Fort Collins, Colo.-A National Animal Health Monitoring System (NAHMS)study has documented that nearly one in two dairy operations
has disappeared since 1991, with roughly a 4-5 percent decrease in numbers per year.
NAHMS adds that there has been a much slower decline in milk cow numbers that represent a 73 percent increase in average herd
size over the same time period.
The retrospective snapshot for the 10-year-period was just released by the United States Department of Agriculture's (USDA)Centers
for Epidemiology and Animal Health (CEAH)of the Animal and Plant Health Inspection Service. In addition, NAHMS also released
more results from its Dairy 2002 study on mycoplasma in bulk tank milk and hemorrhagic bowel syndrome.
Tabel 1: Number of u.s. dairy operations, 1991 to 2001
Brian J. McCluskey, DVM, MS, dipl. ACVPM, an epidemiologist with CEAH, tells DVMNewsmagazine that while the dairy consolidation
has been ongoing, it's still dramatic to see how the industry has consolidated during this 10-year-period.
McCluskey adds, "I think everyone expects that this trend will continue. As the numbers of farms go down, the size goes up.
It seems like establishing an economy of scale is the way to make money in the dairy industry."
The survey adds that milk production increased by 11.9 percent over this 10-year-period, while numbers of milk cows declined
by 7.2 percent. The survey also shows a 20.7 percent increase in milk production per cow.
NAHMs reports that a higher percentage of operations fed a total mixed ration in 2001, 47 percent of operations, than in 1995
Vaccination practicesProducers vaccinating heifers against bovine viral diarrhea (BVD) increased slightly in the Dairy 2002 survey to 71.5 percent,
up from 69.7 percent in Dairy '96. Factoring in the percent error, the statistic is virtually unchanged, he says. Very few
changes were noted in 1995 vaccination practices when compared with the latest numbers. Producers not vaccinating heifers
increased from 8.7 percent in 1991 to 15.6 percent in 2001.
Tabel 2: Rolling herd average milk production
McCluskey adds that vaccination as a preventive measure is an opportunity for veterinarians and producers.
Other vaccination results for heifers included:
- IBR: 67 percent
- Parainfluenza Type 3: 60 percent
- Bovine respiratory syncytial virus (BRSV): 58.2 percent
- Hemophilus somnus: 31.4 percent
- Leptospirosis: 65.1 percent
- Salmonella: 16.8 percent
- E. coli mastitis: 21.3 percent
- Clostridia (blackleg/malignant edema): 32.8 percent
- Brucellosis: 51 percent
- Mycobacterium paratuberculosis (Johne's disease): 4.6 percent
- Neospora: 3.6 percent
PreventionNAHMS says there were no major changes in the use of specific preventive practices between 1995 and 2001. However, there continues
to be a downward trend in the percentage of operations using no preventive practices in dairy heifers.
McCluskey says that is good news. In other words, more producers are adopting more of these prevention strategies for their
MycoplasmaThe Dairy 2002 study looked into mycoplasma prevalence in bulk tank milk. The study data says that 7.9 percent of dairies
tested positive for mycoplasma "when a single bulk tank milk sample was cultured using standard culture methods." M. bovis
was cultured in 86 percent of those testing positive. The other species included M. californicum, M. alkalescens, M. canadense
and M. bovigenitalium.
Tabel 3: Vaccination Practices
States in the West had a greater percentage of operations with positive mycoplasma cultures in comparison to operations in
the Midwest, Northeast and Southeast regions.
NAHMS reports that larger herds were also more likely to have positive mycoplasma cultures when compared to medium herds (100-499)
and small herds (less than 100 head).
Mycoplasma can be economically "devastating to dairies because of the contagious nature of the organism and its resistance
to therapy." Milk transfer during milking is the most common way to mycoplasma mastitis is spread from cow to cow.
NAHMS adds that the percentage of operations positive was likely underestimated because herds were sampled only once.
NAHMS adds that the most effective method of preventing an outbreak of mycoplasma mastitis is to screen all introduced cattle
by collecting composite milk samples at freshening or prior to commingling purchased cattle with the home herd.
Tabel 4: Preventive Practices
But the Dairy 2002 shows that only 11 percent of dairy operations required individual cow milk cultures before introducing
new cattle to the farm.
Only 10.6 percent also required bulk tank milk cultures, the survey says.