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					  Calf milk pasteurization



                                                                          Calves fed pasteurized colostrum
                                                                          and waste milk were worth an extra
                                                                          $8.13 in gross margin/calf.




                                                                          In the ongoing quest for improved



                                                                          I
                                                                          biosecurity and maximum dairy herd
                                                                          health, it stands to reason that pasteur-
                                                                          izing calf milk would be a worthwhile
                                                                          and beneficial management practice.
                                                                          Yet in reality, conservative industry esti-
                                                                          mates indicate that far fewer than half
                                                                          of all dairies currently perform any type
                                                                          of heat treatment on waste milk fed
                                                                          to calves.
                                                                              Is calf milk pasteurization effective?
                                                                          Does it address current disease and bio-
                                                                          security concerns on the average dairy?
                                                                          And if so, what role can dairy practition-
                                                                          ers play in promoting its adoption?

                                                                          Bacteria that pose
                                                                          transmission risks
                                                                          The value of pasteurizing waste milk fed
                                                                          to calves must be evaluated on several
                                                                          fronts. Disease prevention potential,
                                                                          economics and practicality each play
                                                                          separate but important roles.
                                                                             Mark Thurmond, DVM, PhD, veteri-
                                                                          nary epidemiologist at the University of
                                                                          California-Davis School of Veterinary
                                                                          Medicine, says there is little argument
                                                                          that the goal of purifying waste milk fed
                                                                          to calves is a good one. “We want to
                                                              GENI WREN




                                                                          make sure we aren’t inoculating young
                                                                          calves with bacteria in the process of
                                                                          trying to deliver good nutrition to
                                                                          them,” says Thurmond. “Particularly on
                                                                          dairies that are having calf health prob-
                                                                          lems that cannot be solved in other
                                                                          ways, heat treatment of waste milk to
                                                                          reduce the bacterial population in it
                                                                          makes sense.”
                                                                             Thurmond notes that the list of or-
                                                                          ganisms potentially spread to calves via
                                                                          waste milk is a relatively long one. “En-
                                 A closer look at an                      teric diseases caused by Salmonella
                                                                          and E. coli are an immediate threat to
                        emerging dairy management practice.               the immature immune systems of
                                                                          neonates in the first four weeks of life,”
                                        By Maureen Hanson                 he says. “The resulting dehydration, de-

40 Bovine Veterinarian/November-December 2001
pressed appetite, shock                                       and feces. This “wasting”     tive pasteurization of waste milk
and vulnerability to sec-                                     disease typically does not lessens the severity and duration of di-



