## 5 Fermented Products and Quality of the Fat of Broiler Meat
The FP was added to the experimental group at a dose of 10%, with the proportion of CF being reduced by that amount. The FP was fed to the chickens from day 11 until the end of fattening (day 39). The results of the fatty acid composition profile of both breast and thigh muscle fat confirmed the tendency to increase GLA in meat fat [62]. However, the effect was not as much as was expected. This was related both to the low proportion of GLA in the feed of the experimental group and also to the fatty acid profile of the commercial feed as well as the fermented product itself. Maize meal was not a suitable substrate to increase the proportion of significant fatty acids via fermentation. However, the fermentation process significantly improved the nutritional parameters of corn meal; therefore, fermentation of corn by-products to improve their nutritional properties is a good way to recover them and use them for animal nutrition. Furthermore, due to the failure to significantly increase GLA in meat by feeding a fermented product prepared by the lower filamentous fungus _Umhelopsis isabellina_ on cornneal, a new fermented _Umhelopsis isabellina_ product was produced with wheat bran as the substrate. The final product, at a dose of 10%, was fed to chickens separately and in combination with agrimony extract (0.2% _Agrimonia euporia_, L.) [58]. The results confirmed the effect of the FP prepared in this way in increasing the proportion of GLA in the fat of chicken meat. The fermented product, at a dose of 10%, also had an effect on the composition of other fatty acids in the fat of the produced meat. The proportion of LA and DGLA increased in the fat of the breast muscles. In contrast, the proportion of stearic acid and PUFA (AA, EPA, DPA, and DHA) decreased significantly. This was also reflected by a slight increase in the proportion of saturated fatty acids and a decrease in n-3 PUFA. Subsequently, the n-6/n-3 PUFA ratio also increased slightly in the experimental group. All the previous experiments confirmed the possibility of influencing the fatty acid profile via the addition of a FP to broiler chicken feed. Thus, a significant influence on and increase of the proportion of GLA in the fat of the produced meat was obtained. Other PUFA (ALA, DGLA, EPA, DPA, DHA) can also be influenced in the fat of meat by fermented feed, but only if the fermented feed was fed at a proportion of 3 or 5%. At proportions of 10% and higher of the FP, the proportion of important PUFA in the fat of the produced meat began to decline. Therefore, it was necessary to search for a new species of lower fibrous fungus that would ferment cereal by-products and also produce other types of polyunsaturated fatty acids. Based on the previous experiments of the authors [PERSON] et al. [29], [PERSON] et al. [59], and [PERSON] et al. [62], a possibility of the use of an innovative FP in the diet of broilers was examined. The lower filamentous fungus, _Mortierella alynia_, was selected as a substrate for SSF. _Mortierella_ is a very good producer of EPA and AA [70]. To improve the production of EPA in the fermented product, linseed oil (a source of alpha-linolenic acid and ALA) was added to the substrate (wheat bran). The prepared FP contained 2.5% GLA, 6.6% ALA, 4.9% AA, but only 0.3% EPA. A significantly higher proportion of PUFA, n-3 PUFA, and a better n-6/n-3 PUFA ratio was also observed. Although _Mortierella alynia_ is described as a good producer of EPA via solid state fermentation [29; 71; 72; 73], which was partly confirmed by test results, good EPA production was not confirmed via fermentation of the product alone. Even after the addition of linseed oil, there was only partial production of this important acid, and the fermented product itself contained only about 0.3% EPA reflected by the fact that there were only traces of EPA in the feed of the experimental group after mixing 10% of the FP into the commercial mixture.