ANIMAL RESPONSE
 By Marvin Koger

 Methods
 The pasture programs studied during the three successive
phases of the project were evaluated by grazing with a cow-calf
production system supplemented with data from other partici-
pating departments. Multiple use was made of the cattle in the
project by involving them in a comparison of five mating sys-
tems, beginning with a foundation of Brahman-native females
typical of Florida cattle in the early 1950's. The mating systems
compared were: 1, upgrading to Angus sires; 2, upgrading to
Hereford sires; and three 2-breed-of-sire rotations, including
3, Angus and Hereford, 4, Angus and Brahman, and 5, Hereford
and Santa Gertrudis. Since two sire breeds were represented in
Systems 3, 4, and 5, there were a total of eight mating groups.
Cows from each of six of these groups were used to graze each
of the pasture programs which were evaluated during Phases
2 and 3 of the project. Two groups were carried on reserve pas-
tures and utilized as filler cows to replace animals removed from
the experimental pasture programs during the year. Inclusion of
animals from different breeding systems on each of the pasture
programs proved to be a fortunate design since it turned out that
breed groups responded differently to pasture programs.
 Each year in October all non-pregnant cows were eliminated
and replaced with pregnant heifers which had been bred in non-
experimental pastures. The number of cows with which a pasture
was stocked was a subjective decision based on previous ex-
perience. The objective was to maintain enough cattle on the pro-
gram to graze off all of the accumulated forage by November 15
to December 1. At this time, the cattle were removed to fields on
which silage for winter feed had been grown and continued there
until clover was ready for grazing, usually March 1,- 10 days.
The silage fed was charged against the program.
 In evaluating pastures with cows and calves on a system
basis, the pastures must be stocked with a nearly constant num-
ber of cows, with fluctuations in amount of forage being adjusted
by age at which calves are removed and by the amount of supple-
mental feed added to the program. The dry matter content of
estimated forage and silage utilized was equal approximately to
the NRC recommendation for cows and growing calves. It ap-
peared that the amount of forage wasted through trampling was