Hydrated lime was the only bedding treatment that significantly reduced certain mastitis-causing bacteria on both free-stall mattresses and teat ends, according to research from the University of Pennsylvania School of Veterinary Medicine. The researchers also evaluated a commercial bedding conditioner, coal fly ash, wood shavings or no bedding.

The amount of lime — about 1 pound every two days — used during the study did cause some skin irritation on cows’ udders and legs. “This suggests that routine long-term use of more than 0.5 kg (about 1 pound) of lime as the sole bedding source on mattresses may be associated with undesirable side effects despite the benefit in bacteria suppression,” says Michaela Kristula, one of the study’s authors. This could be exacerbated by stall designs that allow manure to build up on the stall surface. More research is needed to test the efficacy of lower lime application rates to avoid skin irritation.

Study results can be found in the May Journal of Dairy Science.