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Nitrogen in Animals: Applications

Nitrogen in Animals: Applications. Overview How are δ 15 N affected by the following processes:. Pregnancy Nutritional Stress Different diets & diet quality Nursing Fasting. Spoiler alert! They all have VERY similar results…. Pregnancy and Nutritional Stress. Studies investigate :

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Nitrogen in Animals: Applications

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  1. Nitrogen in Animals: Applications

  2. OverviewHow are δ15N affected by the following processes: • Pregnancy • Nutritional Stress • Different diets & diet quality • Nursing • Fasting Spoiler alert! They all have VERY similar results…

  3. Pregnancy and Nutritional Stress Studies investigate: δ15N & δ13C values in body of pregnant women with and without nutritional stress (Fuller et al. 2004, 2005) Methods Examine δ15N & δ13C isotopes in the body from pre-conception to delivery by: • Conducting dietary surveys 2) Collect hair samples of mother post-delivery

  4. d15N d13C

  5. Happy Mommy Fuller et al. 2004

  6. Sad Mommy Fuller et al. 2005

  7. Negative nitrogen balance = increased fractionation Sick b/w 10-16 weeks Sick throughout 1st trimester

  8. Why? Well…not completely understood DECREASES IN δ15N due to maternal N conservation: • Assimilation of greater percentage of dietary N with lower δ15N values results in a reduction of steady state diet to body trophic fractionation (0.5-1‰) • Decreased urea synthesis and increased urea salvage in colon (peeing out heavy nitrogen) • Mother decreases in N and fetus increases = fetus literally eating mommy and increasing in trophic level

  9. Reasoning for INCREASE in δ15N: As nutritional stress & weight loss continue, increase of muscle protein breakdown, lighter N is not replaced by dietary protein, & remaining tissues are enriched in heavier N (increased fractionation)

  10. Diet quality 2 Studies: Oreochromis niloticus – “Nile tilapia” (Gaye-Siessegger 2004) Paradosa lugubris – “Wolf spider”(Oelbermann and Scheu 2001)

  11. Nile tilapia Study investigates: Influence of different diets on δ15N & δ13C in fish bodies Methods • 32 fish reared on same diet for 11 weeks to equilibrate on diet, then 7 were killed to estimate initial isotopic composition of body • Provide fish with 3 different protein diets in controlled lab for 8 weeks • Analyze all fish at end of experiment after 48 hour fast

  12. Results • No significant decrease inδ15N & δ13C, body mass, b/w averages of feeding groups • Declining trophic shift for individuals in δ15N (6.5‰- 4‰) & δ13C (4‰-2.5‰) w/ increasing protein retention in individual fish Experiment demonstrates high influence of individual protein balance of δ15N & δ13C in animals – dietary protein was conserved differently in tissue of individual fish = less fraction.

  13. Wolf spider Study investigates: Influence of diet quality on δ15N & δ13C in spiders on different quality diets Methods: Changes in δ15N & δ13C w/ time: - Adult females, hatchlings, spiderlings fed intermediate quality food for 3, 6, & 11 weeks Changes in δ15N & δ13C w/ trophic level and starvation: - Adult and juvenile spiders were fed single species diets (low, med, high quality), mixed (high & low), and starved

  14. Results - Since 14N is preferentially excreted during metabolism, the hatchling N would be isotopically lighter. - As individuals become larger, more isotopically like food item, then become enriched over food item by ≈3‰ Changes in δ15N & δ13C w/ time:

  15. Changes in δ15N & δ13C w/ trophic level: 2.5‰ 2.2‰ 3.3‰ 5.2‰ Stepwise trophic level enrichment

  16. Spiders on high-quality diet were bigger and increased in size faster, & had higher δ15N & δ13C values V. High quality Low quality High quality Intermediate quality V. Low quality

  17. Changes in δ15N & δ13C when starved: Starvation leads to enrichment of δ15N due to recycling body nitrogen (i.e. “eating yourself”)

  18. Sea Lions Methods • Teeth and bone collagen samples from two different species with different weaning behaviors • Using δN values to determine age of pup weaning/ trophic level

  19. Results Northern Fur Seal aka Zalophus (bone collagen)

  20. Tooth dentin Northern Fur seal

  21. Isla Santa Margarita Seal aka Callorhinus (bone collagen)

  22. Applications • May lead to a method for investigating pregnancy and fertility patterns in populations of animals (past & present) • Pregnancy, nutritional stress, diet quality findings need to be considered in diet studies (ca not always assume ≈3‰ fractionation factor for δ15N) • Non-invasive monitoring of nitrogen balance in women during pregnancy – examine overall health • Applied to medical studies of protein stress & N balance: anorexia, bulimia, exercise, disease, weight loss, & burns • Do other tissues detect pregnancy, nutritional stress, changes in diet quality? • Determining feeding habits in animals. • More research to discover the biochemical reasons for δ15N increase and decrease in animals

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