Animal Science Department

 

Date of this Version

12-2-2015

Citation

Warner, 2015

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Animal Science, Under the Supervision of Professors Richard J. Rasby and Terry J. Klopfenstein. Lincoln, Nebraska: December, 2015

Copyright (c) 2015 Jason M. Warner

Abstract

The objective of four experiments conducted was to evaluate production and economic efficiencies of intensified cow-calf production management systems. The first experiment tested the effect of calf age at weaning on cow and calf performance and feed utilization at 2 locations. Body weight change from early to conventional weaning time was greater for early-weaned cows. Cow BCS and conception rates were not impacted by weaning. Calf BW at conventional weaning time was greater for conventionally-weaned calves than early-weaned calves at ARDC, but greater for early-weaned than conventionally-weaned calves at PHREC. Calf ADG per unit of total feed energy intake was greater for nursing pairs at ARDC, but not different between early- and conventionally-weaned pairs at PHREC indicating early-weaning may have minimal effect on reducing feed energy requirements. In Exp. 2, the effect of post-weaning management system and calf age at weaning was evaluated on growing and finishing performance, carcass characteristics, and economics of calves produced from an intensively managed cow-calf system. During growing, fast-track cattle had improved DMI and ADG. Finishing DMI, ADG, HCW, and marbling were greater for slow-track cattle at the same 12th rib fat thickness. Breakeven was similar and profitability greater for fast-track. Weaning age had minimal impact, but post-weaning management influenced subsequent performance and economics demonstrating the value of alternative management systems. The third experiment studied supplementation of ethanol by-products and low-quality forages to cow-calf pairs grazing smooth bromegrass pastures as a method to reduce grazed forage intake. Supplementation replaced approximately 40% of grazed forage intake suggesting that ethanol co-products and low-quality forages can replace grazed forage intake allowing for increased stocking rate without impacting animal performance. An analysis of profitability of intensively managed cow-calf systems utilizing distillers grains and crop residues and the economic sensitivity of profitability to changes in feed costs, feeder cattle prices, replacement female costs, and reproductive rates was conducted in Exp. 4. Greater returns were projected as weaning percentage increased, but the economic feasibility and extent of positive returns of such a system will be dependent on price relationships for feed and calves and cowherd reproductive performance.

Advisors: Richard J. Rasby and Terry J. Klopfenstein

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