Evolution of Udder Hygiene

UPDATE ON BOVINE MASTITIS

0749-0720/93 $0.00 + .20

EVOLUTION OF UDDER HYGIENE Premilking Teat Sanitation J. Woodrow Pankey, PhD, and Peggy A. Drechsler, BS

Prevention of bovine mastitis depends on an effective udder hygiene program.6, 13-1S The major objective of udder hygiene is to prevent new intramammary infection (lMI) by minimizing teat contamination by mastitis pathogens. At least four components constitute a complete udder hygiene program-milking, post-milking, between milking, and premilking periods. Milking machine design has attempted to enhance udder hygiene by preventing cross contamination with quarter milker units. "Ball" claws and liner shields have attempted to minimize air blast against teats during milking. These are important advances toward improved udder hygiene. Post-milking teat antisepsis has received more attention through research and product development than the other time periods. Between milking hygiene emphasizes housing, stall design, bedding management, and corral management for large herds in arid regions. 10, 11 Inorganic bedding materials-sand and crushed limestone-provide lower numbers of environmental pathogens than organic beddings such as straw and sawdust. 10 Maintaining dry bedding, regardless of the type, is imperative to minimize pathogen numbersY The principle of between milking hygiene is simple: "Keep cows clean, dry, and comfortable" 24 hours a day.ll Premilking teat sanitation (predipping) is a relatively new practice first described in the late 1970s in California to aid in the control of mastitis caused by environmental pathogens.s After a brief summary regarding post-milking sanitation, this article focuses on premilking teat sanitation.

From the Department of Animal and Food Sciences, University of Vermont, Burlington, Vermont

VETERINARY CLINICS OF NORTH AMERICA: FOOD ANIMAL PRACTICE VOLUME 9 • NUMBER 3 • NOVEMBER 1993

519

520

PANKEY & DRECHSLER

POST-MILKING TEAT SANITATION

Post-milking teat sanitation was reviewed thoroughly in 1984. l3,18 Sanitation of teats after milking with an effective product consistently reduces incidence of IMI caused by contagious pathogens such as Staphylococcus aureus and Streptococcus agalactiae. 18 Post-dipping has not controlled mastitis caused by environmental pathogens such as Streptococcus uberis-a non-agalactiae streptococci-and coliform bacteria.2, 20 Protocols for efficacy evaluation of post-milking teat dip formulations were developed for experimental challenge and natural exposure conditions.9 Formulations that demonstrate effectiveness under these controlled conditions have the potential to reduce incidence of new IMI by contagious mastitis pathogens. Producers should use only teat sanitizers proven efficacious in controlled studies. PREMILKING TEAT SANITATION

Premilking teat sanitation (predipping) was first discussed by Bushnel1. 5 Teats were immersed in a 1% iodine post-milking teat dip and dried with paper towels prior to machine attachment in an effort to control outbreaks of clinical mastitis caused by coliform bacteria. The 1 iodine dips were more bactericidal than udder washes but tended to increase teat skin irritation and iodine residues in milk. These potential problems were ameliorated by the use of a low-concentration iodinebased dip. BushnelP reported an 80% reduction in new cases of clinical mastitis by pre dipping with a low-iodine dip. Manual drying of teats with paper towels was considered essential to preclude residues in milk. 5 Failure to wipe the dip from teats before milking caused an increase of measurable iodides in milk (350 J.Lg/L). %

Experimental Challenge Studies

Galton et al6 used experimental challenge procedures to compare three premilking udder preparation methods-(l) no udder preparation, (2) wet paper towel plus drying, and (3) predipping with a 0.1% iodine teat product plus drying. All teats were sanitized after milking with a 0.25% iodine product. To simulate environmental contamination of teats between milkings, all teats were immersed into a culture of Streptococcus uberis (ATCC 27958) approximately 3 hours prior to milking. The concentration of the experimental challenge was between 107 and 108 CFU / mL. Compared with no udder preparation, the wet towel/dry protocol and the reduced rate of new IMI by 43% predipping/ dry protocol, by 67%; both reductions were statistically significant (P < 0.05). Predipping/ dry reduced new IMI by 41% (P < 0.1) compared with wet towel/dry. In a subsequent trial, Pankey and Galton15 compared four treatments-(l) control (no udder preparation, no post-milking teat dip); (2)

