Preference of Forages by Horses
Horses are notoriously selective grazers.
Little documentation has established why certain areas are selectively
grazed while other areas are ungrazed or become dunging areas.
A pasture study in Texas reported a repeated tendency for horses
to always graze the fence line of an enclosure and various areas
that represented between approximately 38% of the available acreage.
This grazing area percent would vary with the number of horses
and forage availability (increasing as forage became more limited).
Since young, growing forages tend to be
higher in digestible nutrients, it is reasonable to assume that
the equine grazer repeatedly grazes the same areas to obtain
more tender and less fibrous forage. A study in Texas reported
a 3% difference in Tift 44 crude protein between grazed vs. ungrazed
areas.
Climatic variations result in disparity
among preferred forages by horses. A report from New Zealand
indicated that horses favored prairie grass (Bromus willdenowii),
followed by Italian ryegrass, white clover, and timothy. A creeping
red fescue was favored by horses in Suffolk, England over creeping
red fescue Canadian variety, crested dogstail, cocksfoot, and
perennial ryegrass. In the southern United States where winter
annuals are well suited to the mild climates, horse preferred
annual ryegrass over oats and wheat. The winter annual preference
was particularly evident later in the growing season, even though
the forages were maintained in the vegetative state. Rye and
triticale were avoided by yearlings in this research. A second
cafeteria study demonstrated crimson, Berseem, and Subterranean
clovers were equally preferred while yearlings avoided arrowleaf
clover. Tannin is a chemical in arrowleaf clover which deters
consumption.
Fewer studies have addressed the preference
of the horse for various hay varieties. In response to local
questions about acceptability of the improved Bermudagrass varieties,
research at Georgia was conducted to evaluate five bermudagrass
varieties and establish any correlations with the physical form
of the plant. Coastal bermudagrass was clearly preferred by all
horses, followed by Tifton 44 and Tifton 78. Tifton 85 was a
distant fourth while horses basically refused to eat the coastcross
bermudagrass hay. Morphologically, the Coastal bermudagrass hay
had the smallest stem diameter, leafblade width and length, and
lowest neutral detergent fiber (NDF), a lab analysis value that
indicates the potential energy content, filling effect, and intake
of a forage. The lower the NDF percent, the greater the energy
value and digestibility of a feed. Despite relatively equal crude
protein levels among all hays, the least preferred hays (Tifton
85 and Coastcross) had the widest leaf blade and highest NDF
values.
Is a horse's preference for various forage
varieties an important management question? In many cases, basic
acceptability of a forage seems "good enough", as long
as the horse is in acceptable body condition. But within the
"accepted" forage varieties, can preference impact
growth and body condition significantly? Future research should
be directed toward establishing a greater understanding of the
horse's selectivity for forages to maximize growth and forage
utilization.