                                                          GENI WREN
ondary pathogens caused                                       become clinical until         arrhea in young calves.2
by infection with these or-                                   calves reach adulthood            Whether a killing effect is achieved is
ganisms all can be fatal to Ken Mitchell, DVM,                and is untreatable. Al-       dependent on the temperature to which
young calves.”                  suggests preparing            though not confirmed,         the milk is heated, the duration it stays
    Bovine viral diarrhea       written protocols on          there has been concern        at that temperature and how quickly
virus (BVDV) and bovine         pasteurization for            that M. paratuberculosis      the milk is subsequently cooled. Cur-
leukemia virus (BLV) also       employees.                    may play a role in the        rent technology allows for two main
can be transmitted via un-                                    development of Crohn’s        methods of pasteurization:
                                              disease in humans.1
treated waste milk, as can Staplylococ-
cus aureus, Streptococcus agalactiae and
other mastitis pathogens. While they          Efficacy studies examine
                                                                                           1    Batch pasteurization, which entails
                                                                                                heating a relatively large volume of
                                                                                            milk to a minimum temperature for the
may not pose an immediate threat to           key organisms                                 minimum amount of time required to
calf health, mastitis bacteria have           Numerous studies support the theory           achieve a killing effect, and
proven to be amazingly hardy, surviving that, when performed correctly, heat
on the teat skin for months or even
years and causing mastitis infections in
                                              treatment of waste milk is effective in      2    High-temperature, short-time
                                                                                                (HTST) or flash pasteurization,
                                              killing most “garden-variety” pathogens which is done by raising milk to a high-
pre-fresh and fresh heifers. These or-        in milk such as Staph. spp., Strep. spp.,     er temperature for a few seconds, while
ganisms can be especially troubling           E. coli and Salmonella. A 1997 study by       passing it through a turbulent-flow sys-
when calves are able to suckle one an-        Selim and Cullor at the University of         tem that rapidly reduces the tempera-
other, promoting transmission from the California-Davis concluded that effec-               ture after heating. It is the process used
mouth of one animal to the mammary
system of the next.
    Two other horizontally transmittable
organisms that are of particular con-            The veterinarian’s role
cern are Mycoplasma species and Myco-             Calf care can have a tremendous impact on a dairy’s
bacterium paratuberculosis.                       long-term success, and it’s a management area in
    Mycoplasma can have devastating               which many dairy veterinarians are starting to play a more
effects on calf health in a variety of pre-       in-depth role. Ken Mitchell, DVM, and Mark Thurmond, DVM, PhD, suggest
sentations. According to Thurmond,                these aspects of calf-milk pasteurization with which the veterinarian can assist
stubborn cases of pneumonia, ear infec-           dairies for a mutually beneficial outcome:
tions and joint infections can be com-            s Assessing the overall disease and management situation on the dairy and
mon results of feeding Mycoplasma-                determining if calf-milk pasteurization is advisable.
infected milk. What’s more, Thurmond              s Evaluating and choosing pasteurizing equipment for the dairy.
says Mycoplasma bacteria also can seed            s Conducting a cost:benefit analysis for the dairy to determine if the invest-
themselves in infantile mammary tissue,           ment in equipment and labor will pay off.
lying dormant until freshening, then              s Working with a diagnostic lab to determine the ideal pasteurization time-
surfacing as clinical mastitis infections         temperature variable for the dairy’s pathogen challenge(s) and load.
in fresh heifers. Mycoplasma mastitis is          s Assisting with employee training and periodic review sessions.
highly contagious and a serious threat            s Regularly collecting and culturing samples of pasteurized milk to monitor
to infected animals and their herdmates.          quality.
    M. paratuberculosis — the organism            s Conducting ongoing health monitoring of calves, heifers and cows, including
that causes Johne’s Disease —is an obli-          post-mortem analyses, to stay abreast of the organisms that are challenging
gate pathogenic parasite that is trans-           the dairy, and possibly adjust pasteurization procedures accordingly.
mitted from dam to offspring via milk

                                                                                    Bovine Veterinarian/November-December 2001 41
    Calf milk pasteurization



  to pasteurize milk for consumer con-
  sumption.
      Thurmond says the time-temperature
  relationships for these two methods
  vary depending on the structure of the
  pasteurization system and the main or-
  ganism being addressed. However, he
  cites general guidelines of 145°F (63°C)
  for 30 minutes for batch pasteurization,
  and 162°F (72°C) for 15 seconds for flash
  pasteurization.
      A study specifically examining My-
  coplasma sensitivity to pasteurization by




