selective dry cow therapy when is it appropriate? dry cow... · t 1 st t (lb y) milk yield at 1st...

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

Proportion of Herds Using Dry Cow Therapy: USDA NAHMS

2002 2007 2014


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

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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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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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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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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

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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


Conception Rate Decreases as Mastitis Progresses from Subclinical to Clinical

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Healthy SM during BRPCM during BRP Chronic CM

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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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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


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


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


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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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




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


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




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 = 223,000

25% of Herd > 200,000

Direct costs clinical: $135


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

selective dry cow therapy when is it appropriate? dry cow... · t 1 st t (lb y) milk yield at 1st...

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