Animal Science, Department of


Date of this Version

Spring 4-2016


Tibbitts, B. T. 2016. Beef systems management strategies: calving date selection, estrus synchronization, and post-weaning management. University of Nebraska-Lincoln.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Animal Science, Under the Supervision of Professors Rick N. Funston, Jim C. MacDonald. Lincoln, Nebraska: April, 2016

Copyright (c) 2016 Benjamin T. Tibbitts


The objective of an invited review and four experiments was to evaluate production implications and economic efficiencies of beef systems strategies involving calving date selection, utilization of reproductive technology, and post-weaning management of heifers and steers. The invited review in chapter II considers factors that influence a producer’s decision on when to calve beef females. The calving date decision impacts the entire beef production cycle and must take into account any environmental conditions, available resources, and cite specific advantages and/or disadvantages. Understanding the importance of varying physiological state and nutrient demands associated with lactation and gestation is critical to optimizing calving date. Calving systems vary across geographic regions. The associated differences in management strategies, along with economic drivers, contribute to the complexity of the calving date decision. Chapter III evaluates the effects of overwinter nutrition on subsequent May calving cow performance. Supplemented cows had increased (P < 0.01) BCS and BW change over winter treatment period compared to unsupplemented cows. Cows grazed either dormant upland range or meadow during the winter period. Pasture treatment had an effect on winter BW gain, pre-calving BW, lactation BW gain, pregnancy rate, as well as progeny birth and weaning BW. Pregnancy rate (P = 0.05) and calf birth BW (P = 0.03) were lower, and calf WW tended (P = 0.06) to be lower for cows that grazed dormant range without supplement. Chapter IV compares a modified fixed-time AI protocol to fixed-time AI. Heifer reproductive performance at both AI conception and overall conception rate was similar (P < 0.05) in both treatments. Chapter V evaluates the effects of a Revalor G implant on reproduction and growth performance of 12 mo old beef heifers. Implanting heifers reduced conception rate by 18 percentage points in implanted heifers, but resulted in a 6 kg growth advantage over non-implanted heifers. Chapter VI compares four supplement sources on growth performance of steers grazing irrigated corn residue. Supplementing with dried distiller grains and SoyPass/SBM blend provided sufficient CP in the form of RDP and RUP for steers to gain at rates above 0.45 kg/d, while supplementing with corn grain and corn grain + RDP resulted in gains far below (< 0.2 kg/d) other treatments. Growing steers will require protein supplementation in the form of both RUP and RDP in order to optimize growth performance while grazing corn residue.

Advisors: Richard N. Funston and Jim C. MacDonald