Effects of temperature and CO2 during late incubation on broiler chicken development

Incubation conditions need to be adjusted to meet embryonic requirements to obtain optimal chick quality and hatchability. Eggshell temperature (EST) can be used as a non- invasive method to determine embryo temperature. A high EST of 38.9°C during the second or third week of incubation negatively affects chicken embryo development and survival compared to a constant EST of 37.8°C during that period. These negative effects of high EST might be due to a dis-balance between metabolic rate and oxygen (O2) availability. However, effects of lowering EST, which might restore the balance between metabolic rate and O2 availability, are largely unknown. Besides EST, the carbon dioxide (CO2) concentration during late incubation also seems to affect embryo development and might even interact with EST. Based on the potential effects of (lower) EST during the last week of incubation and of CO2 during only the hatching phase, the following three aims are derived: 1, to investigate effects of EST during the last phase of the incubation process, with special attention for EST below the general accepted optimal EST of 37.8°C, 2, to examine from which day of the incubation process onward EST should be changed from 37.8°C, and 3, to investigate whether CO2 concentrations are interacting with EST during the hatcher phase. Time until hatch was longer when an EST of 35.6°C was applied during the last week of incubation, followed by 36.7, 37.8, and 38.9°C, which is probably caused by the lower metabolic rate at an EST below 37.8°C. Hatchability of fertile eggs was not affected at low EST, and EST did not affect time between internal pipping (IP) and hatch. An EST of 35.6 and 36.7°C, resulted in a higher yolk-free body mass (YFBM) at hatch compared to 37.8 and 38.9°C, and residual yolk weight was higher at hatch at 38.9°C compared to all other EST treatments. An EST of 35.6°C resulted in higher hepatic glycogen concentration and amount at IP and hatch compared to all other EST treatments. The proposed mechanism involved is that at lower EST, metabolic rate is reduced, which prevents the embryo from O2 limitation and ensures that fatty acid oxidation from the yolk can be maintained, resulting in energy production to be invested in growth and development. At an EST of 38.9°C, metabolic rate is high, resulting in a relative O2 shortage for the embryo. Consequently, lipid oxidation is reduced, which forces the embryo to switch to alternative energy sources, such as glycogen. Because glycogen storage is very limited in the egg and embryo, alternative energy sources such as amino acids obtained from muscles might be used. A clear interaction between EST and start day of treatment was found for relative heart weight. Relative heart weight was higher at an EST of 35.6°C and decreased with increase in EST. The differences among EST became larger when the EST treatment started earlier. Effects of CO2 on embryo physiology, embryonic organ development, and chick quality were marginal. EST interacted with CO2 mainly before IP, but effects were minor at hatch. Interactions between EST and CO2 were found at an EST of 36.7 and 37.8°C, but remained absent at an EST of 38.9°C, which might indicate that physiological systems are already challenged due to the higher metabolic rate, which limits the capacity to cope with high CO2 of the embryo. No effect of start day of treatment was indicated for embryonic organ development and chick quality found at hatch, which suggests that EST affected these parameters only in the last phase of incubation, e.g. from E19 onward. However, first week post-hatch performance was affected by start day of treatment. The beneficial effects of a lower EST of 35.6 and 36.7°C applied during the last week of incubation found at hatch, might contribute to an enhanced development during the first week post-hatch as body weight, carcass weight, and gain to feed ratio were increased. In conclusion, results of this thesis show that an EST below 37.8°C during late incubation is beneficial for embryo development, organ growth during incubation, and growth performance during the first week post-hatch. In addition, start day of treatment did not affect chick quality and organ growth, except heart weight, at hatch, which implies that effects of EST occur during the hatching phase, e.g. from E19 onward. Although, an effect of start day of treatment was found on first week post-hatch performance, it remains to be investigated whether an EST below 37.8°C leads to improved later life quality characteristics.</p

High eggshell temperatures during incubation decrease growth performance and increase the incidence of ascites in broiler chickens

High eggshell temperatures (EST; 38.9°C) during the second half of incubation are known to decrease the body and organ development of broiler hatchlings. In particular, relative heart weights are decreased by a high EST, and this may increase the incidence of metabolic disorders that are associated with cardiovascular development, such as ascites. The current study investigated the effects of a high EST on chick quality, subsequent performance, and the incidence of ascites later in life. Eggs were incubated at a normal (37.8°C) or high (38.9°C) EST from d 7 of incubation onward. After hatching, the chickens were housed per EST in pens, and a normal or cold temperature schedule was applied during the grow-out period. Hatchability, hatchling quality, BW, feed conversion ratio, total mortality, mortality associated with ascites, slaughter characteristics, and ascites susceptibility at 6 wk of age were evaluated. Except for total ventricle weight, no interaction was found between EST and the grow-out temperature. Hatchability was comparable between the EST treatments, but the percentage of second-grade chickens was 0.7% higher at the high EST. Yolk-free body mass was 3.0 g lower, and heart weights were 26% lower at hatch in the high compared with the normal EST treatment. Body weight continued to be less during the grow-out period after the high EST incubation. However, breast meat yield was 1.0% higher in the high than in the normal EST. Feed conversion ratio did not differ between EST treatments. Total mortality was 4.1% higher and mortality associated with ascites was 3.8% higher in the high compared with the normal EST treatment. The ratio between the right and total ventricle was 1.1% higher in the high compared with the normal EST treatment at slaughter age. In conclusion, a high EST from d 7 of incubation onward decreased hatchling quality and growth performance, but increased breast meat yield. Furthermore, high EST incubation increased the incidence of ascites, which may be related to the reduced heart development at hatch

