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Survey of Milking Management Practices on Large Dairies and Their Relationship to Udder Health and Production Variables
Survey of Milking Management Practices o n Large Dairies and Their Relationship to Udder Health and Production Variables WILLIAM J. GOODGER, JOHN C. GALLAND, and VALERIE E. CHRISTIANSEN Department of Epidemiology and Preventive Medicine School of Veterinary Medicine University of California Davis and Veterinary Medicine Teaching and Research Center Tulare 93274 ABSTRACT
Milking practices influence mastitis rate (4, 12). F o r example, variations in milking machine vacuum have been shown to permit droplets containing bacteria to enter the teat end (13) and udder washing and drying practices affect mastitis rate (17). These and similar factors are under direct control of management; the manager determines how often milking machine vacuum is checked and machines serviced and how udders are washed and dried. The objective of this paper is to document milking management practices on a smaple of large California dairies and to explore the relationships between these practices and measures of udder health and production.
A survey of 91 milking management practices and 5 measures of udder health and production was conducted on 50 randomly selected dairies in Tulare County, CA. Data were collected by a combination of interview and site visit. On many dairies, there was inconsistent application of recommended milking practices such as careful teat dipping, attending liner slips, maintaining treatment records, efficient parlor usage as measured by throughput, and use of paper towels. Thirteen of 91 practices were associated with at least one measure of udder health or production; the categories of practices that appear to have the most influence are practices related to environmental management and practices related to milking procedures. The implications of the study are that better preventive medicine education programs are needed as well as better analytical tools to permit producers to evaluate quantitatively the economic benefit of preventive medicine practices.
MATERIALS AND METHODS Selection of Dairies for Survey
INTRODUCTION
On large dairies, milking can be a complex 18 h/d task, which must be managed effectively to ensure efficiency and herd health. Failure to manage the milking process and factors related to it may partially explain why in a recent statewide survey of California dairies, 33% of the bulk tanks tested were positive for bacteria that cause mastitis.
Received September 14, 1987. Accepted March 23, 1988. 1988 J Dairy Sci 71:2535-2542
Fifty dairies (a 20% sample) in Tulare County, CA were randomly selected by a random numbers table from a list provided by the county farm advisor. Herds in the county use dry corral systems and average 594 cows with average daily production of 25 kg/cow. The dairies have high density housing, automated milking facilities, and twice daily milking by hired milkers. The survey was conducted during November, December, and January 1984 to 1985. Characterization of Milking Management Practices
The approach taken to characterizing milking management practices was adapted from Goodger et al. (10). Questions, that would elicit measures of good milking management practices were developed from a literature review and from interviews with a group of veterinarians with expertise in mastitis control. A list of questions was developed and tested on several dairies to ensure applicability. Ninety-
2535
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GOODGER ET AL.
one specific measures of milking management were identified. Survey Procedures
The survey was conducted by a veterinary student, who reviewed the literature on the subject and was given field training in milking management practices (training consisted of visits to numerous dairies with veterinarians with expertise in mastiffs control). Dairy managers were interviewed during a single walking tour of their dairy to determine management practices. Many, but not all, of the responses of the dairy manager were checked by observations made by the interviewer on the day of the tour. Characterization of Udder Health and Production
Four measures of udder health and one measure of production were taken from DHIA records: 1) average somatic cell count (ASCC), 2) percent of negative and trace scores on the California Mastitis Test (N&TCMT), 3) percent cows culled per year for low production (CLP), 4) percent cows culled per year for mastitis (CM), and 5) average daily milk production for the herd (AMILK). Data Analysis
Results were described in terms of frequency of practice. Associations between the 91 measures of management practice and the 5 measures of udder health and production were tested by use of the X2 test of independence (BMDP4F) (6). Values of the five udder health and production variables were grouped as those below and those above the median. Average SCC were broken into two groups: 1) ASCC <-<264,000 and 2) ASCC >264,000. Percent culled due to low production was divided into: 1) CLP <7.14% 2) CLP >7.14%. Percent culled due to mastiffs was divided into two groups: 1) CM <.71%, 2) CM >.71%. California Mastiffs Test scores were divided into two groups: 1) dairies having at least 90% of their cows with CMT scores of negative or trace and 2) dairies having fewer than 90% of their cows with CMT scores of negative or trace. Average daily production was divided into two groups: 1) <22.6 kg of milk and 2) >22.6 kg of milk. Each of the 91 milking management pracJournal of Dairy Science Vol. 71, No. 9, 1988
tices was tested for association with each of the 5 measures of udder health and production by use of the X2 statistic. Analysis by X2 was used because we were interested in the frequency with which dairies followed specific milking practices. Significant associations were tabulated and grouped as those practices related to the environment (sanitation and housing) and those related to milking procedures. The frequency with which the dairies shared two practices within a group of practices were tabulated. R ESU LTS
