Dear Doctor – August 2015

When food goes past its expiration date; the pro-estrus cycle of cats; help for bad breath


Pet food and expiration dates

Q I recently bought several large bags of a high-quality cat food on sale at our local pet store. Unfortunately, I just realized that the “best by” date passed by a couple of weeks ago on two of the bags (the third bag’s date is okay).

Should I now consider this food to be unsafe and throw it away?
Bettyjean Murphy

A Dear Bettyjean: Reputable pet food manufacturers set their product expiration dates to ensure that all nutrients are at adequate concentrations throughout the shelf life of the product, based on testing and knowledge of degradation rates of various nutrients with storage.

While pet food with a “best by” date of yesterday is unlikely to cause health problems, it is hard to know at what point after that date the food will no longer meet essential nutrient needs — is it days, weeks or months? The answer depends on the composition of the food and the packaging, as well as how it was stored before and after purchase. The safest bet is to replace food that is past its “best by” or expiration date.

A related concern is how long food should be kept once the package has been opened. Again, this is likely dependent on nutrient composition and storage conditions— but a good rule of thumb for dry food is to buy bag sizes that you can use up in about one month. Opened cans should be covered and refrigerated and kept no longer than three to seven days. While buying large bags may seem cost effective, the risk of nutrient degradation is increased if it takes a long time to finish an open bag. Alternatively, the food manufacturer can be contacted for storage information specific to their diets.

It is best to always store food in the original packaging, tightly closed. However, if you do need to take it out of the package for any reason, be sure to save the portion of the bag or label that includes the lot number, expiration date and manufacturer contact information.
Cailin Heinze, VMD, MS, DACVN
Assistant Professor of Nutrition
Cummings School
of Veterinary Medicine
at Tufts University

An opportunity to spay

Q After leaving a dinner party late one night, my wife and I were walking to the subway station to head back to our apartment when a feral cat adopted us by meowing as loudly as she could and rubbing up against our legs. It turned out she was pregnant, which was fine with both of us, but she had an extremely difficult labor.

The single kitten she had been carrying died during birth; the poor mother kept trying to lick her baby alive. We decided to keep the cat and have her spayed — but after only about 10 days, she is back in heat, and now we have to wait. She is meowing rather obnoxiously and slithering along the floor toward me every chance she gets, even waking us up at night. We are wondering how could she go into heat so quickly after giving birth.
Brian Longfellow

A Dear Brian: Reproductively, cats are different from dogs, people, horses, cows, and most other mammalian species. Most female mammals have regular cycles that are about a month long (except dogs, whose cycles last about six months). The cycle starts with a period of time called pro-estrus, which consists of the hormonal changes leading up to ovulation. Then comes ovulation itself — the releasing of an egg from one of the ovaries. If the animal mates, she becomes pregnant. If not, the hormone levels drop, the egg is no longer viable, and a period of time passes before pro-estrus starts up again.

Cats, on the other hand, don’t ovulate after pro-estrus unless they mate. They are what is known in medical circles as induced ovulators. A male cat’s penis actually has little “spines” on it that stimulate the ovulatory process. Because of that, the hormone levels of a cat who doesn’t become pregnant when she reaches pro-estrus don’t have to “settle down” as much as in other species — there’s no egg to get rid of. That’s why she can enter pro-estrus again so quickly. Thus, what happened to your cat is not at all unusual. An intact female can go into pro-estrus as quickly as every week to 10 days.

Of course, if your cat’s kitten had lived and she nursed it, the lactation would have staved off pro-estrus, just the way nursing inhibits most species’ ability to release a new egg and become pregnant. But because there was no kitten to nurse, your cat was ready to become pregnant again as if she had never given birth.

If your cat’s pro-estrus is driving you crazy, speak to your veterinarian about inducing ovulation with a Q-tip, which is what many breeders do if they don’t want a cat to have kittens at a particular time. Once the cat ovulates, she won’t cycle again for two months — the typical length of a cat pregnancy — and you can have her spayed during that time.
Arnold Plotnick, DVM, DACVIM
Catnip contributor

A Cat With Bad Breath

Q My nine-year-old cat’s breath has always been a little unpleasant, but over the past few months, it has become noticeably worse. I would like to know what might be causing this, and if there’s anything I can do to remedy the problem.

Stephanie Brewer

A Dear Stephanie: There are many possible causes for bad breath in cats, and many of the reasons are the same as they are for humans. Primary causes can include dental disease, a foreign body stuck in the mouth or ulceration of the mouth. However, there are also more severe causes, such as the presence of oral tumors, lung disease and kidney disease.

For that reason, it’s very important that you make an appointment with your veterinarian in the near future to diagnose the problem — and hopefully rule out the more serious conditions. Your veterinarian will likely ask if you have noticed other symptoms, such as oral discharge, or any changes in eating habits or behavior.

Remember: The cat’s owner can truly be the “eyes and ears” of the veterinarian, noticing subtle things at home that may be extremely helpful and informative during the brief visit at the clinic. If your cat receives a clean bill of health, you may consider changing his diet or using a feline finger toothbrush daily or every other day to help freshen his breath.
Michael Stone, DVM, ACVIM
Clinical Assistant Professor
Cummings School
of Veterinary Medicine
at Tufts University


Please enter your comment!
Please enter your name here