For many years, ionophores have been used to control coccidiosis in poultry. However, misuse of ionophores can cause toxicity with significant clinical symptoms. The most critical factors influencing ionophores’ toxicity are administration dose, species, and animal age. Although clinical signs of ionophore intoxication are well studied, the toxicity mechanisms of the ionophores at the molecular level still are not fully elucidated. This review summarizes the studies focused on polyether ionophores toxicity mechanisms in animals at the clinical and molecular levels. Studies show that ionophore toxicity mainly affects myocardial and skeletal muscle cells. The molecular mechanism of the toxication could be explained by the inhibition of oxidative phosphorylation via dysregulation of ion concentration. Tiamulin-ionophore interaction and the synergetic effect of tiamulin in ionophore biotransformation are discussed. Furthermore, in recent years ionophores were candidates for reprofiling as antibacterial and anti-cancer drugs. Identifying ionophores’ toxicity mechanisms at the cellular level will likely help develop novel therapies in veterinary and human medicine.

The effect of effective microorganisms (EM) on internal organ morphology, intestinal morphometry, and serum biochemical activity in Japanese quails under Clostridium perfringens challenge was determined. After 30 days of EM addition, one group of quails was orally inoculated with Clostridium perfringens. The second group did not receive EM and was inoculated with C. perfringens. In the gut, EM supplementation reduced the number of lesions, enhanced gut health, and protected the mucosa from pathogenic bacteria. EM showed an anti-inflammatory effect and fewer necrotic lesions in villi. In the internal organs, EM showed a protective effect against a typical lesion of C. perfringens infection. Necrosis and degeneration of the hepatocytes, necrosis of bile ducts, and bile duct proliferation were more severe in the infected group without EM. Morphometric evaluation showed significantly higher villi in the jejunum after EM addition. A greater crypt depth was observed in the C. perfringens group. Biochemical analysis of the blood indicated lower cholesterol on the 12th day of the experiment and between-group differences in total protein, lactate dehydrogenase (LDH), and albumin levels in the EM group. Further studies are needed to improve EM activity against pathologic bacteria as a potential alternative to antibiotics and to develop future natural production systems.

Cardiovascular diseases occur frequently in domesticated and aviary birds. Reference data on various heart variables are crucial to obtain a proper diagnosis, but the literature on wild birds is extremely sparse or non-existent. Here, we present heart and body morphometric traits of a medium-sized gull, the Black-headed Gull Chroicocephalus ridibundus, in relation to age and sex. The majority of the studied variables increased with age, reflecting the organism’s growth and development. However, heart proportions were usually the highest in chicks and similar in fledglings and adults. In adults, all external biometrical variables were higher in males than in females, except for body mass and total body length. Adult females had significantly higher values of numerous heart size parameters than males. Among all studied external biometric traits, only total head length and wing span were significantly related to fresh heart mass and increased with increasing heart mass. This study provides the first comprehensive reference dataset to support veterinarians in diagnosing pathological changes and anomalies in Black-headed Gull heart development.

Cross-contamination of poultry feed with antimicrobials may cause unintended exposure to residual antibiotic doses, but the immunological consequences remain unclear. We tested whether six antimicrobials (colistin, doxycycline, flumequine, thiamphenicol, tiamulin, and tilmicosin) delivered in feed at 2% of the maximum approved dose modulate immune-related gene expression and splenic histology in broiler chickens. Female Ross 308 chicks received antibiotic-contaminated diets throughout the rearing. Spleen and caecal mucosa were sampled on days 7, 21, and 35, and analyzed by RT-qPCR. Spleen was sampled on day 35 for histopathology. Responses were strongly time- and tissue-dependent, with the largest effects on day 21. In spleen, selected antimicrobials showed selective down-regulation of IL-2, IL-4, IL-6, IL-8, IL-12p40, and IFN-ß, while IFN-γ was significantly up-regulated (p ≤ 0.05). In caecal mucosa, transcriptional modulation was weaker and more limited. Significant changes were restricted to MUC2 on day 21 and to IL-2 and IL-8 on day 35 (p ≤ 0.05). Splenic histopathology showed unchanged lymphatic nodule counts, but increased lymphoid atrophy, necrosis, and inflammatory infiltrates, most frequently in colistin- and doxycycline-fed birds. Overall, residual antimicrobials in feed are not biologically neutral and are associated with distinct structural changes in immune-related gene expression and splenic tissue development.