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Author Topic: Embryo Mortality (when to candle)  (Read 5895 times)
Reeves
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« on: March 25, 2009, 11:48:56 AM »

   The first peak of embryo mortality (fourth day) occurs when the
majority of structures are being formed (Fig. 6-7). There may also be
abnormalities at this time due to an irregular number of chromosomes.
This first peak is usually followed by a long period of low mortality.
    Deficiency of certain nutritional ingredients can cause a mid-
peak of mortality (twelfth day) comparable to that of the first peak.
The third peak  (twenty-second day) is associated with hatching prob-
lems. On the twenty-first day, the embryo has its head between its
thighs and there still is an external yolk sac and a little remaining
albumen.



   During the last three days, the embryo gets its head under its
right wing and picks into the air cell then pips in a counter clockwise
direction. With pipping, pulmonary respiration begins. The allantois
regresses at this time and the yolk is brought in through the yolk sac's
umbilicus. When the chick pips, all the albumen should have been
utilized as it can stick against the nostrils and cause asphyxiation.
Asphyxiation can also result from excessive humidity if moisture en-
ters the chick's nostrils as it pips.
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Reeves
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« Reply #1 on: March 25, 2009, 12:32:16 PM »

                    All eggs should be candled twice during incubation
and those showing abnormal embryonic development should be re-
moved, broken out, and examined. For large hatches a representative
sample may be examined. The first candling should take place after a
week of incubation and the second just before transferring the eggs to
the hatcher. This procedure will permit the hatchery operator to di-
vide mortality into three periods: 1) the first week, 2) from the first
week to transfer, 3) during the hatching process. Under normal condi-
tions, about one-third of the total mortality occurs during the first
period, very little during the midperiod, and about two-thirds during
the last critical period. Eggs removed at the first candling test will fall
into two categories: those that show no signs of development (clears)
and those with a blood ring.

    1.   Clears: If the eggs in the clear group are broken out and exam-
          ined, some further distinctions can be made. Under normal
          conditions, clears will consist largely of true infertiles; however,
          under certain problem conditions, the clear group will also con-
          tain fertile eggs that have not developed (FNDs), preoviposital
          deads (PODs), and positive developments (PDs). A significant
          number of any of these indicates that the problem is not one of
          fertility. Fertiles without development often occur in eggs that
          have been subjected to extreme temperatures, such as near
          freezing for several days or high temperatures during washing.
                 PODs die before the egg is laid (these are very difficult to
          distinguish from infertile eggs). PODs are rare in normal stock,
          but may be found in highly inbred lines or in stock characterized
          by some  parthenogenesis.

  2.     Blood rings: Blastoderms without embryo (BWE) resemble early
          dead (ED) embryos under candling, but are structurally more
          similar to PDs. The BWE is an advanced PD in which blood-
          forming tissues have developed. BWEs, like PDs, are fertile
          blastoderms and should be considered as fertiles when hatch-
          ability calculations are made. BWEs are rare under normal
          conditions, but their incidenceis increased by the same factors
          that increase the incidence of PDs.
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Reeves
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« Reply #2 on: March 25, 2009, 12:50:57 PM »

   Early and Late Embryo Mortality
 

        Early deads (EDs) are easily identified by break-out analysis and
a few occur in most normal groups. EDs die soon after the develop-
ment of a basic organ system begins. Failure of one or more systems to
form properly is usually the cause of early embryonic death under
standard conditions; however, many factors can cause the exaggera-
tion of what we term "normal losses at this time." Table 6-5 lists some
of the most common causes of EDs.
         The late embryo mortality peak occurs at the end of incubation
and is associated with the following: the embryo's changes in position
as it gets ready to pip, its utilization of the remaining albumen, its
utilization of the yolk reserves, and its change from allantoic to pulmo-
nary respiration. These changes must be properly coordinated to re-
sult in a hatchable chick. At this critical time, marginal conditions in
the incubator, such as poor sanitation, dietary problems, genetic ef-
fects, and many other factors, cause mortality.
         Embryos that die during this late stage are usually categorized
more easily than the ones found at the first candling, and may be more
important to the diagnosis of a hatching problem. The incubator oper-
ator should note the approximate age at death of these late deads and
note any abnormalities, aside from malpositions, found in more than 3
to 4 percent.
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Reeves
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« Reply #3 on: March 25, 2009, 12:58:07 PM »

   Handling of a Hatch
 

         Never open the machine and disturb the eggs during the hatch-
ing period. Hatched chicks should only be removed from the trays
after the hatch is completed. To disturb the hatch prematurely will
disrupt the environmental conditions of the hatcher and may prevent
the remaining eggs from completing a normal hatch. Eggs should be
set at regular intervals, such as every seven days for most game bird
eggs.
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Reeves
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« Reply #4 on: March 25, 2009, 08:49:36 PM »

The information was taken from the book below. It is only a small part of the information that would be conected to 20? 30? 50? other pages of information ?

Get the book, and others like it.

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CharlieHorse
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Northern Bobwhites

« Reply #5 on: March 25, 2009, 10:22:49 PM »

 tu2    od1
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tenbears
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Personal Text

« Reply #6 on: May 13, 2013, 09:15:56 PM »

My son and I have just started trying to hatch Bob White. Of the first ten eggs only 3 hatched and 1 died shortly after birth. On the subsequent hatches we've had 0 eggs hatch, but when we break open the eggs they are fully formed, just dead. Any thoughts or suggestions would be greatly appreciated.
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