ANIMAL FEEDS AND FEEDING 143
 MINERALS FOR CATTLE
 Cattle require quality, quantity, and balance of digestible nutri-
ents to perform normally. However, if there are mineral
deficiencies, mineral toxicities, or abnormal balance of minerals
in the feed ration, the benefits of balanced nutrient intake are
not sufficient to allow the animal to produce the maximum poten-
tial of its inherited capacity. Deficiencies or toxicities from trace
elements cause ill health or disease, and we know that unhealthy
cattle are not efficient in their ability to use the nutrients in their
feed ration. The cow is capable, within reasonable limits, of ad-
justing her intake of mineral elements, and producing some of
the essential vitamins through bacterial action in her rumen. This
capacity is limited when certain elements are not present in ade-
quate amounts or when some elements are present in quantities
which constitute an overdose or toxic level. This subject is thor-
oughly discussed in Morrison's Feeds and Feeding.4
 Analyses records of Costa Rican forages for minerals are very
limited. For best study of this subject, several hundred forage
samples should be carefully prepared and analyzed. A start was
made in 1953 when Romano Orlich and George K. Davis5 took
40 forage samples, prepared them in the El Alto laboratory, and
sent them to the University of Florida, Gainesville, for analysis.
The results follow.
 1. All 40 samples were very low in magnesium, representing
approximately one-tenth of what is considered normal in forage.
 2. Most of the samples contained normal to slightly high content
of copper.
 3. While 2 parts per million is considered a toxic level of molyb-
 denum, these samples showed levels from less than one to as high as
 9.8 parts per million.
 4. Of the 40 samples:
 40 were low in magnesium
 22 were high in molybdenum-more than 2 ppm.
 12 were low in phosphorus-less than 0.2 per cent.
 7 were high in manganese-more than 100 ppm.
 5 were low in copper-less than 10 ppm.
 2 showed less calcium than phosphorus.