Cats Select for Adequate Methionine but Not Threonine

Abstract

EXPANDED ABSTRACT KEY WORDS: dietary choice feline nutrition methionine threonineCats are more selective than dogs in the foods they eat. Selectivity can be exaggerated in situations often termed ''finickiness'' when cats are inadvertently trained to eat only one food by the owner routinely replacing a less-acceptable food with a desirable food. This finickiness does not appear to be learned taste aversion or caused by nutrient deficiency or excess and may be unique to cats. There is a paucity of information on the extent that dietary selection of cats is driven by odor, taste, texture (mouth feel), and metabolic feedback from the nutrients in the diet. Much is known about the effects of nutritional deficiencies and excesses on dietary choice in rats (1), whereas little is known for cats. Cats, unlike other species, will not select for sweetness (2) or for sodium even if they are sodium deficient (3), but when they are acidotic, cats will select diets containing extra sodium (4). Apart from positive palatability factors associated with proteins, cats do not select for or against protein even if the random choice results in protein deficiency and decreased weight gain (5). Cats are less sensitive than rats to leucine-isoleucine and valine antagonisms. A mild antagonism is exhibited by cats when isoleucine is limiting in the basal diet (6), but they do not avoid the diet containing a great excess of leucine (100 g/kg of diet) (7). The question arises, If cats do not select for or against protein, do they select for or against specific essential amino acids? The purpose of this study was to determine the dietary choice of cats when given threonine (Thr)-or methionine (Met)-deficient diets vs. more balanced diets. METHODSSpecific pathogen-free cats from the Feline Nutrition and Pet Care Center, University of California, Davis were individually housed and adapted to a purified diet until they were growing normally (kittens) or maintaining weight (adult cats). During the choice phase, cats were offered various choices between two diets in bowls fixed to the front of their cages. The bowl positions and diets were switched daily, and excess quantities of each diet were available at all times. The cats were maintained in accordance with the Guide for the Care and Use of Laboratory Animals (8).In each experiment, we tested whether cats would select or avoid a diet least deficient in an essential amino acid. For the Thr-choice studies, growing kittens (1.7 6 0.1 kg, n ¼ 9) were offered a choice of two of four purified diets that contained 325 g/kg of amino acids 5 and either 0, 4, or 6 g of Thr/kg of diet (9) or a proteinfree diet. The amino acid mixture contained concentrations of all essential amino acids (except Thr) that exceeded the minimal requirements. Alanine was exchanged for Thr in the amino acid diets, and equal weights of starch and dextrose replaced the amino acid mixture in the protein-free diet.For the Met-choice study, after adaptation to a complete purified diet, adult cats (5.1 6 0.4 kg, n ¼ 8) were fed e...

Might nitrogen limitation promote omnivory among carnivorous arthropods? Comment

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“…Therefore in rats, the decrease in food intake causes the decrease in weight gain, whereas in kittens, the decrease in food intake appears to be secondary to the decrease in weight gain. That is, there is a decrease in energy need of kittens because inadequate quantities of the limiting EAA are constraining body weight gain (Rogers et al., 2004). All four EAAs, that when limiting, showed increased body weight gains at the higher concentrations of dietary CP were also present at higher concentrations in the plasma when the diet contained the higher concentration of dietary CP, although the differences were not statistically significant.…”

The Brain's Response to an Essential Amino Acid-Deficient Diet and the Circuitous Route to a Better Meal

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