Caloric Feeding for Dogs

Caloric Feeding for Dogs

The method discussed in this guide uses “biomath” to calculate the number of calories or kcals a dog particularly needs each day. 

The information on this page contains excerpts taken from one of the modules/units in the Balanced Diet Formulation for Adult Dogs course

Dogs Eat to Meet Their Energy Needs

What is Energy? Energy is the capacity to do work. It is needed for metabolic work which includes maintaining and synthesizing body tissues and regulating body temperature.

Energy is step one in determining a dog’s diet needs.

When we talk about a dog’s energy needs, we are referring to caloric needs. 

A specific amount of energy is needed to maintain body weight, and even modest variances can bring about weight gain or weight loss in a dog.

To determine the amount of food a dog requires daily, it is necessary to know the dog’s energy requirement (how many calories it needs a day) as well as the energy content of the foods being fed (how many calories are an ingredient).

Energy cannot be measured as mass or in dimensions but the chemical energy contained in foods is transformed by the dog’s body into heat which can be measured.

Energy Factors (EF)

 There is more information about maintenance energy requirements further along in this guide.

Simplifying it for the Average Feeder

Sometimes when people start reading terms like “metabolizable energy requirements for dogs” or they get asked “how many kcals does your dog eat a day?” or they are presented in an online group with abbreviations like RER & MER; they get nervous and feel like they are about to get in over their head. DON’T BAIL, I’M GOING TO HELP YOU!

Let’s Get Into It from the Ground Up, Beginning with What a Calorie Is

Definition of a Calorie:

Athe amount of heat required at a pressure of one atmosphere to raise the temperature of one gram of water one degree Celsius that is equal to about 4.19 joules abbreviation cal

 called also gram caloriesmall calorie

Bthe amount of heat required to raise the temperature of one kilogram of water one degree Celsius 1000 gram calories or 3.968 Btu abbreviation Cal

 called also large Calorie, Cal, Kilogram calorie, Kilocalories, & kCals. <—-This is what we use when feeding dogs. Calories and kCals are used interchangeably in casual conversation and they represent a unit of energy.

More About Measuring Energy in the Diet

As explained above, we commonly substitute the word calorie for kilocalorie, which is really 1/1000 of a kilocalorie. A dog’s body burns food to produce energy in the form of heat. Nutrition scientists measure the amount of heat produced by metabolizing food in units called kilocalories.

The caloric value of foods can be measured by using direct calorimetry.

The simplified explanation of this process so that it is easy for you to understand is:

Nutrition scientists measure the number of calories in food by actually burning food in a bomb calorimeter, which is a box with two chambers, one inside the other. A sample of food is weighed and put onto a dish and the dish is put into the inner chamber of the calorimeter. The inner chamber is then filled with oxygen and the chamber is sealed shut. The outer chamber is filled with a measured amount of cold water, and the oxygen in the first chamber (inside the chamber with the water) is electrically ignited. When the food burns, the rise in the temperature of the water in the outer chamber is recorded.

If the water temperature increases 1 degree per kilogram, the food has 1 calorie; 2 degrees, 2 calories; and 235 degrees, 235 calories, etc.

Sometimes foods that seem to be low-calorie aren’t. We have to factor in protein, fat, and any carbs. As discussed throughout the website, not all foods are created equal. Skinless chicken breasts and 75% lean beef are not one and the same.

Now that you know what a Calorie/kCal is, how it’s measured, & that we use it for measuring a dog’s energy requirements; we need to talk about Basal Metabolic Rate (BMR) and Resting Energy Requirements (RER).

Energy Requirements 

Basal Metabolic Rate (BMR)

The Basal Metabolic Rate (BMR) as I will call it from here forward; is defined as the energy required to maintain homeostasis in a dog in a post-absorptive state. <— This means the dog has been fasted or it’s laying down after a long period of not eating such as overnight; and is then awake in a thermoneutral environment that it is accustomed to.  