                                                                                            GENI WREN




                                                                                                                                                     GENI WREN
  Butler et al. at Iowa State and Cornell
  Universities in 2000 concluded that all
  Mycoplasma bacteria in milk were inacti-     BVDV and BLV can be transmitted to                       Colostrum is more difficult to
  vated by heat treatment to 158°F (70°C)      neonatal calves through waste milk.                      pasteurize, but it can be done.
  for three minutes. While some Mycoplas-
  ma species were susceptible at lower         minutes. Periodic culturing under the                    concluded that, at this time-tempera-
  temperatures and/or treatment times,         old protocol never showed a positive                     ture ratio, pasteurization lessened, but
  M. canadense did not succumb until this      Mycoplasma sample over a period of                       did not eliminate, growth of M. paratu-
  time-temperature ratio was achieved.         two months, but the ear infections per-                  berculosis.4
  The researchers suggest that when            sisted. When the temperature was                            It appears that flash pasteurization
  Mycoplasma is a concern, on-farm pas-        raised, samples remained negative, and                   may be more effective in eliminating the
  teurization protocols should be devel-       the ear infections stopped abruptly                      organism. A study by Stabel, et al. at the
  oped to inactivate M. canadense, be-         within two months.                                       USDA National Animal Disease Center
  cause it proved to be the most heat-re-          “Some other management changes                       compared the results of batch vs. flash
  sistant of the Mycoplasma pathogens.3        were adopted at the same time, so it’s                   pasteurization on milk samples experi-
      The threat of Mycoplasma infections      tough to say the higher pasteurization                   mentally inoculated with two strains of
  is the main reason why approximately         temperature was the cure-all,” says                      M. paratuberculosis. The conclusions:
  one-third of the dairies and virtually all   Mitchell. “The inherent presence of My-                  While both procedures resulted in a
  of the calf ranches served by Valley Vet-    coplasma in cattle — particularly in the                 dramatic reduction in bacterial load of
  erinarians, Inc., Tulare, Calif., practice   respiratory tract — also makes it im-                    M. paratuberculosis, the turbulent flow
  some form of heat treatment of waste         possible to prevent all Mycoplasma dis-                  of milk during pasteurization aids in the
  milk. Ken Mitchell, DVM, recently con-       ease. But I do believe that 155-160°F                    complete killing of M. paratuberculosis,
  ducted an on-farm Mycoplasma bovis           should be the pasteurizing temperature                   because the organism may clump more
  screening evaluation on a client dairy       goal for Mycoplasma and that reaching                    readily in a static environment and pro-
  that was experiencing severe Mycoplas-       these levels will help prevent disease.”                 tect themselves from heat penetration.5
  ma ear infections in month-old calves,           M. paratuberculosis also has been the
  plus periodic cases of Mycoplasma mas-       subject of specific pasteurization effica-               Economic considerations
  titis in fresh heifers.                      cy studies. A recent study by Meylan et                  Feeding waste milk that otherwise
      The dairy had been heat-treating         al. evaluated the effect on M. paratuber-                would be discarded has obvious finan-
  waste milk to 150°F for 10 minutes. They     culosis when experimentally inoculated                   cial appeal to dairy producers and calf
  increased the temperature to 155°F and       colostrum samples were heated to                         ranchers. But the disease side effects of
  continued to heat the milk for at least 10   145°F (63°C) for 30 minutes. The study                   feeding raw milk could quickly offset
                                                                                                        those savings in some cases.
                                                                                                            Thurmond and a group of colleagues
                                                                                                        at the University of California-Davis con-
I believe that 155-160°F should be the pasteurizing                                                     ducted a large-scale economic study in
temperature goal for Mycoplasma and that                                                                1996, to evaluate the cost:benefit ratio
                                                                                                        of pasteurizing waste milk and colos-
reaching these levels will help prevent disease.                                                        trum vs. feeding raw products. The
                                                                                                        study took into account a broad range
                                                                                                                              Continued on page 44
  42 Bovine Veterinarian/November-December 2001
  Calf milk pasteurization

                                               The economic benefit
of factors, including feed costs, health-      of pasteurization
related expenses, pasteurization-related
costs, labor and energy. Batch pasteur-
                                               should be evaluated for
ization was used.
    Results indicated that calves in the
                                               each individual dairy.
treatment group had significantly higher
mean weight gain and fewer days in                 Thurmond believes the process does
which they were affected with diarrhea         have value, though, and is possible with
and pneumonia. The investigators con-          a little fine-tuning. “The trick is to not
cluded that calves fed pasteurized             exceed the time and temperature neces-
colostrum and waste milk were worth an         sary for the desired killing effect,” he
extra $8.13 in gross margin/calf. They         advises, “then cool it right back down.”




