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The present study was developed based on data from eggs incubation from three lines of turkeys: Layer Light turkey - LL, Meat Heavy turkey -MH and North Caucasian Bronze Turkey - NCB at 36 weeks of age. The degree of influence of the incubation traits was determined: number of set eggs, number of fertilized eggs, number of dead embryos 1st review and number of dead embryos 2nd review on the number of hatched turkeys by applying a correlation analysis. The obtained relations were presented by mathematical models compiled after using a regression analysis. The significant dependencies between these signs were demonstrated by mathematical models compiled using regression analysis. Mathematical models were built to present these relations in analytical form.

During incubation of chicken embryos, environmental conditions, such as temperature, relative humidity, and CO2 concentration, must be controlled to meet embryonic requirements that change during the different phases of embryonic development. In the current review, the effects of embryo temperature, egg weight loss, and CO2 concentration on hatchability, hatchling quality, and subsequent performance are discussed from an embryonic point of view. In addition, new insights related to the incubation process are described. Several studies have shown that a constant eggshell temperature (EST) of 37.5 to 38.0 degrees C throughout incubation results in the highest hatchability, hatchling quality, and subsequent performance. Egg weight loss must be between 6.5 and 14.0% of the initial egg weight, to obtain an adequate air cell size before the embryo internally pips. An increased CO2 concentration during the developmental phase of incubation (first 10 days) can accelerate embryonic development and hatchability, but the physiological mechanisms of this acceleration are not completely understood. Effects of ar increased CO2 concentration during late incubation also need further investigation. The preincubation warming profile, thermal manipulation, and in ovo feeding are new insights related to the incubation process and show that the optimal situation for the embryo during incubation highly depends on the conditions of the eggs before (storage duration) and during incubation (environmental conditions) and on the conditions of the chickens after hatching (environmental temperature).

To investigate the effect of incubation conditions on layer hatchlings, an experiment was performed in which layer eggs were incubated at a normal (37.8 degrees C) or high (38.9 degrees C) eggshell temperature (EST) and a hole was punctured in the air cell of half of the eggs in both EST treatments from d 14 of incubation onward. Chick development, plasma metabolites, and hepatic glycogen were measured at 12 h after emergence from the eggshell. Embryo mortality was not affected by the EST or hole treatment. At the high EST, yolk-free body mass was 0.7 g lower and residual yolk weight was 0.7 g higher than at the normal EST. This may be related to the shorter incubation duration at the high EST. Relative heart, lung, stomach, liver, spleen, and intestinal weights were lower in the high EST than in the normal EST group. Yolk-free body mass did not differ between eggs with or without a hole, but residual yolk weight was slightly lower in eggs with a hole (0.3 g). Relative lung weights were higher in eggs with than without a hole, whereas no effect on other organs was found. Plasma glucose, lactate, and uric acid concentrations did not differ between the EST or hole treatments. Hepatic glycogen was lower in the high EST (7.3 mg) than in the normal EST group (11.2 mg) at 12 h after emergence from the eggshell, and this effect may be related to the shorter hatching process at the high EST. Hepatic glycogen levels were lower in eggs with a hole (8.6 mg) compared with eggs without a hole (10.0 mg), and this may be related to the longer period between external pipping and hatching in eggs with a hole. In conclusion, the EST and hole treatment did not interact, and neither treatments affected embryonic survival. High EST negatively affected hatchling development and seemed to change the carbohydrate metabolism in layer embryos. The effect of a hole in the air cell was limited.

Environmental conditions during incubation such as temperature and O(2) concentration affect embryo development that may be associated with modifications in nutrient partitioning. Additionally, prenatal conditions can affect postnatal nutrient utilization. Using broiler chicken embryos, we studied the effects of eggshell temperature (EST; 37.8 or 38.9 degrees C) and O(2) (17, 21, or 25%) applied from d 7 until 19 of incubation in a 2 x 3 factorial design. Effects of these factors on embryonic survival, development, and nutrient utilization were assessed in the pre- and posthatch period. High EST reduced yolk-free body mass compared with normal EST (36.1 vs. 37.7 g), possibly through reduced incubation duration (479 vs. 487 h) and lower efficiency of protein utilization for growth (83.6 vs. 86.8%). Increasing O(2) increased yolk-free body mass (from 35.7 to 38.3 g) at 12 h after emergence from the eggshell, but differences were larger between the low and normal O(2) than between the normal and high O(2). This might be due to the lower efficiency of nutrient utilization for growth at low O(2). However, the effects of O(2) that were found at 12 h were less pronounced at 48 h posthatch. When O(2) was shifted to 21% for all treatments at d 19 of incubation, embryos incubated at low O(2) used nutrients more efficiently than those incubated at normal or high O(2). An additional negative effect on survival and chick development occurred when embryos were exposed to a combination of high EST and low O(2). Possible explanations include reduced nutrient availability for hatching, decreased body development to fulfill the energy-demanding hatching process, and higher incidence of malpositions. In conclusion, EST and O(2) during incubation affect nutrient utilization for growth, which may explain differences in survival and development. Embryos raised under suboptimal environmental conditions in the prenatal period may develop adaptive mechanisms that still continue in the posthatch period.

During incubation of chicken embryos, environmental conditions, such as temperature, relative humidity, and CO2 concentration, must be controlled to meet embryonic requirements that change during the different phases of embryonic development. In the current review, the effects of embryo temperature, egg weight loss, and CO2 concentration on hatchability, hatchling quality, and subsequent performance are discussed from an embryonic point of view. In addition, new insights related to the incubation process are described. Several studies have shown that a constant eggshell temperature (EST) of 37.5 to 38.0 degrees C throughout incubation results in the highest hatchability, hatchling quality, and subsequent performance. Egg weight loss must be between 6.5 and 14.0% of the initial egg weight, to obtain an adequate air cell size before the embryo internally pips. An increased CO2 concentration during the developmental phase of incubation (first 10 days) can accelerate embryonic development and hatchability, but the physiological mechanisms of this acceleration are not completely understood. Effects of ar increased CO2 concentration during late incubation also need further investigation. The preincubation warming profile, thermal manipulation, and in ovo feeding are new insights related to the incubation process and show that the optimal situation for the embryo during incubation highly depends on the conditions of the eggs before (storage duration) and during incubation (environmental conditions) and on the conditions of the chickens after hatching (environmental temperature).

This-study was carried out with the aim of eliminating the stress factors caused by the increase in metabolic heat of the embryo during incubation via AA application, and by providing a supplementary energy source to the embryo prior to hatching through glucose application, and determining its effects on embryonic mortality, hatchability and chick hatch weight. Experiment I was carried out on the 13(th) day of incubation after candling and live embryos were subjected to the following treatments, using the in ovo injection system: 1 - uninjected (control); 2 - eggs injected with 0.5 ml sterile saline solution; 3 - eggs injected with 0.5 ml of saline solution containing 1, 3, 5 or 7 mg of AA per egg. In experiment 2, glucose injection at varying concentrations was applied to the eggs before hatching. For this purpose live embryos candled prior to transfer were subjected to the following treatments on day 18 using in ovo injection (Embrex) system: I - uninjected (control); 2 - eggs injected with 0.5 ml deionized sterile water; 3 - eggs injected with 0.5 ml of deionized sterile water containing 5, 10 or 15 mg of glucose. The effect of AA injection on the hatchability of fertile eggs was found to be significant (P < 0.01). The highest hatchability was obtained from the group treated with AA at. 3 mg concentration. No effect of glucose injection was determined on the hatchabilty and chick weight.