Worried that your old feline friend is rejecting her classic milk and eggs platter? No, she is not mad that you forgot to kiss her goodbye in the morning. No, she hasn't stopped loving you. Your good old friend doesn't want the protein-rich food simply because her body cannot take it.
A recent study found that while younger cats wanted protein, older cats were more likely to prefer carbohydrates, owing to a different gut microbiome than their younger mates.
It could be because the concentrations of sulfated microbial catabolic products -- protein-breakdown leftovers that in humans are connected to cardiovascular and kidney disease -- were significantly higher in older cats.
"Just like with older people, older cats may have a different gut microbiome than younger cats, which would mean different microbial metabolic activities," said Jean Hall, Professor at the Oregon State University, US.
Analysing younger cats, the team found that those with less lean body mass tended more strongly towards protein consumption than cats with more lean body mass; younger cats in general wanted protein more than older cats.
Basically, if a younger cat gets more protein than it can use, it can safely deal with and dispose of the excess a lot better than an older cat can, Hall noted.
For the study, published in the Journal of Experimental Biology, the team included a small group of cats, who were allowed to choose among high-fat, high-carbohydrate, high-protein and balanced foods.
Cats were found to eat in a weight-maintenance way by adjusting their intake based on the food's energy density, even if given unlimited access to food that tastes how they like it.
Cats on average chose to get 43 per cent of their calories from carbs and 30 per cent from protein, the study showed.
Hall also found that the older cats' blood had much lower levels of DHA -- a long-chain omega-3 fatty acid important for the brain, heart and eyes -- than the younger cats.
"None of the foods had ingredient sources of DHA or EPA, another long-chain omega-3, but cats are able to synthesise DHA by elongating and desaturating fatty acids," Hall said.
"The older cats, though, are a lot less efficient at that," he said.