The aim of this case series was to describe how the selective dry-off therapy affected the udder health of Bavarian dairy farms under field conditions as well as to record whether a long-term reduction in antibiotic dry-off therapy was feasible. Between 2016 and 2021, 90 herds participated. A subset of dairy herds participated over a period of several years. Quarter milking samples were taken annually from all lactating cows in the herds, and treatment and test day results were evaluated. Major pathogens were detected during the initial whole herd testing (e. g., Streptococcus agalactiae, Streptococcus canis) and the treatment regimen needed to be adjusted. Even though the median treatment risk decreased, at least numerically, from 63% to 50%, the treatment rate in individual herds could vary greatly between years (-60% to+40%). Selective dry-off therapy can be implemented without endangering the udder health of the herd.
Objective: Infections with Salmonella enterica subspecies diarizonae serovar 61: k: 1, 5, (7) (SASd) are widespread in sheep. SASd is considered as host associated with low virulence. The aim of the study was to determine the time of infection of lambs after birth with consideration of the Salmonella status of the mother.
Material and methods: Fecal and nasal swabs from 88 ewes of a flock with known SASd status but unknown intraherd prevalence were examined for SASd in the period of 6 weeks before the beginning of the lambing period. Fecal and nasal swabs from one female lamb from each of these ewes were also examined for SASd at 4-6 time points between the 4th and 50th day of life and at 7, 30 and 40 months of age.
Results: In the first two weeks after birth, significantly more lambs were positive in the nasal swab than in the fecal swab. SASd positive nasal swabs were mainly found in lambs originating from ewes also positive in nasal swabs. 43 lambs remained SASd-negative until day 50 of age. There was no correlation between the SASd status of ewes and their off-spring. At 7 months of age, the number of animals with a positive detection of SASd increased significantly. 32% of the nasal swabs and 62% of the fecal samples were positive for SASd.
Conclusions: There is no rapid and intensive transmission of SASd from ewes to their offspring. Most likely, the infection begins by colonising the nasal mucosa of the lambs and does not cause any clinical symptoms.
Clinical relevance: Even with a high intraherd prevalence, infections with SASd are very unlikely to cause clinical symptoms.
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