Hatching egg and newly hatched chick yolk sac total IgY content at 3 broiler breeder flock ages.

During the first week of the posthatching period, before the immune system is mature enough to produce its own B lymphocytes, a chick's humoral immunity depends on maternal antibodies (IgY) received from the egg yolk. During incubation and after hatching, the yolk sac (YS) membrane transfers nutrients (including IgY) from the egg yolk to the developing embryo or newly hatched chick. The objective of this study was to determine the effects of breeder flock age on the total IgY content of egg yolks and chick YS from a commercial broiler breeder strain. Hatching eggs from the same broiler breeder flock were collected at 32, 40, and 55 wk of age. One group of eggs per flock age was used to determine the egg yolk total IgY content. Another group of eggs was incubated for 21.5 d, and upon hatching, the YS of newly hatched chicks were collected to determine the total IgY content. Egg and egg yolk weight increased with flock age, but YS weights did not reflect egg yolk weight. The total IgY content per gram of egg yolk increased with flock age; this fact plus the observed yolk weight increase with flock age notably increased the total IgY contained in yolks of eggs laid by 55-wk-old breeders. However, chicks hatching from 55-wk-old breeders had less IgY per gram of YS than chicks from 32- and 40-wk-old breeders. Whether there are differences in the rates of YS absorption between chicks of different breeder ages is unknown. This research provided total IgY values for broiler breeder egg yolk and chick YS of a commonly used meat-type chicken strain. Differences in egg yolk and YS total IgY contents due to flock age in this type of bird had not been previously reported. Research on the physiological consequences of YS absorption rates in chicks from different breeder ages is advised.

Broiler egg storage induces cell death and influences embryo quality.

It is well known that egg storage reduces embryo performance, but the fundamental reasons for reduced embryo quality remain unclear. The objective of this study was to investigate possible cellular and molecular mechanisms that might reduce embryo quality after egg storage. Broiler hatching eggs were obtained from the Ross 308 broiler strain, divided into 2 groups, and stored (4 and 14 d) under the same temperature and humidity conditions. Samples of the eggs were used to assess embryo quality by determining daily embryo weight (wet and dry) from 4 to 21 d of incubation. To understand possible cellular and molecular mechanisms that might affect embryo quality, blastoderms (unincubated embryos) were isolated from a sample of eggs from each storage group, dissociated into single cells, and subjected to flow cytometry analysis to differentiate between viable, apoptotic, and necrotic cell populations. Quantitative real-time PCR analysis was used to compare the expression of selected apoptotic genes (Bcl-2 homologous antagonist/killer gene, Bcl-2-associated X gene, Bcl-2-related ovarian killer gene, B-cell lymphoma 2 gene, and B-cell lymphoma xL gene) in blastoderms and embryos (6 d old after incubation). Data were analyzed by the MIXED model procedure of SAS (SAS Institute, Cary, NC), with significance set at P ≤ 0.05. After covariance analysis of initial egg weights, the results showed decreased daily embryo weights (wet and dry), an indication of decreased embryo quality that could affect hatch quality. In addition, a decrease in blastodermal cell viability was associated with an increased percentage of apoptotic cell deaths (P < 0.0001). Expression of pro-apoptotic genes (Bcl-2 homologous antagonist/killer gene, Bcl-2-associated X gene, and Bcl-2-related ovarian killer gene) were upregulated at the blastodermal level as the storage duration increased, but all genes were downregulated after 6 d of incubation. This suggests that an increase in egg storage duration could activate mechanisms of apoptotic cell death at the blastodermal level, which may be one of the molecular mechanisms that leads to reduced daily embryonic weight during incubation. Experimental controls capable of reducing the cellular and molecular mechanisms of egg storage should be used to increase embryo quality.

Influence of parent flock age on embryonic metabolism in modern turkey strains.