EVOLUTION OF UDDER HYGIENE

521

post-dip only (no udder preparation with post-milking teat dip); (3) predip only (predip and manual dry, no post-milking teat dip); and (4) pre- and post-milking teat dipping. A 0.25% iodine teat sanitizer was used for pre- and post-milking teat antisepsis. Contact time was 20 to 30 seconds prior to manual drying with paper towels. Teats were challenged with Streptococcus uberis as described for the first triaL6 Compared with the control, new Streptococcus uberis IMls were reduced 25.1 % (P > 0.05) by post-dipping only; 68% (P < 0.001) by predipping only; and 71.4% (P < 0.001) by pre- and post-milking teat dipping. Compared with post-milking teat dipping only, new IMls were reduced 57.20/0 (P < 0.025) by predipping only and 61.8% (P < 0.025) by pre- and postmilking teat dipping. In summary, premilking teat sanitation significantly reduced new IMI when teats were challenged 3 hours prior to milking.

Natural Exposure Studies

The efficacy of predipping with three different iodine-based teat dips was determined under natural exposure conditions on four Vermont dairy farms.19 A split herd design was used and treatment groups were balanced at initiation of the trial for parity, days-in-milk (DIM), and bacteriologic status.9 Treatment groups were "predip" or "control"; "predip" included good-udder-preparation (CUP) prior to milking, with pre- and post-milking teat antisepsis. The "control" group included CUP prior to machine attachment and post-milking teat antisepsis. CUP included (1) teats and base of udder cleaned with a paper towel wet with udder wash solution (approximately 50 ppm iodine); (2) forestripping; (3) teats of cows in predip group immersed "full length" in one of the iodine formulations and a minimum contact time of 30 seconds allowed; and (4) teats of both groups dried with individual paper towels. All cows were milked in a routine manner. The same teat dip was used as both pre- and post-dip within each herd. 19 The three iodine-based teat sanitizers evaluated as dips contained 0.1 %, 0.25%, and 0.55% available iodine. 19 The 0.25% iodine product was used in Herds A and B; the 0.1 % iodine product in Herd D; and a 0.55% iodine plus 1.9% linear dodecyl benzene sulfonic acid product was used in Herd C. All three formulations had demonstrated efficacy as postmilking teat sanitizers in controlled studies.4, 16, 17 Diagnosis of an IMI was based on one of the following: (1) isolation of greater than 100 CFU/mL of a pathogen from a clinical sample, (2) isolation of greater than 500 CFU / mL of a pathogen from two consecutive samples, (3) isolation of less than 400 CFU/mL of a pathogen from three consecutive samples, and (4) clinical cases with abnormal milk that were bacteriologically negative for each of the duplicate samples?' 10 Farmer-collected "clinical" samples that appeared "normal" to laboratory personnel and that were bacteriologically negative were not considered as representing IMI.19

522

PANKEY & DRECHSLER

Previous work had emphasized the importance of predipping in the control of mastitis caused by environmental pathogens.s This trial was designed to evaluate the effectiveness of predipping against mastitis caused by all pathogens. A summary of results from all four herds determined that new IMIs by environmental mastitis pathogens were reduced 51.5% (P < 0.001) by predipping compared with GUP alone. Infections by non-agalactiae streptococci were reduced 48.2% (P < 0.025), and those by coliforms were reduced 54% (P < 0.005). Both subclinical and clinical forms of mastitis were included in the diagnosis of new IMIs.19 All New Intramammary Infections by Herd

