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.

Source: Dairy Calf and Heifer Association



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