Mục tiêu của nghiên cứu nhằm đánh giá ảnh hưởng của bổ sung mannan oligosaccharides (MOS) và colistin trong thức ăn đến khả năng sinh trưởng và đáp ứng miễn dịch ở gà Lương Phượng. Tổng số 288 con gà mái 1 ngày tuổi (giống Lương Phượng) được bố trí vào ba nghiệm thức th...

Porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDV), both economically detrimental to the swine industry, can be spread through contaminated truck cabins, posing significant transport biosecurity risks. This study evaluated the effectiveness of gaseous ozone technology in decontaminating PRRSV and PEDV on non-porous surfaces in truck cabins. An incomplete factorial study comprising 26 treatment groups, including controls, and ozone treatments at three capacities (30, 38, and 68 g/h) was conducted over varied exposure times (0.5, 1, or 2 hours) in a climate-controlled truck cabin, where PRRSV or PEDV contaminated rubber coupons were subjected to treatments under continuous environmental monitoring, followed by virus elution and titration in cell cultures. Statistical analyses included regression models and ANOVA with Tukey’s comparisons, standard deviations for ozone machines, and Pearson correlations between ozone concentration and environmental factors. Ozone treatments showed variable results with less than two-log viral titer reduction. Ozone concentrations varied across identical setups (SD: 4.75 ppm for 30 g/h, 5.43 ppm for 38 g/h machines) during the first 30 minutes, while across the entire study period, ozone concentration showed weak negative correlation with virus titer (p > 0.05), moderate positive correlation with temperature (r = 0.5, p < 0.0001), and moderate negative correlation with humidity (r = -0.56, p < 0.0001). In conclusion, ozone treatments showed inconsistent and limited effectiveness in PRRSV and PEDV decontamination, influenced by temperature and humidity under the tested conditions.

As the sows constitute a major source of porcine reproductive and respiratory syndrome virus (PRRSV) infection in piglets, undetected PRRSV in sows poses a significant challenge to the success of PRRSV control and elimination programs. The dynamics of PRRSV persistence in individual sows remains unanswered majorly because of the lack of practical individual sampling tools. The objective of this study was to characterize the dynamics of PRRSV RNA positivity in sows and associated risk factors using a practical Tonsil-Oral-Scrubbing (TOSc) collection method on sows over a complete reproductive cycle. This field study was conducted in a commercial breed-to-wean farm intending to eliminate PRRSV by herd closure and using live virus inoculation (LVI) for whole herd exposure after an outbreak. Pre- and post-LVI, periodic TOSc samplings at four-week intervals were performed on 275 conveniently selected sows with evenly distributed parity categories (Parity 0, parity 1–2, and parity 3 and above) and production phases categories (wean-breed, early gestation, middle gestation, late gestation, and farrowing) until 24 weeks post-LVI. Overall, PRRSV RNA positivity declined over time from the first sampling point- 2 days before LVI until the end of the trial. At 16 weeks post-LVI, the PRRSV RNA positivity reached 4.43%, below the defined threshold of a low prevalence scenario of 10% positivity, and remained low prevalence until the end of the study. In the low prevalence scenario, there was a rebound of positivity to 8.00% at 24 weeks post-LVI. Parity demonstrated a significant effect on PRRSV RNA positivity in sows. At a high prevalence scenario (>10% positivity), both P0 and P1-P2 groups constantly showed significantly higher PRRSV RNA positivity than the P3 + group (p<0.05 for all pairwise comparisons). The P0 positivity was consistently numerically higher than P1-P2. The production phase effect was evident when the herd reached low prevalence (<10% positivity); sows in farrowing had consistently higher PRRSV RNA positivity than sows in other production phases. The mean positivity increased to 28.56% and 34.49% in the farrowing group at 20 weeks post-LVI and 24 weeks post-LVI, respectively. PRRSV RNA positivity in sows based on TOSc samples decreased over time and reached low prevalence at 16 weeks post-LVI. PRRSV RNA positivity decreased significantly with the increase in parity. And the production phase effect on PRRSV RNA positivity was more evident at low prevalence compared to high prevalence scenarios.

Tonsil oral scrubbing (TOSc) is a simple and practical method recently developed for detecting PRRSV RNA in sows. This study evaluated how pooling and freeze-thaw procedures affect PRRSV RT-rtPCR results in TOSc samples. To assess pooling effects, 22 PRRSV-positive samples were divided into three Ct categories and diluted with negative TOSc samples at various ratios before testing. To assess freeze-thaw effects, 90 TOSc samples were split into two equal aliquots: one tested immediately, and the other tested after one freeze-thaw cycle. Results showed that PRRSV RNA detection probability decreased and Ct values increased as dilution (pooling) ratios rose. Samples with Ct values > 35 had significant drops in probability of detection beginning at a 1:3 dilution (≤71%). In contrast, samples with Ct values <35 maintained a high probability of detection until 1:10 dilution (≥85%). The freeze-thawed samples showed significantly higher Ct values and numerically lower probability of detection compared to non-freeze-thawed ones. In conclusion, pooling and freeze-thaw negatively impact PRRSV RNA detection in TOSc samples. Pooling may be acceptable for samples with a Ct value < 35 for up to 1:10 dilution, but should be avoided when the Ct value > 35. Similarly, the freeze-thaw process should be minimized during TOSc sample handling.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a significant cause of economic loss in the swine industry, yet its control remains challenging in wean-to-harvest sites. This prospective observational study followed 95 wean-to-harvest sites across six U.S. states for one production cycle. Sites were required to be PRRSV-negative or vaccinated with a modified live virus (MLV) and free of major coronaviruses. Outbreaks were defined as RT-qPCR-positive in unvaccinated sites or detection of ORF5 sequences distinct from the MLV strain. Biosecurity data were collected through a survey, and oral fluids were tested every four weeks. PRRS outbreaks occurred in 14/42 nurseries (33.3%), 8/12 wean-to-finish (66.7%), and 35/41 finishers (82.4%), with lineage 1C.5 most frequently detected. In univariate models, higher odds of outbreaks were associated with transporting pigs of unknown status (OR 9.80, 1.73–55.37), rendering (OR 6.47, 1.62–25.84), and employee cohabitation (OR 6.15, 1.51–25.09). Protective factors included exclusive pumping equipment (OR 0.07, 0.01–0.43) and overnight downtime for multi-site workers (OR 0.15, 0.04–0.56). In multivariable models, finisher sites (OR 17.47, 2.44–125.19) and greater swine site density within one mile (OR 1.62, 1.09–2.41) significantly increased outbreak odds. These results support targeted biosecurity practices, helping farmers and the swine industry reduce PRRS outbreaks.