Second Look

The trouble to understand you pig's physiology

Knowing how to balance your animals’ physiological needs may make the difference between success and failure in your operation

by RICHARD SMELSKI

If you're in the pig business, it’s important to understand something about the physiology of the pig. Too often, without understanding how different organs of the body function, we jump to conclusions because of a one-time experience or observation -- for example, what we believe causes scouring, lack of appetite or laboured breathing. A better analysis can be done if you understand the physiology of the problem.

Probably the first part to understand is the animal’s brain and nerve system. Secondly, you should know how the lungs and circulatory system works. Then you should be aware of how the immune system functions and how the body reacts to outside stresses. The digestive system, muscle and bone structure and reproductive systems react more to nutrients and medication than do other organs.

The nerve system produces a fight or flight hormone (adrenaline) that can change the whole physiology of the body. In a stress situation, the adrenaline diverts the nutrients, reduces feed intake and makes the immune system vulnerable. Thus, the stress level can increase the risk of disease.

Simple things such as temperature, large group size, changes to routines, pecking order or noise can create an adrenaline flush. Pigs have 320-degree visibility, strong social patterns, acute taste buds and a strong sense of smell, are only a few of the nerve signals. They have a quicker learning curve than dogs, and respond to a stock person accordingly. The nerve system is what communicates all signals given out by the body and produces the reaction to situations. The goal is to maintain the animal in a minimal stress situation.

Look at the animal's breathing pattern. It normally breathes 25-35 times per minute and has a heart rate of 75-85 times per minute. The lungs replace carbon dioxide in the blood with fresh oxygen. The heart and circulatory system distribute this oxygen and nutrients to every part of the body.

Dust and pneumonia destroy the capillaries in the lungs, making the lungs less efficient and increasing the respiration rates so that the pig can still get ample fresh air. Also, a growing pig breathes out one gallon of moisture per day, so this has to be calculated into the ventilation or stress equation. That is why some judges look for chest capacity in an animal, so that the animal has a good capacity for respiration, in spite of odd stresses.

The digestive system is the next level of understanding. Digestion begins in the mouth and works best with slow, uninterrupted eating to create a good mix with saliva and enzymes. Moist feeds ease palatability. The capacity of an adult pig's stomach is 20 litres while a baby pig's is 15 millilitres. This small capacity is the reason why baby pigs need to eat 20 times per day.

Piglets, like humans, also lose their baby teeth. The pig does not care about feed ingredients -- it absorbs nutrients. These nutrients need to be in a digestible form so that they can easily be transferred through the gut wall. Any contamination creates a flushing effect within the intestine, known as scours. Being aware of the factors that enhance feed digestion within the gut will also help you understand feed efficiency. If feed is diverted for comfort or toxin eradication, do not expect it to be used for muscle deposition.

We raise pigs for the meat (lean deposition), but this lean deposition becomes dependent on the skeletal frame to set the muscle upon. Genetics is the blueprint for how much lean an animal can deposit; the rest is dependent on availability of nutrients, prioritization and well-being. Feed intake is going to be crucial for maximizing this lean deposition, as will nutrient balance, comfort and health. Muscle is 70 per cent water, so a good water supply is important.

The intent of this article is not to give you a short course in physiology, but rather to show the importance of understanding why and how a pig reacts to a certain situation. As a manager, your job is to know how to balance these physiological needs within an economic model. Success or failure is often determined by details and the physiological details may prove to be the things that make the difference. BP

Richard Smelski is general manager of Ontario Swine Improvement Inc. and a former Ontario government swine specialist.