I. van den Anker

Effect of eggshell temperature and oxygen concentration during incubation on the developmental and physiological status of broiler hatchlings in the perinatal period

This study evaluated the influence of incubation conditions on the developmental and physiological status of birds in the perinatal period, which spans the end of incubation until the early posthatch period. Embryos were incubated at a normal (37.8°C) or high (38.9°C) eggshell temperature (EST) and a low (17%), normal (21%), or high (25%) O(2) concentration from d 7 until 19 of incubation. After d 19 of incubation, EST was maintained, but O(2) concentrations were 21% for all embryos. Body and organ weights, and hepatic glycogen levels were measured at d 18 of incubation and at 12 and 48 h after emergence from the eggshell. In addition, blood metabolites were measured at 12 and 48 h after emergence from the eggshell. Embryos incubated at a high EST and low O(2) concentration had the highest mortality in the last week of incubation, which may be related to their low yolk-free body mass (YFBM) or a reduced nutrient availability for hatching (i.e., hepatic glycogen). High EST, compared with normal EST, decreased YFBM. This may be due to the shorter incubation duration of 8 h, the lower weight of supply organs (i.e., heart and lung), or a lack of glucose precursors. Because of this lack of glucose precursors, embryos incubated at high EST may have used proteins for energy production instead of for body development at the end of incubation. The YFBM at d 18 of incubation increased with an increase in O(2) concentration. However, differences between the normal and high O(2) concentration disappeared at 12 and 48 h after emergence, possibly because the high O(2) concentration had difficulties adapting to lower O(2) concentrations in the perinatal period. Blood metabolites and hepatic glycogen were comparable among O(2) concentrations, indicating that the physiological status at hatch may be related to the environment that the embryo experienced during the hatching process. In conclusion, EST and O(2) concentration differentially influence the developmental and physiological status of broilers during the perinatal period.

Effect of eggshell temperature and oxygen concentration on survival rate and nutrient utilization in chicken embryos

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.

Effect of Single or Combined Climatic and Hygienic Stress in Four Layer Lines: 1. Performance

Effects of long-term climatic stress (heat exposure), short-term hygienic stress [lipopolysaccharide (LPS)], or a combination of both challenges on performance of 4 layer lines were investigated. The lines were earlier characterized by natural humoral immune competence and survival rate. At 22 wk of age, 80 hens per line were randomly divided over 2 identical climate chambers and exposed to a constant high temperature (32 degrees C) or a control temperature (21 degrees C) for 23 d. Half of the hens housed in each chamber were i.v. injected with LPS at d 1 after the start of the heat stress period. The effect of heat, LPS, or a combined challenge on feed intake, BW, hen-day egg production, egg weight, and egg shell thickness were investigated. Feed intake, BW, hen-day egg production, egg weight, and egg shell thickness were significantly reduced by heat stress. Administration of LPS significantly reduced feed intake, BW (LPS x time interaction), hen-day egg production, and egg weight (LPS x time interaction). Hens were able to recover from LPS administration but did not completely adapt to heat stress. Hens still lost weight, had a lower feed intake and hen-day egg production after 23 d of continuous exposure to heat stress. These data suggest a different nature of short-term LPS exposure versus long-term heat exposure affecting performance parameters of laying hens, and different adaptation mechanisms of hens toward these stressors. Neither natural humoral immune competence nor survival rate, for which the lines had been earlier characterized, were indicative of the response to different stressors. However, significant line x heat interactions were found for feed intake and hen-day egg production, and a line x heat x time interaction for BW, whereas a line x LPS interaction was found for hen-day egg production and a line x LPS x time interaction for BW. The lines had similar response patterns, but differed in response levels, suggesting that some lines were better able to adapt to stressors than others.

Effect of eggshell temperature and a hole in the air cell on the perinatal development and physiology of layer hatchlings

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.

Effect of eggshell temperature throughout incubation on broiler hatchling leg bone development

Leg problems in broiler chickens may partly be prevented by providing optimal circumstances for skeletal development during incubation. One of the factors demonstrated to affect bone development is eggshell temperature (EST), which provides a reliable reflection of embryo temperature. The present experiment aimed to investigate the effect of EST on development and asymmetry of the femur, tibia, and metatarsus in broiler chicken hatchlings. Eggs were incubated from d 0 until hatch at 1 of 4 EST: low (36.9°C), normal (37.8°C), high (38.6°C), and very high (39.4°C). At hatch, chick quality was determined in terms of chick length, yolk-free body mass, navel score, and organ weights. Tibia, femur, and metatarsus were weighed, their length and width (mediolateral diameter) and depth (craniocaudal diameter) at the middle of the shaft were measured, and their ash content was determined. Relative asymmetry of the leg bones was determined from their relative dimensions. Hatchability, chick quality, and organ development were lower for very high EST compared with all other treatments. Very high EST resulted in lowest tibia and metatarsus lengths (-3.1 to -8.4%) compared with all other treatments, and lower metatarsus weight (-9.1%) and femur length (-4.9%) compared with high EST. Relative asymmetry and ash content did not differ among treatments and no relation between EST and bone parameters was found. To conclude, very high EST resulted in lower bone development, hatchability, and chick quality. Few differences in bone development and chick quality were found between low, normal, and high EST.

