TECHNICAL ARTICLES Broilers/Layers/Breeders

Water – The often neglected nutrient

People are not always reminded or aware of the very important role that water plays in the everyday life of their poultry.

In the first week of a chicken’s life, water makes up 80% of the body mass. It means that you will be able to fill a 300 ml Coke bottle with the water that you can squeeze out of 10 day-old broiler chickens. Sixty-five percent of the increase in body mass to slaughter age is water (and then the public complains about the few grams of water that drips from a frozen carcass!)

What are the functions of water in the body of poultry?

In the first instance what we call meat is in fact muscle and it consists of at least 65% water, the rest, 35%, is high quality protein and of similar composition as the muscle fibres in our bodies. Water is the fluid in which substances are in solution inside the muscle cells and growth is simply the process by which the muscle cells multiply and enlarge themselves. All the reactions inside muscle cells for the growth processes can only take place in a watery medium. Insufficient water to fill new cells directly results in retarded growth.

Secondly, the substances (building blocks) that are used for the formation of muscle cells are carried by the blood stream from the digestive tract and the liver to the muscle cells in the different parts of the body, e.g. the breast muscles, wing and leg muscle, abdominal muscles et etc. Blood consist mainly of water: in a 100 ml blood only 8 ml is solid material (protein of blood cells) the rest is water.

In the third instance: why does feed intake stop when poultry has nothing to drink?

Water has several functions in feed intake and digestion processes: Water is necessary to enable the bird to swallow the feed. The saliva consists almost entirely of water and acts as a lubricant to enable feed passage down the intestinal tract.

In the crop water softens the feed to be digested in the small intestine. Before digestion the feed is ground to a fine and watery paste by the muscular stomach. If this does not happen the feed cannot pass down the intestinal tract to get digested.

In the small intestine the digestive processes takes place in a watery medium. The chemical reactions that break up the pasty feed particles into units that can be absorbed, require water. A chemical reaction can only take place in a watery medium.

What happens in the digestive tract in the absence of water? Those reactions that digest feed cannot proceed and it means that undigested feed accumulates inside the gastro-intestinal tract. The distension of the gut wall sends a message to a centre in the brain that tells the bird not to eat because all feed has not yet been digested. Feed intake thus stops and growth rate or egg production will also stop or drop. The volume of water that a bird drinks per day is twice the amount of the feed it eats. If water intake drops it is a sign that something is wrong in the poultry house.

Water has a very important role to enable the bird to maintain a constant body temperature. Heat production within the body occurs because the muscle cells generate heat during contraction of the heart, the abdominal muscles for respiratory processes, inside muscle cells heat is produce during their multiplication and growth and the oviduct liberates heat during the formation of eggs. Heat is thus the obvious and essential result of many processes in a chicken. (It is only a dead bird that produces no heat).

A very important principle must now be understood. If the body does not lose heat at the same rate that it produced, the body temperature will increase and the bird will die. Under normal environmental conditions poultry will lose the heat they generate mainly by means of radiation and convection. (The heat generated by a motorcar engine can easily be given off by means of the airflow through the car’s radiator at low environmental temperatures. On a cold day one can feel the heat that is radiated by the hot radiator. The cold air that is pulled through the radiator removes heat by means of convection and the engine stays cool. However, on a very hot day it often happens that cars overheat because heat loss is not rapid enough, the radiation to surrounding air is slow and convection is not effective because hot air is pulled through the radiator).

A similar situation exists in chickens during high environmental temperatures of 30°C. T he loss of heat by means of radiation and convection is not rapid enough to prevent the body temperature from increasing and the bird starts to pant. Fortunately the chicken has mechanism that the motorcar does not have: it starts to evaporate moisture from the membranes that form the linings of the upper respiratory tract. During this process when moisture evaporates it absorbs heat from the body it is in contact with and cools that surface. The blood that is contact with those upper linings of the respiratory tract is cooled and heat is thus removed from the body of the bird get. The bird depends on the availability of drinking water to cool itself during very hot weather for the process of evaporative cooling.

Another very important function of water is to remove waste products that originate from the normal metabolic processes in the body. These products have to be excreted as urine by means of the kidneys where the urine is filtered out of the blood. The waste products are in the form of uric acid, which is a very insoluble substance, and a lot of water is necessary to flush it from the kidneys to the cloaca. If the body is in a state of dehydration the uric acid will accumulate in those tubes and that will cause kidney stones and death.

In the day-old chicken water has a crucial role to enable the chicken to fend off bacteria. The moist surfaces of the respiratory tract are covered with hairlike structures known as cilia. During normal conditions the cilia are able to perform sweeping actions to prevent disease-causing organisms to penetrate the body. However, if the chicken is in a state of dehydration such movements are impossible. A further complication is that the linings of the respiratory tract becomes dry and microbes are able to enter into the body by means of small cracks that appear on the surface of the linings of the respiratory tract and to cause the disease and an infection such as is seen in infectious bronchitis. In Figure 1 an enlarged picture of normal cilia is shown on the left and on the right it can be seen what happens during dehydration and high levels of ammonia in the air.


Figure 1: Normal surface of the lining of the respiratory tract of the chicken. On the right the sloughed-off cilia due to dehydration and high levels of ammonia in the air.

In summary.

Water is essential to sustain life due to its involvement in a large number of functions: maintenance of health, temperature regulation, digestion of feed and for growth and egg production. The constant availability of clean drinking water cannot be overstressed.

Date published: 2006-04-07

Prof. Emeritus