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Performance of Crosses among Hereford, Angus and Simmental Cattle with Different Levels of Simmental Breeding. III. Heifer Postweaning Growth and Early Reproductive Traits^1,2,

Northern Agricultural Research Center, Havre, MT 59501 and Montana State University, Bozeman 59717

Abstract

Postweaning growth and early reproductive traits in heifers whose potential for milk production differed were studied during the years 1976 through 1979. Data were collected on 230 heifers raised by 3-yr-old Hereford dams. Heifers were comprised of the following breed groups: Hereford (HH), Angus-Hereford (AH), 25% Simmental—75% Hereford (1S3H) and Simmental-Hereford (SH). Postweaning growth rate during a 140-d period was greatest for SH heifers (.75 kg/d), intermediate for AH and 1S3H groups (.70 and .68 kg/d, respectively) and slowest for HH heifers (.64 kg/d). At 1 yr of age, SH heifers were heavier, taller and had larger pelvic areas than all other groups (P<.01). Least-squares means for yearling weight, hip height and pelvic area for HH, AH, 1S3H and SH heifers were 283, 303, 298 and 317 kg: 111, 112, 114 and 118 cm, and 132, 136, 139 and 148 cm², respectively. Ninety-one percent of the heifers reached puberty by the end of the breeding period. Crossbred heifers reached puberty at younger ages and had higher pregnancy rates than HH heifers (P<.01). Least-squares means for pubertal age, weight and height for HH, AH, 1S3H and SH breed groups were, respectively, 407, 371, 382 and 368 d; 300, 302, 305 and 313 kg, and 115, 114, 117 and 119 cm. Percentage of heifers reaching puberty by 14 mo of age was 64, 99, 85 and 94 for HH, AH, 1S3H and SH, respectively. Respective pregnancy rates were 59, 90, 77 and 86%, but were not significantly different among breed groups when only heifers reaching puberty by the end of the breeding period were studied. No differences among breed groups were found for date of pregnancy.

¹ Montana Agr. Exp. Sta., Journal Ser. No. J-1633.

² The authors gratefully acknowledge a semen grant from American Breeders Service Division, W. R. Grace and Co., Route 1, DeForest, WI 53532.

³ Dickinson State College, Dickinson, ND 58601.

⁴ Dept. of Anim. and Range Sci.

⁵ Northern Agr. Res. Center, Star Route 36-Box 43, Havre, MT 59501.