Average herd size of the sample was 616 cows (range: 110 to 1800 cows), with average per cow daily production of 23 kg (range: 9 to 28 kg/cow). Production data were consistent with county-wide data. The ASCC for the sample herds, measured by the DHIA testing program, was 299,000 cells (range 123,000 to 704,000). Eighty percent of the cows in these herds had N&TCMT. The percentage of cows CM ranged from 0% to more than 6% of the total herd. Culling for low production averaged 10% (range 2.0 to 25%). Results of the milking management practices were compared with a sample of recommended practices from the literature (Table 1). Table 1 is not intended to be comprehensive; rather it shows inconsistencies in management practices and recommended practice on the 50 dairies surveyed. Of the 91 individual practices, 13 were associated P<.05 with at least 1 of the 5 measures of udder health and production and 3 practices were associated P < . I (Table 2). These 16 practices were grouped as practices related to environmental management, practices related to milking procedures, and practices related to milking parlor system and mastitis control (Table 1). Milking management practices found to be associated by use of the X 2 statistic with at least one of the 5 measures of udder health and production were cross tabulated. Tables 3 and 4 show the relative frequency with which the dairies adhered to pairwise combinations of practices related to the environment (Table 3) and to milking procedures (Table 4). Dairy managers who maintained clean water troughs were most likely to follow recommended
MILKING PRACTICES AND UDDER HEALTH
2537
TABLE 1. Comparison of a representative sample of Tulare County, CA. milking management practices with recommendations commonly found in the literature. Percent dairy managers complying with the recommendation
Recommendation All teats should be dipped after milking (3, 12, 15) ~ Milker reacts quickly to squawking liners (13, 16) Dry cow therapy should be used (3, 20, 21, 22) Dry cow therapy should be done by manager, not milker (13) Teats should be dry before milking (5, 9, 17) Throughput per equipment manufacturer's recommendation Cows should be stimulated for milk ejection (13, 17) Teats should be dried with paper towels (9, 12) Linear change per manufacturer's recommendation Milking machines should be maintained regularly (3, 8) Milker should check for abnormal milk (3) Mastitis treatment records are maintained (17)
17 66 96 64 77
34 92 30 50 58 91 34
1References in parentheses.
practice in other areas of environmental management. Most dairy managers who maintained clear water troughs also flushed traffic lanes instead of scrapping them, had corrals that sloped away from the traffic lanes instead of toward them, or had parlors closer to the corrals. Similarly, managers following teat dipping practice (three to four quarters dipped completely) were most likely to follow other recommended milking procedures, e.g., using paper towels, maintaining clean udders, keeping equipment records, and ensuring that their cows did not have wet udders when milked (Table 4).
DISCUSSION
One finding of this survey is that many management practices on large, modern, high technology dairies are not consistent with common milking practice recommendations from the literature and expert opinion (Table 1). For example, the National Mastitis Council rules for good milking technique recommend the use of a single source paper towel to dry udders, but only 30% of the milkers in our survey followed this practice (18). A survey of 111 Minnesota dairy operators found that dairies did not follow recommended practices also: only 30% of Minnesota respondents maintained treatment records of mastitis cases, teats were dried with a single paper towel in
only 20% of the survey herds, only 5.4% of the respondents claimed participation in programs of mastitis control, and only 17% discussed corrective measures with veterinarians (23). Yet, in this study, compliance with other recommended practices, such as in the use of dry cow therapy, was high. Only a small percentage of managers appear to recognize the need to follow a total program of sanitation and proper milking practices. Many take one or two important actions but ignore related actions (Table 3 and 4). These results are consistent with a finding in a more limited survey of 581 Quebec dairies (17). Of the Canadian dairy managers using teat dip, only 18% dried udders and only 44% rinsed teat cups. Among dairy managers using separate towels to wash udders, 45% rinsed teat cups, 58% used a teat dip, and only 17% dried udders. These results suggest that some managers have a fragmented view of the interrelationships of the various factors affecting production and udder health. The primary finding of this study is that dairy managers are not giving proper priority to environmental management practices and milking procedures that reduce mastitis. These were the practices (of the 91 studied) that were associated with measures of udder health and production. On 35% of the dairies, pens drained into traffic lanes despite our results indicating that Journal of Dairy Science Vol. 71, No. 9, 1988
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GOODGER ET AL.
TABLE 2. Associations found by use of the Xa test of independence between 91 milking management practices and 5 measures of udder health and production. 1
Milking management practice
Measure of udder health or production
1. Practices related to environment (sanitation and housing) Corrals scrapped >5 times/yr or Corrals scrapped <5 times/yr
×2
p
N&TCMT >90% or N&TCMT <90% *
4.63
.03
Lanes scrapped or Lanes flushed
vs.
ASCC <264,000* or ASCC >264,000
2.98
.08
Water troughs clean or Water troughs unclean
vs.
ASCC <264,000* or ASCC >264,000
5.97
.02
Corrals slope away from lanes or Corrals slope toward lanes
vs.
CM<.71 * or CM >.71
4.30
.04
Corrals with lockups or Corrals without lockups
vs.
AMILK >22.6* or AMILK <22.6
7.52
.01
Distance to parlor <152.4 m or Distance to parlor >152.4 m
vs.
N&TCMT >90%* or N&TCMT <90%
3.86
.05
vs.
AMILK >22.6* or AMILK <22.6
6.14
.05
Cows teat dipped or Cows not teat dipped
vs.
N&TCMT > 90%* or N&TCMT <90%
7.57
.06
Paper towels used or Paper towels not used
vs.
CLP <7.1%* or CLP >7.1%
4.78
.03
Udders sanitized or Udders not sanitized
vs.
