Study examines sand bedding as source of infection for calves

Can calves contract mycoplasma from mycoplasma-contaminated sand bedding?

Probably not, according to research from Utah State University and reported in the

March 2011 issue of the Journal of Dairy Science.

During the 105-day trial, veterinary researchers exposed six calves from a commercial

dairy farm that was found free of mycoplasma to sand bedding that had been naturally

contaminated with the Mycoplasma bovis organism on a second dairy farm. They assigned

six other calves to a control group, which were housed on clean sand bedding. All

calves were housed in calf hutches, bedded at least twice daily.

The researchers cultured bedding sand from both groups weekly. They also collected

nasal swabs, ear swabs and blood serum samples weekly. Tracheal swabs were collected

monthly.

Culture results showed that the concentration of mycoplasma in the contaminated sand

bedding was 14,200, 1,400, 32,000, 600, 200 and 3,000 colony-forming units per gram

during six of the 15 weeks of the trial.

However, all serum samples, tracheal swabs, nasal swabs and ear swabs from all calves

were negative for mycoplasma. Necropsy test results also showed none of the calves

had lesions indicative of mycoplasma infection. Tracheal, lung and lymph node samples

taken at necropsy also were negative for M. bovis.

The researchers say the repeated testing methods used to detect infection resulted in

a low probability of false-negative results. "Any infections with mycoplasma had

approximately 99 percent probability of being detected under the conditions in this

experiment," says David Wilson, veterinarian at Utah State University.

Wilson and colleagues concluded that sand bedding contaminated with M. bovis was not

a source of infection for young calves under the conditions of this study. However,

the possibility of infection through the teat ends of lactating cows, and perhaps

pre-fresh heifers housed on sand, needs further investigation.

The Dairy Calf & Heifer Association's Gold Standards I recommend that calves, from

birth to 6 months, be placed in an environment that is safe from adult animals and

adult animal diseases, including mycoplasma.