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5.1: Nutrient Requirements and Evaluation

Introduction to Animal Science · LibreTexts

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    From LibreTexts, under CC BY 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Understanding what animals need to eat starts with recognizing why they need those nutrients in the first place. Every animal's body is constantly working to keep itself alive and functioning, but beyond that, different life stages and activities create additional nutritional demands. A growing calf, a lactating dairy cow, and a horse pulling a plow all have vastly different nutrient requirements because their bodies are doing other things. To properly feed and manage animals, you need to understand how these physiological functions drive what they need to consume and how much they need to consume.

    Physiological Functions Dictating Nutrient Needs:

    Animal nutrient requirements are determined by maintenance needs plus production demands:

    • Maintenance supports basal metabolism (cardiovascular, respiratory, and renal function), thermoregulation, and minimal physical activity. This must be met before production can occur.
    • Growth requires nutrients for tissue accretion, with high-quality protein and balanced mineral supply being critical.
    • Lactation imposes substantial energy and nutrient demands, often exceeding intake capacity in early lactation, necessitating mobilization of body reserves.
    • Reproduction encompasses gamete production, fetal development, and parturition, with increased energy, protein, vitamin, and mineral needs, particularly in late gestation.
    • Production/Work increases energy requirements in proportion to activity intensity, including the output of products (milk, eggs, wool).
    • Finishing is the final phase for meat animals, focusing on adding fat tissue. Requires high energy but a lower percentage of protein than the growth phase.

    piglets suckling

    Image credit: Mark Stebnicki from Pexels: Link to piglets suckling image [www.pexels.com]

    This page titled 5.1: Nutrient Requirements and Evaluation was last modified on Sat, 02 May 2026 03:51:26 GMT and is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Deanne Pawlisch.