CLP <7.1%* or CLP >7,1%
3.92
.05
Cows dry when milked or Cows wet when milked
vs.
CM <.71%* or CM >,71%
5.12
.02
Equipment records kept or Equipment records not kept
vs.
CLP <7.1%* or CLP >7.1%
4.29
.04
5.86
.05
2. Practices related to milking procedures Udders clean or Udders not clean
3. Practices related to milking parlor system and mastitis control Pop-up sprinklers or vs. CM <.71%* or Rainbird sprinklers CM >.71% Freestall housing or Dry lot housing
vs.
CM <.71%* or CM >.71%
9.97
.01
Dry cows treated by owner or Dry cows treated by herdsman or Dry cows treated by milker
vs.
CM <.71%* or CM >.71%
5.93
.05
Dry off period not delayed or Dry off period delayed
vs.
CLP < . 7 1 % * o r CLP >.71%
2.79
.09
1Average somatic cell count (ASCC), percent of cows with CMT scores of negative or trace (N&TCMT), percent of cows culled per year for mastitis (CM), percent of cows culled per year for production (CLP), and average daily production (AMILK). The first o f each pair or trio o f practices is the recommended practice. *The measure of udder health or production that increases in frequency with the recommended practice is marked with an asterisk.
Journal o f Dairy Science Vol. 71, No. 9, 1988
~q
o
o
.26 .27
.33 ,22
.15 .36
.24 .42
.31 .25
Scrape corrals 2 to 5 ti m es /y r >5 t i m e s / y r
Lanes Flushed Scraped
Water troughs Clean Unclean
Corrals slope A w a y from lanes T o w ard lanes
Corrals With lockups W it ho ut lockups
Distance to parlor <152.4 m >152.4 m
. .
. .
Practice
. .
Scrape corrals (>5 tim es / yr )
. .
.57 .63
.78 .28
.82 .50
.71 .48
. .
61 60 . .
Lanes flushed
. .
. .
.64 .25
.59 .37
.59 .48
. .
61 37
.50 .64
. .
Water troughs clean
. .
. .
. .
69 60
.56
. .
.63
. .
.24
. .
.71 .50
.81 .32
.73 .55
. .
Corrals with lo ck u p s
.77
.38 ,29
. .
40 30
.50 .18
.41 .18
Corrals slope away from lanes
TABLE 3. Relative frequency of occurrence of statistically significant m i l k i n g m a n a g e m e n t practices related t o the environment.
. .
. .
...
...
69 63
.76 .63
.84 .50
.63 .68
.67 .72
Distance to parlor (< 152.4 m)
~O
t,o
,~
t~
> :Z
> --]
Z ¢3 '~
t"
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GOODGER ET AL.
TABLE 4. Relative frequency of occurrence of statistically significant milking management practices related to milking procedures.
Practice
Udder condition clean
Udder condition Clean Dirty or muddy
. .
Teat dip 0 to 2.25 2.26 to 4.0
.31 .66
Paper towels Used Not used
.46 .51
.85 .59
Udder Sanitized Not sanitized
.50 .50
.7 .65
Cows dry when milked Yes .56 No .36
.74 .45
Equipment records Kept .41 Not kept .53
1.00 .57
. .
. .
Paper towels used
Teat dip I
. .
79 48 . .
. .
. .
Udders sanitized
Cows dry when milked
Equipment records kept
.25 .29
.21 .21
.83 .68
13 35
.19 .23
.6 .83
29 19
1.00 .66
.43 .16
82 75
.27 .23
. .
. . . . . . . . .36 .26
. .
.39
.23 .18
.50 .21
.25 .21
0
. .
. .
. . . .
. . .19 .72
.21 .29 0 .32
. .
. .
28 08 ... ...
Three or four teats.
