July 2007                                                                     VetInfo Digest

Table of Contents:

Calorie Counting

Cancer Prognoses

Promeris (tm)

This Month’s Note:

I am sorry for the delay in getting this month’s issue of the VetInfo Digest out.  June was an extremely busy month at the clinic and it just limited the time that I had to devote to it.  Most of the time we enjoy a pretty slow pace of life compared to folks in the city. We usually schedule appointments every half hour to give plenty of time to collect medical histories, examine pets and make decisions. In the few really busy months that we have from year to year I get a little empathy for my colleagues who must deal with tight time schedules all year long. It makes it a little more tempting to try to do things from memory rather than taking the time to look up disease syndromes, it is harder to get to know clients and pets and the time spent doing lab work in house rather than sending it out suddenly does seem to matter. All in all, I am very glad that I practice in a rural area with it’s own sense of time – slower than most of today’s fast paced lifestyles.

I thought I better get this issue out so it has not been proofread.  Hopefully, you’ll overlook most of the mistakes.

Calorie Counting

Pet obesity is becoming more of a problem in veterinary medicine.  Part of this is due to overfeeding and part of it is due to the increasing tendency for pets to be live a more sedate lifestyle than in the past when many pets were allowed to roam free all day.  Even in our rural area pets are more likely to live indoors most of the time or to be confined to fenced in yards than in the past. In general this is a good thing but it does mean less exercise for most dogs.  The decrease in exercise contributes to the problem with weight gain in pets.

One of the problems with weight control is that people really have no idea of the caloric requirements for their dogs and cats. It takes a surprisingly small number of calories to meet the needs of a cat or small dog and even large dogs require fewer calories than most humans.

Each pet has an individual need for a certain number of calories per day to maintain the correct body weight.  It is important to recognize that some pets will require fewer calories and some pets higher caloric intake to stay at an ideal weight.  There has to be a starting point for calculating the amount of food to give a pet, though.  A simple formula which will get you into the right ballpark is 30 x (kg body weight) + 70 = kcal/day.

To give you some examples of using this formula:

75 lbs. dog =  75 lbs./2.2 lbs./kg =  34.1 kg

30 x 34.1kg + 70 =  1093 calories

25 lb. Dog = 25 lbs. / 2.2 lbs/kg =  11.4 kg

30 x 11.4kg + 70 =  411 calories

OR

11 lbs. cat =  5kg

30 x 5kg + 70 = 220 calories

Knowing approximately how many calories your pet needs is the first step in deciding how much food to give in one day. There are a number of ways to individualize this process a little more, such as using basal metabolic rate information to amend the results or factoring in extra exercise, or extreme lack of exercise. It is easiest, after getting into the approximate range of caloric needs to just observe you pet carefully and to feed less when you can’t feel ribs easily or feed a little more if you can see more than 3 to 5 ribs easily.

Knowing how many calories are in the food that you are using is the next step in calculating the dietary needs.  There are lots of places that you can get the number of calories in foods that humans consume but it is harder to find information on calories/cup of most pet foods.

The calories per cup of most dog foods can be obtained from the company but very few dog food manufacturers put this information on the bag. It is not clear to me why that is the case, as it would help a great deal for pet owners to have an idea how many calories they are feeding their pets. Ohio State University has a good web site for obtaining this information:   http://vet.osu.edu/1442.htm or you can contact the manufacturer through their web site or contact information on the pet food.

Most dry foods for dogs contain between 300 and 450 calories/cup. Some contain as much as 600 calories per cup and a smaller number contain 250 calories or so. You can use the general figures as a starting point but it is better to try to find out how many calories there are in a cup (1 cup dry measure using a real measuring cup).   To calculate a dog’s caloric needs you just figure the need per day as previously described and then divide by the number of calories/cup to get the amount of food the dogs needs.  This assumes that the dry food is the only thing that you intend to feed your pet, though. Realistically, most people don’t do that. Most people supplement their dog’s diets in some way.

