*Article* **The Effect of Low Doses of Zearalenone (ZEN) on the Bone Marrow Microenvironment and Haematological Parameters of Blood Plasma in Pre-Pubertal Gilts**

**Magdalena Mróz 1 , Magdalena Gaj˛ecka 1,\* , Katarzyna E. Przybyłowicz <sup>2</sup> , Tomasz Sawicki <sup>2</sup> , Sylwia Lisieska-Zołnierczyk ˙ <sup>3</sup> , Łukasz Zielonka <sup>1</sup> and Maciej Tadeusz Gaj˛ecki <sup>1</sup>**


**Abstract:** The aim of this study was to determine whether low doses of zearalenone (ZEN) influence the carry-over of ZEN and its metabolites to the bone marrow microenvironment and, consequently, haematological parameters. Pre-pubertal gilts (with a body weight of up to 14.5 kg) were exposed to daily ZEN doses of 5 µg/kg BW (group ZEN5, *n* = 15), 10 µg/kg BW (group ZEN10, *n* = 15), 15 µg/kg BW (group ZEN15, *n* = 15), or were administered a placebo (group C, *n* = 15) throughout the entire experiment. Bone marrow was sampled on three dates (exposure dates 7, 21, and 42—after slaughter) and blood for haematological analyses was sampled on 10 dates. Significant differences in the analysed haematological parameters (WBC White Blood Cells, MONO—Monocytes, NEUT—Neutrophils, LYMPH—Lymphocytes, LUC—Large Unstained Cells, RBC—Red Blood Cells, HGB—Haemoglobin, HCT—Haematocrit, MCH—Mean Corpuscular Volume, MCHC—Mean Corpuscular Haemoglobin Concentrations, PLT—Platelet Count and MPV—Mean Platelet Volume) were observed between groups. The results of the experiment suggest that exposure to low ZEN doses triggered compensatory and adaptive mechanisms, stimulated the local immune system, promoted eryptosis, intensified mycotoxin biotransformation processes in the liver, and produced negative correlations between mycotoxin concentrations and selected haematological parameters.

**Keywords:** zearalenone; low dose; bone marrow microenvironment; haematology; pre-pubertal gilts

**Key Contribution:** The administered ZEN doses and the duration of ZEN exposure were negatively correlated with three haematological parameters in pre-pubertal gilts.
