|
 |
|
|
|
|
|
|
|
|
|
DISEASES AND DISORDERS OF THE AVIAN CROP
The ingluvies (the correct anatomic name for the crop) of birds is an outpocketing of the esophagus made up of similar cell types, stratified squamous epithelium, and like the esophagus, containing mucous glands, although limited to the area adjacent to the esophagus. The main crop function is storage of food material before it passes into the proventriculus. In the pharyngeal cavity (the mouth) and through the esophagus and crop, mucous begins to soften and moisturize food. Some enzymes, such as amylase, may be released in the mouth and crop to aid the digestive process.
Failure of the crop to empty, or delayed emptying of the crop, is the most common symptom of stress and disease in baby birds. It is critical to understand that crop stasis (slow crop) is a symptom of another and potentially more serious problem. Many causes exist for this symptom, from primary crop disorders to generalized gastrointestinal (gut) stasis and disease.
A primary crop disorder is one that directly affects and relates to the crop. While many etiologies or causes exist, the most common primary crop disorder is a crop infection. Generally, crop infections are caused by yeast, gram negative bacteria (especially E. coli), fungi and occasionally gram positive pathogenic bacteria. The crop of baby birds is much larger in comparison to body size than in adults and typically holds more food. Therefore, it is more prone to infections in babies. Also, babies are immunologically naive (it takes a while before their immune systems are strong enough to fight off pathogens such as bacteria).
Yeast infections, such as those caused by the notorious Candida albicans, are frequently implicated in slow crop cases in babies. Candida is a common yeast in our environment, but an overload can occur under certain situations. A very important, and avoidable, cause of yeast infections in chicks is due to antibiotic therapy. Antibiotics give yeast a competitive advantage by killing bacteria (both normal and beneficial as well as pathogenic bacteria) in the digestive tract. For this reason, antibiotics should be avoided unless specifically prescribed by your avian veterinarian. Clinical reports also exist of spontaneously developing yeast infections in baby birds, probably due in part, again, to their still developing immune systems. These are treated using antifungal agents.
Bacterial crop infections are also common in baby birds, due primarily to inadequate disinfecting of feeding equipment and supplies. It must be remembered that microbiological organisms are ubiquitous in our environment (in other words, bacteria are everywhere). Hand-feeders must, therefore, make every effort possible to reduce these contaminants from their nurseries. Significant sources of bacteria include the water supply (even faucets can harbor dangerous bacteria such as Pseudomonas), drains, improperly stored bottled water, humidifiers and dehumidifiers, water brooders, and air conditioners. Basically, any moist area should be considered a potential breeding ground for bacteria and thus should be monitored and disinfected frequently.
Improperly stored hand-feeding formula, especially that subjected to a humid environment, or that contaminated by poorly disinfected spoons or other feeding utensils, may become contaminated. This is best avoided by careful storage and dispensing of dry hand-feeding formula (such as a separate dispensing scoop kept with product, keeping product sealed and airtight, or storing the hand-feeding formula (unmixed) in the refrigerator or freezer). Care must be taken to prevent condensation from forming in the formula container walls, because it will dampen dry product and allow potential microorganism growth. This problem is easily avoided by removing only small amounts from the refrigerator at one time and disinfecting, rinsing, and thoroughly drying feeding utensils (including scoops) frequently.
The main reason producers of hand-feeding formula recommend discarding old formula and mixing fresh at each feeding is because, once mixed with water, hand-feeding solutions are exposed to bacteria in the environment and become a possible breeding ground because of their high water and nutrient content. For this same reason, crop slow down and delayed emptying can result in sour crop, a term which describes the action of fermenting food. It is important to realize, again, that sour crop is a symptom of a larger problem, just as is slow crop.
Other primary crop disorders, which manifest as slow crop, include foreign body ingestion, crop burns, over stretched crop, aerophagia (air in the crop) and trauma. Poor substrates for babies include corn cob bedding, soils or peat, small wood chips, and bedding that holds moisture. Some companies tout organic bedding as great for baby birds because they can pass through the system, but any bedding with feces on it should not be allowed to be eaten. The crop will normally pass most materials if consumed, but large amounts frequently cause blockage of the normal passageway. For these reasons, it is recommended to keep babies on clean paper toweling that can be frequently and economically changed.
