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Most
livestock producers know that animals can spread seed. The most common
way this happens is when livestock consume seed while grazing, then
deposit droppings that contain seed at various points where they wander.
This
brings to mind the idea that it might be feasible to feed seed to
livestock (perhaps mixed with a ground feed material) for the purposes
of introducing certain forage species into pastures or increasing their
population. Dr. W.R. Ocumpaugh, a professor with Texas A&M
University, has studied distribution of seed by livestock in recent
years, and the remainder of this article is based primarily on his
findings.
Cattle
begin excreting seed within 10 to 12 hours after they are consumed, and
in most cases all the seed consumed will have been excreted within 72
hours after ingestion. A single cow will defecate 10 to 12 times daily,
so the potential for a group of cattle distributing seed in numerous
places over a pasture is rather high. However, whether this actually
results in increasing forage plant populations depends on several
factors.
The level
of seed survival in the digestive tracts of animals varies greatly.
While seed survival of some forage species is high, virtually all the
seed of other species will be digested or will not be viable (capable of
germinating) after leaving the digestive tract. Most cool season forage
grasses such as tall fescue have poor seed survival, while seed survival
of some warm season forages such as bahia grass (which has a protective
waxy seed coat) is quite good.
In
legumes, the trait required for survival in an animal’s digestive
system is hardseededness. Virtually all legume seed that are not
"hard seed" will be digested, and end up being nothing more
than expensive protein supplementation. Unfortunately, the percent of
hard seed for most legumes is no more than 15 to 20 percent. Also,
legumes require infection with Rhizobium bacteria in order to
effectively fix nitrogen. Since these bacteria cannot survive in the
digestive system of an animal, depending on seed contained in fecal
material amounts to planting raw seed. Thus, if the bacteria required
for nodulation are not already present in the soil, nodulation will not
occur.
Regardless
of seeding technique, a seed must be placed in a spot where it can
germinate and become established. Also, the ability of the seedling to
compete in the setting in which it has been placed is critically
important. For example, placement of a seed in the middle of a thick,
vigorous clump of tall grass is not a likely site for successful
establishment, regardless of how well the introduced species is adapted.
Much
livestock fecal material is deposited under trees, near a water source,
or along the edges of pastures. Even with frequent rotation of animals
from pasture to pasture, the distribution of fecal material will be far
from even, which means poor distribution of any seed within the fecal
material as well. |
