Over recent years, many new maize hybrids (such as sweet maize, waxy maize, high oil maize and fodder maize) have been developed to supply fresh maize grain for human consumption or supply feed for livestock. The by-products from maize grain processing or maize stover after maize grain harvested are one of the most important sources of feed for ruminant production, especially in the areas where high quality fodder is not sufficient. Making full use of these by-products will contribute to resolve the problems of feedstuff resource inadequacy in China. 

Variety, seedtime and maturity stage influenced nutritive value of maize stover greatly. Available literature is limited for assessing seedtime influence on stover quality, and nutritive value of maize stover generally decreased with the increase of maturity stage, but it increased for some newer genotype maize stover. In the first study, in vitro gas production and in situ degradation techniques were used to estimate the effects of variety of maize, seedtime and maturity stage on nutritive value of maize stover. Results shown that crude protein (CP) and fiber contents decreased with increasing maturity stage. Maize sown in spring had greater (P < 0.05) CP and fiber contents than that maize sown in summer. In vitro fermentation parameters were affected (P < 0.05) by maize variety and seedtime. High oil maize variety had the lowest EDDM and EDNDF. Advanced stage increased (P < 0.01) ADM, ANDF and EDNDF, but decreased (P < 0.05) LDM and BNDF values of stover. Maize sowing in summer had greater (P < 0.05) ADM, BDM, EDDM and EDNDF, but lower (P < 0.01) CDM, ANDF and LNDF values than that maize sowing in spring. The overall results suggested evidence of varietal differences in stover quality. Chemical composition and incubation parameters response to two or three way interaction effects among variety, seedtime and maturity suggested effective seedtime, variety and harvest date management practices for sustainable maize stover.

The second study was conducted to estimate the effect of maize endosperm type, e.g., waxy, conventional, fodder, sweet, and high oil, and maturity stage on chemical composition and in vitro fermentation characteristics of morphological fractions. The Results showed that the proportion of leaf blade, leaf sheath and husk, and crude protein (CP) and phosphorus (P) contents decreased, whereas the proportion of stem and fibre content increased with the increasing of maturity stage. High oil, sweet, fodder and conventional had the highest proportion in leaf blade, leaf sheath, stem and husk, respectively. Leaf blade had the highest CP and P contents and husk had the highest neutral detergent fibre content. Conventional had the highest (P < 0.05) acid detergent fibre content but the lowest (P < 0.05) CP content than the others. Fodder and high oil had the highest P and organic matter (OM) content. In vitro gas production parameters of b, a+b, in vitro OM disappearance (IVOMD), and concentrationof total volatile fatty acid (TVFA) decreased (P < 0.05) with the increase of maturity. Maize stover parts from waxy variety had the highest values of b, c and a+b, whereas the morphological fractions from conventional variety had the highest IVOMD. The morphological fractions differed in c value and potential gas production in the following order: husk > leaf sheath > stem > leaf blade. The highest and lowest values of IVOMD were observed in husk and stem, respectively. The highest TVFA concentration, molar proportion of acetate and propionate were noted in high oil, waxy and sweet, respectively. The result indicated that the nutritive value of maize stover could be improved through the selection of endosperm type and appropriate maturity stage. (Tang et al. J. Anim. Feed Sci. 2009)

In the third study, five morphological fractions (leaf blade, leaf sheath, stem, husk and cob) of stover of five maize genotypes, namely waxy, conventional, fodder, sweet and high-oil maize, respectively, were used to test the effects of genotype and morphological fractions on chemical composition and in vitro fermentation characteristics. The waxy maize had a higher (P < 0.05) stem but lower (P < 0.05) leaf blade proportion and fodder maize had a higher (P < 0.05) leaf blade but lower (P < 0.05) leaf sheath proportion than other genotypes, respectively. Maize genotype had a significant effect (P < 0.001) on the chemical composition of stover parts except for organic matter (OM) concentration. Chemical composition of stover parts was affected (P < 0.001) by morphological fractions. The interaction effects between genotype and morphological fraction on the fiber content of stover parts were significant. Over 0.40 and 0.50 of phosphorus (P) and crude protein (CP) of whole-plant maize stover were averagely contributed by leaf blade. Leaf blade, stem and cob contributed over 0.75 of OM, CP, P and fiber in the whole plant. There were significant effects of genotype and morphological fraction on both in vitro gas production parameters and in vitro organic matter disappearance of maize stovers. The genotype and morphological fraction of maize stover and their interaction had significant effects on NH3-N and total volatile fatty acid concentration and the molar proportion of volatile fatty acid in the supernatant after 72 h of incubation except for valeric acid. The present data indicated that the genotype and morphological fraction of maize resulted in variation in the nutritive value of maize stover. (Tang et al. Animal, 2008)