Effects of repeated thermal manipulation of broiler embryos on hatchability, chick quality, and post-hatch performance

Multilevel sensor for monitoring external and internal environment of eggs

Although it is well known that incubation environment has a great influence on embryogenesis and post-hatching performance of birds, not much is known about how external thermal, sound and light stimuli are isolated by eggshells and perceived by embryos. In this context, this study aimed to develop, calibrate and evaluate a multilevel sensor for integrated monitoring of the external (incubator) and internal environment of eggs. The variables of interest for the external environment were air temperature and relative humidity. For the internal environment, shell temperature, internal temperature, luminosity and sound pressure level were considered. The sensor was developed with an ATmega328 microcontroller, in open-source prototyping, using electronic components which are compatible with the egg's physical structure. Calibrations were carried out in a controlled environment, comparing the multilevel sensor with commercial equipment, obtaining coefficients of determination of R 2 > 0.90 for all variables studied. The multilevel sensor was also validated, simulating a commercial incubation situation and comparing eggs with 2 shell colors (white and brown) and internal volume (intact and empty). Validation results showed that white-shelled eggs insulate less external light (P < 0.001) and full eggs presented higher internal temperatures, greater light and lower sound pressure levels compared to empty eggs (P < 0.001). The multilevel sensor developed here is an innovative proposal for monitoring, simultaneously and in real time, different variables of interest in the commercial incubation environment.

Embryonic thermal manipulation of poultry birds: Lucrative and deleterious effects

The major efforts to improve feed conversion, increase the body weight and breast muscle yield of broilers have been focused on feeding and management at the post hatch period. However, incubation temperature is the most significant factor for the egg hatching rate, chick quality, and post hatch performance. Therefore, incubation factors affecting the performance should be taken with necessary precautions. Incubation temperature not only affects the early development of the hatchlings but also has a lasting impact on the characteristics of the chicks, such as final body weight and meat quality traits. This article provides an overview about embryonic thermal manipulation (TM) of domestic fowls and review the lucrative and deleterious effects of embryonic TM on embryo development, muscle growth, thermotolerance acquisition, and immunity.

Effect of thermal manipulation on embryonic development, hatching process, and chick quality under heat-stress conditions

Thermal stress is a risk that threatens poultry welfare and productivity. Thermal manipulation during egg incubation is considered a prevention strategy used to mitigate the detrimental effects of high ambient temperatures on birds. This study aimed to investigate the impact of thermal manipulation, applied to chicken breeder's eggs during the incubation period, on embryonic development, hatching characteristics, and chick quality, as well as posthatch thermotolerance and performance. A total of 1,200 fertile eggs were randomly and equally assigned into 2 groups of 3 replicates (200 eggs/replicate), using a randomized experimental design followed by t test. The first group eggs (G1) were subjected to a commercial setter temperature of 37.5°C with 55% relative humidity (RH) throughout the incubation period (1-18 d) and served as a control, while the second group eggs (G2) were treated the same commercial setter conditions until the 11th day of the incubation, then the eggs were exposed to a higher temperature of 39.5°C with 60% RH for 4 h daily from the 12th to the 18th day of incubation. All eggs in both groups were exposed to the same temperature condition of 37.2°C with 70% RH from the 19th to the 22nd days of the incubation (hatching period). Three hundred hatched female chicks per each treatment group were transferred into a closed-system house and distributed randomly into 20 floor pens (15 birds per pen). At the 8th week of age, birds were exposed to a daily heat challenge by raising the temperature to 35°C for 6 h until the 18th week of the chick's age. According to the results, thermal manipulation at 12 to 18 d of egg incubation positively (P ≤ 0.05) affected several studied traits. It improved some embryonic development traits, such as embryonic weight and tibia length, as well as some hatching parameters, such as hatching time and pipped eggs. It also improved hatched chick quality traits, including the chick's weight, length, and activity. In addition, it enhanced the posthatch chick's thermotolerance and body weight. Hatched chicks of G2 had significantly (P ≤ 0.05) higher total protein, albumin, IgM, glucose, calcium, total antioxidant, and T3 than G1 chicks. They also had significantly (P = 0.001) higher body weight (23%) at the 18th week of age than G1, as well as a lower feed conversion ratio (20.71%) than G1 chicks at 8 to 18 wk of age. Therefore, it is recommended to apply thermal manipulation during egg incubation, particularly at 12 to 18 d, for its positive effects on the pre- and posthatch performance.

