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The objective of this study was to evaluate the effect of HMB on selected indicators of immunity in calves. The experiment was performed on 14 calves aged 30±2 days, divided into two equal groups of control (group I) and experimental (group II) animals. The feed administered to experimental group calves was supplemented with HMB at 40 mg/kg BW, whereas control calves were administered standard farm-made feed without supplementation. Blood was sampled from the jugular vein immediately before the experiment (day 0) and on experimental days 15, 30 and 60 to determine the following parameters of immunity: proliferative response of LPS-and ConA-stimulated lymphocytes (MTT), respiratory burst activity (RBA) and potential killing activity (PKA) of phagocytes. The results revealed a significant increase in RBA and MTT values in calves administered HMB in comparison with the control group throughout the experiment. In the group of animals receiving HMB, an increase in PKA values was noted only on day 30.

In this study two analytical methods, one based on matrix solid phase dispersion (MSPD) and the other on liquid–solid extraction (LSE), coupled with gas chromatography, were evaluated and used to determine the presence of 163 pesticides (6 acaricides, 62 fungicides, 18 herbicides and 77 insecticides) in various herbs. Both methods were optimized considering different parameters (sample to sorbent mass ratio, extracting solvent, sorbents for clean-up step, etc.). The results of these validated sample preparation procedures were compared. Under optimum conditions, the mean recoveries obtained were in the range of 70–119 % for MSPD for most pesticides and 70–118 % for LSE, but with several exceptions. Precision values, expressed as relative standard deviation (RSD), were ≤16 % for MSPD and <18 % for LSE. Correlation coefficients were higher than 0.99254 for both methods. LODs (limits of detection) and LOQs (limits of quantification) for MSPD were within the ranges of 0.003–0.03 and 0.005–0.04 mg/kg, respectively. The data demonstrate that the MSPD method was successfully used for the analysis of 163 pesticides in the following herbs: chamomile (Matricaria chamomilla L.), linden (Tilia), lungwort (Pulmonaria L.), melissa (Melissa L.), peppermint (Mentha piperita L.) and thyme (Thymus vulgaris L.). This paper indicates the potential of MSPD for qualitative and quantitative analysis of pesticide residues. This method was therefore validated at three spiking levels (the first ranging from 0.005 to 0.05 mg/kg, the second from 0.05 to 0.5 mg/kg and the third from 0.25 to 2.5 mg/kg) and applied to real samples (n = 15). MSPD proves to be a simple, fast and very useful multiresidue method and can be recommended for routine pesticide monitoring studies in various herbs.