“Recycled sand can safely be used to bed free-stalls on dairy farms.” That was the conclusion of an on-farm study published in the December 2005 Journal of Dairy Science.  

Most dairy producers bed free-stalls with sand once a week. Yet, few studies have evaluated the safety of using recycled sand, let alone compared bacterial growth in both clean sand or recycled sand during this time.

 However, this study found that the number of environmental-mastitis-causing pathogens in recycled sand was similar to that found in clean sand up to seven days after bedding.

The first part of the study took place during the winter of 2003. During that time, 12 dairy producers who used either recycled sand or clean sand in their free-stalls collected samples from the back one-third of 10 percent of the stalls. Sample collection began on the day that sand was taken from a pile and put into the free-stalls and continued for about a week. In order to replicate the study on each farm, the producers collected samples on two separate occasions. The entire procedure also was repeated during the summer at 11 facilities that used either recycled sand or clean sand.

 Back at the lab, the researchers estimated the number of colonies of gram-negative   bacteria, coliforms, Klebsiella and Streptococcus per gram of bedding in each sand sample. They also estimated amounts of dry matter and organic matter in each sample.

 “Clean sand and recycled sand had the same bacterial counts when compared at any sampling time,” say the research team, made up of researchers from the University of Pennsylvania, AET Consulting of Lititz, Pa., and the Ohio State University. However, the average number of bacteria in both the clean sand and the recycled sand varied during the course of the study. Here’s a snapshot of some of the results:

  • Bacterial counts increased significantly in both clean sand and recycled sand between day 0 (when sand was taken from the pile) and day 1 (24 hours after the stalls were bedded) for gram-negative bacteria, coliforms and Streptococcus during both winter and summer.
  • Counts of gram-negative bacteria, coliforms, Klebsiella and Streptococcus in both clean sand and recycled sand did not differ between day 1 and day 7 in the winter.
  • Total counts of gram-negative bacteria in both clean sand and recycled sand did not differ between day 1 and day 7 in the summer. Coliform counts were lower on day 1 than on day 5 to day 7 in the summer. Klebsiella counts were lower on day 1 than on day 3 to day 7 in the summer.
  • During the entire sampling period, the number of coliform and Klebsiella in both clean and recycled sand stayed below 1 million colony-forming units per gram of bedding. However, the number of Streptococcus was high in both clean sand and recycled sand.
  • Recycled sand contained more organic matter, but less dry matter, than clean sand in winter and summer.

The researchers say that different management systems used on the farms in the study may have influenced the number and types of bacteria found in both clean and recycled sand. More-frequent bedding, such as twice per week, “could be advantageous,” say the researchers, particularly to help control high numbers of Streptococcus in both winter and summer. Twice a week bedding also could help control coliforms and Klebsiella in the summer.

 Allow the recycled sand to sit in piles for about one month before reusing it in the stalls, adds Michaela Kristula at the University of Pennsylvania, one of the study’s authors. This helps increase the dry matter in the recycled sand. “When it comes to bedding, drier is always better,” Kristula says.

December 2005 Journal of Dairy Science