The aim of this study was to assess the toxic effects of zearalenone (ZEA) on the immune function. Ovariectomised rats were treated daily by gavage with 3.0 mg/kg of ZEA for 28 days. Body weight gain, food consumption, haemotological parameters, lymphoid organs, and their cellularities were evaluated. Moreover, acquired immune responses and macrophage activity were also assessed. ZEA promoted reduction in body weight gain, which is not fully explained by diminished food consumption. Despite no effect on haematological parameters, ZEA caused thymic atrophy with histological and thymocyte phenotype changes and decrease in the B cell percentage in the spleen. With respect to acquired and innate immune responses, no statistically significant differences in delayed-type hypersensitivity were noticed; however, in the ZEA-treated rats, antibody production and peroxide release by macrophages were impaired. The observed results could be related to ZEA activity on ERs; thus, ZEA is an immunotoxic compound similar to estrogen and some endocrine disruptors.

Antimicrobial growth promoters (AGPs) in animal production have been related to the increase in multidrug-resistant bacteria. The AGP ban in many countries has highlighted the growing need for alternatives for feed additives. Considering the non-antibiotic anti-inflammatory theory of AGPs, chicks received three different doses of sodium salicylate (SS) in feed (10, 30, 90 mg/kg), basal diet (BD) was used as a negative control, and zinc bacitracin (ZB) was used as a positive control. Chicks were individually housed to increase the accuracy of the dose of SS ingested. Performance parameters and footpad dermatitis were evaluated weekly, while haematology, serum biochemistry, histopathology, and tibial dyschondroplasia were determined on Days 21 and 42. A linear dose-dependent decrease in haemoglobin concentration was observed, but the values were within the normal reference range. Among all the other evaluated parameters, no relevant differences between treatments were observed; however, not even the AGP group performed better than the control group. It is possible that the conditions in which the birds were raised were not stressful enough to allow for anti-inflammatories to demonstrate their beneficial effects on performance. Studies should be conducted where the animals are exposed to commercial conditions, as the presence of natural stressors could allow a better evaluation of the efficacy of the anti-inflammatory agent as a growth promoter.

Repeated blood collection in long-term studies in rodents is challenging and may compromise animal welfare. Rabbits represent a robust alternative model for longitudinal studies due to their larger blood volume and ease of repeated sampling. However, standardized assays to assess rabbit immune function remain scarce. This study presents standardized and optimized flow cytometry–based protocols for evaluating oxidative burst, phagocytosis, and lymphocyte proliferation in rabbits. Oxidative burst and phagocytic activity were analyzed in heparinized whole blood using DCFH and fluorescently labeled Staphylococcus aureus. Lymphocyte proliferation was assessed in CFSE-labeled PBMC stimulated with ConA. Flow cytometric analysis enabled simultaneous quantification of reactive oxygen species (ROS) generation, phagocytic uptake, and CFSE dilution modeling. Following stimulation with S. aureus, rabbit heterophils exhibited ROS production in a median of 90.4% (IQR: 84.8–92.9%) of gated cells, with a median phagocytic uptake of 23.6% (IQR: 13.4–27.2%). PMA-stimulated cells showed near-complete oxidative burst (median 99.1%, IQR: 98.7–99.5%), confirming their functional similarity to mammalian neutrophils. Lymphocytes exhibited measurable proliferative responses to ConA, validating PBMC-based assays for adaptive immune assessment. These standardized methods offer a framework for investigating innate and adaptive immune functions in rabbits, contributing to immunotoxicological and safety evaluation studies.

