"Supplementation and Reproductive Strategies for Beef Females as Part o" by Alicia Caitlin Lansford

Animal Science, Department of

 

First Advisor

Richard N. Funston

Second Advisor

Jennifer R. Wood

Date of this Version

4-2018

Document Type

Article

Comments

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 Richard N. Funston and Jennifer R. Wood. Lincoln, Nebraska: April, 2018

Copyright (c) 2018 Alicia Caitlin Lansford

Abstract

The objective of these 4 studies was to evaluate the effects of management decisions on reproductive performance of beef females. Experiment 1 evaluated the efficacy of a novel s.c. prostaglandin F2a injection on estrus synchronization and pregnancy success in yearling beef heifers. Heifers receiving a 2 mL s.c. injection of Lutalyse HighCon had similar estrus response and pregnancy rates compared to 5 mL Lutalyse i.m. within 2 different estrus synchronization programs. In experiment 2, May-calving heifers and primiparous cows were allotted to receive either no supplementation or supplement (0.45 or 0.91 kg/d per animal, heifers or primiparous cows, respectively) throughout the breeding season. Although supplementation increased BW, pregnancy rates were not impacted. In experiment 3, May-calving females were allotted to graze either sub-irrigated meadow or upland range throughout the breeding season. No differences in pregnancy rate were detected, despite differences in BW and BCS gain over the breeding season. Finally, experiment 4 examined the effects of varying levels of late gestation nutrition on dam and subsequent progeny performance. Multiparous, May-calving dams were allotted to graze either meadow or range forage and then to receive either no supplement or 0.45 kg/d per cow of a 33% CP supplement during late gestation. Prepartum meadow grazing tended to increase dam rebreed pregnancy rates. Heifer progeny had increased rebreed pregnancy rates as a primiparous cow, and steer progeny had increased marbling score if their dam grazed meadow. Dam supplementation increased BW of progeny over 2 generations. In summary, these experiments demonstrate the following findings: 1) a higher concentrate s.c. injection of prostaglandin F2a is effective in synchronizing estrus of beef heifers, 2) supplementation or differing forage type during the breeding season of a May-calving herd does not impact reproductive response, and 3) differences in late gestation nutrition of a May-calving herd results in altered progeny growth and performance.

Advisors: Richard N. Funston and Jennifer R. Wood

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