The All Heifer, No Cow (AHNC) beef production system is an alternative to conventional cow/calf production that involves insemination of nulliparous heifers with sexed semen to produce female calves that are early weaned at 3 mo of age. Dams are finished on a high-concentrate diet and harvested before reaching 30 mo of age. Objectives of this research were to document reproductive, feedyard, calf, and carcass performance of an AHNC herd; evaluate effects of carcass maturity on carcass quality; and determine if performance of initial cohorts (i.e., cohorts 1 and 2) differed from sustaining cohorts (i.e., cohorts 3-5). A total of 272 heifers were enrolled in the AHNC system via five annual cohorts. The system was initiated with 51 yearling, Angus-based heifers, and a replicate set (n = 56) was started 12 mo after. Heifers in cohorts 3 (n = 53), 4 (n = 56), and 5 (n = 56) were primarily offspring of prior cohorts (i.e., cohort 3 heifers born to cohort 1 females), but some were purchased to maintain inventory. Angus replacement heifers were purchased in cohorts 3 (n = 26), 4 (n = 26), and 5 (n = 28). Mean (±standard deviation) pregnancy rate at 30 d after fixed-time artificial insemination (AI) with sexed semen was 50.8% ± 9.4%, and 140-d pregnancy rate was 93.0% ± 1.5%. With AHNC, 61.0% ± 6.5% of females replaced themselves with a heifer. During finishing, average daily gain (ADG) was 1.9 ± 0.4 kg • d-1 and dry matter intake (DMI) was 14.9 ± 1.9 kg • d-1. Hot carcass weight (HCW) was 367 ± 35 kg. The USDA grading system classified 20.5% of all carcasses (n = 220) as C maturity (A00 = 100, B00 = 200, etc.), 62.4% ± 29.1% of carcasses as USDA Choice. USDA yield grade (YG) was 2.6 ± 0.7. Based on cohorts 1 and 2, there were no differences (P = 0.96) in Warner-Bratzler shear force values between A and B maturity vs. C maturity carcasses. Across all cohorts, there were no differences in USDA YG, marbling score (MA), and lean maturity between A and B maturity vs. C maturity carcasses; there were differences in age (P < 0.001), bone maturity (P < 0.001), and overall maturity (P <0.001). A comparison of initial vs. sustaining cohorts showed that initial cohorts had lower (P < 0.001) DMI, heavier (P < 0.001) HCW, and more advanced (P < 0.05) bone maturity. However, there were no differences for 30- and 140-d pregnancy rates, ADG, USDA YG, and MA between initial and sustaining cohorts. The AHNC beef production system can effectively produce female calves and quality carcasses for harvest.
Keywords: beef production system; biological efficiency; cattle; sex-selected semen; single-calf heifer.
© The Author(s) 2020. Published by Oxford University Press on behalf of the American Society of Animal Science.