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.

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

The current study aimed to evaluate the effects of embryonic thermal manipulation (TM) on hatching criteria, chick quality, and subsequent growth performance of broiler chickens under heat stress (HS) condition. Two thousand fertile eggs were randomly divided between 2 groups and incubated under standard (37.8 °C and 56% relative humidity (RH)) and TM (39.5 °C and 65% RH) conditions. Temperature and humidity were identical in both groups within the first 10 days. The eggs in the TM group were exposed to 39.5 °C and 65% RH for 3 h/day from 11 to 16 days of incubation. Egg weight (EW) was measured in 1, 11, and 18 days of incubation, and eggshell temperature (EST) was recorded daily. Chick quality was, also, evaluated according to the Tona method on hatch day. Samples of the chicks (n = 20) were euthanized and dissected at 0-day post-hatch, and different carcass parts were weighed, and blood samples were collected for hormones analysis. The post-hatch growth performance of both groups was also recorded under HS (37 °C for 5 h beginning at 22 days) condition. The results showed that TM did not significantly affect hatchability and embryonic mortality (P > 0.05). The female chick percentage was higher in the TM group (P < 0.05). Eggshell temperature and serum concentrations of corticosterone and T₄ were significantly higher in the TM compared with the control chicks (P < 0.05). The chick length was considerably shorter in TM chicks (P < 0.05). Chick quality was not influenced by TM. There was no significant difference between the two groups in the post-hatch growth performance (P > 0.05). In conclusion, exposing broiler embryos to the controlled TM did not have adverse effects on chick quality and post-hatch growth performance.

Early age thermal manipulation on the performance and physiological response of broiler chickens under hot humid tropical climate

Initial brooding temperature is critical for post-hatch growth of broiler chickens. A study was conducted to investigate the early age thermal manipulation (EATM) on the performance and physiological responses broiler chickens under hot humid tropical climate. A total of 260 unsexed day-old Arbor-acre broiler chicks were assigned to five thermal treatments of brooding temperature regimens having 4 replicates of thirteen birds each. The heat treatments were: initial brooding temperature of 35 °C for the first 2 days, and then decreased subsequently, gradually to 22 °C at 21 d of age (CT), initial temperature of 35 °C, sustained for the first 4 days and then decreased gradually (conventionally) (FD), initial temperature of 35 °C for the first 7 days (SD), the birds in CT, but the brooding temperature was raised to 35 °C again for another 3 days from day 7 (SD3), initial brooding temperature of 35 °C for the first 10 days (TD). Data were collected on daily feed intake and weekly body weights. Blood samples were collected from 8 birds per treatment weekly for the determination of plasma uric acid, triglycerides, triiodothyronine (T₃) and creatinine kinase. Data obtained were laid out in a Completely Randomized Design (CRD). Results showed that the final weights of the birds in FD were higher (P < 0.05) than those of the other treatments at the finisher phase. Feed intake of the birds in FD was higher than those of SD3 and TD. FCR of broiler chickens in CT, SD, SD3 and TD was higher than that of FD. The rectal temperature, plasma MDA and blood glucose of the thermally challenged birds in FD was generally better (P < 0.05) than those of the other treatments. It was concluded that EATM can be used to improve performance and also protect broiler chickens from acute heat stress at market age.

The effect of alternative feeding strategies for broiler breeder pullets: 2. Welfare and performance during lay

Feeding broiler breeders to satiety has negative consequences on their health and reproduction. Alternative feeding strategies during rearing can improve welfare, although their implications during lay are not well understood. The objective was to examine the effect of rearing feeding treatments on the reproductive performance and feeding behavior of broiler breeders under simulated commercial conditions. At 3 wk of age, 1,680 Ross 308 pullets were allocated to 24 pens under 1 of 4 isocaloric treatments: 1) daily control diet; 2) daily alternative diet (40% soybean hulls and 1 to 5% calcium propionate); 3) 4/3 control diet (4 on-feed days, 3 non-consecutive off-feed days per week); and 4) graduated control diet. Feeding frequency of the graduated treatment varied with age and finished on a daily basis. At 23 wk of age, group sizes were adjusted to 40 hens, and 5 mature Yield Plus Males roosters were introduced to each pen. Pens were under the same daily feeding management and same diet during lay. The performance of broiler breeders (growth rate, body weight uniformity, and reproductive performance) was determined until 64 wk of age. At the end of lay, feeding motivation was examined with a feed intake test and a compensatory feeding test. Data were analyzed using linear mixed regression models, with pen nested in the models and age as a repeated measure. The laying rate of hens reared on the graduated treatment decreased slower compared to control hens, resulting in a higher cumulative egg production (178.2 ± 3.8 eggs/hen) than control hens (165.2 ± 3.8 eggs/hen, P < 0.01) by 64 wk of age. Hens reared on non-daily feeding treatments laid lighter eggs with relatively heavier yolks and had higher feed intake at the end of lay than hens fed daily during rearing (P = 0.02). In conclusion, rearing feeding treatments impacted the growth rate and body weight uniformity during lay, feeding motivation at the end of lay, and the laying rate and hatchability depending on hens' age.