Effect of relative humidity during incubation at a set eggshell temperature and brooding temperature posthatch on emryonic mortality and chick quality

Previous studies have shown that RH during incubation of chicken eggs influences water loss from the egg and embryonic mortality. In those studies, eggshell temperatures (EST) were not monitored or controlled. Because RH influences the egg’s heat loss through evaporation, EST might have been different between RH treatments, influencing embryonic mortality and development. To eliminate the effect of EST, in the current study eggs were incubated at an EST of 37.8°C from embryonic d (E) 0 until E18 and at a high (55 to 60%) or low (30 to 35%) RH from E2 until hatch. Embryonic mortality, hatch curve, and several chick quality characteristics (length, weight, navel quality, organ weights, and DM of the yolk free body mass and yolk) were determined on E18 and at hatch. Low RH increased egg weight loss between E0 and E18 (+3.0%) and third week embryonic mortality (+3.0% of fertile eggs) and decreased hatch of fertile eggs (-2.9% of fertile eggs) compared with high RH. Hatch duration and chick quality characteristics did not differ between RH treatments. To assess the effect of RH during incubation on posthatch performance under suboptimal conditions, hatchlings were brooded at a normal (35.0°C at d 0, decreasing to 27.0°C at d 4) or cold (27.8°C at d 0, decreasing to 25.6°C at d 4) temperature until 4 d posthatch. Incubation RH and brooding temperature significantly interacted with posthatch growth but not development. Both low and high RH × cold brooding temperature resulted in lower (-6.9 and -6.0 g, respectively) BW than high RH × normal brooding temperature at 4 d of age. The cold brooding temperature resulted in lower daily feed intake (-1.3 g/chick) than the normal brooding temperature. In conclusion, incubating eggs at a low RH compared with a high RH and maintaining the EST at 37.8°C decreased hatch of fertile eggs, but had little effect on chick quality or posthatch performance

Temperature and CO2 during the hatching phase. I. Effects on chick quality and organ development

The objective of this study was to investigate the effect of eggshell temperature (EST) and carbon dioxide (CO2) concentration during only the hatching phase on embryonic development and chick quality. Three batches of eggs were incubated at an EST of 37.8°C until d of incubation (E) 19. From E19, embryos were incubated at low (36.7°C), normal (37.8°C), or high (38.9°C) EST and at low (0.2%) or high (1%) CO2 concentration. Organ growth and embryo and chick quality were measured at E19, internal pipping (IP), hatch, and 12 h after hatch. A few interactions between EST and CO2 were found at IP, hatch, and 12 h after hatch, but all of these interactions were temporary and in most cases weak. High EST resulted in a lower relative heart weight compared with low (¿ = 0.05) and normal EST (¿ = 0.06) at IP, compared with low (¿ = 0.11) and normal EST (¿ = 0.08) at hatch, and compared with low (¿ = 0.11) and normal EST (¿ = 0.08) at 12 h after hatch. At hatch, high EST resulted in a lower YFBM compared with low EST (¿ = 0.65). At 12 h after hatch, high EST resulted in a lower relative liver weight compared with low EST (¿ = 0.12). At low EST, greater relative intestinal weight was found compared with normal (¿ = 0.41) and high EST (¿ = 0.37). The effect of CO2 solely was found at 12 h after hatch at which a higher relative heart weight (¿ = 0.05) and a higher relative lung weight (¿ = 0.0542) was found at high CO2 compared with low CO2. High EST during only the hatching phase negatively affected chick development, mainly expressed by the lower relative heart weight at IP, hatch, and 12 h after hatch and lower YFBM at hatch. The resolving effect of CO2 demonstrates that CO2 only seem to have a temporary effect during the hatching phase

High eggshell temperatures during incubation decrease growth performance and increase the incidence of ascites in broiler chickens

