You would probably avoid eating food that's been sitting out there uncovered and unrefrigerated for a few hours, wouldn't you? But what about cat food? For how long can you leave out the food in your cat's dish? How long before cat food spoils? When is it no longer safe for your cat to consume?
We have some answers that might surprise you.
Many cat care resources will tell you that you should remove the cat's food within 20-30 minutes. For some owners that's not a realistic timeframe. Some cats eat more slowly than others and may take their time, grabbing a few bites and returning later for more. Some owners may need to leave their home shortly after serving Kitty's meal and need to know if that's risky or not.
In fact the 20-30-minute rule is probably taking things too far for most cats and owners.
Let's take a look at the risks associated with leaving food out and see how they pertain to different types of cat food. Then we'll talk about how long you can leave out each type of cat food - the times do vary!
Oh, and before we begin - this article does not address automatic cat feeders. Check out our Automated Cat Feeders Guide to see which models offer cooling options.
When Cat Food Spoils: The Risk of Bacterial Contamination
How does food spoil? Generally speaking, it becomes contaminated with microorganisms that break up the nutrients for their own needs. In the process, they also secrete toxins. These microscopic creatures can be either fungi (such as mildew) or bacteria.
Whenever you leave food out it becomes contaminated with some amount of bacteria and microscopic fungi. Fungi (mildew) takes a while to develop - usually days. Unless the food had already been severely contaminated by fungi, it's unlikely to become moldy within the first 24 hours.
Bacteria are much faster. Given the right conditions, germs can multiply significantly within several hours. Thus, the main risk associated with leaving out cat food is that of bacterial contamination by dangerous bugs such as salmonella and listeria.
Several factors can contribute to bacterial contamination. These are the risk factors that can make food spoil sooner rather than later:
Type of bacteria
Some bacteria are more likely to cause disease than others. If these types of bacteria are present in the food, the risk for infection and sickness increases. Salmonella and listeria are probably the most dangerous ones.
Fortunately, listeria and salmonella are not the type of bacteria that can just drop from the air in your home on the food. They are found mostly in raw eggs and chicken but also - to a far lesser extent - in commercial dry cat food.
Initial amount of bacteria
Bacteria multiplies fairly quickly. Given the right conditions, salmonella doubles in numbers every hour. The more bacteria you start out with, the more you'll get within a few hours. The severity of a salmonella infection depends on the amount of germs consumed, so the longer you wait, the more dangerous the food becomes.
Salmonella, listeria and other bugs thrive at temperatures of 80-100 degrees Fahrenheit. That can easily be the temperature in your home on a hot day. While cold temperatures and even freezing do not kill these hardy bacteria, they can prevent them from multiplying.
Germs like humidity because water is required for their life cycle to be complete. Some types can survive without water, but they can't grow in numbers in a dry environment.
Types of Cat Food: How quickly do they spoil?
Now that we know what conditions can make food spoil faster, let's take a look at common types of cat food.
Dry cat food
Kibble can have an initial amount of bacteria, but the dry conditions will make it harder for the germs to multiply. Moreover, harmful bacteria are not likely to be found in dry cat food because it is heavily processed at very high temperatures.
It's important to note that kibble can sometimes become cross-contaminated with salmonella, but it's a rare occurrence. Batches are routinely scanned for contaminants and bacteria by the FDA, and any amount of salmonella is cause for a recall. Obviously, manufacturers go to great lengths to prevent that.
How long can you safely keep dry cat food out for?
You can safely leave dry cat food out for several days and it won't spoil. The bacteria simply won't thrive in such a dry environment. However, it's best to throw out leftovers and wash the dish on a daily basis, to keep Kitty's food fresh and appealing.
Wet/canned cat food
Canned food is considered sterile until opened. The food is thoroughly cooked in the can which allows it to last for so long. Most formulas also contain some preservatives - which can be natural substances such as certain types of vitamins.
Once you open the can, bacteria from the surrounding environment begin to invade the food. In a home environment, these are relatively benign bacteria - rarely salmonella, listeria or E coli - but given enough time the food will eventually spoil.
How long can you safely keep wet/canned cat food out for?
Leading pet food manufacturer Purina suggests removing uneaten wet food after one hour, while Hill's says it's safe to leave the food out for up to four hours at room temperature. Anywhere in between in a cool room is probably safe.
Many cat owners leave wet food out for the day with no harm to their cats. That food is highly unlikely to become contaminated with virulent bacteria such as salmonella, E coli or listeria, but even less dangerous germs found in our homes will spoil the food eventually. If you're feeding a kitten, an elderly or sick cat, it's best to err on the side of caution and serve canned food only when it's fresh.
When removing the leftovers, throw them away. Serving only half a tin? Cover the can and refrigerate immediately after pouring the desired amount into Kitty's food dish.
Homemade cooked food
As long as you thoroughly cooked the food and refrigerated it right away, homemade cooked food is a lot like canned food. It starts out nearly sterile and with no pathogenic microbes such as salmonella. Without any preservatives added, it may be easier for microbes to develop in homemade cooked food.
How long can you safely keep homemade cooked cat food out for?
Remove leftovers within a few hours, depending on room temperature and on the consistency of the dish. The drier the food and the larger the pieces (for example, chunks of cooked chicken breast), the longer you can safely keep it out. If you're not sure about the length of time appropriate for the recipe you're using, consult with a veterinarian.
According to the FDA, even human-grade meat and eggs can be legally marketed when harboring pathogenic salmonella. That's why the public health recommendations call for thoroughly cooking eggs and meat - they assume they are always or almost always contaminated. Freezing the meat does not kill the bacteria, and once the meat is thawed, the germs are free to multiply.
That makes raw meats - whether commercial or homemade - the most sensitive to bacterial contamination of all types of cat food. Ground raw will spoil even faster because the grinding process allows bacteria better access to the nutrients in the meat.
How long can you safely keep raw cat food out for?
The shorter the better. Salmonella doubles its population within 40 minutes, given the right conditions. Raw chicken and eggs on a warm day provide these very conditions. It's best to remove any leftovers as soon as your cat has finished eating.
When The Food Doesn't Taste Good Enough
Even if you keep the food within the safe time limit, it simply may not taste as good a few hours later. Wet food tends to congeal or dry up within a few hours. Dry food will go stale within a day or two. The food is still safe to consume, but some cats still choose not to eat it because it's not fresh enough for their taste.
By the way, don't rely on your cat's sense of smell or taste as a way to tell when food is unsafe for consumption. Cats do get food poisoning from consuming small amounts of harmful bacteria that doesn't affect the food's odor or flavor.
Read more - Salmonella in Cats: 9 Things Every Cat Owner Needs To Know.
So, what's your choice? For how long do you leave your cat's food out? Let us know in a comment and don't forget to mention the type of diet you're feeding.