as dairies have corrals that slope away f r o m traffic lanes, culling for mastitis decreases (Table 2). Studies have shown that high a m o u n t s of moisture f r o m m u d d y lots allow bacteria to grow in large numbers exposing the teat end to large numbers o f microorganisms (2, 11). Also, cows need m o r e washing on dairies where corral e f f l u e n t drains into traffic lanes that are n o t cleaned before milking (1, 12). A n o t h e r practice influencing e n v i r o n m e n t a l c o n t a m i n a t i o n is the distance cows walk to the milking parlor. Our results show that w h e n this distance is less than 152.4 m (500 ft) m o r e CMT scores are negative or trace. On those dairies where the distance is greater, stress m a y be placed on the cow because o f additional t i m e spent on hard surfaces (concrete), which m a y contribute to fatigue influencing cows to lie d o w n sooner after milking (11, 14). T h e r e was neglect of r e c o m m e n d e d milking procedures also. Milkers p e r f o r m e d well on all basic procedures such as preparing cows, checking for abnormal milk, and attaching machines within i rain o f milk ejection but did not follow advise to dip all teats after milking Journal of Dairy Science Vol. 71, No. 9, 1988
(Table 1). Teat dipping following milking was associated with an increasing percent of N & T C M T (Table 2). Teat dipping reduces the rate of new infections o f Streptococcus agalactiae and Staphylococcus aureus by 50% (7, 15, 19), but o n l y 17% of the dairies in this study teat dipped all f o u r teats (Table 1). An e x p l a n a t i o n for this result might be that with a u t o m a t i c t a k e o f f units the milker no longer must return to the cow to r e m o v e the machine, and so teat dipping after milking is frequently. inadequately p e r f o r m e d or a b a n d o n e d (5). The time-consuming task of drying the udder before milking was not d o n e by m o s t milkers (61%) and yet cows with dry udders w h e n milked was associated with a reduced CM (Table 2). Moisture on the udder above the teats drips d o w n o n t o the rim of the teat cups, t h e r e b y allowing the water, m o s t likely laden with bacteria, to drain into teat cups during milking (9). In this study, only 35% o f managers k e p t mastitis t r e a t m e n t records. When e q u i p m e n t m a i n t e n a n c e records were kept, the n u m b e r of CLP and CM decreased. Encouraging producers
MILKING PRACTICES AND UDDER HEALTH to keep a d e q u a t e records m a y thus have an indirect i m p a c t on udder health; the manager w h o keeps records may be more carefully m o n i t o r i n g the entire o p e r a t i o n and m a y thus be able to take actions to reduce mastitis. The inconsistencies and fragmented view of the interrelationship of milking m a n a g e m e n t practices m a y reflect a lack of k n o w l e d g e of preventive medicine. If this is true, then veterinarians engaged in dairy practice and e x t e n s i o n personnel have a significant educational task facing t h e m . Programs of preventive m e d i c i n e that stress the i m p o r t a n c e o f consistent and integrated milking m a n a g e m e n t practices m a y have to be developed. The lack of giving proper priority to env i r o n m e n t a l m a n a g e m e n t practices and milking procedures m a y reflect a lack of data to support e c o n o m i c justitication of preventive medicine. T h e r e are no standard analytical programs that allow managers to calculate the potential e c o n o m i c risk of not teat dipping or the potential net benefit to be gained f r o m a consistent program o f teat dipping. W i t h o u t such analytical tools, the manager may decide to save m o n e y rather than risk funds for an u n k n o w n return. Professional persons involved in preventive medicine for udder health m a y k n o w that the risks far outweigh the savings, but t h e y need tools that allow t h e m to show this to the individual dairy manager in terms of the actual net return e x p e c t e d for the individual dairy. This survey covered a broad range of milking m a n a g e m e n t practices. It establishes a baseline a b o u t practices used on high t e c h n o l o g y , large-scale dairies. The survey presented here will be used as a starting p o i n t for a m o r e detailed analysis of the relationship b e t w e e n e n v i r o n m e n t a l and milking practices, and overall u d d e r health and productivity. This can be accomplished in a prospective study where data on m a n a g e m e n t practices, p r o d u c t i o n , and u d d e r health will be collected in multiple herds. ACKNOWLEDGMENTS
The authors gratefully acknowledge J e r r y Mitchell, Valley Veterinarians, Tulare, CA and Charles Franti, Statistician, D e p a r t m e n t o f E p i d e m i o l o g y and Preventive Medicine, Davis, CA.
2541
REFERENCES
