Thesis
The biological basis for understanding and predicting dietary-induced variation in nitrogen and sulfur ratio discrimination
Washington State University
Master of Science (MS), Washington State University
2011
Handle:
https://hdl.handle.net/2376/104198
Abstract
Accurately predicting isotope ratio discrimination is central to using mixing models to estimate assimilated diets of wild animals. This process is complicated when omnivores consume mixed diets because their discrimination is unlikely to be the weighted average of the various dietary constituents as occurs in current models. Thus, we sought a basic understanding of how protein quality and quantity determine ∆ 15N and D 34S. Dietary protein is the primary source of both elements. Low protein quality and high protein content have the potential to increase ∆ 15N by increasing protein turnover. Protein quality, defined as the relative amount of the most limiting amino acid, accounted for 87 to 90% of the variation in ∆ 15N when mammals and birds consumed plant matter and mixed diets of plants and animals with protein of intermediate quality and quantity. However, foods containing relatively large amounts of high quality protein (i.e., vertebrate flesh) and foods with exceptionally low quality protein (e.g., lentils, Lens culinaris) had disparate nitrogen discriminations relative to what would be predicted from protein quality alone. Supplementation of plant and animal diets with carbohydrates and fats to reduce protein quantity did not reduce ∆ 15N in three plant-based diets, but reduced ∆ 15N in two of three meat diets with > 50% protein. D 34S was weakly correlated to ∆ 15N (R2 = 0.48) but was highly correlated to dietary d 34S (R2 = 0.89), presumably because methionine, a sulfur amino acid, was the most limiting amino acid in all diets. Therefore, sulfur should be highly conserved as indicated by the lack of any change in D 34S when diets were supplemented with additional energy. Predictive equations incorporating both protein quality and quantity accounted for 81% of the variation in ∆ 15N and offer the opportunity to create more realistic mixing models to accurately estimate assimilated diets.
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Details
- Title
- The biological basis for understanding and predicting dietary-induced variation in nitrogen and sulfur ratio discrimination
- Creators
- Scott T. Florin
- Contributors
- Charles T. Robbins (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525007801842
- Language
- English
- Resource Type
- Thesis