High eggshell temperatures (EST; 38.9°C) during the second half of incubation are known to decrease the body and organ development of broiler hatchlings. In particular, relative heart weights are decreased by a high EST, and this may increase the incidence of metabolic disorders that are associated with cardiovascular development, such as ascites. The current study investigated the effects of a high EST on chick quality, subsequent performance, and the incidence of ascites later in life. Eggs were incubated at a normal (37.8°C) or high (38.9°C) EST from d 7 of incubation onward. After hatching, the chickens were housed per EST in pens, and a normal or cold temperature schedule was applied during the grow-out period. Hatchability, hatchling quality, BW, feed conversion ratio, total mortality, mortality associated with ascites, slaughter characteristics, and ascites susceptibility at 6 wk of age were evaluated. Except for total ventricle weight, no interaction was found between EST and the grow-out temperature. Hatchability was comparable between the EST treatments, but the percentage of second-grade chickens was 0.7% higher at the high EST. Yolk-free body mass was 3.0 g lower, and heart weights were 26% lower at hatch in the high compared with the normal EST treatment. Body weight continued to be less during the grow-out period after the high EST incubation. However, breast meat yield was 1.0% higher in the high than in the normal EST. Feed conversion ratio did not differ between EST treatments. Total mortality was 4.1% higher and mortality associated with ascites was 3.8% higher in the high compared with the normal EST treatment. The ratio between the right and total ventricle was 1.1% higher in the high compared with the normal EST treatment at slaughter age. In conclusion, a high EST from d 7 of incubation onward decreased hatchling quality and growth performance, but increased breast meat yield. Furthermore, high EST incubation increased the incidence of ascites, which may be related to the reduced heart development at hatch

Temperature and CO2 during the hatching phase. II. Effects on chicken embryo physiology

The objective of this study was to investigate the effect of eggshell temperature (EST) and carbon dioxide concentration during only the hatching phase on physiological characteristics of embryos and chicks. Three groups of eggs were incubated at an EST of 37.8°C until d 19 of incubation (E19). From E19, embryos were incubated at a low (36.7°C), normal (37.8°C), or high (38.9°C) EST and at a low (0.2%) or high (1.0%) CO2 concentration. For E19, internal pipping (IP), hatch, and 12 h after hatch, blood parameters were analyzed and hepatic glycogen was determined. At IP, hatch, and 12 h after hatch, interactions were found between EST and CO2, but all these interactions were temporary and in most cases weak. High EST resulted in a lower hepatic glycogen concentration compared with low (¿ = 21.1) and normal EST (¿ = 14.43) at IP, and a lower hepatic glycogen concentration compared with low EST (¿ = 6.24) at hatch. At hatch, high EST resulted in lower hematocrit value (¿ = 2.4) and higher potassium (¿ = 0.5) compared with low EST. At 12 h after hatch, high EST resulted in a higher lactate concentration compared with low (¿ = 0.77) and normal EST (¿ = 0.65). And high EST resulted in higher potassium compared with low (¿ = 0.4) and normal EST (¿ = 0.3). An effect of CO2 solely was only found at IP, at which high CO2 resulted in a lower pH (¿ = 0.03) and a lower hepatic glycogen concentration (¿ = 7.27) compared with low CO2. High EST during only the hatching phase affected embryo and chick physiology, indicated by the lower hepatic glycogen levels at IP and hatch. High CO2 affected pH and hepatic glycogen at IP. Effects of CO2 were only found at low EST, which emphasizes the large effect of EST during the hatching phase

Temperature during the last week of incubation. I. Effects on hatching pattern and broiler chicken embryonic organ development

We investigated the effects of an eggshell temperature (EST) of 35.6, 36.7, 37.8, and 38.9°C applied from d of incubation (E) 15, E17, and E19 on hatching pattern and embryonic organ development. A total of 2,850 first-grade eggs of a 43-week-old Ross 308 broiler breeder flock were incubated at an EST of 37.8°C until E15. From E15, E17, or E19 onward, eggs were incubated at an EST of 35.6, 36.7, 37.8, or 38.9°C. Moment of internal pipping (IP), external pipping (EP), and hatch was determined, and organ development was measured at E15, E17, E19, IP, EP, and hatch.A lower EST extended incubation duration compared to a higher EST. The lower incubation duration was mainly caused by the extended time until IP, whereas time between IP and hatch hardly varied between treatments.Relative heart weight was affected by EST already from 2 d after the start of EST treatment on E15, and effects became more pronounced at longer exposure time to various EST treatments. At hatch, the largest difference in relative heart weight was found between an EST of 35.6 and 38.9°C started at E15 (Δ = 64.4%). From E17 onward, EST affected yolk-free body mass (YFBM) and relative stomach weight, where a lower EST resulted in a lower YFBM and relative stomach weight before IP and a higher YFBM and relative stomach weight after IP. From E19 onward, a lower EST resulted in a higher relative liver and spleen weight regardless of start time of treatment. Yolk weight and relative intestine weight were not affected by EST before and at E19, but a higher EST resulted in a higher yolk weight and lower relative intestine weight from IP onward.Based on the higher YFBM and higher relative organ growth found at hatch, we concluded that an EST lower than 37.8°C from E15 onward appears to be beneficial for optimal embryo development