1 Armstrong, D. V. 1985. Milking procedures and their effect on milk quality. Pages 49-51 in Proc. 24th Annu. Mtg., Natl. Mastitis Counc., Las Vegas, NV. 2 Bramley, J. 1985. The control of coliform mastitis. Pages 4 - 1 7 in Proc. 24th Annu. Mtg., Natl. Mastitis Counc., Las Vegas, NV. 3 Bringe, A. 1979. Milking procedures and cow management. Page 132 in Proc. 18th Annu. Mtg., Natl. Mastitis Counc., Louisville, KY. 4 Britt, J. S. 1977. Mastitis problem herds. J. Am. Vet. Med. Assoc. 170:1239. 5 Bushnell, R. B. 1984. Practical hygiene control of milk contamination and udder infections. Page 31 in Proc. 23rd Annu. Mtg., Natl. Mastitis Counc., Kansas City, MO. 6 Dixon, W. J. 1983. BMDP Statistical Software. Univ. California Press, Los Angeles. 7 Dohoo, I., W. Martin, and A. Meek. 1984. Disease, production, and culling in Holstein-Friesian cows: via effects of management on disease rates. Prev. Vet. Med. 9:15. 8 Fisher, K. 1979. Milking machines should be tested regularly. NZ. J. Agric. 4:24. 9 Gatton, D. M., L. G. Peterson, and W. G. Merrill. 1984. Effects of various premilking udder hygiene on decreased bacterial populations, sediment and chemical residue in milk. Page 19 in 23rd Annu. Mtg., Natl. Mastitis Counc., Kansas City, MO. 10 Goodger, W. J., R. Ruppanner, B. D. Slenning, and J. E. Kushman. 1984. An approach to scoring management on large-scale dairies. J. Dairy Sci. 67:675. 11 Goodhope, R. G., and A. H. Meed. 1980. Factors associated with mastitis in Ontario dairy herds: A case control study. Can. J. Camp. Med. 44:351. 12 Guterbock, W. M. 1984. Practical aspects of mastitis in large dairy herds. Part II. Milking hygiene. Camp. Cont. Ed. 6:$651. 13 Guterbock, W. M. 1985. Practical aspects of mastitis control in large dairy herds. Part IV. Milking Management. Camp. Cont. Ed. 7:$6. t4 Jarrett, J. A. 1984. Environmental effects on mastitis and milk quality. Vet. Clin. N. Am. Large Anita. Pract. Symp. on Bovine Mastitis 6:371. 15 Jezeski, J. J. 1979. Farm practices cleaning and sanitizing in relation to mastitis. Page 135 in Proc. 18th Annu. Mtg., Natl. Mastitis Counc., Louisville, KV. 16 MacKay, R. D. 1984. The economics of herd health programs. Vet. Clin. N. Am. Large Anita. Pract. Symp. Bovine Mastitis 6:401. 17 Moxley, J. E., B. W. Kennedy, B. R. Downey, and J.S.T. Bowman. 1978. Survey of milking hygiene practices and their relationship to somatic cell counts and milk production. J. Dairy Sci. 61:1637. 18 Nicolai, J. H., and W. N. Philpot. 1974. NMC rules for good milking technique. Natl. Mastitis Counci., Washington, DC. 19 Philpot, W. N. 1979. Control of mastitis by hygiene and therapy. J. Dairy Sci. 62:168. 20 Philpot, W. N. 1984. Economics of mastitis con-
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trol. Vet. Clin. N. Am. Large Anim. Pract. Symp. Bovine Mastitis 6:233. 21 Reneau, J. K. 1983. Proper dryoff prevent early mastitis. Dairy Herd Manage. 20(7):24. 22 Robinson, T. C., E. R. Jackson, and A. Marr. 1983. Within herd comparison of teat dipping and dry
Journal of Dairy Science Vol. 71, No. 9, 1988
cow therapy with only selective dry cow therapy in six herds. Vet. Rec. 112:315. 23 williamson, N. B., and W. Brown. 1983. Minnesota dairy farmers attitudes to and knowledge of bovine mastitis control. Pages 3 2 - 4 2 in Proc. 22nd Annu. Mtg., Natl. Mastitis Counc., Louisville, KY.
Milking practices influence mastitis rate (4, 12). F o r example, variations in milking machine vacuum have been shown to permit droplets containing bacteria to enter the teat end (13) and udder washing and drying practices affect mastitis rate (17). These and similar factors are under direct control of management; the manager determines how often milking machine vacuum is checked and machines serviced and how udders are washed and dried. The objective of this paper is to document milking management practices on a smaple of large California dairies and to explore the relationships between these practices and measures of udder health and production.
A survey of 91 milking management practices and 5 measures of udder health and production was conducted on 50 randomly selected dairies in Tulare County, CA. Data were collected by a combination of interview and site visit. On many dairies, there was inconsistent application of recommended milking practices such as careful teat dipping, attending liner slips, maintaining treatment records, efficient parlor usage as measured by throughput, and use of paper towels. Thirteen of 91 practices were associated with at least one measure of udder health or production; the categories of practices that appear to have the most influence are practices related to environmental management and practices related to milking procedures. The implications of the study are that better preventive medicine education programs are needed as well as better analytical tools to permit producers to evaluate quantitatively the economic benefit of preventive medicine practices.
MATERIALS AND METHODS Selection of Dairies for Survey
INTRODUCTION
On large dairies, milking can be a complex 18 h/d task, which must be managed effectively to ensure efficiency and herd health. Failure to manage the milking process and factors related to it may partially explain why in a recent statewide survey of California dairies, 33% of the bulk tanks tested were positive for bacteria that cause mastitis.
Received September 14, 1987. Accepted March 23, 1988. 1988 J Dairy Sci 71:2535-2542
Fifty dairies (a 20% sample) in Tulare County, CA were randomly selected by a random numbers table from a list provided by the county farm advisor. Herds in the county use dry corral systems and average 594 cows with average daily production of 25 kg/cow. The dairies have high density housing, automated milking facilities, and twice daily milking by hired milkers. The survey was conducted during November, December, and January 1984 to 1985. Characterization of Milking Management Practices
The approach taken to characterizing milking management practices was adapted from Goodger et al. (10). Questions, that would elicit measures of good milking management practices were developed from a literature review and from interviews with a group of veterinarians with expertise in mastitis control. A list of questions was developed and tested on several dairies to ensure applicability. Ninety-
2535
2536
GOODGER ET AL.