The metabolic response of some galliform embryos to embryonic heat production (EHP) and how incubation conditions have been adjusted to prevent overheating of embryos is well established in broiler breeders. However, the daily metabolic status of turkey embryos has not been studied or established in turkey embryos. The objectives of the current research were therefore to determine the respiratory (eggshell conductance, G) and metabolic status (EHP) of 2 modern turkey genetic strains [Hybrid (H) and Nicholas (N)] and 4 parent flock ages [young (Y, 30 wk), peak (P, 34 wk), mature (M, 55 wk), and old (O, 60 wk)] during incubation. To measure G, moisture loss from 15 eggs/genetic strain per flock age and saturated vapor pressure measured between the eggshell and its immediate environment were used. Daily embryonic O(2) consumption and CO(2) production rates were assessed 6 times each day from embryos of eggs (n = 11 eggs/genetic strain per flock age) incubated in individual metabolic chambers and were used to determined daily EHP. Data were analyzed using the mixed model procedure of SAS at P ≤ 0.05. The results showed that the G values (g/d per mmHg) were significantly different for the interaction between genetic strain and parent flock age (H × Y = 17.71, H × P = 17.53, H × M = 19.73, H × O = 26.46, N × Y = 16.70, N × P = 20.96; N × M = 25.47, N × O = 26.05; P = 0.0227). Daily EHP (mW) was higher in embryos from the O flock than in embryos from the Y flock during all days presented except at 8, 25, and 28 d of incubation (4 d: Y = 1.00, P = 0.93, M = 1.60, O = 1.75; 12 d: Y = 19.0, P = 20.0, M = 21.6, O = 23.4; 16 d: Y = 51.7, P = 60.5, M = 65.9, O = 70.8; 20 d: Y = 129, P = 146, M = 144, O = 155; 24 d: Y = 154, P = 188, M = 167, O = 180; 26 d: Y = 169, P = 199, M = 197, O = 230; and 27 d: Y = 231, P = 265, M = 288, O = 307; P < 0.05). The data showed that metabolic differences existed between embryos from flocks of different ages and that embryos from older flocks were metabolizing at a higher rate and could be subject to overheating, which requires further investigation. On the basis of the data, turkey eggs from flocks of different ages should be incubated separately for optimal physiological performance.

Hatching egg characteristics, chick quality, and broiler performance at 2 breeder flock ages and from 3 egg weights.

The objective of this study was to determine the effects of flock age and egg weight on hatching egg characteristics, fertility, hatchability, salable chick production, and broiler performance using a commercial Cobb 500 broiler breeder flock. Hatching eggs from the same breeder flock in 3 weight categories (light, average, and heavy) were obtained from a commercial hatchery when the birds were 29 and 59 wk of age. One group of eggs per age and weight category was selected to assess specific gravity and was broken open to weigh egg components. Another group of eggs was incubated for 21.5 d and incubation parameters were measured. At hatching, all salable chicks were individually weighed and placed in floor pens, where they were grown out for 41 d. Daily mortality, weekly feed consumption, and individual BW at 21 and 41 d were recorded. Irrespective of flock age and egg weight, all eggs had a specific gravity lower than 1.080, the commercial set value. Eggs from the young flock age had a smaller proportion of yolk and a greater proportion of albumen. Age affected fertility, with a lower value observed at 29 wk of age. Chicks from the flock at 59 wk hatched earlier than chicks from the flock at 29 wk, and light eggs hatched earlier than both average and heavy eggs. Broilers from the 29-wk-old breeders had a lower final BW than broilers from the 59-wk-old breeders. The smaller proportion of yolk in eggs from 29-wk-old broiler breeders may be associated with the low final BW observed in their offspring. This could mean that chicks hatching from young broiler breeders, which produce eggs with small yolks, may be at a disadvantage when reared under the same conditions as chicks produced by older broiler breeders whose eggs have larger yolks.

Dissociation of chicken blastoderm for examination of apoptosis and necrosis by flow cytometry.