A between-herd comparison for all new IMIs reveals variation in effectiveness of predipping (Table 1). Percent reduction for predipping compared with GUP ranged from 7.3% to 51.3%. Statistically significant reductions were observed in two of the four herds. New IMIs with coagulase-negative staphylococci (CNS) were an important factor in the two herds in which reductions were insignificant. Percent quarters diagnosed with new CNS IMIs were 16% and 9% for predip and GUP groups Table 1. ALL NEW INTRAMAMMARY INFECTIONS, SUBCLINICAL AND CLINICAL, DIAGNOSED IN THE EVALUATION OF PREMILKING TEAT SANITATION Herd

A T Number quarters Bacteriologic status: Staphylococcus aureus Coagulase-negative staphylococci Streptococcus aga/actiae Non-aga/actiae streptococci Coliforms Clinical mastitis (bacteriologically negative) Total infections Percent Reduction: All new infections Pvalue Major pathogenst Pvalue Environmental pathogens§ Pvalue *T

t

B

C

149 122

D

C

Treatment Group· T T C C

94

82

T

C Totals

137 137 239 213

0 24 0 7 2 1

3 11 0 10 6 0

0 7 0 6 3 3

2 12 0 13 5 2

3 28 0 2 7 2

4 26 0 6 12 6

3 12 0 3 9 0

2 10 3 2 18 6

= 17 = 130 =3 = 49 = 62 = 20

34

30

19

34

42

54

27

41

= 281

7.3 NSt

57.0 0.025 54.2 0.05

51.3 0.005 52.2 0.025 56.4 0.025

22.1 NS 50.0 0.025 49.6 NS

41.4 0.025 56.8 0.005 46.8 NS

= Treatment; C = control

= Not significant

+

Staphylococcus aureus, Streptococcus aga/actiae, non-aga/actiae streptococci, coliforms, and clinical mastitis (bacteriologically negative) § Non-aga/actiae streptococci and coliforms

EVOLUTION OF UDDER HYGIENE

523

in Herd A and 20% and 19% in Herd C. In Herds B and D, fewer than 10% of predipped quarters developed new CNS IMls. Natural exposure studies on predipping at Cornell University15 determined that new CNS IMls were not controlled by predipping. Post-milking teat dipping was more important to reduce incidence of CNS IMls. CNS are normal teat skin colonizers; sanitation after milking probably reduces the number of CNS and eliminates much of the residual milk from the skin. The presence of milk could enhance growth of CNS between milkings and increase infection rate. Efficacy of predipping compared with GUP alone was consistent across the four herds for all IMls by major mastitis pathogens and for environmental pathogens (see Table 1). Without the influence of CNS, reductions for major pathogen IMls ranged from 50% to 57%; all reductions were significant. Bacteriologically negative clinical mastitis cases were included in the "major pathogen" category for this article; these were excluded in Pankey's 1987 report. 19 Percent reductions for environmental pathogens ranged from 46.8% to 56.4%. Reductions were statistically significant for only two herds.

