The present invention relates to a method for identifying a pepsin resistant alpha amylase enzyme for use in a feed supplement comprising: i) providing an alpha amylase enzyme ii) admixing said alpha amylase with corn based feed and buffer solution comprising a pepsin concentration of 9000 U/ml at pH 3, 40°C, 500 rpm for at least 120 minutes and analysing alpha amylase activity on said alpha amylase compared to a control sample wherein said control sample differs in that no pepsin is present during incubation and iii) selecting an alpha amylase enzyme which substantially maintains alpha amylase activity under the assay conditions feed supplements and feedstuffs comprising a pepsin resistant alpha amylase and the use of pepsin resistant alpha amylases in feed.La presente invención se refiere a un suplemento alimenticio, caracterizado porque es: a) un suplemento alimenticio para aves de corral que comprende una alfa amilasa resistente a pepsina o b) un suplemento alimenticio para animales monogástricos que comprende una alfa amilasa resistente a pepsina y por lo menos un portador fisiológicamente aceptable que se selecciona del grupo que consiste de maltodextrina , caliza (carbonato de calcio), ciclodextrina, trigo o un componente de trigo, sacarosa, almidón Na2SO4, talco, PVA, sorbitol, benzoato, sorbato, glicerol, sacarosa, propilenglicol, 1, 3-propanodiol, glucosa, parabenos, cloruro de sodio, citrato, acetato, fosfato, calcio, metabisulfito, formiato y mezclas de los mismos.
