Nutritional adequacy of permanent forages.

 The nutritional quality of permanent forages is affected by type of soil,
type of forage, fertilization program, degree of grazing, maturity of forage,
amount of rainfall and season of the year. For example, differences exist in
the chemical composition of pasture grasses on organic soils and mineral soils.
Generally, the crude protein of well-managed grass on organic soil will seldom
fall below 10 percent on a dry matter basis. On mineral soils unless grasses
are provided heavy nitrogen application or planted with legumes the crude pro-
tein will more often be less than 10 percent and this will decrease sharply in
fall and winter months. Differences in mineral analyses also exist between
grasses grown on the two types of soils.

 Differences exist in the productivity of grasses, both on organic and
mineral soils. Also legumes have a different productivity. Grass-legume mix-
tures, on sandy soils, generally will provide an increase in amount of avail-
able dry matter, crude protein and phosphorus per acre, resulting in greater
production per cow, than will grass alone.

 Carrying capacity of permanent grasses is greatly reduced during
fall and winter months, both on organic and mineral soils. If cattle are not to
be penalized during this period inventories must be reduced or supplemental feed
provided. Changes in plant maturity coincide with the fall and winter months
and unless nitrogen application or legumes are used on mineral soils the protein
content of the grass will decrease, fiber content will increase and total
digestible nutrients will decrease. Unless supplemental nitrogen is provided
the protein content of permanent grasses on mineral soil should be conr:~.dered
nearly undigestible in the fall and winter months. Grass pastures on ,organic
soils, if not severely damaged by cold, drowth or excessive rainfall, will not
have as large a change in chemical composition as those on mineral coils. How-
ever, carrying capacities will be reduced 60 to 65 percent. Under extreme con-
ditions protein and energy may both be limiting factors on organic soils but
generally it would appear that energy is the most important to consider in a
supplemental feed for cattle.

 The nutritive value of pasture forages is difficult to assess. Chemical
analyses of the forage can be used as an index. Another factor to consider is
the leaf-stem ratio. The digestibility of the forage is closely related to the
ratio of leaf to stem.. More leaf than stem usually indicaies a relatively
high digestibility. More stem than leaf usually indicates low digestibility.