PREDIPPING VERSUS CLINICAL MASTITIS

In field trials, 1MIs are monitored using bacteriologic diagnosis on aseptically collected, quarter milk samples. Subclinical and clinical infections are included in the database. Dairy producers usually determine effectiveness of mastitis control practices, particularly for environmental pathogens, by observing changes in the incidence of clinical mastitis. Clinical mastitis can arise from existing IMI or from eligible quarters that develop "new" IMls diagnosed in the clinical state. Infection data from the four Vermont cooperator herds were analyzed based on clinical mastitis. 19 Two "types" of clinical mastitis were considered: (1) "all clinical mastitis cases" (cases that developed from existing IMls and "new" IMls diagnosed as clinical mastitis) and (2) "new clinical cases" (cases that were new IMls diagnosed in the clinical state among eligible quarters. A total of 125 clinical mastitis cases were reported for the four herds (Table 2). Environmental pathogens were the most frequent cause of clinical mastitis; coliforms were isolated from 39.2% of clinical cases and non-agalactiae streptococci from 24.8%. For individual herds, frequency of environmental pathogens from clinical cases ranged from 50% to 80%. Bacteriologically negative clinical cases accounted for 17.6% of cases. CNS were isolated from 11.2%, Staphylococcus aureus from 4.8% and Streptococcus agalactiae from 2.4% of all clinical cases. New IMls diagnosed in the clinical state represented 66.40/0 (83 of 125) of all clinical cases (Table 3). Coliforms caused 45.8% of new clinical mastitis cases, bacteriologically negative and non-agalactiae streptococci, 24.1% and 21.7%. Frequency of environmental pathogens ranged from 50% to 100% of all new clinical cases in the various herds. For new clinical cases, CNS were isolated only once. Three new Streptococcus

524

PANKEY & DRECHSLER

Table 2. SUMMARY OF ALL CLINICAL MASTITIS CASES Herd

T

Staphylococcus aureus Coagulase-negative staphylococci

Streptococcus agalactiae Non -agalactiae streptococci Coliforms Clinical mastitis (bacteriologically negative)

Total clinical cases *T

=

Treatment; C

C

149 122

Number quarters Bacteriologic status:

=

c

B

A

o

Treatment Group* T T C C

94

T

C Totals

82 137 137 239 213

0 1 0 4 4 1

0 1 0 6 4 2

0 1 0 4 0 3

1 2 0 8 2 1

3 5 0 3 8 3

0 1 0 4 10 6

2 1 0 1 6 0

0 2 3 1 15 6

=6 = 14 = 3 = 31 = 49 = 22

10

13

8

14

22

21

10

27

= 125

control

agalactiae IMIs and three new Staphylococcus infections were diagnosed in Herd D as clinical cases. The percentage of clinical mastitis among all new IMIs was 61.3% (38 of 62) for coliforms, 36.7% (18 of 49) for non-agalactiae streptococci, 17.6% (3 of 17) for Staphylococcus aureus, 0.8% (1 of 130) for eNS, and 100% (3 of 3) for Streptococcus agalactiae. These values for clinical mastitis by environmental pathogens were similar to the ranges reported?O All Clinical Mastitis: Herd, Parity, Days-in-Milk, and Effects

Incidence of all clinical mastitis cases and all clinical cases caused by environmental pathogens was compared for treatment groups by herd, Table 3. SUMMARY OF CLINICAL MASTITIS CASES DIAGNOSED AS NEW INTRAMAMMARY INFECTIONS

Herd B

A

T

149 122

Number quarters Bacteriologic status:

Staphylococcus aureus Coagulase-negative staphylococci

Streptococcus agalactiae Non-agalactiae streptococci Coliforms Clinical mastitis (bacteriologically negative)