We describe a method of isolating blastodermal cells for characterization through flow cytometry. Particular attention was placed on cell viability and integrity issues faced by conventional protocols. The method allowed us to examine mechanisms behind cellular death. Our protocol was optimized by the spatial resolution of the ImageStream multispectral imaging flow cytometer. Overall, the technique provides both quantitative and qualitative information on blastodermal cells. The methodology was applied to the current biological problem in which prolonged (14 d) versus short-term (4 d) layer egg storage reduces embryo viability. Data were obtained between 3 egg storage treatments (unstored, 4 d, and 14 d); the data were analyzed by the PROC MIXED model procedure of SAS at P < or = 0.05 and least squares means separated by the PDIFF procedure of SAS. The results showed that egg storage increases the rate of cell death by both apoptosis and necrosis. Importantly, our study showed higher percentages of necrosis and late apoptosis in long-term versus short-term stored eggs. The percentage of live cells decreased significantly when eggs were stored for 14 d (71.42 + or - 3.36%) compared with eggs stored for 4 d (83.58 + or - 2.15%). The percentage of early apoptotic cells was not significantly different between the 2 treatments. The percentage of necrotic cells and late apoptotic-necrotic cells was higher in eggs stored for 14 d (16.75 + or - 1.73%; 7.36 + or - 1.53%) versus eggs stored for 4 d (3.56 + or - 1.64%; 2.31 + or - 1.52%), respectively. This could negatively affect embryo survival because of the potential effect that necrosis has on surrounding tissue integrity. The technique will be particularly relevant in studies requiring single cells from chicken blastoderms or as a basis to characterize genes that regulate apoptosis in avian species.

Impaired intestinal villi growth in broiler chicks with unhealed navels.

By the time of hatching, the residual yolk sac (RYS) should be completely internalized into the body cavity of the chick via the navel and the navel should be closed (healed). After hatching, the RYS contents are used for general growth and development including growth of the small intestine. This research examined the relationship between the presence of navel buttons (an unhealed navel covered with a scab) and the RYS weight and intestinal villi height of broiler chicks from 0 to 5 d posthatching. Hatching eggs containing live embryos were collected at 18, 19, and 20 d of incubation (n = 5/d). At 21 d of incubation, chicks with healed navels (H) and chicks with navel buttons smaller than 3 mm in diameter (B) were obtained (n = 30/group). The BW and RYS of embryos (n = 5/d) and chicks (n = 5/treatment per day) were weighed. Samples of the small intestine (duodenum and ileum) were processed for histological evaluation to measure villi height. The trial was replicated in time 4 wk after the first collection using eggs and chicks from the same flock. Data were analyzed using SAS PROC MIXED (P < or = 0.05). No significant differences in BW were observed between H and B chicks. Average RYS weight and percentage RYS were greater in B than in H chicks. The interaction of age and navel condition significantly influenced both duodenal and ileal villi heights. On most of the days, duodenal and ileal villi were shorter in B than in H chicks. The presence of small navel buttons at hatching is indicative of impaired absorption of the RYS content and decreased intestinal villi growth. Further research on the relationship between navel buttons, intestinal physiology, and yolk sac infections is advised.

Spraying hatching eggs with electrolyzed oxidizing water reduces eggshell microbial load without compromising broiler production parameters.

An experiment was conducted to determine whether spraying hatching eggs with electrolyzed oxidizing (EO) water would decrease eggshell microbial load and hence improve hatchability, chick quality, and broiler growth performance. Eggs were collected from a broiler breeder flock; half the eggs were sprayed with EO water and the other half were left untreated. Enterobacteriaceae and total aerobic bacteria present on the eggshells of eggs from both treatments were enumerated. The eggs were incubated, and the broiler chicks were grown out to 39 d. Eggshell microbial load was significantly decreased by spraying the eggs with acidic EO water before incubation, with no effect on cuticle structure [as measured by egg weight (moisture) loss], normal embryonic development, and hatchability. Chick quality, as determined by visual assessment and BW at the time of hatch, was also not affected. However, broiler mortality during the first 2 wk of the production period was significantly reduced in the chicks that hatched from eggs sprayed with EO water compared with chicks hatching from control eggs. The ability of EO water to reduce eggshell microbial load without negatively affecting hatchability or chick quality may make it a useful product for hatching egg sanitation.

Evaluating broiler growth and mortality in chicks with minor navel conditions at hatching.