one specific measures of milking management were identified. Survey Procedures
The survey was conducted by a veterinary student, who reviewed the literature on the subject and was given field training in milking management practices (training consisted of visits to numerous dairies with veterinarians with expertise in mastiffs control). Dairy managers were interviewed during a single walking tour of their dairy to determine management practices. Many, but not all, of the responses of the dairy manager were checked by observations made by the interviewer on the day of the tour. Characterization of Udder Health and Production
Four measures of udder health and one measure of production were taken from DHIA records: 1) average somatic cell count (ASCC), 2) percent of negative and trace scores on the California Mastitis Test (N&TCMT), 3) percent cows culled per year for low production (CLP), 4) percent cows culled per year for mastitis (CM), and 5) average daily milk production for the herd (AMILK). Data Analysis
Results were described in terms of frequency of practice. Associations between the 91 measures of management practice and the 5 measures of udder health and production were tested by use of the X2 test of independence (BMDP4F) (6). Values of the five udder health and production variables were grouped as those below and those above the median. Average SCC were broken into two groups: 1) ASCC <-<264,000 and 2) ASCC >264,000. Percent culled due to low production was divided into: 1) CLP <7.14% 2) CLP >7.14%. Percent culled due to mastiffs was divided into two groups: 1) CM <.71%, 2) CM >.71%. California Mastiffs Test scores were divided into two groups: 1) dairies having at least 90% of their cows with CMT scores of negative or trace and 2) dairies having fewer than 90% of their cows with CMT scores of negative or trace. Average daily production was divided into two groups: 1) <22.6 kg of milk and 2) >22.6 kg of milk. Each of the 91 milking management pracJournal of Dairy Science Vol. 71, No. 9, 1988
tices was tested for association with each of the 5 measures of udder health and production by use of the X2 statistic. Analysis by X2 was used because we were interested in the frequency with which dairies followed specific milking practices. Significant associations were tabulated and grouped as those practices related to the environment (sanitation and housing) and those related to milking procedures. The frequency with which the dairies shared two practices within a group of practices were tabulated. R ESU LTS
Average herd size of the sample was 616 cows (range: 110 to 1800 cows), with average per cow daily production of 23 kg (range: 9 to 28 kg/cow). Production data were consistent with county-wide data. The ASCC for the sample herds, measured by the DHIA testing program, was 299,000 cells (range 123,000 to 704,000). Eighty percent of the cows in these herds had N&TCMT. The percentage of cows CM ranged from 0% to more than 6% of the total herd. Culling for low production averaged 10% (range 2.0 to 25%). Results of the milking management practices were compared with a sample of recommended practices from the literature (Table 1). Table 1 is not intended to be comprehensive; rather it shows inconsistencies in management practices and recommended practice on the 50 dairies surveyed. Of the 91 individual practices, 13 were associated P<.05 with at least 1 of the 5 measures of udder health and production and 3 practices were associated P < . I (Table 2). These 16 practices were grouped as practices related to environmental management, practices related to milking procedures, and practices related to milking parlor system and mastitis control (Table 1). Milking management practices found to be associated by use of the X 2 statistic with at least one of the 5 measures of udder health and production were cross tabulated. Tables 3 and 4 show the relative frequency with which the dairies adhered to pairwise combinations of practices related to the environment (Table 3) and to milking procedures (Table 4). Dairy managers who maintained clean water troughs were most likely to follow recommended
MILKING PRACTICES AND UDDER HEALTH
2537
TABLE 1. Comparison of a representative sample of Tulare County, CA. milking management practices with recommendations commonly found in the literature. Percent dairy managers complying with the recommendation
Recommendation All teats should be dipped after milking (3, 12, 15) ~ Milker reacts quickly to squawking liners (13, 16) Dry cow therapy should be used (3, 20, 21, 22) Dry cow therapy should be done by manager, not milker (13) Teats should be dry before milking (5, 9, 17) Throughput per equipment manufacturer's recommendation Cows should be stimulated for milk ejection (13, 17) Teats should be dried with paper towels (9, 12) Linear change per manufacturer's recommendation Milking machines should be maintained regularly (3, 8) Milker should check for abnormal milk (3) Mastitis treatment records are maintained (17)
17 66 96 64 77
34 92 30 50 58 91 34
1References in parentheses.
practice in other areas of environmental management. Most dairy managers who maintained clear water troughs also flushed traffic lanes instead of scrapping them, had corrals that sloped away from the traffic lanes instead of toward them, or had parlors closer to the corrals. Similarly, managers following teat dipping practice (three to four quarters dipped completely) were most likely to follow other recommended milking procedures, e.g., using paper towels, maintaining clean udders, keeping equipment records, and ensuring that their cows did not have wet udders when milked (Table 4).
DISCUSSION
One finding of this survey is that many management practices on large, modern, high technology dairies are not consistent with common milking practice recommendations from the literature and expert opinion (Table 1). For example, the National Mastitis Council rules for good milking technique recommend the use of a single source paper towel to dry udders, but only 30% of the milkers in our survey followed this practice (18). A survey of 111 Minnesota dairy operators found that dairies did not follow recommended practices also: only 30% of Minnesota respondents maintained treatment records of mastitis cases, teats were dried with a single paper towel in
only 20% of the survey herds, only 5.4% of the respondents claimed participation in programs of mastitis control, and only 17% discussed corrective measures with veterinarians (23). Yet, in this study, compliance with other recommended practices, such as in the use of dry cow therapy, was high. Only a small percentage of managers appear to recognize the need to follow a total program of sanitation and proper milking practices. Many take one or two important actions but ignore related actions (Table 3 and 4). These results are consistent with a finding in a more limited survey of 581 Quebec dairies (17). Of the Canadian dairy managers using teat dip, only 18% dried udders and only 44% rinsed teat cups. Among dairy managers using separate towels to wash udders, 45% rinsed teat cups, 58% used a teat dip, and only 17% dried udders. These results suggest that some managers have a fragmented view of the interrelationships of the various factors affecting production and udder health. The primary finding of this study is that dairy managers are not giving proper priority to environmental management practices and milking procedures that reduce mastitis. These were the practices (of the 91 studied) that were associated with measures of udder health and production. On 35% of the dairies, pens drained into traffic lanes despite our results indicating that Journal of Dairy Science Vol. 71, No. 9, 1988
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GOODGER ET AL.
