Metabolic responses of chick embryos to short-term temperature fluctuations

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.

Broiler resilience to colibacillosis is affected by incubation temperature and post-hatch feeding strategy

Colibacillosis is a poultry disease that negatively affects welfare and causes economic losses. Treatment with antibiotics raises concerns on antimicrobial resistance. Consequently, alternative approaches to enhance poultry resilience are needed. Access to feed and water directly after hatch (early feeding) may enhance resilience at later ages. Additionally, a high eggshell temperature (EST) during mid incubation may improve chick quality at hatch, supporting potential positive effects of early feeding. Effects of EST [37.8°C (control) or 38.9°C (higher)] during mid-incubation (embryo days 7–14) and feeding strategy (early feeding or 48 h delayed feeding) were tested in a 2 × 2 factorial arrangement. At hatch, ~ 1,800 broilers were divided over 36 pens and grown for 6 wk. At d 8 post hatch, avian pathogenic E. coli (APEC) was inoculated intratracheally as model to investigate broiler resilience against respiratory diseases. Incidence and severity of colibacillosis, local infection, and systemic infection were assessed at 6 moments between 3 h and 7 d postinoculation. Broilers were weighed daily during 13 d postinoculation and weekly thereafter. At higher EST, early feeding resulted in higher incidence of systemic infection compared to delayed feeding whereas at control EST, systemic infection was not different between feeding strategies. Regardless of EST, early compared to delayed feeding resulted in lower incidence of local infection, fewer BW deviations, and higher growth until d 35. In conclusion, early feeding could be considered as a strategy to enhance broiler resilience, but only when EST is not too high.

Effects of Early Nutrition of Hatched Chicks on Welfare and Growth Performance: A Pilot Study

Simple Summary

It is common practice that one-day-old chicks can be deprived of feed for about 48 h or more before they are housed on farms. Thus, we hypothesized that early nutrition on-farm hatched chicks might overcome the adverse effects of delayed nutrition on-hatchery hatched chicks regarding some animal welfare issues such as foot pad health as well as growth performance of birds. Our results confirmed that early nutrition on-farm hatched chicks together with using new fresh litter at d 7 of life led to a reduction in the severity of foot pad lesions and improved the growth performance of broiler chickens.

Abstract

This study aimed to investigate the possibility of rearing newly hatched chicks with immediate access to feed and water in the same hatching unit one week prior to transferring them to the conventional broiler house with special regards to foot pad health and growth performance. Two trials were performed with a total of 6900/6850 (trials 1/2) broiler chickens (ROSS 308). A total of 3318/3391 chicks (trials 1/2) were transported from the hatchery (duration of about 3 h) and reared in a conventional broiler house (control group: delayed nutrition on-hatchery hatched). The control group did not receive any form of nutrition until they were taken to conventional broiler housing. Additionally, a total of 3582/3459 (trials 1/2) embryonated eggs (d 18) were obtained from the same parent flock of the same commercial hatchery and taken to the farm facility. After on-farm hatch, the chicks had immediate access to water and feed (experimental group: early nutrition on-farm hatched). After d 6/7 of life, the on-farm hatched chicks (trials 1/2) were transferred to the broiler house on the same facility. The delayed nutrition on-hatchery hatched groups displayed a significantly lower dry matter content in the litter compared to the early nutrition on-farm hatched groups (two-factorial analysis) at d 6/7 and d 14 of life. However, thereafter, no significant differences were noted. Based upon two-factorial analysis, the early nutrition on-farm hatched groups revealed lower foot pad lesions from d 14 of life onwards and showed a higher body weight (BW) throughout the rearing period compared to the delayed nutrition on-hatchery hatched groups (p < 0.05). Overall, early nutrition on-farm hatched chickens is of critical importance together with using new litter at d 7 to maintain healthy foot pads as well as to enhance nutrient utilization and optimize the growth performance.

Wider Angle Egg Turning during Incubation Enhances Yolk Utilization and Promotes Goose Embryo Development

We aimed to investigate how wide-angle turning of eggs during incubation affected yolk utilization and the associated molecular mechanism, along with improved goose embryonic development. In total, 1152 eggs (mean weight: 143.33 ± 5.43 g) were divided equally and incubated in two commercial incubators with tray turning angles adjusted differently, to either 50° or 70°. Following incubation under the standard temperature and humidity level, turning eggs by 70° increased embryonic days 22 (E22), embryo mass, gosling weight at hatching, and egg hatchability, but reduced E22 yolk mass compared with those after turning eggs by 50°. Lipidomic analyses of the yolk revealed that egg turning at 70° reduced the concentrations of 17 of 1132 detected total lipids, including diglycerides, triglycerides, and phospholipids. Furthermore, the 70° egg turning upregulated the expression of genes related to lipolysis and fat digestion enzymes, such as lipase, cathepsin B, and prosaposin, as well as apolipoprotein B, apolipoprotein A4, very low-density lipoprotein receptor, low-density lipoprotein receptor-related protein 2, and thrombospondin receptor, which are genes involved in lipid transportation. Thus, a 70° egg turning angle during incubation enhances yolk utilization through the upregulation of lipolysis and fat digestion-related gene expression, thereby promoting embryonic development and improving egg hatchability and gosling quality.