To use some of the information we can obtain on human food calories to see how they might impact a dog or cat’s dietary needs it is best to look at the number of calories in treats that you might give your pet and to think about how that impacts their overall needs.

MacDonald’s hamburger = 250 calories

MacDonald’s cheeseburger = 300 calories

One potato chip = 8 calories

One slice American cheese = 70 calories

One egg = 76 calories

½ cup of peas = 60 calories

One “baby” carrot = 3 calories

1 green bean = 2 calories

As you can see, if you have a 25 lbs. dog and you give it a cheeseburger since you’re going through the drive through for lunch, you have given a significant chunk of the day’s calories in one meal.   A 25 lb dog needs 411 calories/day.  A cheeseburger is 300 calories. This only leaves 111 calories to fulfill the day’s requirements, or about 1/3 of a cup of dog food.

Cats often eat canned food entirely.  Most cans of cat food contain between 200 and 300 caloies.  This means that one can per day is sufficient to meet the needs of most cats and is more calories than necessary for some cats.  Dry foods meant for cats tend to run between 350 and 500 calories per cup for adult maintenance foods and between 225 and 300 calories per cup for “lite”, “indoor” or “less active” type foods.  For our 11 lb cat this means that  ½ cup of food, or less, per day, is usually sufficient using maintenance cat foods and a little less than a cup sufficient for less active type foods.  Most of my clients assume that their cats need much more food than this.

Cats don’t get as much drive through food as dogs but they still get treats. If you feed your cat a slice of American cheese it is getting about 110 calories. Since our 11 lbs cat only needed 220 calories per day, that is half of its daily caloric need.  It is hard to keep a well balanced diet when you are restricted to meeting vitamin, mineral and protein requirements on half of the normal amount of calories.

Dog and cat treats contain calories, too. It is not possible to list the calories in a wide number of dog treats but these examples should give you some idea about the need to consider the calories that your pet is getting through treats. There is no reason that you have to give a big dog large size dog biscuits.

Milk Bone ™ dog treats:        puppy 9 k/cal/treat

                                                Small biscuits 19 calories/treat

                                                Medium           36 calories/treat

                                                Large               112 calories/treat

Pig Ears (low fat)                    160 kcal/ear

Pig Ears normal                       260 kcal/ear

Rawhide                                  130 calories/ounce   (sizes vary widely)

Friskies Ocean Whitefish and Tuna Treats for Cats               2.4 calories/treat                                 

Feline Greenies ™                  approximately 2 calories/treat

One thing to consider when choosing treats is that you must compensate for the calories in the treats by cutting down on the other food that you give your pet. Therefore, there is some benefit to using a treat that comes close to meeting the nutritional needs of your pet, or combining various treats in a way that meets nutritional needs.  Milk-Bone treats are nutritionally complete based on AAFCO standards, for instance.  You could also get closer to nutritionally complete treating by combining green beans, kitty grasses or other vegetable type treats with the less nutritionally valuable treats like pig ears or cheeses.  As you can see looking back at the calories listed for some of the treats that people tell me they give their pets, there is a huge difference between a couple of green beans and a slice of American cheese.  Many dogs really like green beans and carrots. Lots of cats will willingly eat peas. You can make a difference in your pet’s weight by choosing appropriate snacks.

Cancer prognostications

I hear clients say things similar to “my vet gave my dog six months to live when he diagnosed this cancer and my dog is still going strong after a year,” or worse, “my vet gave my dog six months to live with cancer and she died a week later.”  The part of the sentence that always bothers me is the “my vet gave….”   As a veterinarian I have no control at all over what cancer decides to do. In fact, the internal medicine instructor who taught oncology at my veterinary school used to write on the board the first day of class each year, “Cancer does what cancer wants. Never forget that!”  Clients almost always want prognostic information about cancers. When I give it, I am trying to give my clients the best possible advice about what to expect. I’m not trying to give an exact date for when cancer will cause their pet to die.

