Objectives: The clinical efficacy of the use of probiotics, prebiotics, synbiotics and postbiotics (biotics) in cats is unknown, despite their use in daily practice. The objectives of the study is to evaluate the effectiveness of biotic supplementation in treating and preventing gastroenteropathies, and in reducing gastrointestinal signs associated with antibiotics in cats.Materials and Methods: A systematic review was conducted by searching four databases for publications before August 2, 2024, following a pre‐registered protocol. Eligible publications were trials involving healthy cats or those with gastroenteropathies, supplemented with biotics (and an inactive control), studying outcomes such as faecal consistency, faecal microbiota or vomiting. Risk of bias and quality of reports were assessed. Effects were synthesised by meta‐analyses and vote counting based on direction of effect. Certainty of evidence was rated using GRADE approach.Results: Twenty reports were included, presenting unclear or low risk of bias. The evidence did not permit a high‐confidence evaluation of the effectiveness of biotics, although five of the seven probiotic trials showed beneficial effects on faecal consistency. Synbiotics presented no clinically relevant effect in reducing antibiotics‐associated vomiting, with very low certainty, in a meta‐analysis including 32 adult cats. Probiotics significantly reduce the Bacillota/Actinomycetota ratio, with low certainty, in a meta‐analysis involving 34 healthy young‐adult cats. Following vote counting, probiotics improved immune profile in young cats, and increased butyric acid concentration in healthy cats.Clinical Significance: Current data highlight the need for further research, especially focused on at‐risk groups and sick cats, before advocating the use of biotic supplementation.

Salmonella Typhimurium is an important pathogen affecting both animal production and public health, with pigs representing a major reservoir. The increasing prevalence of antimicrobial resistance highlights the need for alternative or complementary therapeutic strategies. Carvacrol, a phenolic constituent of Origanum vulgare essential oil, has recognized antimicrobial activity and may contribute to the modulation of antimicrobial resistance mechanisms. The present study investigated the antimicrobial activity of carvacrol and tetracycline, individually and in combination, against swine-derived multidrug-resistant Salmonella Typhimurium strains. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) were determined by broth microdilution. Interactions between both compounds were assessed by checkerboard assays using the fractional inhibitory concentration index (FICI). In addition, the modulatory effect of carvacrol on the expression of the tetracycline resistance genes tetA and tetB was evaluated to provide preliminary insight into the molecular basis of these interactions. Relative expression of tetracycline resistance genes was analysed by quantitative real-time PCR in selected isolates exposed to tetracycline alone or combined with carvacrol. Carvacrol MIC values ranged from 0.5 to 16 mg/mL, with MIC₅₀ and MIC₉₀ values of 2 and 4 mg/mL, respectively. MBC and MIC values were identical in 84.9% of the isolates, indicating a strong bactericidal effect. Tetracycline MIC₅₀ and MIC₉₀ values were 256 and 512 µg/mL, respectively. Checkerboard assays showed synergistic interactions in 14.3% of strains, additive effects in 50.0%, indifferent responses in 28.6%, and antagonism in 7.1%. Combined exposure reduced tetA and tetB expression in most tested isolates compared with tetracycline alone, although responses were strain-dependent. These findings demonstrate that carvacrol exhibits antimicrobial activity against swine-derived multidrug-resistant Salmonella Typhimurium and may enhance tetracycline activity in a subset of isolates under the experimental conditions evaluated, while modulating resistance-associated gene expression. These findings provide a basis for future transcriptomic and proteomic studies aimed at further elucidating the molecular mechanisms underlying the interaction between carvacrol and tetracycline.