Effects of sublethal application of Deepwater Horizon oil to bird eggs on embryonic heart and metabolic rate

Following large crude oil spills, oil from feathers of brooding birds and oiled nesting material can transfer to eggs, resulting in reduced embryonic viability for heavily oiled eggs. Eggs may also be subjected to trace or light oiling, but functional teratogenic effects from sublethal crude oil exposure have not been examined. We assessed whether sublethal application of weathered Deepwater Horizon crude oil to the eggshell surface alters heart rate and metabolic rate in Zebra Finch (Taeniopygia guttata) embryos. We first determined sublethal applications with a dosing experiment. Embryo viability for eggs exposed to 5 μL or more of crude oil decreased significantly. We conducted a second experiment to measure heart rate and metabolic rate (CO₂ production) 5 and 9 d after 1 sublethal application of crude oil to eggshells on day 3 of incubation. One application of 1.0 or 2.5 µL of crude oil reduced embryonic heart rate and metabolic rate on day 12 of incubation. Using unfertilized eggs, we measured the transfer of polycyclic aromatic hydrocarbons (PAHs) from the eggshell surface to egg contents 9 d after a single application of sublethal crude oil. Our results suggest avian eggs externally exposed to small amounts of crude oil may exhibit protracted embryonic development and impaired postnatal cardiac performance.

A review on yolk sac utilization in poultry

During incubation, embryonic growth and development are dependent on nutrients deposited in the egg. The content of the yolk can be transferred to the embryo in 2 ways: directly into the intestine via the yolk stalk or through the highly vascularized yolk sac membrane. It has been suggested that, as a result of genetic selection and improved management, the increase in posthatch growth rate and concurrently the increase in metabolic rate of broiler chickens during the last 50 yr has also increased embryonic metabolism. A higher metabolic rate during incubation would imply a lower residual yolk weight and possibly lower energy reserve for the hatchling. This might affect posthatch development and performance. This review examined scientific publications published between 1930 and 2018 to compare residual yolk weight at hatch, metabolic heat production, and yolk utilization throughout incubation. This review aimed to investigate 1) whether or not residual yolk weight and composition has been changed during the 88-yr period considered and 2) which abiotic and biotic factors affect yolk utilization in poultry during incubation and the early posthatch period. It can be concluded that 1) residual yolk weight and the total solid amount of the residual yolk at hatch seem to be decreased in the recent decades. It cannot be concluded whether the (lack of) differences between old and modern strains are due to genetic selection, changed management and incubation conditions, or moment of sampling (immediately after hatch or at pulling). It is remarkable that with the genetic progress and improved management and incubation conditions over the last 88 yr, effects on yolk utilization efficiency and embryonic metabolic heat production are limited; 2) factors specially affecting residual yolk weight at hatch include egg size and incubation temperature, whereas breeder age has more influence on nutrient composition of the residual yolk.

Physiological response of broiler embryos to different incubator temperature profiles and maternal flock age during incubation. 1. Embryonic metabolism and day-old chick quality

Broiler strain, maternal age, and incubation temperature influence embryo metabolism. Hatching eggs were obtained from young (Y; 28 to 34 wk, $\bar{\rm x}$ = 31.2 wk), mid (M; 36 to 45 wk, $\bar{\rm x}$ = 40.5 wk) and old (O; 49 to 54 wk, $\bar{\rm x}$ = 51.4 wk) Ross 708 (n = 88; Experiment 1) and Ross 308 [(n = 45; Experiment 2: (Y; 25 to 34 wk, $\bar{\rm x}$ = 30.5 wk), (M; 35 to 44 wk, $\bar{\rm x}$ = 40.2 wk), and (O; 49 to 54 wk, $\bar{\rm x}$ = 51.6 wk)] breeders. Eggs were stored for 2 to 4 d (18°C, 73% RH), and incubated for 14 d at 37.5°C and 56% RH. At 15 d (E15), 8 fertile eggs per flock age were incubated in individual metabolic chambers at 36.0, 36.5, 37.0, or 37.5°C until E21.5. Each temperature was repeated one additional time. O2 consumption and CO2 production were used to calculate embryonic heat production (EHP). Embryo temperature was measured as eggshell temperature (EST). Initial egg weight was used as a covariate; significance was assessed at P < 0.05. In Ross 708, daily EHP tended to be higher in M and O than Y treatments at E16; EHP of M was higher than Y and O eggs at E18; M and O were higher than O eggs at E19. Incubation at 37.0°C resulted in the highest EHP from E15 to E21, except at E17. Embryos at 37.5°C had reduced EHP beyond E17. Daily EST from E15 to E21 was higher at 37.5 and 37.0°C than at 36.0 and 36.5°C. In Ross 308, daily EST was highest at 37.5°C except at E20. Incubation temperature and EST were highly correlated (R2 = 0.90 to 0.89; P < 0.001). Ross 708 chicks were longer and hatched earlier at 37.0°C than at 36.0 and 37.5°C. EST and EHP increased with incubation temperature in Ross 708. In Ross 308, maternal flock age and incubation temperature did not impact EHP. However, EST was highest at 37.5°C except at E20. Ross 708 was more sensitive to incubation temperature than Ross 308.

