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Evaluation of the All Heifer, No Cow Beef Production System to Improve Beef Production Efficiency.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Evaluation of the All Heifer, No Cow Beef Production System to Improve Beef Production Efficiency./
作者:	Harrison, Meredith.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
面頁冊數:	153 p.
附註:	Source: Masters Abstracts International, Volume: 81-02.
Contained By:	Masters Abstracts International81-02.
標題:	Animal sciences. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13807421
ISBN:	9781085589123

Evaluation of the All Heifer, No Cow Beef Production System to Improve Beef Production Efficiency.
Harrison, Meredith.

Evaluation of the All Heifer, No Cow Beef Production System to Improve Beef Production Efficiency. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 153 p.

Source: Masters Abstracts International, Volume: 81-02.

Thesis (M.S.)--Colorado State University, 2019.

This item must not be sold to any third party vendors.

Maintaining a mature cowherd year-round requires costly feed inputs that do not contribute to overall herd productivity, but simply are expended on unproductive, maintenance energy for cows. Alternative herd management strategies with no cows and all heifers may increase feed and economic efficiency, yet prior research addressing these response variables is scarce. The overall objective of this research was to evaluate performance and efficiency of the All Heifer, No Cow (AHNC) beef production system. The AHNC beef production system involves insemination of nulliparous heifers with female sex-selected semen to produce primarily female calves that are early-weaned 3 mo after birth. Dams are finished on a high concentrate ration and harvested before reaching 30 mo of age to produce high quality carcasses. Objectives of this study were two-fold: 1) manage a live AHNC demonstration herd to characterize herd performance, and 2) use data collected from the AHNC demonstration herd to parameterize a system dynamic model to evaluate biological and economic efficiency of the system.Specific objectives of Chapter II were to: 1) document reproductive, feedyard, calf, and carcass performance of a 5-cohort AHNC demonstration herd; 2) evaluate effects of carcass maturity on carcass quality variables; and 3) determine if performance of initial cohorts (i.e., cohorts 1 and 2) differed from sustaining cohorts (i.e., cohorts 3 through 5).To evaluate system performance, 273 heifers were enrolled in the AHNC beef production system via 5 annual cohorts over a 6-yr period. The system was initiated with the purchase of 51 yearling, Angus-based commercial heifers (initial BW = 354 ± 39 kg). Cohort 2 was started with a similar set of purchased heifers (n = 56; initial BW = 307 ± 30 kg) 12 mo after cohort 1. Heifers enrolled in cohorts 3 (n = 53), 4 (n = 56), and 5 (n = 56) were primarily offspring of prior cohorts (e.g., cohort 3 heifers were born to cohort 1 dams, etc.), but some heifers were acquired in a similar manner as cohorts 1 and 2 to ensure maintenance of annual inventory.Ovulation was synchronized, and heifers were artificially inseminated with female sex-selected semen. In cohorts 2 through 5, heifers were resynchronized, and a second AI was performed approximately 18 to 21 d after the first AI. Following insemination, heifers were placed with 1 natural service sire. Overall, heifers achieved a pregnancy rate of 50.4 ± 9.8% approximately 30 d after AI and a pregnancy rate of 93.0 ± 1.5% at 140 d post AI. Across 5 cohorts, percent calf crop was 85.7 ± 8.2%, and 61.0 ± 6.5% of females replaced themselves with a heifer. For cohorts 4 and 5, 67.8% of females replaced themselves with a heifer, requiring remaining heifers to be purchased from outside the system.Calves produced in the system were early-weaned at 105 ± 21 d and weighed 125 ± 28 kg at weaning. After weaning, dams were fed a corn-based finishing ration for 72 ± 8 d. While on the finishing ration, dams gained 1.9 ± 0.4 kg • d-1 and consumed 14.9 ± 1.9 kg DM • d-1. Although dams gained rapidly, their feed conversion was poor. Overall G:F for the 5 cohorts was 0.123 ± 0.025. Body weight at harvest was 637 ± 57 kg.A total of 222 AHNC females were harvested. Across cohorts, HCW and dressing percent were 367 ± 35 kg and 58.8 ± 1.9%, respectively. The packer classified 68.3 ± 5.3% of carcasses as over 30 mo of age based on dentition. Overall USDA yield grade (YG) was 2.6 ± 0.7. Marbling score (MA) was 457 ± 87, which coincided with a marbling level of small57. Overall, 62.4 ± 29.1% of carcasses graded USDA Choice and greater.Carcasses were pooled across cohorts and performance variables associated with carcass quality were compared between youthful (i.e., A and B maturity) and mature (i.e., C maturity and greater) carcasses. Overall, 177 carcasses were classified as youthful (80.5%) and 43 were classified as mature (19.5%) by USDA grading personnel. There were no differences between maturity groups for ribeye area (P = 0.13), USDA YG (P = 0.67), MA (P = 0.26), or lean maturity score (P = 1.00). Mature carcasses had greater (P < 0.001) bone maturity scores and greater (P < 0.001) overall maturity scores compared to youthful carcasses. Additionally, mature carcasses had heavier (P < 0.01) HCW and greater (P < 0.001) dressing percentages. For cohorts 3 through 5, mature carcasses (919 ± 11 d) were older (P < 0.001) than youthful carcasses (902 ± 11 d) at harvest.(Abstract shortened by ProQuest).

ISBN: 9781085589123Subjects--Topical Terms:

3174829
Animal sciences.

Evaluation of the All Heifer, No Cow Beef Production System to Improve Beef Production Efficiency.
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