In nature the excessive quantities of olive leaves and cake as by-products in the production of oil represent an ecological problem as they can inhibit the activity of microorganisms present in the environment due to the presence of phenolic compounds. Because of the compounds contained in olive leaves and cake and due to their favorable effects on the utilization of nutrients, they could be used as animal feed. The main objective of the study was to examine the influence of olive leaves and cake on the utilization of nutrients and energy in pigs. 24 growing pigs were included in the balance test and divided into three experimental groups. The first group was a control group (Kont), the diet of the second group was supplemented with 7.5% of dried olive leaves (Listi) and the third group was supplemented with 7.5% of dried olive cake (Tropine). During the experiment we monitored the feed intake and the excretion of nutrients with feaces and urine. The results showed that olive leaves and cake in compound feed adversely affected the daily growth and final weight of the animals. Animals that had leaves or cake in their diet digested dry matter, organic matter and gross energy less efficiently, while crude fat digestion was only worse with the feed containing leaves. Digestion and the utilization of crude protein were also negatively affected. The cake also had negative effects on digestion of neutral detergent fibre and acid detergent fibre. Olive leaves had negative effects on the digestion of Ca and Cu, while the digestion and utilization of Cu were also negatively affected in the group with olive cake.
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