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- A Behavioural and Physiological Study.
- Developments of the Avian Embryo - A Behavioural and Physiological Study | Freeman | Springer.
- Developments of the Avian Embryo?
How do I find a book? Embryo pathology is different in that embryos have little or no inflammatory response until very late in incubation. The spectrum of host responses is also relatively narrow generally limited to necrosis, heterophilic inflammation, congestion, hemorrhage, and edema.
The Physiology of the Avian Embryo
Autolysis can be a serious problem, because some aviculturists prefer to leave eggs in incubators for several days after embryo death to be absolutely sure the embryo is dead. And it should be obvious by now that considerable background knowledge of aviculture and captive management is required in order to make sense of embryo pathology. This is due in large part to the fact that most of the causes of embryo mortality are related to incubation parameters and management issues.
If all the necessary background information is not available, all we may be able to do is rule-out infectious disease as best we can.
The Physiology of the Avian Embryo - Semantic Scholar
The necropsy: It is very helpful to have a complete history, including parental and incubation data, before starting the postmortem exam. Record egg weight, length and width measured with precision calipers. Assess egg shell shape and quality, smoothness of the shell, degree of surface fecal contamination, and integrity of the cuticle. Then open the blunt aircell end of the egg with old, dull scissors. Examine the air cell membrane and blood vessels, looking for evidence of inflammation, fungal growth, or hemorrhage from vessels lacerated during pipping.
Open the aircell and obtain a bacterial culture of egg content. For late stage near hatching embryo deaths, carefully evaluate the rotational and postural position of the embryo as it is removed from the shell see gross lesions below. For the external embryo exam, determine the stage by comparing appropriate developmental features with Hamburger and Hamilton s staging chart , 1 evaluate the degree of subcutaneous or generalized edema, and look for developmental defects.
If the yolk sac is still external, open it with a sterile blade and swab the yolk for bacterial culture and cytology be careful not to aggressively swab the internal surface of the yolk sac, as hematopoietic cells will contaminate the smears, making it difficult to accurately diagnose an inflammatory process. For the internal embryo exam, limit yourself in most species primarily to looking for deformities, evaluating the quantity and nature of the upper gastrointestinal content which consists of swallowed residual egg content , the color and degree of inflation of the lungs, and gross appearance of the kidneys and liver.
Opening very small hollow organs can cause sufficient tissue damage to render histopathology useless. Obtain the yolk culture and cytology at this time if sac is internal. The normal hatching position in all species is head under right wing, with the body rotated so that the beak is pointed toward the lower slope of the aircell. The most common malpositions are: 1 head over right wing not usually lethal , 2 head under left wing causes moderate to high mortality , 3 rotation away from aircell moderate to high mortality , 4 leg over the head high mortality , 5 upside down high mortality , and 6 head between the legs high mortality.
Keep in mind that positioning is generally only critical in the last hr before hatch i. Fetal membrane entrapment: We sporadically see late embryo deaths due to wrapping of the yolk or allantoic sac around the head or body. We speculate that rough handling or improper turning could contribute to this. We have seen this in parent incubated eggs also, but at lower incidence. Edema or dehydration are non-specific findings, but can be an indicator of weight loss problems during incubation. There are many potential causes of embryo deformities, but incorrect incubation temperature is an often overlooked cause.
Retarded or accelerated development can be due incorrect incubation temperature too low or too high, respectively. Yolk sac infections are very important as a cause of embryo and chick mortality, but are difficult to diagnose grossly because yolk color and consistency is highly variable. Yolk cytology is very helpful in making a rapid diagnosis. In the absence of infection, chorioallantoic membrane necrosis and the reaction to it most likely represents the morphologic consequences of normal blood vessel shut-down during hatch.
Extramedullary hematopoiesis EMH can be very widespread including myocardium for example. Loose aggregates of mature heterophils in a tissue more often reflects regressing EMH than infection. A small amount of residual lung fluid is normal, but this must be distinguished from aspirated egg content. Congestion, hemorrhage, and edema are relatively common non-specific lesions.
An infectious process should be ruled out in these cases through cultures and ancillary diagnostics. In the absence of other evidence of infection, these changes only point to the broad categories of incubation and management parameters, genetics e.
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Because the brain of embryos and young chicks is very soft, we recommend sectioning the entire head for histopathology. This also facilitates evaluation of the nasal cavity and sinuses for evidence of inflammation or aspiration. Yolk sac infections are one of the most common and most important histologic findings.
These infections are typically acquired in one of three ways: in the oviduct of the hen before the shell is formed, immediately after lay air is sucked in through pores in the shell as the egg cools, which can facilitate bacterial penetration , or during the pip and hatch stages when the umbilicus may be incompletely sealed. Proper interpretation of gross and histologic findings requires their integration with clinical and management data at the individual case level, as well as the population level.
Hamburger V, HL Hamilton. A series of normal stages in the development of the chick embryo. Brown AFA.
Unhatched Bird Embryos Communicate With Siblings by Vibrating Their Shells
The Incubation Book. Kuehler C, J Good. Artificial incubation of bird eggs at the Zoological Society of San Diego. Zoo Yb. Kuehler C, MR Loomis. Artificial incubation of nondomestic bird eggs. Saunders Co. Wiley-Interscience, New York. Falcon Propagation.
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