Temperature during the last week of incubation. II. Effects on first week broiler development and performance

Little is known about applying various eggshell temperatures (EST) during the last week of incubation. In particular, the effect of an EST below 37.8°C during the last week of incubation is poorly investigated. Therefore, we investigated effects of EST of 35.6, 36.7, 37.8, or 38.9°C applied from d of incubation (E) 15, E17, or E19 on first week broiler development and performance. A total of 2,850 first grade eggs of a 43 wk 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. Chick quality was determined at placement in the broiler house and organ development was measured at d 7. BW was determined at placement, d4, and d7. Feed intake (FI) was measured at d4 and d7 and G:F was calculated between placement and d4, and between d4 and d7. Chick quality at placement was higher at an EST of 35.6°C compared to all other EST treatments, expressed by a longer chick length and highest prevalence of closed navels. BW d 7 was higher at an EST of 36.7°C compared to all other EST treatments, which was not caused by a higher FI during the first week. A higher G:F between d 0 and d 7 was found at an EST of 36.7°C compared to 35.6 and 38.9°C. At d 7, a higher relative heart weight was found at an EST of 35.6 compared to 38.9°C. This study indicates that an EST of 38.9°C applied from E15 onward negatively affected chick quality, organ development, and G:F until d 7 compared to 37.8°C. Moreover, an EST of 36.7°C had a clear positive effect on chick quality, organ development, G:F, and growth performance until d 7. An EST of 35.6°C resulted in equal or higher chick quality and organ weights compared to 36.7°C, but this was not reflected in performance parameters.

Relationships of eggshell, air cell, and cloacal temperatures of embryonated broiler hatching eggs during incubation

The relationships of eggshell, air cell, and embryo cloacal temperatures in Ross × Ross 708 broiler hatching eggs were determined. Twenty eggs were weighed and set on each of 3 tray levels of a single incubator. Eggshell temperature (EST) of the eggs were recorded once in the morning (AM) and afternoon (PM) between 0 and 19 d of incubation (DOI) using an infrared thermometer (IRT). All eggs were candled and a transponder was implanted in the air cell of eggs containing live embryos (12 per tray level) at 12 DOI. At 19 DOI, transponders were implanted in the cloaca of live embryos from those same eggs. Air cell temperature (ACT) and EST readings were recorded once in the AM and PM between 12 and 19 DOI, and ACT and cloaca temperature (CLT) readings were recorded every 6 h between 19 and 21 DOI. The EST and ACT readings between 13 and 19 DOI were positively correlated. However, their respective mean temperatures between 13 and 19 DOI differed. The EST and ACT were not significantly influenced by tray level. Nevertheless, a main effect due to location (eggshell vs. air cell), and an interaction between DOI and time of day (AM and PM) in the 13 to 19 DOI interval were observed. Furthermore, an interaction was observed between location (air cell and cloaca) and the 6 h sequential time periods in the 19 to 21 DOI interval. However, across the entire 19 to 21 DOI interval, mean ACT and CLT were not significantly different, and were positively correlated. These data suggest that ACT readings are higher than those of EST during the last half of incubation, and that between 13 and 19 DOI, ACT readings may have the potential for use as a minimally invasive method by which to more accurately estimate the true core body temperature of broiler embryos. The effects of this method on hatchability and post-hatch performance need determination to better establish its practicality.

Effects of thermal manipulations during embryogenesis of broiler chickens on developmental stability, hatchability and chick quality

Stress based on high temperature and humidity reduces the production performance of fast-growing broilers and causes high mortality. Temperatures higher than optimum have been applied to broilers in the embryonic period in order to overcome thermal stress. This study was conducted to investigate the effects of exposure to two long-term high-thermal environments on the developmental stability of embryonic growth, hatchability and chick quality. For this purpose, 600 broiler eggs were incubated. Treatments consisted of eggs incubated at 37.8°C at 55% relative humidity throughout (control), heated to 39.6°C at 60% relative humidity for 6 h daily from 0 to 8th day, and heated to 39.6°C at 60% relative humidity for 6 h daily from the 10 to 18th day. Embryo weights and lengths of face, wing, femur, tibia and metatarsus were measured daily between the 10th and 21st day of the experiment. Daily relative asymmetry values of bilateral traits were estimated. The hatchability, the weight of the 1-day-old chicks and chick quality were determined. In conclusion, no negative effects of the treatments of the long-term high-thermal environment in the early and late stages of incubation for epigenetic adaptation were determined on the embryo morphology, development stability and weight of the chick. Moreover, regressed hatchability of embryos that were exposed to a long-term high-thermal environment was detected. Especially between the 10 and 18th day, the thermal manipulation considerably reduced the quality of the chicks. Acclimation treatments of high temperature on the eggs from cross-breeding flocks should not be made long term; instead, short-term treatments should be made by determining the stage that generates epigenetic adaptation.