Resting Energy Requirements (RER)

Resting Energy Requirements, that I am going to refer to as RER from now on, is the minimum energy your dog needs for its body to provide essential functions to live when it hasn’t been fasted. It is also referred to as Resting Fed Metabolic Rate (RFMR). This is the minimum amount of kCals needed to sustain life in a resting state who aren’t in a post-absorptive state.

The difference between BMR and RER is dietary-induced thermogenesis. What is that?? Dietary-induced thermogenesis or DIT is the increase in energy expenditure above basal fasting level, divided by the energy content of the food ingested.

REMEMBER WHEN I SAID DON’T BAIL, I’M GOING TO HELP YOU? 

Here is the math for you to figure out your adult dog’s RER. I also have it built into a calculator for you to use, in case you don’t feel like doing math. You can access that calculator here.

The Formula for Determining Resting Energy Requirements for Adult Dogs (RER)

—-> RER = 70 x (body weight in kg)0.75<—-

This is the minimum amount of calories needed for your adult dog to function in a resting state.

Recap: RER is the minimum number of kCals your dog needs to function. Any type of activity increases that number. Increased activity from a resting state means the dog is burning more energy and therefore needs more kCals to maintain. Daily activity level, pregnancy, & lactation all increase an adult dog’s energy requirements from the RER to MER. 

Maintenance Energy Requirements (MER)

Maintenance Energy Requirements that I am going to call MER here forward, are the kCals needed for a dog to maintain their ideal weight based on their current life stage & their activity level. MER requires more kCals than RER because the dog is doing more than life-sustaining functions. Other factors affecting MER are activity, pregnancy/lactation, climate, and health.

This is also sometimes referred to as Daily Energy Requirements (DER). MER and DER are different when discussing puppies but in common conversation when it pertains to adults, MER and DER are often used interchangeably. 

Examples of Biomath for Determining Metabolizable Energy Requirements for Adult Dogs at Maintenance

MER =  95 x (body weight in kilograms) 0.75 (Less Active Adult Dogs)

MER =  110 x (body weight in kilograms) 0.75 (Typically Active Adult Pet Dogs)

MER =  130 x (body weight in kilograms)0.75 (Active Adult Dogs & Many Larger Breeds)

MER =  140 x (body weight in kilograms)0.75 (Young Adult & More Active Adult Dogs)

MER=  200 x (body weight in kilograms)0.75 (Great Dane)

The calculator includes the other Energy Factors (EF) that are most commonly applied to dogs.

You can access the MER calculator for adult dogs here.

There is more to formulating a balanced diet than just numbers on paper. The dog itself is a living organism and must be considered. The energy of the diet being fed, the bioavailability of nutrients in the foods, the energy and nutrient density, and the digestibility of the food all factor into the proper creation/formulation of a balanced diet. 

Puppies and pregnant, lactating adults, need to be fed a specific diet for that stage of their life. It’s best to reach out for a consult to ensure your puppy or pregnant or lactating female’s diet is correctly formulated.

Nutrient Classifications & Which of Them Provide Energy

Water • Protein • Fats • Carbohydrates & Fiber • Vitamins • Minerals

Of the above nutrient classifications, only protein, fats, and carbohydrates provide energy to dogs. Water while vital to life, does not provide energy; nor do vitamins or minerals.

Water: Important Hydration Note

Water does not, in itself, provide energy to the body, but helps in metabolism which is essential for the body to derive energy, function and repair itself. The water to kcal intake ratio for a typical/healthy dog’s daily water need is estimated to be 1.0:1.0 mL water:kcal of metabolizable energy (ME).

Sources:

Interspecies Comparisons of Micronutrient Requirements: Metabolic vs. Absolute Body Size by Rucker, R and Storms, D; (2002)

Vitamin Requirements Relationship to Basal Metabolic Needs and Functions by Rucker, R and Steinberg, F.M.; (2006)

National Research Council. Nutrient Requirements of Dogs and Cats. Washington, DC: National Academies Press; (2006)

Animal Nutrition, Seventh Edition, Determining Energy Requirements, Andrea J. Fascetti, et, al., Chapter 3, Determining Energy Requirements; (2012)

Balanced Diet Formulation for Adult Dogs, Module Three by Granillo, A; (2019)