MINERAL LEVELS IN WINTER FORAGES FOR BEEF CATTLE
Mineral supplementation is an important and often expensive part of a good
manage ment program for beef cattle. Recent research at NCSU and elsewhere has
understand ing of mineral function, and the requirements of different ruminant animals.
this, supplemen tation recommendations are difficult because little is understood about
minerals present in the forages we produce in North Carolina. Many of our ideas about
supplementation come from research conducted in the western states. Supple ments
designed for use in other areas of the country may not be the best for use in North Caro
because of the great differences in our forages and feeding practices. To improve our
ommendations, efforts are underway to evaluate minerals levels in different areas of the
This paper describes a study that evaluated winter forages on North Carolina beef
in the winter of 1992-1993. Because little is known about how fertilization practices
mineral levels in forages, samples were taken from well managed farms utilizing either
conventional fertilization, or fertilization with poultry litter or municipal sludge.
Materials and Methods
During the winter of 1992-1993 (October to February), samples of forages were
from 29 different sites on 16 farms in 12 different counties, primarily in the Piedmont.
of the samples were of stockpiled fescue, and 15 were of hay. Sixteen of the samples
produced with commer cial fertilizer (8 stockpiled fescue and 8 hay), and 13 were
poultry litter or sludge (6 stock piled fescue and 7 hay). The samples were analyzed by
commercial lab for the minerals of major impor tance including molybdenum (with the
of selenium.) The mineral levels in the forages were compared to the requirements of
average lactating cow to determine which minerals were most limiting. The level of
mineral in forages produced by the two different systems were com pared using
analysis of variance.
Results and Discussion
Mineral requirements, mineral levels mea sured, and the percentage of samples
requirement are given in Table 1. The type of for age
stockpiled fescue) did not influence mineral levels. Considering all the samples, the
minerals were sodium, magnesium, zinc, copper, phosphorus and calcium in that order.
other minerals were high enough such that supple mentation should not be needed.
The minerals that were influenced by fertil ization practice were phosphorus,
so dium, zinc, and molybdenum. The differences were great enough to suggest that we
different recommendations for these two different types of systems. Of the
fertilized samples, 43% were below the phosphorus requirement, while only 8% of
the waste sites were below the phosphorus requirement. Potassium level was elevated
waste sites as well, which may be why grass tetany is so prevalent on these sites. A
high level of
potassium in forages has been shown to be related to a high incidence of this condition.
These data are useful, but additional efforts are underway to further evaluate
levels in forages during different seasons and on a wider variety of farms before
recommendations are altered.
This study showed that the limiting minerals in the forages sampled were sodium,
magnesium, zinc, copper, phosphorus and calcium in descending order. Phosphorus
deficient in many samples from the conventional sites, but not from the waste sites.
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