Comparative evaluation of air cell and eggshell temperature measurement methodologies used in broiler hatching eggs during late incubation

The current study was conducted to compare and contrast the uses of 2 devices (temperature transponder or infrared thermometer) and their locations (inner air cell membrane or outer eggshell surface) in Ross × Ross 708 broiler hatching eggs. The air cells of 14 embryonated and 10 nonembryonated eggs were implanted with temperature transponders on d 13.5 of incubation. Likewise, for these same eggs, eggshell surface temperature was detected with the use of transponders and an infrared thermometer. Temperatures were recorded every 12 h between 14.5 and 18 d of incubation, and graphs and corresponding regression values were used to track the temperatures over these time periods. The temperature readings using all methods in embryonated and nonembryonated eggs were positively correlated. In nonembryonated eggs, temperatures in the air cell and on the eggshell surface using transponders were higher than those on the eggshell surface using an infrared thermometer. Mean air cell temperature readings of embryonated eggs using transponders were higher than those of the eggshell, as determined with the use of transponders or an infrared thermometer. Furthermore, the differences in air cell temperature using transponders and eggshell temperature using an infrared thermometer in embryonated eggs increased with embryonic age. These readings confirmed increased embryo heat production during the incubational period examined. It was further concluded that when compared with actual embryo body temperatures determined in previous studies, the use of transponders in the air cells of broiler hatching eggs detected a higher and closer temperature than eggshell surface temperature. It is suggested that the air cell transponders in embryonated eggs circumvented the confounding effects of the thermal barrier properties of the eggshell and the flow of air across its surface.

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.

Energy partitioning during incubation and consequences for embryo temperature: a theoretical approach

In practice, many hatchability and chick quality problems have been related to the control of embryo temperature (ET) during incubation. Within an incubator, set at a constant machine temperature (MT), ET can vary substantially. Embryo temperature is the result of the balance between heat transfer to and from the embryo and heat production (HP) of the embryo. We investigated which factors theoretically could account for the variation in ET within an incubator. First, the effects egg weight, MT, and oxygen availability on HP of embryos were quantified. Differences in HP could be due only to differences in the amount of energy utilized from the egg or to differences in the efficiency of the conversion of energy in the egg to energy in the chicken, indicated as E(YFB). Results of these analyses showed that differences in HP attributable to egg weight or oxygen availability were mainly a result of the amount of energy used from the egg constituents and not of a change in E(YFB). However, at a given MT, this variation in HP could account for a maximum increase in ET of only 1.21°C, suggesting that other factors played a role because in practice within an incubator, larger differences in ET have been found. The most important factor was probably the difference in air velocity within an incubator, resulting in differences in heat transfer. Because of this variation, ET varied within an incubator and with increasing ET, E(YFB) decreased, resulting in an even higher HP and consequently ET. We concluded that this theoretical approach could explain the wide variation in ET, and consequently could explain the negative effects of high ET on hatchability and chick quality found in the literature. This indicates that, in both practice and in incubation experiments, it is of great importance to realize that any factor affecting HP or heat transfer influences ET. We strongly suggest that ET (or eggshell temperature) be controlled in any incubation experiment involving hatchability or energy utilization.

Brooding temperatures for chicks acclimated to heat during incubation: effects on post-hatch intestinal development and body weight under heat stress

1. The objective was to evaluate the effects of brooding temperature on intestinal development, oxidative organ damage, and performance of chicks acclimated to high temperature during incubation. The effects of acclimation and brooding temperatures on slaughter weights of broilers under heat stress were also investigated. 2. Eggs were incubated at either 378 degrees C (INC(Cont)) or heat-acclimated at 395 degrees C for 6 h daily from d 10 to d 18 of incubation (INC(H)). Brooding temperatures at floor level were set at 32, 335 and 35 degrees C (Bt(32), Bt(335), Bt(35), respectively) for the first 5 d. The temperature was reduced gradually to 30 degrees C from d 6 to d 10. From 21 to 42 d, broilers from INC(Cont) Bt(32) and INC(H) Bt(32) and Bt(35) were divided into two groups; half from each group was exposed to daily cyclic higher ambient temperatures, while the other half was reared at control temperature. 3. INC(H) chicks had lower jejunum, but greater liver and residual yolk sac weights than INC(Cont) chicks on the day of hatching. Although INC(H) chicks from Bt(335) and Bt(35) had lighter body weights than Bt(32) on d 5, no significant differences were observed in the body weight of broilers among treatments at 10 and 21 d. 4. Similar jejunum protein, alkaline phosphatase, maltase, glutathione, and malondialdehyde contents of chicks from INC(Cont) and INC(H) suggested that heat acclimation during incubation has no effect on jejunum enzyme activity or oxidative status of chicks. 5. Taking into account INC(H) Bt(35) chicks having lower T(3) levels on d 5, lower heterophil/lymphocyte (H/L) ratios and similar weights at 42 d under heat stress compared with control broilers, the results suggested that although higher brooding temperatures had no effect on body weights of INC(H) chicks during the brooding period, those broilers may able to cope better with heat stress.