2026

Unregulated antimicrobial application in poultry farming represents a critical public health vulnerability in developing nations like Bangladesh, where improper drug usage promotes chemical residue accumulation in edible tissues and accelerates antimicrobial resistance (AMR). This investigation evaluated the comparative impacts of discriminate (incorporating a withdrawal period) and indiscriminate (omitting a withdrawal period) tylosin administration on tissue residue occurrence, growth traits, and blood parameters in Cobb-500 broiler chickens from January to May 2020. Eighteen day-old chicks were raised for 31 days and randomized on day 16 into three groups (n = 6): Group A (control; no antibiotic), Group B (discriminate; tylosin at 2.5 g/L in drinking water from days 16-22 followed by a withdrawal period), and Group C (indiscriminate; tylosin at 2.5 g/L from days 16-31 without withdrawal). On day 31, blood and tissue samples (liver, kidney, spleen, breast muscle, and thigh muscle) were harvested to screen for tylosin residues via thin-layer chromatography (TLC) and evaluate hematological indices (hemoglobin, total erythrocyte count, and packed cell volume). Broilers in the indiscriminate cohort attained the highest final numerical body weight (1805 ± 2.91 g), followed by the discriminate (1718 ± 3.05 g) and control (1352 ± 3.07 g) groups; though inter-group variations were statistically non-significant (P > 0.05). Active tylosin residues occurred across all target tissues in both medicated groups-with no traces detected in controls-showing markedly higher prevalence in the indiscriminate cohort than the discriminate cohort: liver (100% vs. 83.33%), kidney (100% vs. 50.00%), spleen (83.33% vs. 33.34%), breast muscle (66.66% vs. 16.67%), and thigh muscle (50.00% vs. 16.67%). Hematological parameters displayed a non-significant declining trend as tylosin exposure increased; for example, hemoglobin levels dropped from 7.93 ± 0.16 g/dL (control) to 7.52 ± 0.07 g/dL (discriminate) and 7.12 ± 0.11 g/dL (indiscriminate) (P > 0.05). Overall, continuous tylosin treatment generated widespread residue persistence across all edible tissues, predominantly in hepatic and renal organs, whereas observing the withdrawal window lowered, but did not completely eliminate, detectable residues. Disregarding withdrawal guidelines risks elevating dietary drug exposure for consumers and driving AMR, underscoring the urgent necessity for strict enforcement of withdrawal standards, routine residue monitoring, and responsible pharmaceutical stewardship in commercial poultry operations to safeguard public health.

Motile Aeromonas Septicemia (MAS) is the most significant bacterial disease in freshwater aquaculture, causing substantial economic losses. This study aimed to isolate, identify, and evaluate the antibiogram profile of Aeromonas hydrophila from diseased mrigal. A total of 85 infected fish samples displaying clinical signs of MAS, including hemorrhages, fin erosion, scale loss, and dropsy, were collected from ten different farms. Bacterial loads were determined from the skin, liver, spleen, and kidney, and isolates were characterized using phenotypic, biochemical, physiological, and molecular methods. Molecular confirmation was performed by PCR, targeting a 760 bp amplicon specific to the isolated bacterium. Quantitative analysis revealed varying bacterial loads across organs, with high concentrations in visceral organs such as the kidney, liver, and spleen, indicative of systemic infection. The kidney showed the highest bacterial load, at 5.21 × 10^9 CFU/g, in fish samples from Bhaluka upazila. Antibiotic susceptibility testing against ten commonly used antibiotics demonstrated complete resistance to ampicillin (100%) and penicillin (90%), high resistance to novobiocin (80%) and oxytetracyclines (60%), moderate sensitivity to gentamicin (60%), and high sensitivity to fluoroquinolones (ciprofloxacin 90% and levofloxacin 80%). The calculated Multiple Antibiotic Resistance (MAR) index was 0.41, indicating low but significant multidrug resistance by A. hydrophila. These findings confirm the role of A. hydrophila in MAS infection in farmed mrigal and underscore the need for accurate disease diagnostics, rational antibiotic use, and continuous antimicrobial resistance surveillance in Bangladeshi aquaculture systems. The results provide a foundation for enhancing disease diagnosis, promoting prudent antibiotic use, and strengthening antimicrobial resistance surveillance in freshwater aquaculture.

Crossbreeding with Holstein Friesian (HF) cattle has become a widely adopted strategy for improving dairy productivity in Bangladesh. However, limited information is available regarding the optimum level of HF genetic contribution that maximizes milk production while maintaining disease resilience in crossbred cattle under smallholder farming conditions. This study evaluated the relationship between HF blood percentage, lactation milk yield, and the incidence of common livestock diseases in F1 and F2 crossbred cattle. It was hypothesized that increasing HF genetic contribution would improve milk yield without significantly affecting the occurrence of major diseases. Data were collected from 1,694 crossbred cattle (847 F1 and 847 F2) maintained by marginal farmers across 27 districts of Bangladesh from May, 2022 to October, 2024. Animals were classified according to HF sire blood percentage. Lactation milk yield and the occurrence of Foot-and-Mouth Disease, Hemorrhagic Septicemia, mastitis, reproductive tract disorders, and dystocia were evaluated. One-way ANOVA, Kruskal–Wallis H test, and Pearson's Chi-square test were used to determine the effects of HF blood percentage on productive performance and disease incidence. HF blood percentage had a highly significant effect on lactation milk yield in both F1 and F2 generations (P < 0.001). Crossbred cattle with 93.75% HF blood consistently achieved the highest milk yield in both generations, whereas milk production generally declined with increasing local genetic inheritance. Breed upgradation speed also influenced productive performance, with fast and very fast upgradation producing higher mean lactation yields than normal and moderate upgradation. In contrast, no significant association was observed between HF blood percentage and the incidence of the investigated diseases (P = 0.614), indicating that disease occurrence was largely independent of genetic composition. HF genetic contribution improves milk production, whereas disease susceptibility is influenced primarily by non-genetic factors. Strategic crossbreeding and proper management are essential for sustainable dairy production. The findings support sustainable dairy breeding programmes that combine genetic improvement with effective management to enhance milk production while maintaining the adaptability of crossbred cattle.

Abstract not available