0-10-20 annually) while the carrying capacity of Program 2 was
reduced during the first four years during which 1/4 of the pro-
gram was renovated each year. Following renovation, production
and carrying capacity returned to approximately the same level
of the check program.
 An important feature during Phase 3 was that there was a
highly significant breed group x pasture program interaction for
calf growth traits. This response was in agreement with other
recent reports and emphasized the necessity for considering both
the forage and cattle breeding programs jointly in order to max-
imize production efficiency.
 The response of the cattle to selection and different mating
systems over a 20-year period was evaluated at the termination
of Phase 3. Annual production per cow, averaged over all breed
groups, increased from 225 pounds for the foundation cattle to
448 pounds during Phase 3, an improvement of 99%. Indica-
tions were that most of this improvement was genetic, being due
to a combination of intensive selection and hybrid vigor.
 Summarization of data by the five mating systems showed
highly significant differences in size and growth rate as would
be anticipated from the sire breeds employed. Differences in
weaning rate and estimated total production efficiency were non-
significant. There were indications by the end of the trial, how-
ever, that the grades were beginning to lose stature as compared
with the rotation crosses.

 Literature Cited
 (Animal Response)
1. Butts, W. T., M. Koger, O. F. Pahnish, W. C. Burns, and E. J. Warwick.
 1971. Performance of two lines of Hereford cattle in two environments.
 J. Anim. Sci. 33:923.
2. Crockett, J. R., R. W. Kidder, M. Koger, and D. W. Beardsley. 1973.
 Beef production in a crisscross breeding system involving the Angus,
 Brahman and Hereford. Fla. Agri. Exper. Sta. Bul. No. 759 (technical).
3. Kidder, R. W., M. Koger, J. H. Meade, and J. R. Crockett. 1964. Sys-
 tems of crossbreeding for beef production in Florida. Fla. Agri. Exper.
 Sta. Bul. No. 673.
4. Koger, Marvin, and A. C. Warnick. 1973. Breeding systems for improve-
 ment of native cattle. J. Anim. Sci. 37:235.
5. Koger, Marvin, F. M. Peacock, W. G. Kirk, and J. R. Crockett. 1975.
 Heterosis effects on weaning performance of Brahman-Shorthorn calves.
 J. Anim. Sci. 40:826.
6. Peacock, F. M., M. Koger, W. G. Kirk, E. M. Hodges, and A. C. Warnick.
 1971. Reproduction in Brahman, Shorthorn and crossbred cows on dif-
 ferent pasture programs. J. Anim. Sci. 33:458.