TABLE 2. Associations found by use of the Xa test of independence between 91 milking management practices and 5 measures of udder health and production. 1
Milking management practice
Measure of udder health or production
1. Practices related to environment (sanitation and housing) Corrals scrapped >5 times/yr or Corrals scrapped <5 times/yr
×2
p
N&TCMT >90% or N&TCMT <90% *
4.63
.03
Lanes scrapped or Lanes flushed
vs.
ASCC <264,000* or ASCC >264,000
2.98
.08
Water troughs clean or Water troughs unclean
vs.
ASCC <264,000* or ASCC >264,000
5.97
.02
Corrals slope away from lanes or Corrals slope toward lanes
vs.
CM<.71 * or CM >.71
4.30
.04
Corrals with lockups or Corrals without lockups
vs.
AMILK >22.6* or AMILK <22.6
7.52
.01
Distance to parlor <152.4 m or Distance to parlor >152.4 m
vs.
N&TCMT >90%* or N&TCMT <90%
3.86
.05
vs.
AMILK >22.6* or AMILK <22.6
6.14
.05
Cows teat dipped or Cows not teat dipped
vs.
N&TCMT > 90%* or N&TCMT <90%
7.57
.06
Paper towels used or Paper towels not used
vs.
CLP <7.1%* or CLP >7.1%
4.78
.03
Udders sanitized or Udders not sanitized
vs.
CLP <7.1%* or CLP >7,1%
3.92
.05
Cows dry when milked or Cows wet when milked
vs.
CM <.71%* or CM >,71%
5.12
.02
Equipment records kept or Equipment records not kept
vs.
CLP <7.1%* or CLP >7.1%
4.29
.04
5.86
.05
2. Practices related to milking procedures Udders clean or Udders not clean
3. Practices related to milking parlor system and mastitis control Pop-up sprinklers or vs. CM <.71%* or Rainbird sprinklers CM >.71% Freestall housing or Dry lot housing
vs.
CM <.71%* or CM >.71%
9.97
.01
Dry cows treated by owner or Dry cows treated by herdsman or Dry cows treated by milker
vs.
CM <.71%* or CM >.71%
5.93
.05
Dry off period not delayed or Dry off period delayed
vs.
CLP < . 7 1 % * o r CLP >.71%
2.79
.09
1Average somatic cell count (ASCC), percent of cows with CMT scores of negative or trace (N&TCMT), percent of cows culled per year for mastitis (CM), percent of cows culled per year for production (CLP), and average daily production (AMILK). The first o f each pair or trio o f practices is the recommended practice. *The measure of udder health or production that increases in frequency with the recommended practice is marked with an asterisk.
Journal o f Dairy Science Vol. 71, No. 9, 1988
~q
o
o
.26 .27
.33 ,22
.15 .36
.24 .42
.31 .25
Scrape corrals 2 to 5 ti m es /y r >5 t i m e s / y r
Lanes Flushed Scraped
Water troughs Clean Unclean
Corrals slope A w a y from lanes T o w ard lanes
Corrals With lockups W it ho ut lockups
Distance to parlor <152.4 m >152.4 m
. .
. .
Practice
. .
Scrape corrals (>5 tim es / yr )
. .
.57 .63
.78 .28
.82 .50
.71 .48
. .
61 60 . .
Lanes flushed
. .
. .
.64 .25
.59 .37
.59 .48
. .
61 37
.50 .64
. .
Water troughs clean
. .
. .
. .
69 60
.56
. .
.63
. .
.24
. .
.71 .50
.81 .32
.73 .55
. .
Corrals with lo ck u p s
.77
.38 ,29
. .
40 30
.50 .18
.41 .18
Corrals slope away from lanes
TABLE 3. Relative frequency of occurrence of statistically significant m i l k i n g m a n a g e m e n t practices related t o the environment.
. .
. .
...
...
69 63
.76 .63
.84 .50
.63 .68
.67 .72
Distance to parlor (< 152.4 m)
~O
t,o
,~
t~
> :Z
> --]
Z ¢3 '~
t"
2540
GOODGER ET AL.
TABLE 4. Relative frequency of occurrence of statistically significant milking management practices related to milking procedures.
Practice
Udder condition clean
Udder condition Clean Dirty or muddy
. .
Teat dip 0 to 2.25 2.26 to 4.0
.31 .66
Paper towels Used Not used
.46 .51
.85 .59
Udder Sanitized Not sanitized
.50 .50
.7 .65
Cows dry when milked Yes .56 No .36
.74 .45
Equipment records Kept .41 Not kept .53
1.00 .57
. .
. .
Paper towels used
Teat dip I
. .
79 48 . .
. .
. .
Udders sanitized
Cows dry when milked
Equipment records kept
.25 .29
.21 .21
.83 .68
13 35
.19 .23
.6 .83
29 19
1.00 .66
.43 .16
82 75
.27 .23
. .
. . . . . . . . .36 .26
. .
.39
.23 .18
.50 .21
.25 .21
0
. .
. .
. . . .
. . .19 .72
.21 .29 0 .32
. .
. .
28 08 ... ...
