Influence of the protein distribution of maize endosperm on ruminal starchdegradability

This study was aimed at determining the influence of the protein distributi on of maize endosperm on ruminal starch degradation using 14 maizes differi ng in endosperm texture (eight dent and six flint maizes). Ruminal starch d egradability was determined by an in situ technique on ground samples with a particle size of 3 mm. The distribution of endosperm proteins was assayed by a method based on their differential solubilities in solvents. The (alp ha,beta,delta)-zeins and the true glutelins were the predominant proteins i n the endosperm. The (alpha,beta,delta)-zeins (66.1 and 70.1 g kg(-1) of re covered protein for dent and flint types respectively) and the true gluteli ns (21.8 and 18.4 g kg(-1) of recovered protein for dent and flint types re spectively) were related to the vitreousness, ie the ratio of vitreous to f loury endosperm. Ruminal starch degradability averaged 619 and 462 g kg(-1) for dent and flint maizes respectively. It was correlated negatively with the (alpha,beta,delta)-zeins and positively with the true glutelins. The (a lpha,beta,delta)-zeins located in the protein bodies should limit the acces sibility of starch granules to ruminal micro-organisms and, as a consequenc e, the ruminal starch degradability. (C) 2000 Society of Chemical Industry.