As commercial hatcheries become more automated, there are fewer opportunities for chicks with minor unhealed navel conditions to be identified and removed before being shipped to farms. An experiment was undertaken to evaluate the effect of common navel conditions occurring at hatching on subsequent broiler performance. In each of 2 trials, chicks with normal navels and minor navel conditions (navel button or leaky navel) were collected from a commercial hatchery on the day of hatch. Chicks were feather sexed and placed in floor pens. Individual BW and mortality were recorded weekly until shipping at 41 d of age. As expected, male broilers had heavier BW at 41 d than females. Broilers with navel buttons and leaky navels had lower 41-d BW than those that had normal navels at hatching. Birds with navel buttons also had higher mortality over the entire production period than birds with leaky or normal navels. The results of this research clearly show that when chicks have even minor navel conditions at hatching, the end result is a reduction in broiler production efficiency.

The effect of broiler breeder genetic strain and parent flock age on eggshell conductance and embryonic metabolism.

The effect of genetic strain (Ross 308; Cobb 500) and parent flock age [young (29 wk), peak (Ross = 34 wk; Cobb = 36 wk), postpeak (40 wk), mature (45 wk), old (55 wk), and very old (59 wk)] on eggshell conductance and embryonic metabolism were examined. At each flock age, eggs from each strain were incubated for 21.5 d in individual metabolic chambers to measure embryonic O(2) intake and CO(2) output. From these data, the respiratory quotient (RQ) and metabolic heat production were calculated. Data were analyzed by the GLM procedure of SAS at P < or = 0.05. Neither strain nor flock age influenced conductance. Total embryonic O(2) consumption, CO(2) output, RQ, and metabolic heat production over the entire incubation period were not affected by strain. Daily differences existed between strains for embryonic O(2) intake (1, 7, 16, 17, 19, 20 d of incubation), CO(2) output (1 to 4, 16 to 20 d of incubation), and heat production (4, 7, 16 to 19 d of incubation). Embryos from young, mature, old, and very old flocks produced significantly more total embryonic heat over the entire 21 d (1,712, 1,677, 1,808, and 1,832, respectively) than embryos from peak (1,601) and postpeak (1,693) flocks. Average RQ for the entire incubation period was higher in embryos from mature flocks compared with all other flock ages. Daily differences among embryos from different flock ages were shown for O(2) consumption (all but d 8 of incubation), CO(2) production (all but d 7 and 9 of incubation), and heat output. The results showed that genetic strain and parent flock age influence daily embryonic metabolism, especially during the early and latter days of incubation. These daily differences coincide with the days of incubation having a higher incidence of embryonic mortality; these 2 factors may be related. Further investigation into the relationship between embryonic metabolic heat production and mortality during incubation may lead to the development of specific incubation conditions for different genetic strains and flock ages.

Egg storage and the embryo.

In domestic avian species, eggs are stored at cool temperatures until they can be placed into an incubator. The low temperature-induced diapause enables the embryo to survive until optimal temperature and humidity incubation conditions can be provided to support embryonic growth. Egg storage is a logistical necessity for the hatching egg industry both at the breeder farm and at the hatchery. However, it is well known that egg storage longer than 7 d negatively influences hatchability. At the cellular level, long-term egg storage induces cell death. This appears to be occurring both via necrosis and apoptosis. The result is higher embryonic mortality and, consequently, lower hatchability. In addition, long-term egg storage influences embryonic development and metabolism. Embryos of eggs stored long-term can be affected such that they do not initiate growth after proper incubation temperatures are provided; they initiate growth, but grow at a slower rate than eggs stored short term; and they are affected in both of the previously mentioned ways. Development of equipment to measure the embryonic metabolism of individually incubating eggs over the entire 21 d of incubation has provided further evidence that embryo metabolism has changed due to storage. One of the methods to reduce the negative effects of long-term storage has been to incubate eggs for short periods before storage. In both turkey and chicken eggs, this technique has been successful in improving the hatchability of long-term stored eggs. It is hypothesized that particular embryonic developmental stages are better able to survive long-term storage. Future research should focus on the mechanisms behind this improved ability to survive storage.

