implementing and evaluating a selective dry cow therapy program

Copyright ©2017 Pamela L. Ruegg, all rights reservedImplementing and Evaluating a Selective Dry Cow Therapy

Program

Pamela Ruegg, DVM, MPVM

University of Wisconsin, Madison

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

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None 1-33% 34-66% 67-99% 100%

Proportion of Herds Using Dry Cow Therapy: USDA NAHMS

2002 2007 2014

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

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Isolation of Bacteria from >77,000 Milk Samples, WI, USA

Staph aureus Strep agalactiae

Makovec & Ruegg, 2003. J Dairy Sci

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?

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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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 ©2017 Pamela L. Ruegg, 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 teat sealants to prevents new infections

• Selective dry cow programs are NOT simply stopping use of DCT

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 78:489Scherpenzeel et al., 2014 S97:3606

Cameron et al., 2014 JDS 97:270 & 2014 JDS 97:2427


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


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

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

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

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

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

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%

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Annual Cost of Products Used for Dry Cows

DCT Only DCT & Orbeseal Selective (50% Less AB)

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 = 195,00015% of Herd > 200,000Direct costs clinical: $135

36% of cost is prevention

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




Culling Cost $1,750 $21,000 $105


Mastitis Prevention Costs$2,463 $29,555 $148

Total Cost $6,856 $82,269 $411

Bulk Tank SCC = 223,00025% of Herd > 200,000Direct costs clinical: $135

COST NO DCT Herd/ MonthHerd / Year COW/ Year




Culling Cost $1,750 $21,000 $105


Mastitis Prevention Costs $2,296 $27,550 $138

Total Cost $7,265 $87,183 $436

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

implementing and evaluating a selective dry cow therapy program

Education