- Copper deficiency and Mo-induced Cu deficiency are nutrition
problems of ruminant livestock in the Burns and Klamath Falls area
of Oregon. Chemical analysis of plant and soil samples was used to
survey Cu and Mo levels in forage in these areas. The objectives
were to assess the possibility of animal nutrition problems and to
study the relationship between forage levels of Cu and Mo and plant
species, stage of plant maturity, time of growing season, management
factors, and soil characteristics.
A total of approximately 400 plant samples was collected during
the 1972 grazing season. The samples from Burns were taken from
an alfalfa maturity experiment, improved pastures, native meadows,
and a forage nursery. The legumes sampled were alfalfa (Medicago
sativa), Ladino clover (Trifolium repens), and sainfoin (Onobrychis viciaefolia). Grasses sampled were Fawn tall fescue (Festuca
arundinacea), Manchar brome (Bromus inermis), Greenar and Oahe
intermediate wheatgrass (Agropyron intermedium), wildrye (Elymus
triticoides), Rush (Juncus sp.), and Sedge (Carex sp.). The Klamath
samples were from an Alta tall fescue (Festuca arundinacea)-quack-grass (Agropyron repens) comparison and from 13 sites on a variety
of pastures throughout the area. In addition to alfalfa, clover, sedge,
rush, Alta fescue and quackgrass, the species sampled were Kentucky
bluegrass (Poa pratensis), orchardgrass (Dactylis glomerata), and
meadow foxtail (Alopecuris pratensis). Most of the sites were clipped
periodically to simulate grazing and were sampled at two week
intervals from May through August.
Plant analysis was valuable for indicating the type of livestock
nutrition problem encountered in a particular area. The Burns forage
contained high levels of Mo and a Mo-induced Cu deficiency is probable.
The survey in the Klamath area identified two sites on muck soils with
potentially toxic Mo levels. Several sites had such low Cu levels that
uncomplicated Cu deficiency may be a problem in livestock. A wide
range of values was encountered and forage analysis would be valuable
for identifying problems on a local basis.
Large differences were found in Cu and Mo levels between plant
species. Legumes contained much higher levels of Cu and Mo than
did grasses. Changes in maturity, or clipping interval, had different effects on Cu and Mo content for grasses and legumes. Alfalfa was
found to decrease in Cu and Mo content with increased maturity.
However, legumes in pastures maintained relatively constant levels
through the grazing season. Many grasses were found to decrease
markedly in Cu levels, and some to increase in Mo levels as the
season progressed. This may result in a reduction in the Cu/Mo
ratio through the season.
Forage analysis was shown to be a valuable technique for
identifying potential Cu and Mo livestock nutrition problems and for
investigating environmental and management factors which may
regulate Cu and Mo levels in forage plants.