Carbohydrates herbivore diets

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 ... 

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 ... 

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-... 

Herbivores typically eat diets with high carbohydrate and low protein and lipid. F is about 0.15, and the protein is mainly plant derived and not very different in S C from the non-protein (i.e., Dp is close to Dn). For carnivores, F is typically 0.5 or over, and carbohydrate is low. Animal protein is generally isotopically heavier, while the non-protein is much higher in lipid, so that Dp - Dn is generally quite large (>5%o). The spacing, Bcolla Bcarb. for the two diets is evaluated according to the equation above. 

The nature of the diet sets the basic pattern of metabohsm. There is a need to process the products of digestion of dietary carbohydrate, lipid, and protein. These are mainly glucose, fatty acids and glycerol, and amino acids, respectively. In ruminants (and to a lesser extent in other herbivores), dietary cellulose is fermented by symbiotic microorganisms to short-chain fatty acids (acetic, propionic, butyric), and metabohsm in these animals is adapted to use these fatty acids as major substrates. All the products of digestion are metabohzed to a common product, acetyl-CoA, which is then oxidized by the citric acid cycle (Figure 15-1). 

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