Preventing Disease Risks From Purchased Cattle
Dairy herds typically have a cull rate of about 30 percent
of the milking herd annually. For herds undergoing expan
sion, herds with higher than average cull rates, or herds not
raising replacement heifers, purchased animals may be en
tering the herd. With the purchase of outside cattle comes
the risk of introducing diseases into the herd.
The risk of contagious disease spread is great when pur
chased animals are added to the herd because:
• disease organisms on the farm of origin for purchased
animals may be different from the organisms in your own
herd
• animals that are moved from one farm to another are
stressed by trucking and change of environment-this makes
them more susceptible to disease and more likely to shed
disease organisms they may be carrying
• introduction of animals to a new farm environment is
often done around the time of calving; a time of stress and
reduced immune capabilities for most cattle.
Many different contagious diseases can be introduced by
the addition of purchased cattle. The following are
common, economically-important diseases frequently intro
duced to herds through purchased cattle. It is by no means a
complete listing of all diseases which could be introduced
with purchased cattle.
• Bovine Virus Diarrhea (BVD)
• Bovine respiratory disease (BRD) complex including
IBR, BRSV, and PIS viruses and pasteurella and haemo
philus bacteria.
• Contagious mastitis-including streptococcus agalac
tiae, Staphylococcus aureus, and Mycoplasma species
• Salmonellosis
• Johne’s disease (paratuberculosis)
• Digital dermatitis (hairy heel warts, strawberry warts)
• Interdigital pododermatitis (foot rot)
• Bovine leukosis virus (BLV)
WHAT CAN YOU DO?
Herd Vaccination Plan
Both your cattle and the animals you bring into your herd
need protection against viruses and bacteria that can be
transmitted from animal to animal. Vaccination of healthy
animals will help prevent specific diseases from occurring.
The objective of a vaccination program is to ensure a high
level of immunity at the time of exposure to disease-causing
organisms. A guideline for such a vaccination program
would be:
First 2 weeks of life: Intranasal IBR/PI3
6 months of age: Modified live virus (MLV) intramuscular
(IM)-BVD, IBR, PI3 (Colostral antibodies may persist for
up to 6 months and block the immune response to the vac
cine) 5-way Leptospirosis IM-2 injections 2 to 4 weeks apart
12 months of age: MLV IM-BVD, IBR, PI3 (at least 30
days prior to breeding) 5-way Leptospirosis IM
Piosccurity
Adults: 5-way Leptospirosis IM each 6 months BVD, IBR,
PI3 may be boostered with MLV vaccine while the cow is
open, or with a killed virus product when pregnant or open.
If a killed virus vaccine is recommended by your local vet
erinarian, the first time a killed vaccine is given it must be
followed by a booster dose in 2 to 4 weeks. If not followed by
a booster dose in two to four weeks, the first killed vaccine
dose will not induce immunity. Boosters would then be rec
ommended once to several times per year as she/he would
direct.
Protecting Purchased Animals
Purchased cattle should be protected from diseases
caused by shipping stress, from sale yards, or other influ
ences. Most producers do not know if the animals they are
buying have been vaccinated or not.
Asking about when, how, and for what diseases your pur
chased replacements were vaccinated may help prevent
some problems. If the purchased cattle are vaccinated like
the above protocol, you can feel fairly comfortable that they
are protected from the vaccine-preventable diseases. Other
vaccines such as for Pasteurella or Salmonella immuniza
tion should be determined on a herd by herd basis, by you
and your veterinarian.
Biosecurity
Herd biosecurity refers to those management practices
that
1) reduce the risk of bringing infectious diseases into your
herds
2) reduce or minimize the spread of diseases within your
herd, and
3) minimize the severity or economic impact of infectious
diseases in your herd. Holding or isolation facilities for pur
chased cattle are important to your biosecurity program.
Minimizing spread of disease organisms between cattle is
a challenge facing many dairy farms. Disease transmission
can go both directions; from your cattle to newly-purchased
animals or visa versa. Controlling the spread of disease be
tween new and existing cattle is usually a combination of
management facilities, and equipment.
The selection of methods will depend on the degree of
biosecurity desired, the number of animals involved, how
often and how long the biosecurity is required, available
labor, and the time of year.
The paths of disease spread between cattle include:
• Direct contact between cattle
• Transmission of fluids and secretions (milk, blood,
manure...) between infected and susceptible cattle
• Breathing air containing disease organisms between in
fected and susceptible cattle
• Contact with items that have been in contact with pW'
chased cattle (milking machine, water, barn equipment,
etc.)
(Turn to Pago 39)