Mycoplasma bovis is an important pathogen causing pneumonia, mastitis, and arthritis in cattle, leading to reduced animal welfare and economic losses worldwide. In this cross-sectional study, we investigated the prevalence of M. bovis in bulk tank milk (BTM) and herd characteristics associated with a positive antibody test result in Swedish dairy herds. Bulk tank milk samples from all Swedish dairy herds (n = 3,144) were collected and analyzed with ID Screen antibody ELISA and PCR. Information on herd characteristics was collected from the national Dairy Herd Improvement database. To identify herd characteristics associated with the presence of antibodies in BTM, logistic regression was used in 4 different models. The apparent herd-level prevalence of M. bovis infection based on antibodies in BTM was 4.8%, with large regional differences ranging from 0 to 20%. None of the BTM samples was positive by PCR. All the antibody-positive herds were situated in the south of Sweden. The logistic regression model showed that larger herds had higher odds of detectable antibodies in BTM (herd size >120 cows, odds ratio = 8.8). An association was also found between antibodies in BTM and both a higher late calf mortality (2-6 mo) and a higher young stock mortality (6-15 mo). This study showed a clear regional difference in the apparent prevalence of M. bovis infection based on antibodies. The relatively low prevalence of M. bovis in Sweden is a strong motivator for the cattle industry to take steps to prevent further spread of the infection. It is essential that the M. bovis status of free herds be known, and the regional differences shown in this study suggest that testing is highly recommended when live cattle from high-prevalence areas are being introduced into herds. We do not recommend using PCR on BTM to detect infected herds, owing to the low detection frequency in this study.

Background: Genomic selection enables bulls with desirable characteristics to be identified at a young age, but sperm quality can be poor in the ejaculates of young bulls. Few studies have been done on post‐thaw sperm quality in bulls less than 10 months old. The objective of this study was to determine the age at which post‐thaw sperm quality was acceptable for artificial insemination. Methods: Semen was collected by artificial vagina; samples containing 100–500 million spermatozoa/ml were frozen for this study. Post‐thaw analyses of membrane integrity (MI), mitochondrial membrane potential (MMP), chromatin integrity, morphology, production of reactive oxygen species and sperm kinematics were made. Results: The age at which ejaculates exceeded the breeding company's thresholds of acceptance varied considerably among individuals, with 285 days being the earliest. Morphology ( p < 0.003), MI ( p = 0.0096), high MMP ( p = 0.043) and superoxide production ( p = 0.0084) increased between the first and last ejaculates but reached acceptable levels at different ages for individual bulls. Conclusions: It was possible to obtain acceptable post‐thaw sperm quality from samples even though sperm concentration was lower than the breeding company's threshold. Therefore, it might be feasible to use ejaculates earlier than is currently considered possible, by modifying semen handling protocols.

Interest in using semen from young bulls is increasing due to identifying promising animals by genomic selection. However, sperm quality in these ejaculates may not reach currently accepted standards for the cattle breeding industry. The purpose of this study was to determine if centrifugation of semen from young bulls through the Bovicoll colloid could improve sperm quality sufficiently for the frozen semen to be acceptable for artificial insemination. Ejaculates from 19 young bulls were split and either processed by Single-Layer Centrifugation (SLC) or not (CON) before freezing. After thawing, sperm quality was evaluated by determination of membrane integrity, mitochondrial membrane potential, DNA integrity, production of reactive oxygen species, sperm morphology and motility. Approximately half of the CON samples reached acceptable post-thaw quality (membrane integrity ≥ 40%) despite being below the breeding company´s desired sperm concentration threshold pre-freezing. In the remaining samples, sperm quality was improved by SLC such that 45% of them reached acceptable quality post-thaw. Almost 75% of the young bull sperm samples could have produced usable frozen semen doses by adjusting the breeding company´s current processing protocols. Since lowering the generation interval has a direct effect on the genetic gain per year, SLC could aid genetic progress in cattle breeding.