Mild heat stress enhances differentiation and proliferation of Japanese quail myoblasts and enhances slow muscle fiber characteristics

The objective of this study was to investigate the effect of mild heat stress on muscle fiber hyperplastic and hypertrophic growth in quail primary myogenic cells to better understand the mechanisms leading to increased skeletal muscle development in avian embryos incubated at a higher temperature. Compared to control cultures maintained at 37°C, incubation at 39°C enhanced myotube length (P < 0.01) and diameter (P < 0.001) at 3 days after differentiation (D3). This enlargement of the myotubes incubated at 39°C can be explained by differences in the fusion index (56.7 vs. 46.2%, P < 0.05) and nuclei number per myotube (18.1 vs. 10.8, P < 0.001) compared to the control cells at D3. Additionally, a higher density of myotubes at D3 in cultures exposed to a higher temperature were related to higher levels of Pax-7 (P < 0.05) compared to the control cells incubated continuously at 37°C. These results indicated a higher proliferative capacity in cells exposed to mild heat stress compared to the control cells. On the other hand, mild heat stress enhanced protein levels of slow myosin heavy chain isoform (P < 0.01) and cytochrome c oxidase subunit IV (P < 0.01) compared to the control cells at D3. These discrepancies in protein expression indicated maintenance of slow muscle fiber type characteristics in myotubes incubated at 39°C. Our results suggest that mild heat stress plays a significant role in myogenic mechanisms related to muscle mass and development.

Evidence in duck for supporting alteration of incubation temperature may have influence on methylation of genomic DNA

Incubation temperature has an immediate and long-term influence on the embryonic development in birds. DNA methylation as an important environment-induced mechanism could serve as a potential link between embryos’ phenotypic variability and temperature variation, which reprogrammed by DNA (cytosine-5)-methyltransferases (DNMTS) and Methyl-CpG binding domain proteins (MBPS) 3&5 (MBD3&5). Five genes in DNMTS and MBPS gene families were selected as target genes, given their important role in epigenetic modification. In this study, we aimed to test whether raising incubation temperature from 37.8°C to 38.8°C between embryonic days (ED) 1–10, ED10–20 and ED20–27 have effect on DNA methylation and whether DNMTS, MBPS play roles in thermal epigenetic regulation of early development in duck. Real-time quantitative PCR analysis showed that increased incubation temperature by 1°C has remarkably dynamic effect on gene expression levels of DNMTS and MBPS. Slight changes in incubation temperature significantly increased mRNA levels of target genes in breast muscle tissue during ED1–10, especially for DNMT1, DNMT3A and MBD5. In addition, higher temperature significantly increased enzyme activities of DNMT1 in leg muscle during ED10–20, liver tissue during ED1–10, ED20–27 and DNMT3A in leg muscle and breast muscle tissue during ED10–20. These results suggest that incubation temperature has an extended effect on gene expression levels and enzyme activities of DNMTS and MBPS, which provides evidence that incubation temperature may influence DNA methylation in duck during early developmental stages. Our data indicated that DNMTS and MBPS may involved in thermal epigenetice regulation of embryos during the early development in duck. The potential links between embryonic temperature and epigenetic modification need further investigation

Impact of thermal stress during incubation on gene expression in embryonic muscle of Peking ducks (Anasplatyrhynchos domestica)

Changes in temperature will influence poultry embryonic muscle development. However, little is known about the changes in molecular processes impacted by incubation temperature in avians. In this study, we investigated the effects of increasing the incubation temperature by 1°C from day 11-20 on the embryonic and posthatch skeletal muscle development of the Peking duck, and identified the differentially expressed genes using RNA-seq of leg muscle tissues. The results showed that altering the incubation temperature had immediate and long-lasting effects on phenotypic changes in the embryonic and post-hatching muscle development. It was shown that expression levels of total 1370 genes were altered in muscle tissues by the thermal treatments. The gene ontology (GO) analyses indicated that cellular processes including metabolism, cell cycle, catalytic activity, and enzyme regulatory activity may have involved in the muscle mass impacted by thermal manipulation. TGF-beta and insulin pathways as two classical muscle development related pathways may also involve in regulating muscle mass. These data may be helpful for understanding the physiological and biochemical processes of muscle development under environmental treatments in embryonic avians.