There is a fair amount of information available about various types of cancer and much of that information has prognostic implications. The very first step in discussing cancer is the recognition of the fact that cancer is not a single disorder. It is a group of hundreds of different disorders with different causes, different clinical effects and different prognoses. A mast cell tumor is not like a fibrosarcoma, an osteosarcoma or a lipoma.  Each type of tumor or cancer has its own individual characteristics. Lumping them all together under the heading “cancer” confuses the issues surrounding the way that the individual cancers tend to act. As a minimum you need to know what type of cancer is present and it is better to know the grade and stage of the tumor before making any assumptions about prognosis.

Perhaps the biggest obstacle to providing an accurate prognosis for a particular tumor type is the inability of researchers to gather enough pets with a particular tumor type, a particular grade of that tumor and a particular stage of that tumor and the same breed as the patient – all necessary to be able to provide accurate statistical information. It is rare in veterinary medicine to find a good study that matches a particular patient’s situation well.  Veterinarians do the best they can to try to give clients some idea what to expect when a patient has cancer but there is too much variation to take their advice as anything more than a guess at what might happen.

One of the confounding things about cancer is that several types of cancer have occasional complete remissions, without treatment. There are well documented cases of this for osteosarcoma, lymphoma and mast cell tumors. It is likely that this is also happening in some cases in which cancer is treated. When it does, the treatment looks good, no matter what it was, as long as the treatment itself didn’t kill the patient. While complete natural remission is rare the effect of one spontaneous remission is to give a hope to a much larger number of clients whose pets have cancer. This is one of the reasons that “miracle” cures continue to be touted in anecdotal articles and advertisements.

A source of confusion exists in the use of the word cancer, as well. In human medicine there is a tendency to use the word tumor to describe benign growths that are not likely to spread and cancer to describe malignancies.  Veterinarians tend to call any abnormal cell growth cancer but to divide cancers into benign and malignant. Pet owners who are familiar with the use of the terms in human medicine are sometimes confused by the way that veterinarians use the terms.  I tend to think that veterinarians are right in the way the terminology is used but it is understandable how the human variation came about. Physicians and veterinarians both tend to try to make terms overly simple for people rather than trying to explain a complex issue.  The hope is to make the issues less confusing but it doesn’t always work that way. Most of our clients are smart enough to understand the concepts of benign and malignant  and overall I think they are less confused by an accurate description of what might happen with their pet’s cancer.

How do you make decisions about cancers affecting your pet if you can’t rely on the statistical information available to give you an accurate prognosis?  This can be a very difficult thing to do but for many people the decisions are not quite as hard to make as they might appear on the surface.

I tend to focus on the expected quality of life of my patients rather than on time frames.  I don’t think that pets benefit much from living a few extra months because I don’t think that pets feel the need to put their life in order or to put things right with a loved one.  They don’t have the need for time that would drive them to live with pain or severe disability the way that it drives some people to accept these things. This helps me to put things in focus.

The first thing that I am concerned about in the decision making process is whether there is hope for an actual cure. Many forms of cancer are actually curable with surgical removal. For this group of cancers there doesn’t seem to be much decision making to do. Other forms of cancer may or may not respond completely to surgery. An example is a Grade 2 mast cell tumor. A planned surgical excision, in which the surgeon knows the type of cancer and has an idea how wide the incision margins need to be for that type of tumor, has about a 50% chance of curing this type of cancer.  For most of my clients those are good enough odds to justify the expensive of surgery.  There may be factors such as age or other health problems that impact the decision but it is still relatively easy to decide whether to pursue surgery, or not.

What do we do in the case of  a patient who has approximately a 10% chance of successful surgery? This is where making decisions in cancer cases gets very difficult, especially since these are also usually the patients who require the most aggressive surgeries, often involving limb amputation, removal of organs or portions of organs and who may be in worse overall health due to cancer effects.

It makes sense tome to consider amputation of a limb in the case of osteosarcoma. The tumor is painful and removal of the limb removes the pain for several months even if the tumor is in the process of spreading. The quality of life is good for most dogs with amputated limbs if they are not very large dogs. Even large dogs often do well with rear leg amputations. Cats do very well with limb amputations, either front or back legs.  Even though the cure rate for limb amputation is only 10%, there are other benefits to make it worth considering, especially the reduction in pain associated with the tumor.

