Date of Graduation

2002

Document Type

Thesis

Degree Type

MS

Committee Chair

Paul E. Lewis

Abstract

The effects of weight; high (HW) or low (LW), and diet; high-energy (HE) or low-energy (LE), on the fertility of 118 yearling Angus, Hereford, and Angus x Hereford beef heifers were investigated. Heifers were blocked by body weight, and randomly assigned to diets for 47 and 42 days in years, 1 and 2, respectively. Estrus was synchronized with MGA (8 d, 0.5mg/hd/d), PGF2α (25 mg i.m.), and estradiol benzoate (400 µg i.m, 48 h after PGF2α) regimen. Heifers were artificially inseminated between 78-84 h after the PGF2α injection and then exposed to a bull for the second service. Overall pregnancy rate was affected by weight (LW = 83 ± 0.06 vs HW = 65 ± 0.06 %). Follicle size, (observed in 13 heifers per group) was affected by the weight and diet interaction (LWHE = 12.3 ± 0.5 vs HWHE = 10.3 ± 0.5 mm).

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