## 4 Fermented Products in Chicken Nutrition
The results of the experiment confirmed the positive effect of the addition of the FP on the growth parameters of the chickens. Lower feed consumption, higher final weight, and better feed conversion was observed compared to the control group. In another experiment, broiler chickens of hybrid Cobb 500 were fed 5% fermented feed [40]. The FP was prepared via SSF fermentation using the lower filamentous fungus _Cunningham elegans_; however, spelt bran was used as the substrate. The product produced was energetically superior to commercial feed (CF), containing more fibre but mainly GLA (8.5%). The FP was added to the feed of chickens from day 20 of fattening, with a total fattening period of 35 days. The results clearly showed a significantly lower feed consumption in the experimental group (\(p<0.05\)), higher final weight, and better feed conversion rate. In further conducted experiments, the proportion of fermented feed was increased to 10%, reducing the amount of CF by this amount. The FP were prepared with a higher proportion of GLA and betacarotene or GLA, ALA, EPA, and AA. In one of the experiments, the fermented feed was prepared by fermenting corn meal (waste from corn processing) using the lower filamentous fungus _Umbelopsis isabellina_[55]. The fermented feed was fed to Cobb 500 hybrid broiler chickens from day 10 to day 38 of fattening. Replacing 10% of the CF with the fermented product did not have a negative effect on growth parameters. Feed consumption was slightly lower in the experimental group, but feed consumption and conversion were statistically insignificantly higher. A positive effect of the addition of the FP on the haematological and immunological parameters of chickens was also recorded [56]. Lower total and LDL-cholesterol values were measured in blood samples of the experimental animals (\(p<0.05\)). Significantly higher levels of the haematocrit and haemoglobin and a lower number of eosinophils and basophils were recorded in the experimental group (\(p<0.05\)). The experimental group also showed higher numbers of B lymphocytes and a greater phagocytic capacity (\(p<0.05\)) [41; 57]. The effect of adding the FP in a concentration of 10% alone and in combination with agrimony extract (0.2%; _Agrimonia eupatoria_, L.) on growth parameters of chickens was investigated in another experiment [58]. The fermented product was prepared by fermentation of wheat bran using the lower filamentous fungus _Cunningham echinulata_[25]. Although replacing 10% of the CF with the fermented product had reduced feed consumption (\(p<0.05\)), final chick weights and gains were not affected in the experimental group as reflected in the slightly better feed conversion rate compared to the control group (1.57 and 1.60; \(p>0.05\)). A more pronounced effect on gain and final weight of chicks was observed with the feeding of a FP with agrimony extract, which led to the highest recorded final weight of chicks and lower feed consumption as well as feed conversion rate compared to the control group. On the contrary, feed consumption was higher (\(p<0.05\)) compared to the experimental group when the FP was fed alone. These experiments also confirm that SSF using lower filamentous fungi can recover by-products and prepare a complete feed component for broiler chicken diets. A new type of fermented product with a higher proportion of essential fatty acids (GLA, alpha-linolenic acid--ALA, arachidonic acid--AA, and eicosapentaenoic acid--EPA) was prepared in another experiment. The _Mortierella alpina_ strain was used for fermentation as a producer of AA and EPA. Wheat bran was used as a substrate for fermentation; to increase the production of EPA in the feed, 1% linseed oil was used. The resulting product contained 2.19% GLA, 6.67% ALA, 0.33% EPA, and 4.93% AA [59]. The fermented product was added to the experimental group's feed at a rate of 10% and the proportion of commercial feed was reduced by this amount.