Document Type

Dissertation - Open Access

Award Date

2026

Degree Name

Doctor of Philosophy (PhD)

Department / School

Animal Science

First Advisor

Zachary Smith

Abstract

The objective of this dissertation was to evaluate how previous plane of nutrition and anabolic implant timing interact to influence growth performance, composition of growth, and the carcass characteristics in ruminants. Three experiments were conducted using cattle and sheep models to determine the metabolic adaptations driving compensatory growth. In experiment 1, yearling beef steers (n = 192) were fed ad libitum for 141 days (ADLIB) or restricted to 92% of ad libitum intake for 56 (RES56) or 86 (RES86) days followed by realimentation. Cumulative dry matter intake (DMI) was reduced in both restricted groups (P = 0.002) with no difference in average daily gain (ADG) or final shrunk body weight (SBW; P ≥ 0.71). Cumulative feed efficiency (G:F) was improved in RES86 compared to ADLIB (P = 0.035), suggesting that a longer restriction followed by an adequate realimentation period can enhance efficiency without sacrificing growth. Experiment 2 used backgrounded beef steers (n = 232) in a 2 × 2 factorial evaluating limit feeding (ad libitum for 142 days [ADL] vs. 92% of ad libitum for 63 days followed by realimentation [RES]) and implant timing (day 1 [INI] vs. day 63 implant [DEL]). DEL increased ribeye area and mature body weight (P ≤ 0.016) while RES reduced cumulative DMI by 2.5% (P = 0.025) without affecting ADG, final SBW, or G:F (P ≥ 0.30). Experiment 3 used 30 finishing lambs fed ad libitum for 56 days (CON) or restricted to 92% of ad libitum intake for 28 (28L) or 56 days (56L). The longer restriction length decreased DMI (P < 0.001). The 56-d restriction resulted in increased muscle and bone mass (P ≤ 0.038); however, the 28-d restriction was likely too short for full metabolic reduction, resulting in a tendency for poorer ADG during the realimentation period (P = 0.060). Collectively, these experiments demonstrate that the composition of gain and carcass characteristics can be altered via temporal management of intake and anabolic stimulus. The duration of both the restriction and realimentation period is critical to capturing efficiency improvements and minimizing carcass quality loss. This dissertation provides a structure for developing management strategies that leverage metabolic adaptations to improve beef sustainability.

Publisher

South Dakota State University

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Rights Statement

In Copyright