may in fact be real. One of the items of greatest interest in these
data was annual production per cow expressed as a percent of
cow weight. It was used in this study as an indicator of total
efficiency during the preweaning phase of the production cycle.
As shown in Table 14, this value varied from 39% to 41%, indi-
cating little difference in total production efficiency. Likewise,
there were no large differences in feed conversion by steers, with
feed required per pound of liveweight gain varying from 10.8
for grade Angus to 10.1 for the Hereford-Santa Gertrudis rota-
tion group.
Because of differences between early generation grade animals
and straightbred cattle, these results are not directly comparable
with other cross-breeding studies in Florida, all of which have
shown significant advantages for crossbred cattle in weaning
rate, growth rate, and annual production per cow (2, 3, 5, and
6). Previous investigations have utilized purebred or high grade
cattle as reference groups. The lower grade animals in this study
descended from a Brahman-native-British crossbred foundation
with most of the grades being less than four generations re-
moved from this base. It is not surprising, thus, that the grades
in this study compared more favorably with crossbreds. A study
of time trends in these cattle indicated that at the close of the
trial the grade animals were losing stature as compared with
the rotation crossbreds (4).
 Possibly the most significant response observed in this long-
term study was the comparative performance of the different
breed groups on the different pasture programs. The analyses of
variance for Phase 3 (Table 12) show that, overall, pasture pro-
gram did not significantly influence production performance.
Pasture programs, however, did show a highly significant inter-
action with breeding system, agreeing with previous results from
the Ona Agricultural Research Center (5, 6) and with results
from the genotype-environment interaction study in which the
Brooksville station has been involved (1). If such interactions
are real, as the evidence indicates, it means that both the animal
and forage components of the production system must be con-
sidered jointly to achieve maximum results.
 Summary
 Individual animal response data from Phase 3 showed no
significant influence due to pasture program. Program 3, which
was irrigated, had a slightly higher carrying capacity than the
check program (number 1, fertilized at the rate 300 pounds of