                                                                                                                                           GOODNATURE
also determined that — using the pas-              The Meylan study that examined
teurization system employed in the             pasteurization for M. paratuberculosis
study — the minimum number of calves           also evaluated the effect of pasteuriza-      Advancements in new, on-farm
on feed necessary to make pasteuriza-          tion on IgG concentrations in colos-          pasteurization technology are producing
tion economically feasible was 315             trum. The researchers found that IgG          units that make calf-milk pasteurization
calves per day, equivalent to a dairy of       levels were affected by pasteurization,       more efficient and practical for dairies of
approximately 1,260 cows.6                     and were impacted more in high-quality        all sizes.
    Thurmond cautions that the econom-         colostrum than colostrum of lesser
ic benefit of pasteurization should be         quality. They concluded, however, that        pasteurizer, how to watch the thermo-
evaluated for each individual dairy. Dif-      although colostral IgG concentrations         stat, how to record in the log and how to
ferent pasteurization units will make the      were significantly decreased by pas-          clean the equipment.
capital equipment investment variable,         teurization, the difference was not to an     s Conduct periodic, follow-up training
and some disease conditions — particu-         unmanageable level that would pre-            and review sessions to reinforce proce-
larly those that do not respond to treat-      clude use of the colostrum for passive        dures.
ment — will affect the relative value of       immunity transfer.7                           s Perform regular post-mortem and cul-
pasteurization for individual herds.                                                         ture/sensitivity evaluations on bacterial
    He also notes that economic compar-        Implementation is critical                    causes of morbitity and mortality.
isons between pasteurized milk and milk        Mitchell and Thurmond agree that the              Mitchell notes that the last point is
replacer must accommodate more than            biggest pitfall of calf milk pasteurization   important as a guide to general hygiene,
the up-front cost of each feed source.         is consistent implementation on the           environmental challenges and antibiotic
“It’s hard to beat the real thing,” he says.   dairy. Training must be a priority, and       selection. The information also can
“In every study I’ve ever conducted, pro-      quality control monitoring should be          serve as an indirect indication of pas-
ductivity of calves is much better on          ongoing.                                      teurizer function and milk delivery.
whole milk, so any economic decision               Mitchell offers these tips for helping        Thurmond adds that improper on-
between milk and milk replacer must be         dairies perform pasteurization consis-        farm implementation can cause pasteur-
based on the cost of the feed source and       tently and accurately:                        ization to quickly go awry. “Just because
relative productivity.                         s Routinely culture samples of pasteur-       milk has been pasteurized does not
    “It’s also worth mentioning,” he adds,     ized milk to monitor product quality.         mean it is completely sterile, and its bac-
“that milk replacer is not necessarily         s Pull samples at random times so that        terial loads will not stay low indefinitely,”
bacteria-free. Simply choosing milk re-        implementation is consistent every day,       he cautions. Just as pasteurized milk
placer does not eliminate the risk of bac-     not just on “sample day.”                     from the grocery store will still spoil if
terial contamination.”                         s Conduct face-to-face training sessions      left unrefrigerated, pasteurized calf milk
                                               with all employees responsible for pas-       will become contaminated again if it is
What about colostrum?                          teurization, emphasizing why the pro-         not either fed immediately or chilled
Colostrum is a more difficult product to       cess is important.                            properly for storage.
handle in pasteurization because its           s Keep a daily log of who prepared the
high viscosity tends to “gum up” equip-        milk and how long it reached the “goal”       Equipment wish list
ment, making cleaning difficult and un-        temperature — then correlate this to          Both veterinarians have seen many dif-
appealing to laborers. As a result,            culture results.                              ferent systems that work well for calf-
Mitchell says most of his clients do not       s Prepare written protocols — in En-          milk pasteurization. Some are supplied
pasteurize colostrum.                          glish and Spanish — for running the           by milking machine manufacturers, and
                                                                                                                    Continued on page 46
44 Bovine Veterinarian/November-December 2001
  Calf milk pasteurization

