Control diet

One control cycle (control diet) then one cycle on diet supplemented with 60 g Arcon F (n = 5)... 

Ambrose and Norr (1993) and Tieszen and Fagre (1993) have shown that 5 C of carbonate in bone apatite (6 C,p) is the most accurate measure of the whole-diet composition (Ambrose and Norr 1993 28). The actual 5 C of total diet is related to that of apatite by an isotopic offset (fractionation) which Ambrose and Norr estimate to be 9.5 0.6%o. Other estimates range from 9.6 0.1%o for small mammals on controlled diets (DeNiro and Epstein 1978) to 12%o for large herbivores on natural diets (Lee-Thorp et al., 1989). The origin of this offset is of some concern to us here. We can only use 5 Cap as a measure of total diet if we know A,p.j,e, and also know that this fractionation is a constant, at least for a given species, and does not itself depend on the quality of the diet. 

The data set actually used for modeling, from controlled diet experiments of Ambrose and Norr (1993) and Tieszen and Fagre (1993), is shown in Table All.l. 

Controlled Diet and Climate Experiments on Nitrogen Isotope Ratios of Rats... 

Table 12.1. Diec-lissue differences iri 5 N CA N) in controlled diet experiments and within modern natural ecosystems.

Controlled diet to brme shrimp +4.9 Whole animal Minagawa Wada 1984... 

Controlled diet to mouse +2.9 Muscle DeNiro r Epstein 1981... 

Controlled diet to rats +3.3-4.9 Various organs Yoneyama ti a. 1983... 

The nutrient stress hypothesis can be tested by comparing diet-tissue A N values of animals on low versus normal and high protein diets. Our controlled diet experiments, although primarily designed to trace carbon from different dietary macronutrient fractions (proteins versus carbohydrates, fats and sugars) to animal tissues under different levels of nutrient stress (Ambrose and Norr 1993) may be suitable for testing this hypothesis because they contain diets with 5, 20 and 70% protein by weight. 

Eleven controlled diet and environment experiments have been designed in a way that can be used to investigate the effects of protein nutrition and heat and/or water stress on diet-tissue A N. Laboratory rats were raised on purified, pelletized diets in which the isotopic composition of proteins, lipids and carbohydrates were well characterized and their proportions accurately and precisely measured (Ambrose and Norr 1993). Four experiments involved manipulation of temperature and/or water availability. Of these four experiments, one used a diet with high (70%) protein concentrations and heat/water stress (36°C) and three used normal (20%) protein concentrations. Seven experiments were conducted at normal temperature (21°C) with water ad libitum. Of these seven experiments, two used diets formulated with veiy low protein (5%), three with normal protein and two with high protein concentrations. 

Figure 12.1. Relationship between collagen 8 N values and age of male and female rats raised on controlled diets, and sacrificed at 40 day intervals beginning 91 days after birth.

Ambrose focuses on stable nitrogen isotope ratios and reports the results of controlled diet and climate experiments on rats. He explores trophic level differences and heat stress and their effects on stable isotopes of nitrogen. As with the preceding chapters by Schwarcz and Hedges and van Klinken, Ambrose explores the various biochemical principles that explain why variation is expected under these circumstances. 

Interestingly, a 5.2-fold increase of lutein in the diet of the chickens for 4 weeks led to a substantial 4.4-fold increase in lutein in the plasma of the WHAM chickens, but only a 2.5-fold increase in control chickens (Connor et al., 2007). Overall, the plasma level of lutein was still 4.8 times greater in the control chickens than in WHAM chickens fed a lutein-rich diet. Furthermore, both types of chickens on lutein-rich diet reached similar levels of lutein in their heart and liver. Yet, the difference in the levels of lutein in the retina of the control and WHAM chickens on lutein-rich diet became even greater than in chickens on the control diets. The retinas of WHAM chickens accumulated only 6% as much lutein as was accumulated in retinas the control chickens. 

Cao G, Booth, SL, Sadowski JA and Prior RL. 1998. Increases in human plasma antioxidant capacity after consumption of controlled diets high in fruit and vegetables. Am J Clin Nutr 68(5) 1081—1087. 

Mink 1.0 mg/kg diet daily for 4 months then every other day for 4 months alternating with control diet High mortality after 4 months when subjected to cold stress significant placental transfer to the fetus 9... 

Eggs from hens fed 218 or 257 mg Zn/kg diet containing a maximum of 14 mg/kg FW, equivalent to about 25% more zinc than eggs produced by control hens. Eggs from the two higher-dose diets had a maximum of 19 mg/kg FW or 57-90% more zinc than eggs produced by hens fed a control diet of 26-28 mg Zn/kg (Stahl et al. 1988). 

Dairy cows fed control diet (310 mg Zn/kg DW feed) or control diet supplemented with 1000 or 2000 mg Zn/kg DW ration (as ZnS04 H20)... 

Continuous exposure to diets containing PCBs from Saginaw Bay carp induced cytochrome P-450 activity in a dose-dependent manner. Cytochrome P-450 activity in animals switched to the control diet from the PCB-containing diet was the same as controls. EROD hepatic activity is a potential biomarker for current exposure to PCBs and other similar cytochrome P-450 inducers... 

Adults males given a choice between a control diet or diets with 5, 10, or 20 mg Se/kg ration as selenomethionine Adult males were fed diets supplemented with 0, 10, 20, 40, or 80 mg Se/kg ration as selenomethionine for 16-week exposure that began in November. Survivors were fed untreated diets for 4 more weeks... 

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