Mycoplasma bovis is an important pathogen causing pneumonia, mastitis, and arthritis in cattle all over the world entailing reduced animal welfare and economic losses. In this longitudinal study, we investigated the presence of M. bovis antibodies in bulk tank milk (BTM) and in milk from primiparous (PP) cows at 4 sampling occasions over 2 yr. Herd characteristics associated with a positive antibody test result in PP cows were investigated. The participating dairy herds (n = 149) were situated in southern Sweden, samples were collected and analyzed with ID Screen antibody ELISA. Information on herd characteristics was retrieved from the national DHI database. To identify herd characteristics associated with the presence of antibodies in PP cows, mixed linear regression with herd and sample as random factors were used. The apparent herd-level prevalence of M. bovis infection based on antibodies in BTM was 17%, but with the addition of PP cows, the prevalence increased to 28%. The results showed that larger herds and introduction of cattle was associated with higher antibody levels in PP cows. In conclusion, this study showed a clear difference in the apparent prevalence of M. bovis infection based on antibodies in BTM or in PP cows: The number of positive herds was almost doubled when including PP cows. This motivates repeated sampling of a few PP cows to find newly infected herds in an early stage. Finally, the results showed that introduction of cattle influences the level of M. bovis antibodies. This is important in the control and prevention of further spread of the infection. It is essential for free herds to know their M. bovis status, and antibody testing is highly recommended if introducing cattle.

Increased evidence suggests that cattle are the primary host of Influenza D virus (IDV) and may contribute to respiratory disease in this species. The aim of this study was to detect and characterise IDV in the Swedish cattle population using archived respiratory samples. This retrospective study comprised a collection of a total 1763 samples collected between 1 January 2021 and 30 June 2024. The samples were screened for IDV and other respiratory pathogens using real-time reverse transcription quantitative PCR (rRT-qPCR). Fifty-one IDV-positive samples were identified, with a mean cycle threshold (Ct) value of 27 (range: 15–37). Individual samples with a Ct value of <30 for IDV RNA were further analysed by deep sequencing. Phylogenetic analysis was performed by the maximum likelihood estimation method on the whole IDV genome sequence from 16 samples. The IDV strains collected in 2021 (n = 7) belonged to the D/OK clade, whereas samples from 2023 (n = 4) and 2024 (n = 5) consisted of reassortants between the D/OK and D/660 clades, for the PB2 gene. This study reports the first detection of IDV in Swedish cattle and the circulation of D/OK and reassortant D/OK-D/660 in this population.

Mycoplasma bovis causes severe diseases among cattle. Sweden has a favorable situation for control of this disease, with a low prevalence of M. bovis infected and seropositive herds detected only in the southern parts of the country. To prevent the spread of the infection, analyzing antibody levels is a cost-effective method to determine herd pathogen exposure status. In this study, our aims were to monitor the antibody dynamics in infected herds over time using IDvet ELISA, to both evaluate risk-based sampling and investigate the effect of M. bovis exposure on health and production. We visited and sampled 35 dairy herds, 31 of which were sampled at least 2 times and 26 sampled 4 times and followed for 2 yr. The patterns of herd seroprevalence varied depending on the status before the herd's entry into the study and remained relatively stable at the herd level, although antibody status could differ among age groups. Overall, herds with high exposure prevalence (75%-100% positive cows, n = 13/26), and herds with low exposure prevalence (<25% positive cows, n = 5/26), maintained their exposure status throughout the study. The changes in status observed within the herds, both among calves and cows, included transitions from positive to negative, as well as from negative to positive. In 5 herds, the calf group transitioned from positive to negative, while in 1 herd, the reverse occurred. Three herds exhibited an increase in antibody levels; in 2 of these herds, the cows transitioned from negative to positive, and in 1 herd with positive cows, the calves shifted from negative to positive. A cost-effective test strategy to find likely infected herds involved sampling bulk tank milk and cows with a high SCC, which gave a 90% probability of locating infected herds by the second sampling. Milk production was reduced by 404 kg (1.3 L/d, P = 0.012) in cows positive for M. bovis antibodies. Therefore, controlling the spread of M. bovis infection will likely have a positive effect on reducing income loss for dairy herds in Sweden.