An Introduction to Pet Food Nutrition -

An Introduction to Pet Food Nutrition

Before we can truly dive into pet food nutrition, we need to understand how a dog’s immune system functions in its simplest form. With that said, let’s get right to your pet’s first line of defense.

Table of Contents

Your Dog's Immune System: First Line of Defense

Science will agree, the key to good health in humans and our beloved pets is good nutrition and exercise.

However, before we dive into specific dog foods and how they can help, we must first understand why we pursue nutrition and physical activity in the first place. 

It all boils down to our immune system and we are happy to say this applies to your furry family members as much as it does our non-furry, human, family counterparts. This is a great place to start as we share an introduction to pet food nutrition – The Immune System. 


Just as our human skin is our largest organ in the body, the same holds true for your dog. This vital component is one of the first lines of defense for both humans and pets. It provides a whole-body barrier to several outside challengers who wish to gain entry and wreak havoc. In the world of biology, these are called antigens. 

Your dog’s skin is a physical barrier that is recognized as being a part of its ‘self’ and therefore not a target. It also encourages the growth of good bacteria which is essential for healthy skin.

Antigens, on the other hand, are recognized by a normal, healthy immune system as invaders and they will trigger an attack response in order to defend your furry family member from illness and harm. Here are some examples of antigens that may attack the skin:

  • Chemical agents
  • Microorganisms (i.e. viruses)
  • Other foreign substances

In order for your dog’s immune system to respond and protect, it must first recognize the antigen on the attack. Without getting too far in the weeds, let’s just say your pet’s defense system understands its own cellular makeup and flags each component as part of its ‘self’. A chemical agent, virus, or other foreign matter that is not marked as such is identified as an invader.

This allows your dog’s immune system to go on the attack with a number of resources that we’ll briefly discuss below. For now, let’s move on to the other lines of defense worth mentioning.

blackwood sensitive skin and stomach -

Blackwood Sensitive Skin and Stomach Dog Food

Blackwood, a Brightpet Nutrition Group brand, offers an excellent kibble for dogs with sensitive skin and stomachs. Read our review here.

Tears | Mucus | Saliva


As you have probably already guessed, tears, mucus, and saliva are all lubricants that also protect your dog from various foreign invaders. 

The human and canine eye do not contain blood vessels (on the surface) which, as we were taught in grade school biology, carry essential nutrients and also oxygen to this vital organ. We rely, as do our pets, on tears to bring oxygen and nutrients to our eyes.


Have you ever wondered why your body produces mucus? Your nose isn’t the only place for this sticky, protective fluid. Like your body does, your dog produces mucus via several membranes strategically located throughout the cranial areas. 

Mucus, also known as phlegm, acts as another barrier between the outside world and the lungs of your beloved pet. Its adhesive nature collects dust, dirt, germs, viruses, and other antigens, keeping them from entering the body where they can do damage.

In addition to physically stopping foreign invaders from entering the body, mucus also contains protective proteins that kill and disable germs (bacteria and viruses).


Yes, you guessed it, saliva is another protective lubricant found in both humans and dogs. In both cases, it provides moisture for comfort and also aides in digestion.

What many people don’t know is that saliva also contains protective proteins that help kill harmful bacteria. It also helps prevent tooth decay and gum disease while also protecting enamel. Saliva is the bodies first line of defense for keeping the bad guys from making their way down the hatch and into your dogs stomach.

High antibody levels in your dogs saliva can help you determine which foods to avoid for your furry companion.

Your Dogs Second Line of Defense

Phagocytic Cells

Phagocytic cells sound like something out of a science fiction novel. In reality, they are actually quite simple in structure. They are, in fact, a type of white blood cell. We all know that white blood cells make up a large part of our immune system. This is also the case when it comes to your dogs immune system.

For purposes of this article, let’s just say that phagocytic cells take in and destroy microbes that enter the body through tissue. This type of protection is called ‘innate immunity’.


Inflammation is also considered an ‘innate immunity’. 

When your dog’s body tissue is damaged, inflammation occurs to bring more white blood cells to the affected area. This results in swelling, pain, heat, and redness at the site of injury. 


Have you ever wondered if your dog can have a fever? Did you know that their average body temperature ranges between 101 and 102.5F? As you can see, they run a bit hotter than we do. However, the reason for such a response is the same as the trigger for humans. When this average temperature rises, it means their body is fighting off an infection and the higher temperature helps to inhibit bacterial growth which also helps increase the rate of tissue repair.

Instant Ear Thermometer for Pets -

Instant Ear Thermometer for Pets

Simple, easy to use, effective way to check your dog's temperature.

Your Dog's Immune Response

Boots on the Ground

Your Dog's Third Line of Defense​

Imagine for a moment a military commander assembling his or her troops in preparation for battle. We don’t have to be experts in combat preparedness in order to understand that there are more than likely several key roles that make up a strong defense mechanism. There are soldiers on the front lines, boots on the ground, and various air, sea and land vehicles in place to respond to both domestic and foreign threats. This is called adaptive immunity.

Your dog’s immune system, as is our own, is made up of various immune ‘systems’ that both prevent and destroy antigens. We talked earlier about your dog’s first line of defense (innate immunity via the skin, mucus and saliva). Other examples of innate immunity, also discussed above, are phagocytic cells, inflammation and fever.

Much like our own immune system, your dog’s built-in ‘boots on the ground’ have the ability to ‘remember’ their interaction with various pathogens during their lifetime. The result is a memory that allows them to effectively respond to similar, future attacks. 

It is very important, as it is with humans, that your dog maintains a strong immune system. This includes both the innate and adaptive immunities. Without their innate (skin, mucus, and saliva health) immunity, their bodies are overwhelmed with foreign invaders (antigens and pathogens). This presents an enormous challenge for the troops in the trenches as they are inundated with foreign invaders. 

On the contrary, without the existence of your dog’s adaptive immunity, survival is extremely difficult. 

An Introduction to Pet Food Nutrition -

Dr. Tim's ImmuShield Supplement

Fast and easy way to support a strong immune and digestive system health in adult dogs.


We all know how important it is to maintain a healthy diet along with exercise and rest. This keeps our immune system in tip top shape. We tend to apply this train of though in our human lives, but what about our pets? 

It is just as important to provide the right nutrition, exercise and rest for our dogs as it is our fellow human family members. They too need a strong immune system in order to live a long and healthy life. There’s a saying that we take seriously here at Good Boy Bone and that is “garbage in, garbage out”. 

We hope you enjoyed an introduction to pet food nutrition. Stay tuned for more content on nutrition and be sure to check out our Dog Food Reviews as we strive to bring you the information you need to make smart, informed, decisions.