Total clinical cases (New infections) *T

=

Treatment; C

C

= control

0

C

Treatment Group* T T C C

94

T

82 137 137 239

C Totals 213

0 0 0 4 3 1

0 0 0 4 3 0

0 0 0 3 0 3

0 0 0 3 2 2

1 0 0 2 3 2

0 1 0 2 9 6

2 0 0 0 6 0

0 0 3 0 12 6

=3 = 1 =3 = 18 = 38, = 20

8

7

6

7

8

18

8

21

= 83

EVOLUTION OF UDDER HYGIENE

525

parity, DIM, and season (Table 4). Changes in the incidence of all clinical mastitis cases in the predipped group ranged from an increase of 5% to a reduction of 65.8% between herds. Factors within herds affected the ability of predipping to reduce the rate of IMI. Specific factors were not determined. A trend was noted that suggested an inverse relationship between efficacy of predipping and parity. Predipping resulted in significant reductions among first- and second-lactation cows and was ineffective among cows of third and greater lactations. These results are comparable to those reported by Smith et a1. 20 Trends were not apparent for DIM; insignificant reductions were determined across lactation. Season of the year affected efficacy of predipping on all clinical cases. Significant reductions in incidence of IMI in the predip group were observed during the summer and winter. The summer months of the study were dry. All cows were housed during the winter, basically from November through March. For all clinical cases caused by environmental pathogens, efficacy of predipping ranged from 21.6% to 64.8% among herds (see Table 4). Only one herd demonstrated a significant decrease for the predip group. For environmental pathogen-caused clinical cases by parity, only secondlactation cows had a significant reduction-64.3 %; first-lactation cows had a 36.8% reduction and older cows had only a 27.4% reduction with predipping. Predipping resulted in nonsignificant reductions in all clinical cases across DIM. Reductions of 79.3% in the summer and 64.3% in Table 4. EFFECT OF HERD, PARITY, DAYS-IN-MILK, AND SEASON ON EFFICACY OF PREMILKING TEAT SANITATION AGAINST ALL CLINICAL MASTITIS CASES Percent Reduction Variable Herd A B C

0

All Cases·

Pvalue

Envt

Pvalue

37.4 50.3 +5.0 65.8

NS:t: NS NS

34.2 64.8 21.6 61.8

NS NS NS

0.005

0.05

Parity

1 2 3+

52.4 46.4 3.7

0.025 0.05

1-100 101-200 201 +

21.6 29.8 38.3

Season Spring Summer Fall Winter

+25.0 58.9 22.2 72.7

0.025

NS

36.8 64.3 27.4

NS NS NS

40.5 33.0 33.9

NS NS NS

NS

22.2 79.3 25.8 64.3

NS NS

Days-in-milk

0.005 NS

0.025

*All clinical mastitis cases

tAli clinical mastitis cases diagnosed with non-agalactiae streptococci and coliforms ;Not significant

NS

0.005 NS NS

526

PANKEY & DRECHSLER

the winter were obtained for environmental pathogens in the predipped group; only the reduction during summer was significant. New Clinical Mastitis: Herd, Parity, and DIM Effects

Two herds realized significant reductions in the predip group for all new IMIs diagnosed as clinical mastitis (Table 5). As was noted for all clinical cases, an inverse relationship was observed for parity. Percent reduction decreased with increases in parity. Significant reductions were observed in the predip group for only first- and second-lactation cows. The influence of DIM was inconsistent; reductions were approximately 52%, 39%, and 54% from parturition through 100 DIM, 101 to 200 DIM, and 201 + DIM, respectively, for all new clinical cases. Predipping resulted in a significant reduction-72.5 %-in new clinical mastitis cases only during the summer. Reductions of 51.5% in the fall and 45.5% in the winter were not significant. For all new clinical cases diagnosed with environmental pathogens, only Herd C realized a significant reduction of 70.2% from predipping. Herds Band Chad 47.5% and 55% reductions with predipping; these were not significant. For parity, reductions tended to decrease with increased age, as already mentioned. For new clinical cases with environTable 5. EFFECT OF HERD, PARITY, DAYS-IN-MILK, AND SEASON ON EFFICACY OF PREMILKING TEAT SANITATION AGAINST CLINICAL MASTITIS CASES DIAGNOSED AS NEW INTRAMAMMARY INFECTIONS Percent Reduction Variable Herd A

8 C

0

All Cases·

Pvalue

Envt

Pvalue

5.3 24.7 55.7 74.8

NSi NS

17.5 47.5 55.0 70.2

NS NS NS

0.05 0.005

0.05

Parity

76.6 57.4 20.0

0.005 0.05

1-100 101-200 201 +

51.5 39.2 53.8

NS NS

Season Spring Summer Fall Winter

+10.0 72.5 51.5 45.5

1 2 3+

NS

58.1 69.2 39.7

NS

0.025 NS

Oays-in-milk

0.05 NS

0.005 NS NS

64.0 58.9 36.4 14.3 81.5 51.8 44.4

0.05 NS NS NS

0.005 NS NS

*All clinical mastitis cases diagnosed as a new intramammary infection tAli clinical mastitis cases diagnosed as a new intramammary infection with non-agalactiae streptococci or coliforms :t:Not significant

EVOLUTION OF UDDER HYGIENE

527

mental pathogens, a significant reduction was observed for predipping during early lactation-1 to 100 DIM. Efficacy for predipping was significantly better in summer than any other season.