This study characterized the long‐term pharmacokinetic profile of a 1% fipronil pour‐on formulation in Nellore bulls under field conditions. Seventeen animals received a single topical dose (1 mg/kg), and plasma concentrations of fipronil and its metabolites (sulfone and desulfinyl) were monitored for 175 days using LC–MS/MS. Fipronil was rapidly absorbed, reaching a maximum concentration C _max of 42.3 ± 4.1 ng/mL on day 1, but became undetectable by day 35. Conversely, fipronil sulfone was the predominant systemic analyte, reaching C _max 60.2 ± 5.6 ng/mL on day 13 and persisting for up to 140 days. The metabolite‐to‐parent AUC _{0– t} ratio (6.2) and the protracted terminal phase are consistent with flip‐flop kinetics, where systemic persistence is governed by slow release from the dermal/sebaceous reservoir rather than metabolic clearance. Fipronil desulfinyl was sporadically detected at low levels, confirming that in vivo photodegradation occurs on the animal's surface. These findings consolidate fipronil sulfone as the most reliable marker residue for food safety assessments. Furthermore, the sporadic detection of fipronil desulfinyl confirms that in vivo photodegradation occurs under field conditions, warranting further investigation regarding its contribution to residue dynamics in cattle.

In both aquaculture and scientific experimentation, fish handling often requires anesthesia to facilitate immobilization and minimize handling-associated disturbances. This study aimed to compare the anesthetic performance of different anesthetic agents in Astyanax lacustris, assessing induction, recovery, and safety to support protocol selection for tropical freshwater fish. A total of 114 yellowtail tetra Astyanax lacustris were used, including 54 fish in a preliminary experiment and 60 fish in the main experiment, with 10 fish per concentration in each anesthetic treatment during the main experiment. Fish were exposed to different concentrations of propofol (5.0 and 6.5 mg L⁻¹), eugenol (40 and 50 mg L⁻¹), and MS-222 (120 and 130 mg L⁻¹). Anesthetic efficacy and complementary physiological responses were assessed through induction and recovery times, responsiveness during recovery, opercular beat rate (OBR), hematological parameters, and plasma concentrations of glucose, lactate, and cortisol. Data were analyzed using analysis of covariance (ANCOVA) followed by appropriate post hoc tests (p < 0.05). All anesthetics successfully induced stage IV anesthesia at the evaluated concentrations, although distinct induction and recovery profiles were observed. MS-222 promoted significantly faster progression to deep anesthesia and shorter recovery times, whereas propofol induced prolonged recovery and marked reduction in OBR, with residual ventilatory depression after recovery. Eugenol showed an intermediate anesthetic profile associated with pronounced excitation during induction and an altered recovery pattern. Hematological parameters and plasma lactate concentrations did not differ significantly among anesthetic types or concentrations. Plasma glucose concentrations increased at higher anesthetic concentrations, whereas plasma cortisol concentrations differed significantly between propofol and eugenol groups (p < 0.05). Overall, the findings demonstrate that propofol, eugenol, and MS-222 produce distinct anesthetic and ventilatory responses in A. lacustris, highlighting the importance of selecting anesthetic protocols according to the intended experimental or handling procedure.

The use of morphine and methadone in patients with cancer is a subject of ongoing debate because of their potential to either stimulate or inhibit tumor cell proliferation in various types of cancers. This study investigated the effects of morphine and methadone on the growth of Ehrlich ascites carcinoma, a widely used mouse tumor model. Twenty-four hours after intraperitoneal tumor inoculation (2 × 106 cells), the animals were randomly allocated to one of seven groups (n=8): 5, 7.5, or 10 mg/kg morphine, 2.85, 4.4, or 5.7 mg/kg methadone, and Saline. The treatments were administered subcutaneously at 6-hour intervals over 9 days, with daily evaluations of body weight and abdominal circumference. The animals were then euthanized, and the ascitic fluid was collected for the analysis of fluid characteristics, total volume, tumor cell count, and cell cycle. The volume of the peritoneal ascitic fluid was lower in the 5 and 10 mg/kg morphine- and methadone-treated groups than in the Saline group. Both morphine and methadone increased the percentage of cells in the G1 phase than Saline group. This study suggests that morphine and methadone may modulate tumor growth and ascitic fluid dynamics, with potential antiproliferative effects.Cite this article as: Rusch, E., Bovi, M. F., Raspantini, L. E. R., Martinelli, E. C., Gorniak, S. L., Fukumasu, H., & Carregaro, A. B. (2025). Morphine and methadone reduce ascites and promote cell cycle arrest in mice with erlich’s tumor. Acta Veterinaria Eurasia, 51, 0055, doi: 10.5152/actavet.2025.24055.