A meta-analysis of experiments linking incubation conditions with subsequent leg weakness in broiler chickens

A series of incubation and broiler growth studies were conducted using one strain of broiler chicken (fast feathering dam line) observing incubation effects on femoral bone ash % at hatch and the ability of the bird to remain standing at 6 weeks of age (Latency-To-Lie). Egg shell temperatures during incubation were consistently recorded. Parsimonious models were developed across eight studies using stepwise multiple linear regression of egg shell temperatures over 3-day periods and both bone ash at hatch and Latency-To-Lie. A model for bone ash at hatch explained 70% of the variation in this factor and revealed an association with lower egg shell temperatures during days 4–6 and 13–15 and higher egg shell temperatures during days 16–18 of incubation. Bone ash at hatch and subsequent Latency-To-Lie were positively correlated (r = 0.57, P<0.05). A model described 66% of the variation Latency-To-Lie showing significant association of the interaction of femoral ash at hatch and lower average egg shell temperatures over the first 15 days of incubation. Lower egg shell temperature in the early to mid incubation process (days 1–15) and higher egg shell temperatures at a later stage (days 16–18) will both tend to delay the hatch time of incubating eggs. Incubation profiles that resulted in later hatching chicks produced birds which could remain standing for a longer time at 6 weeks of age. This supports a contention that the effects of incubation observed in many studies may in fact relate more to earlier hatching and longer sojourn of the hatched chick in the final stage incubator. The implication of these outcomes are that the optimum egg shell temperature during incubation for broiler leg strength development may be lower than that regarded as ideal (37.8°C) for maximum hatchability and chick growth.

Effects of in ovo injection of carbohydrates on embryonic metabolism, hatchability, and subsequent somatic characteristics of broiler hatchlings

The effects of the in ovo injection of different carbohydrate solutions on the internal egg temperature (IT), hatchability, and time of hatch of embryonated Ross × Ross 708 broiler hatching eggs were determined. In addition, the BW, liver weight, yolk sac weight (YSW), and yolk-free BW (YFBW) of the embryos on d 19.5 of incubation and of the chicks on day of hatch were determined. Eggs containing live embryos were injected in the amnion on d 18.5 of incubation using an automated multiple-egg injector. Solution injections delivered 1.2 mL of physiological saline (0.85%) alone or with a supplemental carbohydrate. The following supplemental carbohydrates were separately dissolved in saline at a concentration of 0.3 g/mL: glucose, fructose, sucrose, maltose, and dextrin. Temperature transponders were implanted in the air cells of embryonated and nonembryonated eggs after in ovo injection for the detection of IT at 6, 14, and 22 h after injection. The IT of embryonated eggs was significantly greater than that of nonembryonated eggs at all 3 times after the treatment period. Eggs that were injected with saline with or without supplemental carbohydrates experienced a reduction in IT when compared with control eggs whose shells were perforated without solution delivery, and the decrease in IT was associated with a delay in hatch time. Liver weight was negatively related to YSW and positively related to YFBW, and YSW was negatively related to YFBW. Although the saline and carbohydrate solution injections increased chick BW compared with noninjected controls, chick YFBW was decreased in the maltose- and sucrose-injected groups. In conclusion, the injection of 1.2 mL of saline with or without supplemental carbohydrates lowered embryonic metabolism, as reflected by a lower IT and a delay in time of hatch. However, effects of the different carbohydrate solutions on yolk absorption and tissue deposition in yolk-free embryos varied. These results suggest that lower volumes for solutions containing maltose, sucrose, or fructose should be considered for in ovo injection.

Effects of eggshell temperature and oxygen concentration on embryo growth and metabolism during incubation

Embryo development and heat production (HP) were studied in eggs of similar size (60 to 65 g) that were incubated at normal (37.8 degrees C) or high (38.9 degrees C) eggshell temperature (EST) and exposed to low (17%), normal (21%), or high (25%) O(2) concentration from d 9 through 19. High EST initially increased HP, but gradually O(2) became more important for HP than EST. Finally,HP was highest for the combination of high EST with high O(2) and lowest for the combination of high EST with low O(2). High EST decreased hatch time, BW, yolk free BW, and relative heart weight. The EST had no effect on residual yolk weight, chick length, or relative liver weight. Increased O(2) increased yolk free BW and chick length and decreased residual yolk weight at hatch. No interactions between EST and O(2) were observed with regard to embryo development and hatchling characteristics. If embryo development is reflected by HP, it can be concluded that high EST primarily increased embryonic development until the second week of incubation. During the third week of incubation, O(2) had a greater effect in determining embryo development than EST.