FIELD TRIALS IN THE UNITED KINGDOM

Three field trials have been conducted in the United Kingdom in the past 2 years to evaluate premilking teat dipping against routine udder preparation by comparing incidence of clinical mastitis. 1, 8, 12 In Trial 1, three herds with a total of 310 cows cooperated for 20 weeks. The trial was conducted during the winter housing period, when the majority of environmental mastitis cases occur and cows are in early to midlactation. 8,12 Half the cows were prepared for milking as usual and half were subjected to premilking teat disinfection. Premilking disinfection was with a formulation that contained 0.25% available iodine. All teats were sanitized after milking with a 0.5% iodine product. Groups were balanced for lactation number, stage of lactation, and previous history of mastitis. Cows calving were added in tum to either group. Cows in the predip group were prepared by dipping at least the distal 4 cm of all teats in disinfectant and drying with paper towels after a minimum of 30 seconds contact time. Bacteriologic status of quarters was determined at initiation and termination of the trial and for cows entering or leaving the trial. Diagnosis of clinical mastitis was by farm staff who identified abnormal milk or udder appearance, usually when staff administered antibiotic therapy. Duplicate quarter milk samples were collected and cultured from all clinical cases prior to therapy. Incidence of new IMls for all three herds was reduced 40% (P < 0.001) and clinical mastitis was reduced 33% (P > 0.05). As in the Vermont trial,t9 considerable variation was noted among herds. Reductions of new IMls, in the predip group were 74.2% and 19.4% for two herds. In the third herd, only four new IMls were diagnosed, three in the predip group and one in the controls. A reduction in clinical cases of 60% was observed in one herd, with 10.2% fewer than the control in a second. For the third herd, only one clinical case developed and it was in the control group. The overall results are similar to the Vermont data; a positive effect was determined for premilking teat sanitation for all herds combined, but wide variations in response were noted among herds. A number of factors may have influenced the United Kingdom trial. The experimental 0.25% iodine formulation had not been evaluated for efficacy-the ability to prevent new 1M!. All three iodine products used in the Vermont trial had proved efficacious as post-milking teat dips.4, 16,17 In the United Kingdom trial, teats were dipped "at least 4 cm." In the Vermont trial, cooperators were instructed to immerse the "full length" of teats. Ironically, milkers in the Vermont Herd A routinely immersed only the lower portion of teats when applying post dip. This practice continued with application of predip throughout the trial. Herd A was one cooperator herd in which predipping efficacy was suspect

