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

Abstract

The cat (Felis silvestris catus ) has a higher dietary protein requirement than omnivores and herbivores, thought to be due to metabolic inflexibility. An aspect of metabolic flexibility was examined with studies of whole-body protein turnover at two levels of dietary protein energy, moderate protein (MP; 20 %) and high protein (HP; 70 %), in five adult cats in a crossover design.

Effects of substitution of dietary protein with carbohydrate on lactation performance in the mink (<i>Mustela vison</i>)

“…In another strict carnivore, the cat, the activities of some key transaminating and gluconeogenic enzymes did not change noticeably in response to changes in dietary protein supply (Rogers et al, 1977), but recent results suggest that the cat is capable of metabolic flexibility: hence net protein oxidation of cats fed diets with 35.3 vs 51.9%o protein energy was significantly higher among cats on the highest protein supply (Russell et al, 2002). Furthermore, data from whole-body protein turnover studies on cats given more extreme dietary protein supplies (20 vs 70%o protein energy) demonstrated that flux, protein synthesis and protein breakdown were all significantly lower in cats given the lowest protein supply (Russell et al, 2003). Corresponding data are almost lacking for the mink but the few available results indicate that the mink has a high activity of hepatic gluconeogenic enzymes (Sorensen et al, 1995) as well as a high glycolytic capacity (Fink et al, 2002a,b), and the present results concur with the concept of ability to regulate protein oxidation rate.…”

Hypercarnivory and the brain: protein requirements of cats reconsidered

“…According to the general model of nitrogen catabolism in mammals, the lower limit of amino acid catabolism an animal can adapt to is dictated by the rate of whole-body protein turnover and the concomitant obligatory nitrogen loss (Waterlow 1999). Yet, protein turnover in cats is only one-half to one-third of rates measured in other mammals (Russell et al 2003), and thus cannot explain why cats need to catabolise amino acids at the high rates observed. In the words of Russell et al (2003), ''the apparently high feline protein requirement remains unexplained and is probably not a simple reflection of an inability to adapt hepatic catabolic capacity to variation in protein intake''.…”

“…Yet, protein turnover in cats is only one-half to one-third of rates measured in other mammals (Russell et al 2003), and thus cannot explain why cats need to catabolise amino acids at the high rates observed. In the words of Russell et al (2003), ''the apparently high feline protein requirement remains unexplained and is probably not a simple reflection of an inability to adapt hepatic catabolic capacity to variation in protein intake''.…”

“…However, animals in general have a limited capacity to store nitrogenous compounds, necessitating tight synchronisation between the intake and catabolism of protein (Millward 1995;Russell et al 2000), and this also applies to cats. Cats can adjust protein oxidation to match a range of dietary protein concentrations provided their diet contains at least 14-20% of metabolisable energy (ME) intake as protein (Russell et al , 2003Green et al 2008;Wester et al 2008).…”

“…Cats can adjust protein oxidation to match a range of dietary protein concentrations provided their diet contains at least 14-20% of metabolisable energy (ME) intake as protein (Russell et al , 2003Green et al 2008;Wester et al 2008). This is considerably higher than the minimum of 6-8% of ME required by humans, rats and dogs for maintenance (Rogers and Morris 2002;Rand et al 2003;NRC 2006;Green et al 2008).…”