Effects of Thermal Manipulation on mRNA Regulation of Response Genes Regarding Improvement of Thermotolerance Adaptation in Chickens during Embryogenesis

The phenomenon of increasing heat stress (HS) among animals is of particular significance when it is seen in economically significant industries, such as poultry. Due to the identification of the physiological, molecular, and genetic roots of HS responses in chickens, a substantial number of studies have focused on reducing the effects of HS in poultry through environmental management, dietary manipulation, and genetic alterations. Temperature manipulation (TM) during embryogenesis has been claimed to increase the thermal tolerance and well-being of chickens without affecting their capacity for future growth. There has been little investigation into the vulnerability of the epigenome involving TM during embryogenesis, although the cellular pathways activated by HS have been explored in chickens. Epigenetic changes caused by prenatal TM enhance postnatal temperature adaption and produce physiological memory. This work offers a thorough analysis that explains the cumulative impact of HS response genes, such as genes related to heat shock proteins, antioxidants, and immunological genes, which may aid in the enhanced adaptability of chickens that have undergone thermal manipulation during their embryonic stages.

Effects of late incubation temperature and moment of first post-hatch feed access on neonatal broiler development, temperature preference, and stress response

Early life experiences are known to be of great importance for later life. For instance, exposure to stress during early life can increase fearfulness at later age. In broilers, delayed feeding after hatch may cause metabolic stress. Besides, delayed feeding after hatch may affect neonatal broiler development and thermogenesis and consequently preferred ambient temperature. Moreover, these effects of feeding strategy may be dependent on late incubation temperature. To study this, eggs (n = 1,338) from a 54-wk-old Ross broiler breeder flock were incubated at 37.8°C (control) or 36.7°C (lower) eggshell temperature (EST) during late incubation (≥ embryonic d 17). At hatch, two feeding strategies were applied (direct access (early feeding) or 51 to 54 h delayed access (delayed feeding)). Broilers (n = 960) were equally divided over 32 pens and grown for 3 wk. Stress was assessed by determination of corticosterone in blood at 0 h, 48 h, 96 h and d 21 after hatch. Fearfulness was assessed by tonic immobility at d 13. Temperature preference was assessed at d 2 and d 12. Broiler development was determined at 0 h, 48 h, and 96 h after hatch. There was no EST × feeding strategy interaction for any parameter (P ≥ 0.07). Early feeding resulted in a 2.5× lower plasma corticosterone concentration at 48 h (P < 0.01) and a 2.2°C and 2.0°C lower preference temperature for d 2 and d 12 respectively (P = 0.01) compared to delayed feeding. Tonic immobility was not affected. In conclusion, early feeding reduces exposure to stress in the short term and stimulates thermoregulatory ability of broilers in the longer term.

Molecular and morphometric changes in the small intestine during hot and cold exposure in thermally manipulated broiler chickens

Background and Aim:

Thermal stress (hot or cold) is one of many environmental stressors that severely affects the health of broiler chickens. One negative effect of thermal stress is the disruption of the intestinal barrier function in broiler chickens. This study aimed to evaluate the effect of thermal manipulation (TM) on the small intestine in terms of histomorphometry as well as junctional, heat-shock, and immune response gene expression during post-hatch exposure to thermal stress.

Materials and Methods:

The experiment was conducted by dividing 928 fertile Ross eggs into three incubation groups: The control (C) group (incubated at 37.8°C and 56% relative humidity [RH] for the whole incubation period), the TM using low temperature TML group (incubated at 36°C and 56% RH for 18 h/day from embryonic days 7 to 16), and the TM using high temperature (TMH) group (incubated at 39°C and 65% RH for 18 h/day from embryonic days 7 to 16). On post-hatch day 21, 90 chicks were randomly selected from each incubation group and were equally subdivided into three subgroups for the post-hatch thermal stress experiment: The TN subgroup (room temperature maintained at 24°C), the heat stress (HS) subgroup (room temperature maintained at 35°C), and the cold stress (CS) subgroup (room temperature maintained at 16°C). After 1 day of thermal stress exposure (age 22 days), five birds from each subgroup were euthanized and ileum samples were collected to evaluate the transcription of the Claudin (CLDN1), CLDN-5, Occludin, Cadherin-1, heat shock factors (HSF1), HSF3, 70 kilodalton heat shock protein, 90 kilodalton heat shock protein, Interleukin6 (IL6), IL8, toll-like receptors-2 (TLR2), and TLR4 genes by Real-Time Quantitative Reverse Transcription polymerase chain reaction analysis. Finally, after 4 and 7 days of thermal stress (age 25 and 28 days, respectively), nine chicks were euthanized, and their jejunum and ileum were collected for histomorphometric analysis.

Results:

After exposure to 1 day of thermal stress, the C subgroups exposed to thermal stress (HS and CS) possessed significantly increased expression of junctional, heat-shock, and immune response genes compared to the C-TN subgroup, and similar results were observed for the TMH. In contrast, thermally stressed TMH subgroups had significantly lower expression of the studied genes compared to C subgroups exposed to thermal stress. Furthermore, no significant changes were detected between the TML subgroups exposed to thermal stress and TML-TN. Moreover, significant alterations in villus height (VH), villus surface area, crypt depth (CD), and VH to CD ratio were observed between the TML, TMH, and C subgroups exposed to CS.

Conclusion:

It might be suggested that TM may have a protective impact on the small intestine histomorphometry and epithelial integrity of broilers during post-hatch exposure to thermal stress.