Effect of various doses and forms of selenium (organically bound vs. inorganic) on selected parameters of ruminal fluid and blood in sheep was evaluated. The trial was performed with 15 sheep divided into two groups. Animals from group A (n = 8) received a feeding mixture with selenomethionine, while sheep from group B (n = 7) were fed a mixture with sodium selenite. During the first 14 days, animals from both groups were fed a mixture with optimum dose of selenium (1 mg Se/kg dry matter). For another 28 days, all experimental animals received a Se-deficient mixture (0.1 mg Se/kg dry matter), whereas in the last 21 days of the experiment, animals were fed a high-Se diet (5.0 mg Se/kg dry matter). Throughout the trial, 4 samples of blood and ruminal fluid were taken from each animal. The samples of ruminal fluid were analyzed to determine the concentration of Se and identify other parameters of ruminal fermentations. Selenium levels were also determined in ruminal biomass. In blood, Se concentration, glutathione peroxidase (GSH-Px) activity, and other selected biochemical parameters were measured. The results of the present study demonstrate that the actual intake of both organic and inorganic Se is reflected in Se concentration in ruminal fluid and ruminal biomass and, similarly, in Se content and GSH-Px activity in blood. The form of supplemented selenium did not have a significant effect on ruminal fermentation parameters in dependence on different doses of Se contained in feeding rations (except for the negative effect of a sudden start of feeding high levels of organically bound Se on infusoria count, which was accompanied by the increase of GMT, LDH, and AST enzymes activity in ruminal fluid). The results also suggest possible negative interaction between the intake of organically bound selenium and the concentration of copper in blood of sheep.

The aim of this trial was to compare the effect of long-term supplementation of goats with different forms of selenium on body reserves of selenium in their kids at the time of weaning. Thirty-three pregnant goats were divided into five groups. Group C was control while the other four groups were supplemented with selenium (Se) for 6 weeks before parturition (0.3 mg/goat/day) and after parturition (0.9 mg/goat/day). Group "Se-I" received sodium selenite and three other groups received organic forms: "Se-L," lactate-protein complex; "Se-P," Se-proteinate; and "Se-Y," Se-yeast. The kids were weaned at 3 months of age and samples of tissues (liver, pancreas, myocardium, lungs, kidneys, spleen, thigh, tongue, and diaphragm) were taken after slaughtering. The long-term supplementation of goats with Se influenced Se concentration in all examined tissues of kids. Significant differences (p≤0.01) were found between the control and all experimental groups, except for the renal cortex and pancreas (Se-I). The average increase of Se concentration in overall examined tissues in comparison with the control (100%) was as follows: Se-Y, 192%; Se-P, 167%; Se-L, 161%; Se-I, 144%. The highest efficiency was found in the group supplemented with Se-yeast with a high content of selenomethionine, also the other two organic forms of Se were more efficient than the inorganic form.

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