$4,000
$5,000
$6,000
SpectDC &/or Orbeseal Tomorrow &/or Lockout
Annual Cost of Products Used for Dry Cows on a 200 Cow Dairy
DCT Only all cows DCT + Sealant all cows
Selective (50% Less AB)
Investments in Mastitis ControlExample 200 Cow Dairy
• Control of mastitis requires investment
• Outputs include– Pre & Post teat dip
• 2.5 gal/cow/year
– Sand Bedding – 50 lb/stall/d• Allocate 50% to udder health?
– J5 Vaccination
– Culturing all clinical cases
– Dry cow treatment • Antibiotic & sealant
– $25.00 per cow
– Milking procedures• Towels & machines
Prevention Costs Per Month
Teat Dip $833.33
Bedding $760.42
Milk Machine Checks $150.00
Vaccination $62.50
Culturing costs $20.00
Dry Cow Rx $354.17
Towels $182.50
Miscellaneous $100.00
Total $2,462.92
Costs of Mastitis: 200 CowsBaseline Scenario
COST OF MASTITIS
Herd Size (lactating) 200
Incidence Rate%/mastitis/mth 2%
# of cases/month 4
Value of a milk cow $1,500.00
Avg Milk Production 80
Avg Milk Withhold in Days 8
Milk Price/ cwt $17.50
Avg # of IMM Tubes 5
Cost / tube $4.50
Death Rate of clinical mastitis 0.50%
Avg cull wt 1,000
Cull Price/cwt 0.45$
Cull Price 450
Replacement cost 1,500.00$ Cost of a Cull $1,050.00
% culling/yr due to mastitis 10.00%
Average Feed cost /cow/day $5.00
COST Herd/ MonthHerd / Year COW/ Year
NonSaleable Milk $448 $5,376 $27
Production loss due to SCC$2,075 $24,898 $124
Total Drug Cost $90 $1,080 $5
Culling Cost $1,750 $21,000 $105
Death Cost $30 $360 $2
Mastitis Prevention Costs$2,463 $29,555 $148
Total Cost $6,856 $82,269 $411
Bulk Tank SCC = 195,000
15% of Herd > 200,000
Direct costs clinical: $135
36% of cost is prevention
COST NO DCT Herd/ MonthHerd / Year COW/ Year
NonSaleable Milk $672 $8,064 $40
Production loss due to SCC$2,367 $28,409 $142
Total Drug Cost $135 $1,620 $8
Culling Cost $1,750 $21,000 $105
Death Cost $45 $540 $3
Mastitis Prevention Costs $2,296 $27,550 $138
Total Cost $7,265 $87,183 $436
Costs of Mastitis: 200 CowsSelective DCT – Mastitis Increases
COST OF MASTITIS
Herd Size (lactating) 200
Incidence Rate%/mastitis/mth 3%
# of cases/month 6
Value of a milk cow $1,500.00
Avg Milk Production 80
Avg Milk Withhold in Days 8
Milk Price/ cwt $17.50
Avg # of IMM Tubes 5
Cost / tube $4.50
Death Rate of clinical mastitis 0.50%
Avg cull wt 1,000
Cull Price/cwt 0.45$
Cull Price 450
Replacement cost 1,500.00$ Cost of a Cull $1,050.00
% culling/yr due to mastitis 10.00%
Average Feed cost /cow/day $5.00
COST with DCT Herd/ MonthHerd / Year COW/ Year
NonSaleable Milk $448 $5,376 $27
Production loss due to SCC$2,075 $24,898 $124
Total Drug Cost $90 $1,080 $5
Culling Cost $1,750 $21,000 $105
Death Cost $30 $360 $2
Mastitis Prevention Costs$2,463 $29,555 $148
Total Cost $6,856 $82,269 $411
Bulk Tank SCC = 223,000
25% of Herd > 200,000
Direct costs clinical: $135
Copyright © Pamela L. Ruegg, DVM, MPVM, 2013, all rights reserved
What herds should be considered for SDCT?
• Has the herd controlled subclinical mastitis?–Review the BTSCC history
• Herds with BTSCC >250,000 cells/mL should continue to use blanket DCT program
– Indication that a large % of cows have subclinical mastitis
– Is the bulk tank free of Staph aureus & Strep agalactiae?
• Does the herd have the ability to adequately monitor mastitis?
–Monthly Individual cow SCC values
–Forestripping to identify Clinical Mastitis & good CM records
Which cows should be considered for SDCT?
• Cows that should get antibiotics– Monthly SCC >150,000 cells/ml
– CM within 90 days of dry off
– Older cows with large udders/milk leakage
• Cows that may not need antibiotics– No CM in last 90 days
– SCC
Herd Level Criteria
Bulk Tank SCC250,000 cells/mL
USE ANTIBIOTIC DCT IN ALL QUARTERS
No Monthly cow SCC or No Clinical Mastitis Records
Have Monthly Cow SCC and Clinical Mastitis
Records
Cow Level Criteria
Use Internal
Teat Sealant
Only
Cow SCC > 150,000 or CM
case last 90 DIM
Cow SCC
What Should You Monitor if you Use SDCT?
• DCT is only given to multiparous cows
• Increased SCC of IMI in Primiparous cows
– Indicates problems with transition cow management
– Not usually DCT problem
• In multiparous cows not given DCT
– SCC at 1st test should be
Conclusion
• The use of selective dry cow therapy can be effective in some herds but entails risks that should be communicated to the farmer
• Selection of cows that need to receive therapy is not a perfect science and usefulness of culturing will vary depending on pathogens
• Herds using selective therapy should have good post-calving surveillance programs
• Reducing DCT to prevent antimicrobial resistance is unproven