Idiosyncratic nutrient requirements of cats appear to be diet-induced evolutionary adaptations

Abstract

Cats have obligatory requirements for dietary nutrients that are not essential for other mammals. The present review relates these idiosyncratic nutritional requirements to activities of enzymes involved in the metabolic pathways of these nutrients. The high protein requirement of cats is a consequence of the lack of regulation of the aminotransferases of dispensable N metabolism and of the urea cycle enzymes. The dietary requirements for taurine and arginine are consequences of low activities of two enzymes in the pathways of synthesis that have a negative multiplicative effect on the rate of synthesis. Cats have obligatory dietary requirements for vitamin D and niacin which are the result of high activities of enzymes that catabolise precursors of these vitamins to other compounds. The dietary requirement for pre-formed vitamin A appears to result from deletion of enzymes required for cleavage and oxidation of carotenoids. The n-3 polyunsaturated fatty acids (PUFA) requirements have not been defined but low activities of desaturase enzymes indicate that cats may have a dietary need for pre-formed PUFA in addition to those needed by other animals to maintain normal plasma concentrations. The nutrient requirements of domestic cats support the thesis that their idiosyncratic requirements arose from evolutionary pressures arising from a rigorous diet of animal tissue. These pressures may have favoured energy conservation through deletion of redundant enzymes and modification of enzyme activities to result in metabolites more suited to the cat's metabolism. However, this retrospective viewpoint allows only recognition of association rather than cause and effect.

Carnivorous mammals: nutrient digestibility and energy evaluation

“…Note that this does not translate into the conclusion that all carnivores should be fed the same diet; differences in adaptations to the physical characteristics or the micronutrient composition of the natural diet need to be considered [e.g. differences in the requirement of taurine, vitamins, or polyunsaturated fatty acids, Morris, 2002]. And although this study is concerned with digestive physiology rather than behavioral needs, behavioral aspects of the feeding of captive wild carnivores should not be dismissed [e.g.…”

Whole-body protein turnover of a carnivore,Felis silvestris catus

“…The high protein requirement of the feline, thought to be for N rather than essential amino acids, is reported to be due to a permanently high hepatic capacity for amino acid catabolism and ureagenesis (Rogers et al 1977;Morris, 2002). This confers a limited ability to adapt to a low-protein diet with a consequent negative N balance.…”

“…Cats (Felis silvestris catus ) are generally thought to have a high requirement for dietary protein compared with both omnivores and herbivores (Rogers & Morris, 1980) and this has been attributed to the apparent inability of the hepatic catabolic, ureagenic and gluconeogenic enzymes of the feline to adapt to dietary protein intake (Rogers et al 1977;Morris, 2002). However, several groups have since reported that the cat does adapt to dietary protein in vitro in terms of both ureagenesis and gluconeogenesis (Kettlehut et al 1980;Silva & Mercer, 1985).…”

Influence of nutrition on feline calcium oxalate urolithiasis with emphasis on endogenous oxalate synthesis

“…3(a), step II), which can directly be used for intramitochondrial gluconeogenesis. This enzymic adaptation appears to be part of a long list of adaptations in this species, such as cysteine dioxygenase and cysteinesulfinate decarboxylase (taurine synthesis), pyrroline-5-decarboxylase and ornithine aminotransferase (citrulline synthesis), dioxygenase (retinol synthesis), glucokinase (glucose metabolism), 7-hydroxycholesterol-D7 reductase (25-hydroxycholesterol synthesis) and picolinic carboxylase (nicotinic acid synthesis) (39,98) . Dietary factors influencing endogenous urinary oxalate synthesis.…”