- Jamroz D, Wiliczkiewicz A, Wertelecki T, Orda J, Skorupinska J. Use of active substances of plant origin in chicken diets based on maize and locally grown cereals. Br Poult Sci. 2005;46:485-93 pubmed..were observed in the 41-d-old chickens from the supplemented groups. 6. An increase in the lipase activity in pancreas and intestine wall was found in older birds fed on the plant extract supplemented diets. ..