528

PANKEY & DRECHSLER

when evaluated by incidence of all and new clinical cases. The short duration of the United Kingdom trial-20 weeks-compounded with housing, winter season, and early DIM also may have influenced results. A second trial was conducted because of the considerable variation among the three herds. B, 12 Comparisons were made on incidence of clinical mastitis. Trial 2 included 18 herds-more than 2400 cows-divided into pairs and was conducted for 24 weeks from November through April, the main winter housing period. In one of each herd pair, normal udder preparation and post-dipping with an iodine product were used. In the other nine herds, preparation included dipping in a 0.25% iodine formulation and drying with a paper towel after a 3D-second contact time. No difference was determined for overall rate of clinical mastitis or for incidence of clinical mastitis by a particular group of pathogens. Benefits of premilking teat dipping were apparent in some pairs, but no overall benefit was observed for predipping. These researchers concluded that the effect of trial supervision imposed on normal practices gave a benefit that overwhelmed any effect of predipping. Uncontrolled variables within and between herd pairs, could have biased results against premilking teat dipping. Importantly, bacteriologic status of individual quarters was not determined at initiation of this trial. Clinical mastitis could have been reported in quarters with existing IMI or in quarters previously uninfected. A third United Kingdom trial was conducted by Blowey and Collis1 and evaluated premilking teat dipping with 0.1% iodine. This product was proved effective as a post-milking teat dip.4 Three herds cooperated for the 12-week trial, January through March, and 100 cows per farm were used. Fifty cows on each farm were assigned to the predip group and 50 were prepared in the normal manner. Clinical mastitis cases were detected by farm staff and samples were collected and cultured. Incidence of clinical mastitis was reduced 57% (12 of 28). As observed in other trials, wide variation was noted among herds. A reduction was realized in each herd, but the reduction varied. The numbers of clinical cases for predip/control groups by herd were 0/3, 9/12, and 3/13. The short duration of the trial, interactions between winter housing and DIM, and a large number of contaminated milk samples reduce the significance of this trial.

DISCUSSION

Specific factors that affect the efficacy of premilking teat sanitation have not been evaluated. Under certain conditions, significant reductions in IMI were realized among predipped cows, indicating the potential for prevention of new IMls and new clinical mastitis cases. Teat skin is a difficult surface to "sterilize." Post-milking teat sanitation has proved an effective procedure to reduce incidence of new IMI with contagious pathogens. Most probably, these pathogens contaminate the teat skin during milking. The milking process tends to clean teats through liner

EVOLUTION OF UDDER HYGIENE

529

action. Teats generally are very "clean" immediately after claw removal and this fact probably contributes to the success of post-milking teat antisepsis. Conversely, teat skin often is "dirtiest" immediately prior to udder preparation. Organic load on teat skin would have a detrimental effect on germicidal activity. Germicidal activity against mastitis pathogens has not been demonstrated on teat skin with a 30-second contact time. A reliable assay is needed. Another factor could be the "time after milking" when teats are contaminated with mastitis pathogens. Penetration of the teat duct between milkings was studied by Bramley et a1. 3 Twenty cows were included in a study and milked with a machine designed to minimize machine-induced penetration of the teat duct. All teat ends were thoroughly disinfected with a cotton pledget moist with 70% alcohol prior to milking and not sanitized after milking once bacterial challenge had commenced. Teats of half the cows were contaminated immediately after milking with Escherichia coli; the other half were contaminated 1 hour before milking. Teats were challenged for 14 successive intermilking periods. Sixteen new IMIs were diagnosed, 14 in the cows challenged immediately after milking and only two among cows challenged 1 hour ,before milking! These data suggest that contamination of teats for a period of time after milking could negate effectiveness of premilking teat sanitation. This 1981 report also may have been the first report of a "predip".3

SUMMARY

Compared with post-milking teat dipping, predipping is in its infancy. Few controlled studies have been published on premilking teat disinfection/ sanitation.1, 5, 6, 8, 12, 15, 19 Experimental challenge procedures resulted in consistent reductions for predipping compared with no udder preparation and conventional udder preparation, indicating a potential for effectiveness.6,15 Challenge studies that included the treatments of predip only and postdip only indicated that interactions during the milking process require elucidation. Positive benefits have been observed for predipping in field trials among some herds, but wide variation has been observed between herds in all field trial evaluations.1,8, 12, 19 Parity, DIM, and season of the year had major interactions on efficacy of predipping in Pankey et aI's 1987 report;19 other trials have been of shorter duration and precluded analysis of these interactions. Interactions among these variables influenced incidence of mastitis by environmental pathogens.zo The length of time after milking before teats are contaminated probably is a major influence on predip efficacy.3 Predipping has reduced incidence of new IMIs and new cases of clinical mastitis. Unfortunately, certain factors negated these positive effects. These factors need to be defined. Producers should monitor effects of predipping to determine whether the investment in product and time has an economic return under the conditions of their dairy.