On the other hand, I have a harder time advising a client to pursue aggressive surgery for a vaccine-associated sarcoma in a cat. The surgery for this requires extensive tissue margins. The tumors are often located in spots in which removal of a great deal of tissue is debilitating. Recovery from the surgery may take several weeks and the tumor tends to spread fairly rapidly if any portion of it is not removed. Given all of these complications it is much harder to justify hoping to be in the 10 to 20% of patients where an initial aggressive surgery may result in a cure. I try not to discourage clients who truly feel the need to pursue all possible therapies because there is some hope but it is hard to enthusiastically push for treatment.

I hope that you can see from these discussions the importance in knowing what type of tumor is present.  It is worthwhile to examine an tissue aspirate from the tumor. Getting these samples is as simple as sticking a needle into the tumor and aspirating with a syringe to suck up a small amount of tumor tissue. Often this is sufficient to determine if a tumor should be biopsied in order to get a better idea what it is.  A larger biopsy sample can be obtained surgically if necessary. This sample should be taken in a way that ensures the biopsy path will be removed along with the tumor, if at all possible – so if it is necessary to cross normal skin to get to the tumor site in a way that cross contamination from the tumor could affect the biopsy path, it is necessary to ensure that the skin that was traversed by the biopsy instrument is removed, as well whenever possible.  Even though there is a small risk of spreading a tumor while taking some biopsy samples (not all), it is usually worth taking that risk to ensure that the surgery and post-surgical care can be planned as carefully as possible. Knowing what type of tumor is present makes the prognostic information much more reliable. In some cases it is even possible to get an idea of the grade of a tumor from the biopsy samples, which further ensures that planning will be based on good information.

Once your vet knows more precisely what type of tumor is present he or she can give you advice on prognosis that is much better.  It still won’t be possible to find prognostic information that specifically applies to your pet in many instances. There just aren’t that many studies that include the exact tumor type, tumor grade, staging information and breed related information to match one particular patient. Your vet will have to make some inferences from the general information available. In addition, your vet has to consider information specific to your pet, especially its health history, in order to give you the most valid prognosis.

Even with all this information you can’t forget the basic maxim for cancer treatment – cancer really does do what cancer wants.  Natural remissions occur. These are rare but they have been well documented in cases of osteosarcoma, lymphoma and mast cell tumor.  Rapid spread of tumors can occur when a pet has a weakened immune system. A tumor that affects liver function will be worse for a pet who already has compromised liver function. These are just a few examples of things that might change a pet’s prognosis. Once in a while a cancer just doesn’t act like it should.  Your vet will do his or her best to help you decide what to do about cancers but you can’t expect a perfect prognostic effort.  All you can do is collect the available information and then make the best decision you can based on your needs and your pet’s needs.

Promeris ™  (metaflumizone):

A new flea treatment for cats from Ft. Dodge Laboratories, which is being called Promeris ™ became available this month.  It is likely that it will be in the same category (very good) as Frontline Topspot ™ , Advantage ™ and Revolution ™ .  It may be slightly less expensive that these other choices but not enough to make a huge difference.  There is no claim for efficacy against ticks or other parasites as far as I know.

It is likely that Promeris Duo, currently approved in Europe for use in dogs to control fleas and ticks, will also become available in the U.S. soon.  This is a combination of metaflumizone and amitraz.   There have been problems with products containing amitraz in the past but Ft. Dodge seems to think these will be minimized by the application method and form of the medication.  Amitraz is very effective at controlling ticks and if it does prove to be safe it will be nice to have an alternative to Frontline since some folks believe that it is not working as well for them now as it has in the past.

Thanks for your Support!
 
The VetInfo Digest is published by:
TierCom, Inc.
P.O. Box 476
Cobbs Creek, VA 23035.
 
The opinions expressed in this newsletter are those of Michael Richards, DVM., author.
Copyright  2007, TierCom, Inc.