Abstract: The invention relates to a method for the treatment of poultry or pigs, including non-therapeutic treatment of poultry or pigs. The treatment comprises orally administering at least one cellulose ester polymer to poultry or pigs in an amount between 0.1 and 10 kg/ton of dry weight of a feed, wherein more than 50% moles of recurring units of the (CE) polymer are recurring units (RCE) of formula (I) as shown below: wherein each of R, equal to or different from each other, is H or an acyl group of general formula —(C?O)—R1 wherein R1 is an alkyl group having from 1 to 10 carbon atoms, and wherein the (CE) polymer has a total acyl group content [TAG content, herein after] of at least 5 weight percent (wt. %), relative to the total weight of the (CE) polymer.