Postweaning growth and reproduction characteristics of heifers sired by bulls of seven breeds and raised on different levels of nutrition
1997
Freetly, H.C. | Cundiff, L.V.
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.
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