The contamination of feed with mycotoxins results in reduced growth, feed refusal, immunosuppression, and health problems. Deoxynivalenol (DON) and zearalenone (ZEN) are among the most important mycotoxins. The aim of the study was to examine the effects of low doses of these mycotoxins on the histological structure and ultrastructure of the large intestine in the pig. The study was performed on 36 immature gilts of mixed breed (White Polish Big × Polish White Earhanging), which were divided into four groups administrated per os with ZEN at 40 µg/kg BW, DON at 12 µg/kg BW, a mixture of ZEN (40 µg/kg BW) and DON (12 µg/kg BW) or a placebo. The pigs were killed by intravenous overdose of pentobarbital after one, three, and six weeks of treatment. The cecum, ascending and descending colon samples were prepared for light and electron microscopy. Administration of toxins did not influence the architecture of the mucosa and submucosa in the large intestine. ZEN and ZEN + DON significantly decreased the number of goblet cells in the cecum and descending colon. The mycotoxins changed the number of lymphocytes and plasma cells in the large intestine, which usually increased in number. However, this effect differed between the intestine segments and toxins. Mycotoxins induced some changes in the ultrastructure of the mucosal epithelium. They did not affect the expression of proliferative cell nuclear antigen and the intestinal barrier permeability. The obtained results indicate that mycotoxins especially ZEN may influence the defense mechanisms of the large intestine.

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Summary The avian pineal is a photosensory organ taking part in the organization of circadian and seasonal rhythms and playing an important role in the regulation of many behavior and physiological phenomena. The morphology of the pineal organ shows an enormous diversity. The aim of study was to investigate the histology and ultrastructure of the pineal organ in the Muscovy duck (Cairina moschata). The study was performed on 14-week-old females kept under natural lighting. The investigated pineals consisted of a wide distal part and narrow middle and proximal parts. The proximal part was attached to the diencephalon via the choroid plexus. The light microscopy showed a mixed structural form of the organ, which comprised both tubulo-follicular and solid parts. The stroma contained the lymphatic tissue, which occurred in a diffused form and as lymphoid nodules. Electron microscopy revealed the huge complexity of the parenchyma architecture, caused by the presence of several lumen-containing structures. According to their size and shape, they were classified into classical follicles, canals (diameter > 1 m) and canaliculi (diameter < 1 m). Pinealocytes were characterized by high variability of their shapes and sizes, frequently occurring partial or total reduction of the apical protrusions and presence of extremely numerous microtubules. The supporting cells constituted a prominent part of the pineal parenchyma and were represented by ependymal-like cells and astrocyte-like cells. Ependymal-like cells limited the lumen of follicles, canals and canaliculi.

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