Ok ok I bow to social pressure and Banty's threats of self immolation 
.
Really I am quite flattered by your interest
. Although I will say I was not a member of the group that did the eggsperiment. I just donated some of my ladies' eggs to the cause.
Background: one of the things that stable isotope studies are used for is dietary reconstruction. Chemically, you really are what you eat (plus a couple of parts per mil). The egg group analyzed shell and egg protein samples from three different groups of eggs (some expensive "vegetarian fed" chicken eggs, some cheap house-brand eggs that didn't promise the hens were vegetarian, and eggs from my free-range birds) to look at the ratios of carbon stable isotopes (C13/C12) and nitrogen stable isotopes (N15/N14).
Carbon isotope ratios are particularly useful for reconstructing the plant portion of an animal's diet, specifically the quantity of C4 photosynthetic plants versus C3 photosynthetic plants. Most major domestic crops including corn and wheat are C4 plants. So are many wild grasses. Most other wild and garden plants are C3 plants.
The results of the study showed all three groups of birds (fancy "vegetarian hens"; unspecified commercial layers; and my birds) had a strong C4 signature. Basically they were all eating a lot of corn. My ladies had slightly more C3 plants in their diet though from free ranging. In general though, the three groups were pretty tightly grouped in terms of their carbon (plant) signatures.
Where things got interesting was with the nitrogen values. The ratio of stable nitrogen isotopes in an animal's tissues can be used to reconstruct trophic level (ie your place in the food chain). All the commercial layers had signatures similar to a vegetarian animal at the very base of the food chain. My ladies had nitrogen levels that were way higher. They looked like they were about 2 rungs higher on the food ladder. So chemically, it looked like my girls had been preying on other chickens
The reality though is that they get bugs, fish, and whatever the can find on the property. Still, I was so proud of my little velociraptors and everyone in class was shocked by the difference.
.Really I am quite flattered by your interest
. Although I will say I was not a member of the group that did the eggsperiment. I just donated some of my ladies' eggs to the cause.Background: one of the things that stable isotope studies are used for is dietary reconstruction. Chemically, you really are what you eat (plus a couple of parts per mil). The egg group analyzed shell and egg protein samples from three different groups of eggs (some expensive "vegetarian fed" chicken eggs, some cheap house-brand eggs that didn't promise the hens were vegetarian, and eggs from my free-range birds) to look at the ratios of carbon stable isotopes (C13/C12) and nitrogen stable isotopes (N15/N14).
Carbon isotope ratios are particularly useful for reconstructing the plant portion of an animal's diet, specifically the quantity of C4 photosynthetic plants versus C3 photosynthetic plants. Most major domestic crops including corn and wheat are C4 plants. So are many wild grasses. Most other wild and garden plants are C3 plants.
The results of the study showed all three groups of birds (fancy "vegetarian hens"; unspecified commercial layers; and my birds) had a strong C4 signature. Basically they were all eating a lot of corn. My ladies had slightly more C3 plants in their diet though from free ranging. In general though, the three groups were pretty tightly grouped in terms of their carbon (plant) signatures.
Where things got interesting was with the nitrogen values. The ratio of stable nitrogen isotopes in an animal's tissues can be used to reconstruct trophic level (ie your place in the food chain). All the commercial layers had signatures similar to a vegetarian animal at the very base of the food chain. My ladies had nitrogen levels that were way higher. They looked like they were about 2 rungs higher on the food ladder. So chemically, it looked like my girls had been preying on other chickens
The reality though is that they get bugs, fish, and whatever the can find on the property. Still, I was so proud of my little velociraptors and everyone in class was shocked by the difference. 
