Herbivores diets

Figure 10.2. Schematic diagram showing how restricted conversion of fatty acids to amino acids influences the fractionation between collagen and CO3 of bone apatite LI = lipid component, PR = protein, T = total isotopic composition AP = COj component of apatite, a) Herbivorous diet (Cj plants only) b) Carnivorous diet, assuming rj = 1 (no barrier to fatty acid conversion to AAs) c) Carnivorous diet, assuming ri < 1 note that carbonate-collagen fractionation is smaller.

These data do not provide strong support for the heat water stress/urea recycling model (Ambrose 1991). This model may be incorrect or inapplicable to rats. Were the experimental conditions inappropriate, with temperatures too low and/or protein levels too low or too high In the heat stress experiments that inspired this research animals were kept at a temperature of 40°C for 12 hours each day rather than 36°C in this study. In our heat and water stress experiments the protein content of the diets were set at 20% and 70%. These are relatively high levels compared to those in herbivore diets. It would be necessary to repeat the experiments with ruminant herbivores or lower protein diets to conclusively determine if rats are an inappropriate model. 

The study of coprolites, particularly of their composition, throws light on the paleodiets (the feeding behavior) of ancient animals as well as humans and on the diseases that affected them. Coprolites composed only of plant material, for example, are indicative of a herbivorous diet bone remains in the feces denote carnivorous behavior, while remains of both plant and... 

Freeland, W.J., Calcott, P.H., and Anderson, L.R., Tannins and saponin interaction in herbivore diets, Biochem. Syst. Ecol, 13, 189, 1985. 

Herbivore diets consist only of plant materials and thus are the simplest diets to understand Herbivores eat the more digestible portions of plants so their diets consist of a preponderance of carbohydrates with only minor contributions of lipids and proteins from the plant material consumed ... 

Lipids form a minor part of the carbon content of herbivore diets As a result, despite the fact that they are used primarily for energy metabolism, their abundance is not sufficient to greatly influence the isotopic composition of blood bicarbonate For this reason, the isotopic composition of lipids will not significantly affect the isotopic ratio of carbon in bone apatite ... 

Protein in herbivore diets is likely to be adequate in amount to satisfy the dietary requirements for net growth of an herbivore (approx 1% of bulk diet), and perhaps also the requirement for tissue turnover The distribution of individual amino acids, however, may not even be close to those required for proper tissue growth or the turnover of existing tissues As a result, it would be expected that a substantial amount of amino acid synthesis would occur, and that the collagen of herbivores would closely reflect the isotopic composition of the herbivore s diet ... 

A theoretical model for carbon isotope fractionation between herbivore diets and herbivore bone is shown in Figure 2A This model shows the isotopic relationship of gelatin to that of hydroxyapatite and the relationship of both to the original plant food diet The gelatin seems to reflect the growth portion of the diet while the apatite seems to reflect the energy portion of the diet The difference of - 1 o/oo between apatite values and gelatin values is due in part to the fact that blood bicarbonate has a enrichment produced by the transfer of CO from blood plasma to expired air This effect has been experimentally verified and will be described elsewhere ... 

Herbivore diets usually contain adequate amounts of protein as evidenced by the net growth of the animal but the mixture of amino acids derived from vegetation is probably different from that required by the animal Thus herbivores probably synthesize a large proportion of their required amino acids by transamination of keto->acids derived from the carbohydrate part of their diet As a result one would expect that the carbon isotopes of both apatite and gelatin in herbivores would show a direct relationship to the mixture of Co and plants consumed ... 

Singer MS, Lichter-Marck IH, Farkas TE, Aaron E, Whitney KD, Mooney KA. Herbivore diet breadth mediates the cascading effect of camivOTes in food webs. Proc Natl Acad Sci USA 2014 lll(26) 9521-6. 

In most cases of secondary protection of insect herbivores by alkaloids the source of the alkaloid is the herbivore diet, i.e. the plant host. There have been several interesting reports on the occurrence of chemical defenses of insects based on alkaloids actively synthesized or at least chemically modified by the insect. One such report showed that deterrence to predation by ants and spiders was afibrded to the Mexican bean beetle Epilachna varivestis) by the production of the homotropane alkaloid euphococcinine (66). This compound which actually may be a polyketide, is not present in the body of larvae or newly hatched adults but is accumulated in the beetles blood within one week of emergence. When attacked, the beetle reflex-bleeds emitting droplets of blood containing as much as 5 pg of euphococcinine. 

Boyd and Goodyear [125] showed that determinations of just energy flow or energv transfer are too coarse simplifications for ecological systems. Carnivorous nutriments are of huge food value due to their content of proteins and thus form a rich diet while the food value of herbivorous diet is much lower with an interme-... 

