A breeder asked me to solve a problem (Egg Drop Syndrome) that was happening to his laying hens. At 37 weeks, his chickens produce eggs without shells. Eggs without the shell are found to multiply every day. The abnormal eggs are found 10-25% per day from a population of 5000 chickens. He also recounted that daily egg production (HD) in the chicken flock dropped dramatically, from 91% decreased to 54% within 4 weeks. No other symptoms can be observed in the hens. Chickens look healthy, good appetite, normal mortality rate. There is no problem with feed nutrition.
Clinical symptoms observed were the production of pale-shelled eggs, quickly followed by production of soft-shelled and shell-less eggs. Transient dullness may be seen in the days (sometimes) before the shell changes are noticed. There are no other symptoms such as respiratory or digestive symptoms, the chicken looks very healthy. But suddenly produce eggs without shells.
Unlike Infectious Bronchitis disease (IB) or Newcastle Disease (ND), the disease spreads slowly, but surely. This happens to chickens kept in a house with a battery cage system. Initially, eggs without shells found only a few eggs, then increased, in chickens that are located in line with chickens that have suffered problems first. Look at the picture above. The spread of the disease seems slower, the disease agent seems to be contagious through contamination. So the pattern of production decline looks slower than the Infectious Bronchitis disease or vvND.
This chicken looks healthy, appetite is very good, but suddenly this chicken produces eggs without a shell. These chickens still produce eggs almost daily, but the eggs are produced without the shell. These eggs can not be sold on the standard market to make money. This is a huge economic loss. Chickens still eat the feed but do not make money for the owner.
In Infectious Bronchitis and VVND, Eggs without shells are sometimes encountered, but not many. But in both these diseases, other clinical symptoms are very significant and easy to observe. Eggs without shells are not typical symptoms of a disease. Many diseases can cause the same symptoms.
At the age of 36-37 weeks, began to look eggs without shells, then the production of eggs began to decline slowly. Production decline reached 40% within 4 weeks, only 55% of chickens that produce eggs that can be sold. 10-25% are eggs without a shell. This chicken flock should produce 90% eggs. Do the other chickens not lay eggs at all?
This is what happened. Many eggs fall, and under the battery cage or on the floor (manure), we will find many eggs without a shell and broke. The number of eggs that fall is a lot. These eggs are not recorded as daily egg production data. Thus, the decline in data on the decline in egg production is biased. In fact, almost all chickens in the flock are still producing eggs well, but without eggshell.
The pattern of data reduction in egg production is very different from vvND or other diseases. In vvND, data on the decrease in egg production occurs because many chickens are sick clinically and do not produce eggs.
Eggs without shells, or soft shells, often stuck in the battery cage. This soft egg, can not roll to the front of the cage. The eggs were trapped inside the battery cage often pecked by chickens, so the eggs are leaked and broke, and fell to the bottom of the cage.
This egg has only a membrane. This membrane is unable to sustain the egg weight when the egg is on the surface of the battery cage. The egg membrane will tear if the eggs are left too long on the surface of the battery. Eggs will break and fall down. So very many eggs are falling and not recorded.
Chickens that produce eggs without shell turns out to have a good growth of egg follicles. Apparently, the chickens have the potential to produce eggs normally. In the picture above, a necropsy is done around 01 pm. This chicken (see figure 4 from above) has produced an egg without a shell in the morning. It turns out to have a good follicle and see there is an egg in the reproduction tract organ.
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In other diseases, such as vvND, a decrease in production is also caused by viral infection of the follicle, resulting in many pathological lesions in the follicle.
There are no significant lesions in the reproductive organs. No internal egg changes. This is very different from some other diseases associated with decreased egg production such as ND and IB. In ND and IB there was a significant change in the internal eggs, watery albumin, blood spot and meat spot.
More often the eggshell changes happen faster, from normal eggs to be without a shell. Egg changes occur in a short time. Only 2-3 days, even many chickens directly produce eggs without a shell, but the day before the chicken is still producing normal eggs.
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Then the chicken that produces eggs without a shell still has the normal frequency to produce eggs every day. These chickens will produce these abnormal eggs for several weeks. Then slowly will occur formation of egg shells. The chickens will produce eggs shelled, thin, brittle, rough and white. Many calcium spots on the surface of eggshells, eggs are crude, but gradually the shell will harden, egg color turns brown, eggs will be normal within 1-3 weeks. Thus, the total time from the beginning of the case occurs until the chicken produces a normal egg takes a long time. This takes 4-10 weeks.
But in eggs with soft shells, albumin is less than normal eggs. The thicker album looks more compact. But the eggs are lighter, smaller. Eggs remain oval shaped normally. Unlike vvNd or IB (malformed eggs). This case occurs in the chicken flock without vaccination against Egg Drop Syndrome virus, EDSv. There was no seroconversion in normal chickens, but it took a long time to find a significant positive seroconversion against the antibody titer against the EDS virus. Seropositive is significant in recovered chickens.
This case actually occurs on 3 different farms. With the origin of the same pullet (the pullet is transferred to three different farm layers). After the chickens lay eggs, farm 1 begins to find eggs without shell at 26 weeks, farm2 at 37 weeks, farm 3 at 38 weeks. Clinical symptoms and patterns of disease spread are the same. No transmission to other flocks or to other chicken houses that have been vaccinated with EDS. Cases occur only on the origin of the same pullet (unvaccinated). Why does this happen? Where did the virus come from? This is a very interesting case to learn. This case can be used as discussion material in the classroom for veterinary students. Field case study. Follow us on social media for other interesting cases. Subscribe our youtube video channel.
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