Pamela Ruegg joins us to discuss selective dry cow therapy. Learn about implementing and evaluating a program, as well as how to decide whether selective therapy might be a good fit for your operation. View the full presentation at https://www.youtube.com/watch?v=VKRAqHQZIng

1. Copyright ©2017 Pamela L. Ruegg, all rights reserved
Implementing and Evaluating
a Selective Dry Cow Therapy
Program
Pamela Ruegg, DVM, MPVM
University of Wisconsin, Madison

2. Almost all 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
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
None 1-33% 34-66% 67-99% 100%
Proportion of Herds Using Dry Cow
Therapy: USDA NAHMS
2002 2007 2014

3. 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 about 200,000
0%
5%
10%
15%
20%
25%
30%
35%
40%
45%
50%
1994 1995 1996 1997 1998 1999 2000 2001
Proportionofisolates
Year
Isolation of Bacteria from >77,000 Milk
Samples, WI, USA
Staph aureus Strep agalactiae
Makovec & Ruegg, 2003. J Dairy Sci

4. Purpose of Dry Cow Therapy is to Reduce
Risk of Mastitis
• Therapeutic
– Cure cows with subclinical infected
quarters at dry off
– Can we identify cows that don’t need
treatment?
• Preventive
– Prevent new infections during high risk
period
– Can we use non-antibiotic tools to
protect these animals?

5. 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
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
<30 31-150 151-250 >250
%ofCowswithSCC>200,000cells/mL
Days in Milk
Prevalence of Subclinical IMI
1 WI Dairy Farm with BTSCC 160,000 cells/mL
Lact 1 Lact 2 Lact 3

6. 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

7. Copyright ©2017 Pamela L. Ruegg, all rights reserved
Selective DCT Means Use of
Antibiotics &/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 teat sealants to prevents new infections
• Selective dry cow programs are NOT simply stopping
use of DCT

8. What Does the Research Tell Us?
• 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
Rajala-Schultz et al., 2011 JDR 78:489
Scherpenzeel et al., 2014 S97:3606
Cameron et al., 2014 JDS 97:270 & 2014 JDS 97:2427

9. Copyright ©2017 Pamela L. Ruegg, all rights reserved
Is SDCT appropriate for your herd?
• Has your 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 your bulk tank free of Staph aureus & Strep agalactiae?
• Do you have the ability to adequately monitor mastitis?
– Monthly Individual cow SCC values
– Forestripping to identify Clinical Mastitis & good CM records

10. Copyright ©2017 Pamela L. Ruegg, 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

11. 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

12. Which cows should be considered for
SDCT?
• Cows with
– Monthly SCC >150,000
cells/ml at the last
monthly test
– History of CM within 90
days of dry off
– SHOULD receive
antibiotic DCT in every
quarter
• Selective dry cow
programs reduce use of
IMM antibiotics by
about 50%
• Those cows should still
receive teat sealants

13. Cows Eligible for Teat Sealant only
• Have no history of CM
in last 90 days
• Have SCC <200,000
cells/ml
• Are CMT <2 on all 4
quarters
• All quarters SCC <300,000
cells/mL
• Internal or External
Sealant?
• Most research has
evaluated internal
sealants but…
– Recent study used
external sealant with
good results
• More research is needed

15. 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 <200,000
cells/ml
• 85% of cows
– Clinical mastitis in 1st month
should be
• <5% of cows
• Culturing 1st week post-calving
is not recommended
– High rate of CNS infections that
self-cure

16. What does Dry Cow Therapy Cost?
200 cow Dairy
• Costs (per cow)
– Orbeseal - $10.50
– SpectramastDC - $19.00
– Tomorrow - $10.00
• 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 Tomorrow
Annual Cost of Products Used for Dry
Cows
DCT Only DCT & Orbeseal Selective (50% Less AB)

17. Costs of Mastitis: 200 Cows
Baseline 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

18. Costs of Mastitis: 200 Cows
Selective 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
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

19. Conclusion
• The use of selective dry cow therapy can be effective in some herds but
risks versus gains need to be assessed
• Selection of cows that need to receive therapy is not a perfect science
• Herds using selective therapy should have good post-calving surveillance
programs
• Reducing DCT to prevent antimicrobial resistance is unproven