Overly stretching the crop results from feeding too large a volume of formula. If this practice is continued, the crop tissue will stretch and not return to normal size, nor have normal peristaltic motion (that wave-like motion which travels across the crop after feeding). This over stretching often results from individuals who attempt to push rapid growth or eliminate more frequent feedings in their baby birds. Treatment in the form of "crop bras" may be necessary.
Minor crop burns often result in delayed food passage time. These burns result most often because of feeding formula that has been microwaved or mixed with very hot water and not tested with a thermometer. Vigorous stirring will eliminate hot spots after microwaving, but the temperature should still be checked before feeding. Major crop burns are, of course, a serious medical problem that requires veterinary treatment.
Aerophagia, or air in the crop, results when the baby gulps air because of poor feeding technique (frequent starting and stopping of formula) or in over exuberant babies that are just big eaters. The air in the crop also prevents the normal peristalsis. Aerophagia is easily treated by "burping" the baby, a motion of gently applying pressure to the crop while holding the head.
Another result of careless feeding or overly excited chicks that can result in poor crop function is pharyngeal (mouth) or esophageal trauma. Feeding with metal gavage tubes or plastic feeding tubes can result in damage to the delicate mucosal tissue of the esophagus or crop if improperly performed.
It is actually more common that crop emptying disorders arise as a result of generalized disease. This is true for both baby and adult birds. As with primary crop disorders, generalized disease is frequently first manifested as a slow crop but is a result of the entire gastrointestinal tract slowing. Bacteria, viruses, fungi and yeast are widespread causes, but chlamydial, mycobacterial, and parasitic infections must also be suspected for causing crop slow down via generalized gut stasis.
Poor environmental conditions (too hot, too cold environment, excessively humid or dry conditions) are probably the most common non-medical causes of transient delays in crop emptying times. These situations are easily remedied and their correction will result in normal crop function. Other causes may include stress (new hatchlings, recently pulled babies, new additions to the nursery, different hand-feeders, loud noises, other unknown stresses), damp or wet nest box/baby area, yolk sac infections, and congenital abnormalities. An easy way to monitor these and other problems is through daily weighing of babies. Environmental and stress issues usually do not result in significant weight loss in the babies.
Clearly then, when a crop slows, it should be considered a serious sign of a potentially dangerous condition (disease, environment, technique, etc.). If, for example, the crop slows as a result of a viral infection like polyoma, the most frequent viral infection of young birds, the baby should be separated from other babies to prevent the spreading of the virus throughout the nursery. Generally, the crop should be observed closely if it does not empty in its normal time (for that age baby). Sometimes warm water added to the crop along with gentle massage will move the contents. This dehydration in the crop contents may occur in any situation that results in crop slow down.
When warm water does not begin normal crop emptying, the crop should be emptied manually and the crop flushed. This procedure is best performed by a veterinarian, but many hand-feeders have become adept at this practice as well. If the crop still does not empty in subsequent meals and after flushing, hospitalization, diagnostics and antimicrobial and antifungal therapy should be initiated by your veterinarian.
To summarize, the most common sign of problems in baby birds is a failure of the crop to empty normally. Many causes exist for this symptom, from primary crop disorders to generalized gastrointestinal stasis. These disorders include:
Primary crop disorders
- crop infections (gram negative bacteria, yeast, fungi)
- over stretched crop (feeding greater than 12-15% body weight)
- aerophagia (air in the crop prevents normal crop motility)
- foreign body (bedding, wood chips, feeding tube, large seeds)
- crop burn (caused by hot spots in formula, inadequate mixing and stirring)
- pharyngeal or esophageal trauma (damage due to feeding tube, crop tube, syringe)
Generalized GI stasis
- generalized disease (bacteria, yeast, viruses, parasitic infection)
- polyoma virus (most common viral disease in neonates)
- hypothermia (baby becomes chilled) or hyperthermia (baby becomes too hot)
- formula fed too cold (below 100 degrees F.) can affect the baby's crop function
- formula fed too hot (above 110 degrees F.) can damage the baby's crop tissue
- improperly mixed formula (too little water, additions to the formula)
- yolk sac infection (improper absorption and subsequent infection)
- damp or wet nest box; excessively humid/dry environment
- stress (new hatchlings, different hand-feeders, loud noises, unknowns)
- congenital abnormalities (more common than once believed)
|
|
|
|
|
 |
