By Anne Lichtenwalner, DVM PhD, Assistant Professor, University of Maine Cooperative Extension, Department of Animal and Veterinary Sciences, Director, University of Maine Animal Health Laboratory, and Associate Professor Emeritus H. Michael Opitz
When you are feeding a formulated diet to animals, they are very dependent on the nutritional balance in every bag of feed. Because chickens are highly selected for rapid growth (broiler breeds) or for high reproductive levels (egg-producing breeds), nutritional problems show up quickly. Those problems can arise because of the content of the feed, whether it is adequately mixed, or how it is stored.
Example: Salt Deficiency
In general, sodium (a component of table salt) is added to chicken feeds at the rate of about 0.15% sodium in the feed mix. Without salt, growth is slowed, and chicks are dull and listless. (See Figure 1.) Getting salt levels back up to required levels will speed up appetite and growth, but often the birds never completely recover from the early setback. In broilers especially, the rapid growth that occurs following correction of feed problems may exceed the development of the heart and lungs. These birds may collapse and die suddenly; opening up the body cavity will reveal fluid accumulations around the lungs and heart. (See Figure 2.)
This is known as broiler ascites syndrome, and if it begins to occur in your flock you should consider early slaughter to avoid losing more birds. In older birds, appetite decreases, pecking behavior may increase and egg production is likely to decrease.
Why does salt deficiency occur?
Occasionally a feed processing company may make a mistake and fail to add ingredients, but more likely a problem may occur with clumping or settling out of ingredients. As well, some forms of salt (like rock salt) are coarser and less miscible than others. In these cases, feed analysis of individual bags of feed may be too low, or too high, in sodium content, although the overall feed mix was correct. In either case there is a problem, because salt is required, but can be toxic at high concentrations.
How do you avoid the problem?
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Image Description: Figure 1. Experimentally salt-deprived (on right) versus normally fed (on left) 3 week-old broiler chicks. Photo by H. Michael Opitz.
Image Description: Figure 2. The abdominal and thoracic cavity of a broiler with ascites syndrome, which can often follow salt deficiency. Yellowish fluid can be seen in the abdomen, and the liver is firm and swollen. Photo by H. Michael Opitz.