530

PANKEY & DRECHSLER

These studies were supported by the Vermont Agricultural Experiment Station, College of Agriculture and Life Sciences, The University of Vermont, Burlington; by IBA INC., Millbury, MA.; and by West Agro Chemical, Inc., Kansas City, MO.

References 1. Blowey RW, Collis K: Effect of pre-milking teat disinfection on mastitis incidence, total bacterial count, cell count and milk yield in three dairy herds. Vet Rec 130:175-178, 1992 2. Booth JM: Update on mastitis: I. Control measures in England and Wales. How have they influenced incidence and aetiology. Br Vet J 144:316-320, 1988

3. Bramley AJ, Godhino KS, Grindal RJ: Evidence of penetration of the bovine teat duct by Escherichia coli in the interval between milkings. J Dairy Res 48:379-386, 1981 4. Bray DR, Natzke RP, Everett RW, et al: Comparison of teat dips with differing iodine concentrations in prevention of mastitis infection. J Dairy Sci 66:2593-2596, 1983 5. Bushnell RB: Symp. Bovine mastitis: The importance of hygienic procedures in controlling mastitis. Vet Clin North Am 6:361-370, 1984 6. Galton DM, Petersson LG, Merrill WG: Evaluation of udder preparations on intramammary infections. J Dairy Sci 71:1417-1421, 1988 7. Harmon RJ, Eberhart RJ, Jasper DE, et al: Microbiological Procedures for Use in the Diagnosis of Bovine Udder Infections. Arlington, VA, National Mastitis Council, 1990, p 165 8. Hillerton JE, Shearn MFH, Teverson RM, et al: The effect of pre-milking teat dipping on clinical mastitis on dairy farms in England. J Dairy Res 1992; in press 9. Hogan JS, Galton DM, Harmon RJ, et al: Protocols for evaluating efficacy of postmilking teat dips. J Dairy Sci 73:2580-2585, 1990 10. Hogan JS, Smith KL, Hoblet KH, et al: Bacterial counts in bedding materials used on nine commercial dairies. J Dairy Sci 72:250-255, 1989 11. Jarrett JA: Environmental effects on mastitis and milk quality. Vet Clin North Am Large Anim Pract 6:371-374, 1984 12. Langridge SA: Teat dipping before milking: Summary of UK field trials. IDF Mastitis Newsletter 17:7, 1992 13. Pankey JW: Postmilking teat antisepsis. Vet Clin North Am Large Anim Pract 6:335348, 1984 14. Pankey JW: Premilking udder hygiene. J Dairy Sci 72:1308-1312, 1989 15. Pankey JW, Galton DM: Premilking teat sanitation: Mastitis control and iodine residues in milk. In Proceedings of the International Conference on Mastitis, St Georgen/Langsee, Austria, 1989 pp 214-221 16. Pankey JW, Boddie RL, Nickerson SC: Efficacy evaluation of two new teat dip formulations under experimental challenge. J Dairy Sci 68:462-465, 1985 17. Pankey JW, Philpot WN, Boddie RL: Efficacy of low concentration teat dips against Staphylococcus aureus. J Dairy Sci 66:155-160, 1983 18. Pankey JW, Eberhardt RJ, Cuming AL, et al: Update on postmilking teat antisepsis. J Dairy Sci 67:1336-1353, 1984 19. Pankey JW, Wildman EE, Drechsler PA, et al: Field trial evaluation of premilking teat disinfection. J Dairy Sci 70:867-872, 1987 20. Smith KL, Todhunter DA, Schoenberger PS: Symposium: Environmental effects on cow health and performance. J Dairy Sci 68:1531-1553, 1985

Address reprint requests to J. Woodrow Pankey, PhD Department of Animal and Food Sciences Terrill Hall University of Vermont Burlington, VT 05405