Investigating the effects of commercial probiotics on broiler chick quality and production efficiency.

A study was undertaken to test the effect of 2 commercially available probiotics on the production efficiency of broiler chickens hatched from the same breeder flock at 3 different ages (28, 43, and 57 wk). At each of the 3 breeder flock ages, 1,600 broiler chickens were hatched and randomly allocated to 1 of 4 treatments: 1) no probiotics (control), 2) probiotic 1 administered in the drinking water, 3) probiotic 1 administered as a spray, and 4) probiotic 2 administered in the feed. A coccidiostat was included in the feed, but no other antimicrobial agents were given. Broilers were then reared on straw litter in identical floor pens for a period of 6 wk. There were no significant differences in broiler BW, feed conversion, or mortality between the probiotic treatments and the control group in any of the trials. The 43-wk-old breeder flock had the highest fertility and hatchability and the lowest percentage of chicks culled at hatching. Throughout the broiler production period, the broilers from the 43- and 57-wk-old breeder flocks had higher BW and weight gains than the broilers produced at 28 wk of breeder flock age. Broiler feed conversion over the 6-wk production period decreased as the breeder flock aged. Probiotics had no effect on chick quality or production efficiency in broilers produced by the breeder flock ages examined.

Investigating the eggshell conductance and embryonic metabolism of modern and unselected domestic avian genetic strains at two flock ages.

The objective of this study was to determine if broiler strain and breeder flock age affect eggshell conductance, fertility, and hatchability parameters; heart and hepatic glycogen concentrations at hatch; and embryonic metabolism throughout incubation. The 3 broiler strains investigated were HBY, a modern commercial broiler strain selected for high breast yield; WBM, a modern commercial broiler strain selected for the whole bird market; and UN78, a female broiler parent strain unselected since 1978. Fertility and hatchability parameters for each of the 3 strains were determined when the flocks were 32, 34, 37, and 38 wk of age. Eggshell conductance was measured on separate eggs produced from flocks at 37, 45, and 53 wk of age. Concurrently, fertile hatching eggs from the 3 broiler strains at 2 flock ages (33 and 38 wk) were incubated in individual metabolic chambers. Total daily CO2 production of each embryo was measured. Strain and flock age did not influence any of the fertility or hatchability parameters. Strain had no effect on conductance, but eggs from the 37-wk-old flocks had higher conductance than eggs from the 45- or 53-wk-old flocks, which did not differ from one another. Strain had no significant effect on average total CO2 production over the entire 21.5 d of incubation. However, embryos from the 38-wk-old flock produced more total CO2 than did embryos from the 33-wk-old flocks. Also, there was an interaction between strain and flock age for total CO2 production; UN78 embryos from the 33-wk flocks had higher CO2 production than WBM embryos, and the CO2 production of HBY did not differ from either strain. When embryos from the 38-wk flocks were compared, WBM embryos had higher CO2 production than did UN78 embryos, and HBY embryos did not differ from either strain. The data showed that in the 3 strains examined in this study, genetic differences in embryonic metabolic rate were dependent upon breeder flock age.

Egg storage alters weight of supply and demand organs of broiler chicken embryos.

Storage of fertilized eggs for more than 10 d prior to incubation decreases embryonic viability. The hypothesis was tested that embryos may grow differently following egg storage. Eggs from which embryos survived following storage (ST) were compared to eggs from a second line that did not (NOST). Three identical, independent trials were conducted using fertile eggs from both lines at two ages (peak lay and > 53 wk). Eggs were stored for 1 or 14 d prior to setting in the incubator. At 3-d intervals during development, embryos were carefully removed from the eggs, the yolks were excised and carcasses were weighed. Beginning at 12 d of incubation whole body, heart, liver and thigh tissues were weighed to assess allometric growth of supply (heart and liver) and demand (thigh muscle) tissues. Storage of eggs from both lines and from hens of both ages decreased BW differently throughout incubation. Line, Age and Storage interacted to affect embryonic BW and organ weights. Embryo weights were consistently heavier in NOST line eggs from older breeder flocks stored for 14 d than those from ST line eggs. It was concluded that extended storage of fertile eggs prior to setting affects embryonic growth to enhance survival.

