Abstract:
We conducted a study in southern New Mexico to determine
seasonal variation in botanical diet composition of cattle and to
compare cow and steer diets. The climate and vegetation is typical
of semidesert grassland Fecal samples were obtained from a
group of cows and steers during spring, summer, fall, 1989; winter
and summer, 1990. Results showed that cattle diets were
highest in grass content during spring (57%), summer (78%),
and winter @I%), while forbs comprised the bigbest proportion
of cattle diets during the fall (47%). Shrubs were moderately
important during winter (18%). Dropseeds (Sporobolus spp.),
black grama (Bouteloua eriopoda ~OIT.] Ton=), tbreeawn species
(Aristidu spp.), and leatherweed croton (Croton poftsii [Iuotxcb]
Muell. Arg.) were key forage species for cattle. The importance
of these species varied with season, availability, physiological
stage, and presence of other species. Differences between cow
and steer diets varied with season. The relative similarity ranged
from 70% (fall) to 90 46 (summer). The lower fall similarity compared
to that in the summer might be related to physiological
variation or past ditferences in grazing experience between cows
and steers. For practical purposes, steer diets might generally be
used to represent cow diets, but caution should be exercised during
periods of low forage quality.
