Bacterial populations on teat ends of dairy cows housed in free stalls and bedded with either sand or sawdust

The main objectives of the experiment were: 1) to compare bacterial populations of mastitis-causing organisms on the teats of lactating dairy cattle housed on sand and sawdust bedding and, 2) to examine the relationship between bacterial counts present in the 2 bedding types with those on teat ends. Sixteen lactating Holstein cows were housed on either sand or sawdust-bedded free stalls using a crossover design with 3 wk per bedding type. Bedding samples were collected on d 0 (prior to animals lying on the bedding), 1, 2, and 6. Teat ends were sampled prior to the morning milking on d 1, 2, and 6. All samples were analyzed to determine coliform, Klebsiella spp., and Streptococcus spp. populations. There were 2 times more coliforms and 6 times more Klebsiella bacteria on teat ends of cows housed on sawdust compared with those housed on sand. In contrast, there were 10 times more Streptococcus spp. bacteria on teat ends of cows when housed on sand compared with sawdust. In both sawdust and sand bedding, coliforms, Klebsiella and Streptococcus counts increased over each experimental week, although patterns varied with bedding and bacteria type. Bacterial counts on teat ends were correlated with bacterial counts in sawdust (r = 0.47, 0.69, and 0.60 for coliforms, Klebsiella spp., and streptococci, respectively) and in sand (r = 0.35 for coliforms and r = 0.40 for Klebsiella spp.). In conclusion, coliforms and Klebsiella spp. on teat ends were more numerous when cows were housed on sawdust bedding, but Streptococcus spp. were more numerous on teat ends of cows housed on sand.