                                Just because milk has been
often are custom-fitted to the  pasteurized does not mean
dairy to utilize existing re-
sources such as chilled waste   it is completely sterile,
water from the dairy’s milking
system for cooling. Others are
                                and its bacterial loads will
being developed by suppliers    not stay low indefinitely.
that specifically manufacture
pasteurizing equipment and
that also may serve other sectors of the     can present their own set of challenges.
food-processing industry.                    Also, he cautions against allowing pas-
    Regardless of the manufacturer,          teurization to create a false sense of se-
Thurmond and Mitchell say the “ideal”        curity on the dairy.
on-farm pasteurizing system should be:           “It’s easy to get a little sloppy in oth-
s Easily or automatically cleaned, so        er procedures, thinking pasteurization
that cleaning is readily performed by        will cover up our mistakes,” he notes.
laborers and bacterial reservoirs do not     “But pasteurization can only do so
build up.                                    much. I like to equate it to scheduling
s Fool-proof, with a system of checks        an elective surgery. If everything else is
and balances to guard against failures in    in good shape, then the investment in
the system.                                  the next improvement of pasteurization
s Capable of reaching the desired tem-       is a good decision. And, like most man-
perature and bringing it back down           agement practices, it’s only as good as
quickly, while handling a large volume of    the ability to carry it out.” s
milk.
s Equipped with a temperature monitor-          References:
ing device or chart to allow management         •1,5 Stabel, J.R., Steadham, E.M., & Bolin,
to track performance and employee               C.A. (1997). Heat inactivation of Mycobac-
compliance.                                     terium paratuberculosis in raw milk: are cur-
                                                rent pasteurization conditions effective?
s Capable of pasteurizing colostrum
                                                Applied Environmental Microbiology 63:4975.
without gumming up or damaging
                                                •2 Selim, S.A., & Cullor, J.S. (1997). Number
colostrum quality.                              of viable bacteria and presumptive anti-
                                                biotic residues in milk fed to calves on
Managing the big picture                        commercial dairies. Journal of the Ameri-
While pasteurizing waste milk provides          can Veterinary Medical Association
clear benefits when done correctly and          211(8):1029.
consistently, it should not be viewed as        •3 Butler, J.A., Sickles, S.A., Johanns, C.J., &
a panacea that will mask other manage-          Rosenbusch, R.F. (2000). Pasteurization of
ment problems.                                  discard Mycoplasma mastitic milk used to
   “Pasteurization is important, but it’s       feed calves: thermal effects on various
                                                Mycoplasma. Journal of Dairy Science
not the only issue,” says Mitchell. “I
                                                83:2285.
think the most important thing is to fo-
                                                •4,7 Meylan, M., et. al. (1996). Survival of
cus on hygiene in the milk delivery sys-        Mycobacterium paratuberculosis and
tem in general. Also, don’t overlook the        preservations of Immunoglobulin G in
simple things like the amount of nutri-         bovine colostrum under experimental con-
ents provided to the calf. Make sure            ditions simulating pasteurization. Ameri-
calves are fed enough to fulfill their          can Journal of Veterinary Research
needs. The milk can be totally sterile,         57(11):1580-1585.
but if a young calf doesn’t get enough en-      •6Jamaluddin, A.A., Carpenter, T.E., Hird,
ergy from the milk we feed them, they           D.W., & Thurmond, M.C. Economics of feed-
will become weak and get sick anyway.”          ing pasteurized colostrum and pasteurized
                                                waste milk to dairy calves. Journal of the
   Thurmond adds that pasteurization
                                                American Veterinary Medical Associa-
provides little to no protection against
                                                tion 209:751.
antibiotic residues in waste milk, which

46 Bovine Veterinarian/November-December 2001

				
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