Persistence of coagulase-negative staphylococci (CNS) in intramammary infections during lactation was studied in a research dairy herd of University of Helsinki. Milk samples from 328 udder quarters of 82 dairy cows (30 primiparous, 52 multiparous) were collected 2 wk before calving, at calving, and every 4 wk thereafter until the end of lactation or until the cow left the herd. The CNS isolated from the milk samples were analyzed with the API Staph ID 32 (bioMérieux, Marcy l'Etoile, France) test (API) and genotyped using amplified fragment length polymorphism (AFLP) analysis. The AFLP patterns were used for similarity analysis between CNS isolates and for species identification. For the latter, AFLP patterns of CNS isolates and staphylococcal type strains were used as operational taxonomic units in numerical analysis. In addition, the somatic cell count (SCC) of the milk samples was measured during lactation. A CNS infection was considered persistent when isolates originating from the same quarter had identical AFLP patterns on at least 3 consecutive samplings. In total, 63 CNS infections were detected during lactation in 30 and 33 quarters in the first and later lactations, respectively. Twenty-nine of these infections persisted and 34 were transient. Most of the persistent infections lasted until the end of lactation. In 57 quarters, CNS infection was detected before calving, at calving, or both, but only half of these quarters were infected by CNS during subsequent lactation. The geometric mean of SCC in quarters during persistent CNS infection was 657,600 cells/mL, and the mean of SCC in quarters with transient CNS infection was 619,100 cells/mL. The median of SCC in quarters during persistent CNS infection was 355,400 cells/mL, and the median of SCC in quarters with transient CNS infection was 133,500 cells/mL. According to both the API test and AFLP results, Staphylococcus chromogenes and Staphylococcus simulans were the CNS species isolated most often. Identification results for API and AFLP corresponded in 71.9% of the isolates.

This experiment compared the effects of sand and straw bedding in free stalls on resting time, cleanliness, hock injuries, and hoof health of dairy cows and tested whether cow preferences for a bedding material depended on the familiarity with the material. A total of 52 dairy cows were kept either on straw bedded concrete stalls or sand stalls for at least 21 wk. The lying behavior was observed, and hock lesions, hoof health, and cleanliness of the cows and stalls were measured. A 5-d preference test between sand and straw stalls was conducted at the end of the experiment. The total daily duration of lying was longer for cows on straw bedding than on sand bedding (straw 749 +/- 16 vs. sand 678 +/- 19 min). During the preference test, cows that had been kept on straw bedding preferred lying in straw stalls [straw 218.7 (133.4 to 239.7) vs. sand 9.0 min (2.8 to 44.8)]; however, cows that had been kept on sand showed no preference [straw 101.3 (51.7 to 205.9) vs. sand 94.3 min (54.1 to 156.1, median and interquartile range)]. Although there were no differences in the dirtiness of stalls, the cows using straw stalls were dirtier than cows using sand stalls [straw 6.04 (5.39 to 6.28) vs. sand 4.19 (3.62 to 5.16)]. At the end of experiment the severity of hock lesions was lower for cows on sand than for cows on straw [sand 0.5 (0.0 to 1.0) vs. straw 1.0 (1.0 to 2.0)]. The improvement in overall hoof health over the observation period was greater for cows kept on sand compared with cows kept on straw [sand -2.00 (-3.75 to -0.25) vs. straw 0.00 (-2.00 to 2.00)]. Straw bedding increased the time that cows spend lying, and cows preferred straw stalls to sand stalls. However, previous experience with sand reduces avoidance of sand stalls. Sand stalls were advantageous for cow cleanliness and health; hock lesions and claw diseases healed more quickly for cows using sand stalls compared with straw.

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