Materials and Methods
Data included weights, heights, and body condition
scores of Angus and Hereford purebred and F1 cows
produced by mating Angus and Hereford dams to seven
breeds of sire. The number of sires and cows mated to
each breed of sire are presented in Table 1. The GPE
program at MARC was designed to examine breed
group differences for major economic traits by comparing
the progeny of all breeds of sires with progeny from
Hereford-Angus crosses. Cycle I began with the 1969
breeding season, with matings by AI of Hereford, Angus,
Jersey, South Devon, Limousin, Simmental, and
Charolais bulls to Hereford and Angus cows. Details
concerning sire sampling were presented by Smith et
al. (1976b). Calves were born during a 70-d calving
season (March to early May) of 1970, 1971, and 1972.
They were allowed to suckle and graze with their
mother, and then were creep fed from mid-July or early
August until weaning in early October at about 200 d
of age. All male calves were raised, fed, and slaughtered
to evaluate growth, feed efficiency, and carcass traits.
All females were retained (Phase 2) for evaluation of
reproduction, mature weight, height, and other cow
traits as well as for maternal performance. Heifers were
managed to have their first calf at two years of age.
Details of postweaning management were presented by
Laster et al. (1976).