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Title: A method for estimating the target for protein energy retention in sheep
Contributor(s): Dougherty, Holland  (author)orcid ; Oddy, Hutton  (author)orcid ; Evered, Mark  (author); Oltjen, James (author)
Publication Date: 2020
Open Access: Yes
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Abstract: Target protein mass at maturity is a common "attractor" used in animal models to derive components of animal growth. This target muscle protein at maturity, M*, is used as a driver of a model of animal growth and body composition with pools representing muscle and visceral protein; where viscera is heart, lungs, liver, kidneys, reticulorumen and gastrointestinal tract; and muscle is non-visceral protein. This M* term then drives changes in protein mass and heat production, based on literature data stating that heat production scales linearly with protein mass but not liveweight. This led us to adopt a modelling approach where energy utilisation is directly related to protein content of the animal, and energy not lost as heat or deposited as protein is fat. To maintain continuity with existing feeding systems we estimate M* from Standard Reference Weight (SRW) as follows: M* (kJ) = SRW * SHRINK * (1-FMAT) * (MUSC) * (CPM)* 23800. Where SRW is standard reference weight (kg), SHRINK is the ratio of empty body to live weight (0.86), FMAT is proportion of fat in the empty body at maturity (0.30), MUSC is the proportion of empty body protein that is in muscle (0.85), CPM is the crude protein content of fat-free muscle at maturity (0.21), and 23800 is the energetic content (kJ) of a kilogram of crude protein. Values for SHRINK, FMAT, MUSC and CPM were derived from a synthesis of our own experimental data and the literature. For sheep, these values show M* to be M* (kJ) = SRW * 0.86* (1-0.3) * 0.85 * 0.21 *23800 = SRW * 2557. This method allows for use of existing knowledge regarding standard reference weight and other parameters in estimating target muscle mass at maturity, as part of a model of body composition and performance in ruminants.
Publication Type: Conference Publication
Conference Details: ASAS-CSAS 2020: 2020 American Society of Animal Science and Canadian Society of Animal Science Annual Meeting and Trade Show, Online Event, 19th - 23rd July, 2020
Source of Publication: p. 1-2
Place of Publication: Online
Fields of Research (FoR) 2008: 070204 Animal Nutrition
070103 Agricultural Production Systems Simulation
Fields of Research (FoR) 2020: 300303 Animal nutrition
300205 Agricultural production systems simulation
Socio-Economic Objective (SEO) 2008: 830310 Sheep - Meat
839899 Environmentally Sustainable Animal Production not elsewhere classified
Socio-Economic Objective (SEO) 2020: 100412 Sheep for meat
HERDC Category Description: E3 Extract of Scholarly Conference Publication
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Appears in Collections:Conference Publication
School of Environmental and Rural Science
School of Science and Technology

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