title: Postweaning growth and reproduction characteristics of heifers sired by bulls of seven breeds and raised on different levels of nutrition.
abstract: 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 were placed in three treatment groups of moderate nutrition (15.8 Mcal ME/d), 80% of moderate nutrition (12.6 Mcal ME/d), or fed as a mixed-breed group (16.3 Mcal ME/d). Average daily gain (ADG) from 228 d of age through breeding was measured. There was a sire breed x group interaction (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 group (346 +/- 4 kg). During breeding, heifers that had been in the low group 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) dams reached puberty at a younger age than did heifers with Hereford dams (380 +/- 9 d). Age at which puberty was expressed differed with sire breed (P < .001). The proportion of heifers that were pregnant at palpation (.90) did not differ between sire breeds (P = .24), dam breeds (P = .40), or group (P = .56). Breed differences in postweaning ADG and in the manner in which the population expresses puberty allow for selection of breed types that will optimize cow herd performance.
authors.affiliation: USDA, ARS, Roman L. Hruska U.S. Meat Animal Research Center, Clay Center, NE 68933, USA.
authors.forename: H C
authors.initials: HC
authors.lastname: Freetly
authors.forename: L V
authors.initials: LV
authors.lastname: Cundiff
mesh_terms: D000375:Aging / Q000502:physiology; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D001835:Body Weight / Q000235:genetics / Q000502:physiology; D001947:Breeding; D002417:Cattle / Q000235:genetics / Q000254:growth & development* / Q000502:physiology*; D005260:Female; D008297:Male; D011247:Pregnancy; D012098:Reproduction / Q000235:genetics / Q000502:physiology*; D012741:Sexual Maturation / Q000235:genetics / Q000502:physiology; D015430:Weight Gain / Q000235:genetics / Q000502:physiology