Author
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Bakst, Murray |
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Welch, Glenn |
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Camp, Mary |
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Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 12/11/2015 Publication Date: 3/8/2016 Citation: Bakst, M.R., Welch, G.R., Camp, M.J. 2016. Observations of turkey eggs stored up to 27 days and incubated for 8 days: embryo developmental stage and weight differences and the differentiation of fertilized from unfertilized germinal discs. Poultry Science. 95:1165-1172. Interpretive Summary: For logistical reasons, egg storage in a cool room prior to incubation is a growing practice in the commercial turkey industry. However, egg storage longer than 7 days leads to embryo mortality during incubation. Incubated turkey eggs are candled at 8 days of incubation to separate those eggs containg a normal embryo from unfertilized eggs and eggs with an early dead embryo (clear eggs). The goal of this study was to describe features on the yolk of the clear eggs that would simplify telling the difference between an early dead embryo from an unfertilized egg. Five groups of turkey eggs were stored for progressively increasing periods of time (5 days or less to 21-27 days), incubated, and then opened and examined after 8 days of incubation. In eggs containing normal embryos, we observed that as the egg storage period increased, embryo weights and their stages of development decreased. Of the fertilized clear eggs, limited blood formation and dead but intact or partial embryos were observed on the yolk surface. The yolks of embryos that died during egg storage were no longer uniform in appearance but possessed whitish sheets of embryonic cells on its surface. Regardless how long the egg was stored, if the egg was unfertilized its yolk was uniform in color and there was a dense, white, irregular shape disc (the site of fertilization) on the yolks surface. These observation can be useful to hatchery personnel and poultry scientists in assessing whether there is a fertility problem or an embryonic mortality problem at the time of egg candling. Technical Abstract: For logistical reasons, egg storage prior to incubation is a growing practice in the commercial turkey industry. In the following study, 5 groups of eggs each from inseminated and virgin hens were stored for progressively increasing periods of time (5 days or less to 21-27 days) and incubated. At 8 days of incubation eggs were candled and the stage of development and embryo weights in normally developed eggs were determined. There was a significant negative correlation between the stage of development and embryo weight and increasing storage periods. Clear eggs from the inseminated and virgin hens were broken-out and the appearance of the yolk and the fertilized and unfertilized germinal discs examined. The yolks of both hen groups with unfertilized ova maintained a homogeneous uniform yellow-orange color. In contrast, yolks of ova that had been fertilized, with or without early dead embryos, and yolks from virgin hens that showed evidence of parthenogenetic development (3%) had a heterogeneous appearance using fluorescence.Microscopy, the heterogeneous appearance was due to sheets of aberrant cells and less frequently dispersed cells and folds of the perivitelline layer. It was concluded that clear egg breakouts need to be performed to more accurately assess the impact of egg storage on embryonic mortality. Furthermore, such break outs should be performed with a high intensity light directed across the surface of the germinal disc to clearly differentiate the subtle differences between an early dead embryo and an unfertilized germinal disc. |