Three or four teats.
as dairies have corrals that slope away f r o m traffic lanes, culling for mastitis decreases (Table 2). Studies have shown that high a m o u n t s of moisture f r o m m u d d y lots allow bacteria to grow in large numbers exposing the teat end to large numbers o f microorganisms (2, 11). Also, cows need m o r e washing on dairies where corral e f f l u e n t drains into traffic lanes that are n o t cleaned before milking (1, 12). A n o t h e r practice influencing e n v i r o n m e n t a l c o n t a m i n a t i o n is the distance cows walk to the milking parlor. Our results show that w h e n this distance is less than 152.4 m (500 ft) m o r e CMT scores are negative or trace. On those dairies where the distance is greater, stress m a y be placed on the cow because o f additional t i m e spent on hard surfaces (concrete), which m a y contribute to fatigue influencing cows to lie d o w n sooner after milking (11, 14). T h e r e was neglect of r e c o m m e n d e d milking procedures also. Milkers p e r f o r m e d well on all basic procedures such as preparing cows, checking for abnormal milk, and attaching machines within i rain o f milk ejection but did not follow advise to dip all teats after milking Journal of Dairy Science Vol. 71, No. 9, 1988
(Table 1). Teat dipping following milking was associated with an increasing percent of N & T C M T (Table 2). Teat dipping reduces the rate of new infections o f Streptococcus agalactiae and Staphylococcus aureus by 50% (7, 15, 19), but o n l y 17% of the dairies in this study teat dipped all f o u r teats (Table 1). An e x p l a n a t i o n for this result might be that with a u t o m a t i c t a k e o f f units the milker no longer must return to the cow to r e m o v e the machine, and so teat dipping after milking is frequently. inadequately p e r f o r m e d or a b a n d o n e d (5). The time-consuming task of drying the udder before milking was not d o n e by m o s t milkers (61%) and yet cows with dry udders w h e n milked was associated with a reduced CM (Table 2). Moisture on the udder above the teats drips d o w n o n t o the rim of the teat cups, t h e r e b y allowing the water, m o s t likely laden with bacteria, to drain into teat cups during milking (9). In this study, only 35% o f managers k e p t mastitis t r e a t m e n t records. When e q u i p m e n t m a i n t e n a n c e records were kept, the n u m b e r of CLP and CM decreased. Encouraging producers
MILKING PRACTICES AND UDDER HEALTH to keep a d e q u a t e records m a y thus have an indirect i m p a c t on udder health; the manager w h o keeps records may be more carefully m o n i t o r i n g the entire o p e r a t i o n and m a y thus be able to take actions to reduce mastitis. The inconsistencies and fragmented view of the interrelationship of milking m a n a g e m e n t practices m a y reflect a lack of k n o w l e d g e of preventive medicine. If this is true, then veterinarians engaged in dairy practice and e x t e n s i o n personnel have a significant educational task facing t h e m . Programs of preventive m e d i c i n e that stress the i m p o r t a n c e o f consistent and integrated milking m a n a g e m e n t practices m a y have to be developed. The lack of giving proper priority to env i r o n m e n t a l m a n a g e m e n t practices and milking procedures m a y reflect a lack of data to support e c o n o m i c justitication of preventive medicine. T h e r e are no standard analytical programs that allow managers to calculate the potential e c o n o m i c risk of not teat dipping or the potential net benefit to be gained f r o m a consistent program o f teat dipping. W i t h o u t such analytical tools, the manager may decide to save m o n e y rather than risk funds for an u n k n o w n return. Professional persons involved in preventive medicine for udder health m a y k n o w that the risks far outweigh the savings, but t h e y need tools that allow t h e m to show this to the individual dairy manager in terms of the actual net return e x p e c t e d for the individual dairy. This survey covered a broad range of milking m a n a g e m e n t practices. It establishes a baseline a b o u t practices used on high t e c h n o l o g y , large-scale dairies. The survey presented here will be used as a starting p o i n t for a m o r e detailed analysis of the relationship b e t w e e n e n v i r o n m e n t a l and milking practices, and overall u d d e r health and productivity. This can be accomplished in a prospective study where data on m a n a g e m e n t practices, p r o d u c t i o n , and u d d e r health will be collected in multiple herds. ACKNOWLEDGMENTS
The authors gratefully acknowledge J e r r y Mitchell, Valley Veterinarians, Tulare, CA and Charles Franti, Statistician, D e p a r t m e n t o f E p i d e m i o l o g y and Preventive Medicine, Davis, CA.
2541
REFERENCES
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trol. Vet. Clin. N. Am. Large Anim. Pract. Symp. Bovine Mastitis 6:233. 21 Reneau, J. K. 1983. Proper dryoff prevent early mastitis. Dairy Herd Manage. 20(7):24. 22 Robinson, T. C., E. R. Jackson, and A. Marr. 1983. Within herd comparison of teat dipping and dry
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cow therapy with only selective dry cow therapy in six herds. Vet. Rec. 112:315. 23 williamson, N. B., and W. Brown. 1983. Minnesota dairy farmers attitudes to and knowledge of bovine mastitis control. Pages 3 2 - 4 2 in Proc. 22nd Annu. Mtg., Natl. Mastitis Counc., Louisville, KY.