| Abstract |
- Pangola digitgrass (Digitaria decumbens), Coastcross-
1 bermudagrass (Cynodon dactylon), and Kazungula
setaria (Setaria sphacelata cv Kazungula) were used in a
two-year study at the C.A.M.P.A. Training Center in
Tampico, Mexico. The objective of the study was to determine
the optimum stocking rate during the grazing season
on these species and the relationship of average daily
gain (ADG) on each grass with several nutritional and
environmental parameters. The grazing seasons were from
June 25, 1975, to January 21, 1976; and from June 16,
1976, to January 27, 1977. The parameters measured were
available dry matter (kg), ADG (kg) during the preceding
14, 28, and 42 days, percentage of soil moisture, and
precipitation (mm). An area of 2.7 ha of each species was
used in this trial. These areas were divided into three
lots of 1.1, 0.9, and 0.7 ha. Each lot was grazed by 9
and 10 zebu steers in a rotational form during the first
and second grazing season, respectively. Each grazing
season was divided into 5 grazing periods of 14 days. Covariance analysis was used to estimate the optimum
grazing pressure. Analysis of variance showed no difference
in ADG during the two grazing season. The estimated
carrying capacities in animal units (animal unit =
A.U. = 450 kg liveweight)/ha were 1.962, 2.062, 2.975,
and 3.291 for Pangolagrass during periods 1, 2, 4, and 5,
respectively. For Coastcross-1 bermudagrass the estimated
rates were 3.492, 2.755, 1.397, and 1.000 A.U./ha for
periods 2, 3, 4, and 5, respectively; while with Kazungula
setaria the optimum grazing pressures were 1.790, 1.917,
1.838, and 1.441 A.U./ha for periods 1, 3, 4, and 5, respectively.
The optimum rates were not estimated for
periods 3, 1, and 2 for Pangolagrass, Coastcross-1 bermudagrass
and Kazungula setaria, respectively, because
the highest grazing pressure was to low to consume pasture
production. The regression equations that best
estimated ADG were: ADG on Pangolagrass (kg) = 1.675
+ 0.000946 available dry matter at 15 cm height or more
-0.558 ADG (kg) during 28 days before -0.0262% soil moisture
from 12-25 cm depth. ADG (kg) for Coastcross-1 bermudagrass
= -0.740 + 0.0598% soil moisture from 12-25 cm
depth. ADG (kg) for Kazungula setaria = 0.1587 - 0.648
ADG (kg) during the 28 days before + 0.00645 precipitation
(mm) during the preceding 14 days.
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