Lorenzo Crosta, Dr. Med. Vet.
Avian, Zoo and Exotic Animal Consulting Clinica Veterinaria Valcurone, Missaglia (LC), Italy
It is of primary importance for the avian practitioner, and even more for the apicultural veterinarian, to focus on the normal development process of the avian chick. If one does not understand the difference between a normal chick and a chick that is starting developing problems, his/her reaction it will often be too late to be successful.
One simple way to check the general status and conditions of a chick, is to control its growth and weight gain rates.
What is much more important is to study the complete growth curve of a chick and compare its shape with the published ones, and not to give a big importance to the weight itself. As a general rule, in the first weeks we like to see a minimum of doubling weight within 7 days. Other good "indicators" of regular growth and good health that must be taken into consideration when assessing the physical condition of a neonate are:
Regular body proportions (versus "stunted" chick)
Normal posture for the species
Skin color, texture and fat deposits
Regular feathers development
Normal shape of the beak
Tone and thickness of the crop
Presence of foreign material in the crop
Feeding response (according to species behavior)
Normal production and appearance of feces
Routine Checks of the Chicks in the Nursery
Avian neonatology involves not only the medical check of single young patients which are sick, but also the control of flocks of birds in a nursery setting. Routine check-ups will allow the clinician to have a detailed history of every chick and identify earlier any deviation from normality, so that potentially ill birds can be isolated from the other chicks in the nursery, as soon as possible.
Our routine is a simple microbiological culture from cloaca and crop of all incoming birds. If potentially pathogenic bacteria are cultured from a chick, a sensitivity test is run, but this does not coincide with the start of an antibiotic treatment, as this will take place only if the chick is also showing symptoms.
The only culture result that will lead to a treatment in any case, is the finding of fungi and yeast. When a chick is showing a poor growth rate, and especially in presence of potentially pathogen bacteria, we also run some blood test, according to the size of the bird and the relative amount of blood we can safely collect. Water and food used in the nursery are also routinely tested for pathogens.
Generally speaking we use two different protocols to run the microbiological cultures from the chicks:
1. Chicks coming from artificial incubation, those chicks are considered "clean". Our experience tells us that an immediate after-hatching microbiological check will lead to misinterpretation of results. In fact, quite often day old chicks don't show any bacterial growth, due both to the limited size of the sample and the fact that no bacterial flora has developed yet, in those young birds. After years of trials, our protocol is to test any incoming bird from the incubator at three-four days of age. This will give the highest chances to identify the presence of potentially dangerous pathogens, before they become a real problem.
2. On the other hand, chicks coming from the nests, and partially parent-reared, are considered "potentially dirty" and will not go into the same room with the chicks from artificial incubation. These birds will be tested at their arrival to the Nursery, and will leave the "quarantine" rooms only when all the chicks in there will be considered healthy.
How to Identify a Healthy, or a Sick Chick
Sick chicks are generally easier to identify than adult birds, as they do not need to hide their symptoms, yet. Naturally there are typical clinical symptoms to be aware of, and some may be obvious, such as, slow crop emptying, swollen abdomen, generalized edema, dehydration, abnormal feces, etc. In our experience, any chick that is deviating from the normal behavior for the species may have a problem and should be carefully monitored.
The Critically Ill Neonate
Young chicks can die very quickly, when seriously ill. For this reason a symptomatic treatment must be started immediately after discovering a sick chick. In most cases test results will be available after when is clear whether the treatment is successful, or not. Despite this assumption, diagnostic samples must be collected before starting a treatment and this at least for two reasons:
1. Treatment can be changed according to results
2. A presumptive diagnosis is already available for chicks with similar symptoms
The typical critically ill chick will appear dehydrated and cold, it will not be able to lift the head properly, very likely its abdomen will look locally or totally swollen. Further symptoms that are very common with sick chicks are inability to pass feces, slow or not emptying crop, crop with gas and swollen eyes (both).
All these cases require a immediate and aggressive antibiotic treatment, plus a quick restoring of the fluid balance, further, to avoid secondary invasion, or overgrowth of fungi and yeast, an antimycotic treatment is always indicated. Typical first choice antibiotics are Enrofloxacin and Marbofloxacin, but since an increasing number of resistant isolates has been observed with fluoroquinolones, third generation cephalosporins, like Ceftriaxone and Cefotaxime, have become rather common, too.
Most commonly fluids will be administered SQ, and this can be safely done also in very small chicks (10 grams BW), but selected cases may require IV, or IO fluid administration. Fluid deficit can be determined by the clinical aspect of patient:
Loss of skin elasticity corresponds to a 5% dehydration
Skin tents and loses its brightness: 10-12% dehydration
The chick is depressed, or comatose, there are signs of shock: 12-15% dehydration
Food will be administered normally, if the chick is able to pass it and there is no risk of vomiting, otherwise the formula will be reduced by 20-50% in volume. If there is a crop stasis, crop can be washed with warm saline or RLS, with or without a few drops of a povidone disinfectant. Some saline may be left in the crop after it has been carefully washed, but in the authors' experience better results are achieved by administering some infusion of fennel seeds. This "fennel-tea" can also be used as a replacement for reconstituting the feeding formula, for the first days after the resolution of the stasis.