Salmonella Typhimurium is an important pathogen affecting both animal production and public health, with pigs representing a major reservoir. The increasing prevalence of antimicrobial resistance highlights the need for alternative or complementary therapeutic strategies. Carvacrol, a phenolic constituent of Origanum vulgare essential oil, has recognized antimicrobial activity and may contribute to the modulation of antimicrobial resistance mechanisms. The present study investigated the antimicrobial activity of carvacrol and tetracycline, individually and in combination, against swine-derived S. Typhimurium strains. Minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC) were determined by broth microdilution. Interactions between both compounds were assessed by checkerboard assays using the fractional inhibitory concentration index (FICI). Relative expression of tetracycline resistance genes was analysed by quantitative real-time PCR in selected isolates exposed to tetracycline alone or combined with carvacrol. Carvacrol MIC values ranged from 0.5 to 16 mg/mL, with MIC₅₀ and MIC₉₀ values of 2 and 4 mg/mL, respectively. MBC and MIC values were identical in 84.9% of the isolates, indicating a strong bactericidal effect. Tetracycline MIC₅₀ and MIC₉₀ values were 256 and 512 µg/mL, respectively. Checkerboard assays showed synergistic interactions in 14.3% of strains, additive effects in 50.0%, indifferent responses in 28.6%, and antagonism in 1%. Combined exposure reduced tetA and tetB expression in most tested isolates compared with tetracycline alone, although responses were strain dependent. These findings demonstrate that carvacrol exhibits antimicrobial activity against swine-derived multidrug-resistant S. Typhimurium and may enhance tetracycline activity while modulating resistance-associated gene expression. Carvacrol could represent a promising natural adjuvant for antimicrobial control strategies in swine production.

Preservation protocols for donkey sperm are based on those developed for horses, despite potential interspecific differences in cooling tolerance. This study compared horse and donkey sperm during long‐term storage at 5°C and 17°C. Ejaculates from four stallions and four jacks ( n = 16) were centrifuged, resuspended in skimmed milk‐based extender, and stored at both temperatures. Sperm motility, plasma and acrosome membrane integrity, and morphology were evaluated after 1, 2 and 7 days. Fresh semen parameters showed no interspecific differences ( p > 0.05). At 5°C, donkey sperm showed reduced motility and membrane integrity from Day 1, whereas horse sperm parameters remained stable at both temperatures up to Day 2. After 7 days, horse doses stored at 5°C maintained significantly higher quality. In conclusion, donkey sperm was more sensitive to storage at 5°C than horse sperm, highlighting the need for species‐specific preservation strategies.

The aim of this study was to evaluate the effect of silver nanoparticles (AgNPs) on donkey sperm parameters and their antimicrobial efficacy on bacteria isolated in the presence of antibiotics. Nine donkey ejaculates were collected and stored in a skim‐milk extender at different AgNPs concentrations (0, 0.01, 0.8, 1.6 and 3.12 mg/mL) at 5°C or 17°C. Sperm parameters, including total and progressive motility (CASA), plasma membrane integrity (PMI) and reactive oxygen species (rROS) production, were evaluated at 0, 24 and 48 h of storage. Additionally, bacteria isolated from donkey semen extended with antibiotics were exposed to AgNPs to determine the minimum inhibitory/bactericidal concentrations (MIC/MBC). Sperm motility parameters were higher at 17°C than 5°C after 48 h. AgNPs showed a dose‐ and time‐dependent cytotoxic effect, with concentrations ≥ 0.8 mg/mL significantly reducing motility, membrane integrity and increasing rROS after 24 h. AgNPs exhibited bactericidal activity at concentrations between 1.56 and ≥ 25 mg/mL. In conclusion, while liquid storage at 17°C is an effective strategy for preserving donkey semen, the use of AgNPs as a standalone antimicrobial is currently limited by their cytotoxicity at effective bactericidal doses.

Bacterial contamination of donkey semen samples is a major concern due to its deleterious effects on sperm quality; this issue is exacerbated during semen storage. Therefore, evaluating the effect of antimicrobials on sperm is of utmost importance. This study identified microorganisms present in donkey semen and evaluated the antimicrobial activity of cinnamaldehyde, determined by the Minimum Inhibitory Concentration (MIC), and its effects on sperm quality. Fourteen semen samples from seven donkeys were analysed, identifying 31 bacterial isolates representing 21 different species. Cinnamaldehyde showed antimicrobial activity (MIC ₅₀ = 0.06 mg/mL; MIC ₉₀ = 4 mg/mL). Reactive oxygen species levels in sperm were decreased, suggesting an antioxidant effect. However, high concentrations of cinnamaldehyde reduced sperm motility. In conclusion, cinnamaldehyde is a promising antimicrobial for semen preservation; however, further studies are needed to ensure antimicrobial efficacy and sperm functionality.