Applied to herbivorous diet some general rules can be stated ... 

Exposure to estrogenic compounds through diet will differ for herbivores and carnivores, the latter being most likely to encounter endogenous steroids in their prey. Efficient uptake of steroids in mammals is illustrated by the use of the contraceptive pill, but routes of absorption in invertebrates remain to be determined. The relationship between endocrine disruption and metabolic toxicity, with reduced reproductive viability a secondary consequence of metabolic disturbance, also merits further study in invertebrate species. 

Vitamin Bjg is not synthesized by animals or by plants. Only a few species of bacteria synthesize this complex substance. Carnivorous animals easily acquire sufficient amounts of Bjg from meat in their diet, but herbivorous creatures typically depend on intestinal bacteria to synthesize Bjg for them. This is sometimes not sufficient, and certain animals, including rabbits, occasionally eat their feces in order to accumulate the necessary quantities of Big. 

Where CO2 in the free atmosphere has a 5 C value of-7%o, C3 and C4 plants are anticipated to have 5 C values of about -26.5%o and -12.5%o respectively (van der Merwe 1989) archaeological maize, however, typically averages -9.5%o(Schwarcz et al. 1985). The isotopic values of modern maize and C3 plant foods in Mesoamerica (Wright 1994 203-206), after correction for the Industrial Effect, average -9.6%o and -26.4%o respectively. Since herbivore collagen is typically enriched by +5%o relative to the diet (van der Merwe 1989), animals from this region with a pure C3 plant diet should... 

Study, ancient Maya diet shows a A N of 4.5%o (humans-herbivores). The 8 N values for mixed-diet humans in Schoeninger et al. (1983) seem always somewhat too positive for their supposed food European agriculturalists are about 8-10%o. Also, Bocherens et al. (1991) and Lubell et al. (1994) give similar values (aroimd +9%o) for medieval French and Neolithic humans from Portugal, respectively. The 8 N values (+9.3 and 11.6%o) of two human (Neanderthal) samples (Fizet et al. 1995) are very similar to those of associated carnivores but are only slightly higher than those of Neolithic humans. 

Table 3.2 shows the 5 Cu and 5 Cc values of herbivores, omnivores, carnivores and humans. The (climate-corrected) trophic level effect between herbivores and carnivores is 0.90%o. Human values are closer to carnivore and omnivore values than to herbivore 5 Cc values. The human 5 Cc values are on average 0.66%o more positive than the herbivore 5 Cc values, a good estimate for a carnivore effect in humans (see section on trophic level effects, below). The average human 5 Cc value is -19.92 1.28%o,which would indicate that Holocene humans in Europe had a diet that consisted of C3 terrestrial foods, whieh is as might be expected. By looking at the humans separate from the total bone data set, we notice potential human food selection (Fig. 3.3) we can see a non-climatic pattern, which is much less uniform than in the total bone data set (Fig. 3.2b). Italy (6 Cc = -21.3%o) has a much more negative 8 Cc value than the Czech Republic (8 Cc =-18.7%o), Spain (8 Cc = -19.3%o) and Greece (-18.9%o but the 8 N of 9.0%odoes not indicate marine food), while the northern European coimtries are closer to a 5 Cc value of-20%o. What the actual causes are for this pattern in the human samples is not clear to better understand these variations it is best to consider, where possible, the 8 N values with the 8 Cc values. 

Kohn, M.J., Schoeninger, M.J. and Valley, J.W. 1996 Herbivore tooth oxygen isotope compositions effects of diet and physiology. Geochimica et Cosmochimica Acta 60 3889-3896. 

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. 

Most accounts of the larger A,p.,.o in carnivores have attributed this effect to higher proportion of lipids in the diet of carnivores. This arises because carnivores obtain all or most of their nutrition from the flesh of other animals, a significant part of which is composed of lipid. By contrast, lipids make up a much smaller fraction of the total carbon pool in the diet of herbivores, particularly mminants which get much of their energy from digestion of cellulose. Humans who selectively use seeds and grains as food sources obtain a... 

We can now appreciate that this explanation is incorrect, because the energy food for an animal is all of its diet and not just carbohydrates and lipids. Therefore we should not expect any selective offset due to the presence of lipids in the flesh of herbivores. Indeed, in general, the average 5 Cof total consumable herbivore tissues (flesh, lipids, etc.) is very close to that of the diet, and we might not expect any difference in the isotopic composition of the collagen or carbonate of a consumer of pure Cj plants as opposed to a consumer of the flesh of Cs-eating herbivores. We must seek elsewhere for the cause of the trophic level effect on A,p.co-... 

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