Maize breeding objectives have, for a long time, been limited to agronomic
criteria, but a high variability in nutritive value for ruminants also is o
bserved among hybrids. Nowadays breeding takes into account the effect of c
hemical composition in the modification of maize nutritional value. The amo
unt and composition of whole plant cell walls, especially their lignificati
on, influences both digestibility and voluntary intake when maize is given
as silage. Consequently, hybrids differ in their capacity to be utilized by
dairy and beef cattle. Starch, the main constituent of grain, is degraded
rather slowly in the rumen, and differences among genotypes exist. Among no
rmal maize hybrids, the differences are mainly related to grain vitreousnes
s, i.e. to the ratio of vitreous to floury endosperm which characterises fl
int and dent grains, respectively. Dent grains contain proteins that are mo
re degraded in the rumen. As a consequence, starch granules are more access
ible to microbial enzymes. Floury varieties obtained by mutation give rise
to extreme cases of dent varieties. Waxy and amylose-extender maizes, origi
nating from a mutation that modifies the ratio at amylose to amylopectin, a
lso show differences in their starch degradation rate. High-oil maize is no
w being developing. No specific problem occurs when high-oil maize is used
in ruminant feeding. Compared to other lipidic sources of the same composit
ion, maize lipids do not have particular consequences on either the efficie
ncy of production or the quality of products.