POSTWEANING GROWTH AND REPRODUCTION CHARACTERISTICS OF HEIFERS SIRED BY BULLS OF 7 BREEDS AND RAISED ON DIFFERENT LEVELS OF NUTRITION

Heifers produced from sires of seven breeds (Hereford, Angus, Belgian Blue, Piedmontese, Brahman, Boran, and Tuli) and Angus, Hereford, and MARC III (four-breed composite) cows were evaluated. Weaned heifers we re placed in three treatment groups of moderate nutrition (15.8 Meal M E/d), 80% of moderate nutrition (12.6 Meal ME/d), or fed as a mixed-br eed group (16.3 Meal ME/d). Average daily gain (ADG) from 228 d of age through breeding was measured. There was a sire breed x group interac tion (P < .0001) for ADG in the drylot. Sire breeds differed in their 365-d BW (P < .0001), and 365-d BW of heifers in the low group (315 +/ - 4 kg) were lighter (P < .0001) than those of heifers in the high gro up (346 +/- 4 kg). During breeding, heifers that had been in the low g roup in the drylot had a higher ADG (.58 +/- .02 kg/d) than heifers in the high group (.39 +/- .03 kg/d). Age of heifers at puberty did not differ (P = .06) between the low (362 +/- 5 d) and high groups (357 +/ - 5 d). Heifers from MARC III (358 +/- 5 d) and Angus (358 +/- 6 d) da ms reached puberty at a younger age than did heifers with Hereford dam s (380 +/- 9 d). Age at which puberty was expressed differed with sire breed (P < .001). The proportion of heifers that were pregnant at pal pation (.90) did not differ between sire breeds (P = .24), dam breeds (P = .40), or group (P = .56). Breed differences in postweaning ADG an d in the manner in which the population expresses puberty allow for se lection of breed types that will optimize cow herd performance.