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. 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.

Effects of breeder age, broiler strain, and eggshell temperature on development and physiological status of embryos and hatchlings

Breeder age and broiler strain can influence the availability of nutrients and oxygen, particularly through differences in yolk size and shell conductance. We hypothesized that these egg characteristics might affect embryonic responses to changes in eggshell temperature (EST). This study aimed to investigate the effect of breeder age, broiler strain, and EST on development and physiological status of embryos. A study was designed as a 2 × 2 × 2 factorial arrangement using 4 batches of 1,116 hatching eggs of 2 flock ages at 29 to 30 wk (young) and 54 to 55 wk (old) of Ross 308 and Cobb 500. EST of 37.8 (normal) or 38.9°C (high) was applied from incubation d 7 (E7) until hatching. The results showed that breeder age rather than broiler strain had an influence on yolk size (P = 0.043). The shell conductance was higher in Ross 308 than in Cobb 500 (P < 0.001). A high EST resulted in a higher yolk free body mass (YFBM) compared to the normal EST at E14 and E16, but at 3 h after hatch YFBM was lower when eggs were incubated at high EST compared to normal EST (all P < 0.001). Cobb 500 eggs yielded embryos with a lower YFBM at E14, E18, and 3 h after hatch (all P < 0.05) than Ross 308 eggs. Breeder age had no effect on YFBM, but the RSY weight was higher in embryos from the old flock compared to the young flock embryos at E14 and E16 (both P < 0.05). A 3-way interaction among breeder age, strain, and EST was found, especially for incubation duration, navel quality, and relative heart and stomach weights at 3 h after hatch (all P < 0.05). Based on the results obtained, we conclude that oxygen availability rather than nutrient availability determines embryonic development, and the egg characteristics affected embryonic responses to changes of EST, especially for variables related to chick quality.

Effects of ambient temperature, feather cover, and housing system on energy partitioning and performance in laying hens

Environmental factors, such as ambient temperature (T), feather cover (FC), and housing system (HS), probably affect energy requirements of laying hens. Using a 3 × 2 × 2 factorial arrangement, interaction effects of T (11, 16, and 21°C), FC (100 and 50%), and HS (cage and floor housing) on energy partitioning and performance of laying hens were investigated. Six batches of 70 H&N Brown Nick laying hens, divided over 2 respiration chambers, were exposed to the T levels in three 2-wk periods. Heat production (HP) was determined by indirect calorimetry. The ME intake was calculated by subtracting energy in manure/litter from that in feed and wood shavings. The NE was calculated by subtracting HP from ME. The ME intake increased by 1% for each degree reduction in T. In hens with intact plumage, HP was not affected by T, whereas at decreasing T, HP increased in hens with 50% FC (P < 0.01). At 21°C, HP was not affected by HS, whereas in the floor system, HP at 16 and 11°C was 5.8 and 3.0% higher, respectively, than in cages (P < 0.05). The NE for production was 25.7% higher in cages compared to the floor system (P < 0.05). In cages, 24.7% of NE for production was spent on body fat deposition, whereas in the floor system, 9.0% of NE for production was released from body fat reserves. The ME intake was predicted by the equation (R(2) = 0.74) ME intake (kJ/d) = 612 BW(0.75) - (8.54 × T) + (28.36 × ADG) + (10.43 × egg mass) - (0.972 × FC). Hen performances were not affected by treatments, indicating the adaptive capacity of young laying hens to a broad range of environmental conditions.

Diet density during the first week of life: Effects on energy and nitrogen balance characteristics of broiler chickens

&NA; This study aimed to determine effects of diet density on growth performance, energy balance, and nitrogen (N) balance characteristics of broiler chickens during the first wk of life. Effects of diet density were studied using a dose‐response design consisting of 5 dietary fat levels (3.5, 7.0, 10.5, 14.0, and 17.5%). The relative difference in dietary energy level was used to increase amino acid levels, mineral levels, and the premix inclusion level at the same ratio. Chickens were housed in open‐circuit climate respiration chambers from d 0 to 7 after hatch. Body weight was measured on d 0 and 7, whereas feed intake was determined daily. For calculation of energy balances, O2 and CO2 exchange were measured continuously and all excreta from d 0 to 7 was collected and analyzed at d 7. Average daily gain (ADG) and average daily feed intake (ADFI) decreased linearly (P = 0.047 and P < 0.001, respectively), whereas gain to feed ratio increased (P < 0.001) with increasing diet density. Gross energy (GE) intake and metabolizable energy (ME) intake were not affected by diet density, but the ratio between ME and GE intake decreased linearly with increasing diet density (P = 0.006). Fat, N, and GE efficiencies (expressed as gain per unit of nutrient intake), heat production, and respiratory exchange ratio (CO2 to O2 ratio) decreased linearly (P < 0.001) as diet density increased. Energy retention, N intake, and N retention were not affected by diet density. We conclude that a higher diet density in the first wk of life of broiler chickens did not affect protein and fat retention, whereas the ME to GE ratio decreased linearly with increased diet density. This suggests that diet density appears to affect digestibility rather than utilization of nutrients.