Relationship Between Corn Vitreousness and Ruminal In Situ Starch Degradability

Abstract

The objective of this experiment was to determine the relationship between corn kernel vitreousness and ruminal in situ starch degradation. Fourteen U.S. and fiveBraziliancornhybridscultivatedintheirrespective countries were evaluated. The U.S. dent hybrids were harvested at one-half milk line, black layer, and 21 d after black layer stages of maturity. Brazilian flint hybrids were harvested only at the latest stage of matu- rity. Vitreousness was determined by manual dissec- tion of the kernels. Ruminal in situ degradation of starch was determined in three lactating Holstein cows fitted with ruminal cannulae. Vitreousness of the five mature Brazilian hybrids averaged 73.1% (range of 64.2% to 80.0%), while vitreousness of the 14 mature U.S. hybrids averaged 48.2% (range of 34.9% to 62.3%). Within the 14 U.S. hybrids, average vitreousness in- creased from 42.8% to 48.2% as stage of maturity pro- gressed from one-half milk line to 21 d after black layer. The correlation between kernel density and vitreous- ness was 0.87. The correlations between kernel vitre- ousness or density andruminal starch availability were −0.93 and −0.87, respectively. With advancing matu- rity, kernel vitreousness and density increased while ruminal starch availability decreased. Kernel vitreous- ness and density may be useful parameters for which to select corn hybrids for high ruminal starch availability. Density may be a more practical measurement than vitreousness for screening large corn data sets.