Prestorage incubation of long-term stored broiler breeder eggs: 1. Effects on hatchability.

Two thousand eight hundred broiler breeder eggs were used to determine if prestorage incubation (PRESI) treatments of 0, 6, 12, or 18 h (at 37.5 C) could improve the hatchability of eggs stored (at 11.5 C) for 4 vs. 14 d. Embryonic development of 30 eggs was established after exposing the eggs to each PRESI treatment. The remaining eggs were cold-stored for 4 or 14 d and then incubated for 21 d. Unhatched eggs were broken open to determine fertility, and if fertile, stage of embryonic death was determined. Statistical significance was assessed at P < 0.05. Embryonic development significantly advanced (P = 0.00001) as the number of PRESI h increased. Therefore, embryos from each of the four PRESI treatments were placed into cold storage at different stages of development. Egg storage for 14 vs. 4 d significantly reduced the hatchability of all eggs set (58.4 and 88.2%, respectively). The PRESI treatments did not have a significant beneficial or detrimental effect on the hatchability of all eggs set for the eggs stored 4 d. However, in eggs stored for 14 d, PRESI for 6 h significantly improved hatchability of all eggs set (79.0%) when compared to eggs that were not PRESI (70.5%). The hatchability of all eggs set for eggs PRESI for 18 h and stored for 14 d was significantly reduced (9.1%) when compared to the other 14-d stored PRESI treatments. The results of this study provide evidence that embryos of eggs that have completed hypoblast formation (PRESI for 6 h) and are stored for 14 d have a survival advantage over embryos of 14-d stored eggs that have not been subjected to any PRESI treatments.

Effects of light intensity from photostimulation in four strains of commercial egg layers: 2. Egg production parameters.

The effects of light intensity (LI) from photostimulation to 45 wk of age on egg production parameters and egg size characteristics were examined in four layer strains. Floor housed pullets were raised in a light-tight facility from 1 d of age until housing in individually illuminated cages at 17 wk of age. At 17 wk of age, two white egg strains, ISA-White (ISA-W) and Shaver 2000 (S2000), and two brown egg strains, ISA-Brown (ISA-B) and Shaver 579 (S579), were assigned to a processing group [Group 1 was killed at sexual maturity (first oviposition); Group 2 was kept to 45 wk] and were photostimulated at 18 wk of age using a LI of 1, 5, 50, or 500 lx (4 x 4 factorial design). One bird from Group 1 and one bird Group 2 were caged together in individually lit cages (one brown and one white egg layer). Cages were equipped with hardware to monitor egg laying time. Data of individual egg weight and time of lay were kept on Group 2 birds until 45 wk of age. Egg production data were analyzed for hen-day production, laying sequence length, egg and egg component weights, time of lay, and egg interval time as related to strain or LI. Hen-day production was greater in brown egg strains (ISA-B = 86.7%, S579 = 88.1%) than in white egg strains (ISA-W = 83.4%, S2000 = 82.3%) and was reduced in birds under 1 lx compared to 5 or 50 lx. A LI of 1 lx resulted in reduced egg production and laying sequence length compared to birds with a 50 or 500 lx. The effects of LI were strain dependant, however. Postpeak sequence length and egg production declined at more rapidly under 500 lx compared to other LI in brown egg strains, indicating possible development of a photorefractory condition. Mean settable egg weight was lower in 500 lx birds (56.1 g) compared to other groups (mean = 57.9 g), reducing total egg mass produced. Mean interval between successive eggs in a sequence was lengthened in 1 lx birds compared to other LI groups. Mean time of lay was earlier in brown egg strains than in white egg strains by 48 min. Mean time of lay was shifted to occur later by an increasing LI. Light intensity affected sexual maturation and egg production, as layers had differential responses to lighting. LI of 1 lx and 500 lx were found to be limiting to the egg production efficiency of layers. Whereas the birds receiving 1 lx had a reduced rate of egg production, those receiving 500 lx had reduced egg size later in the production period in combination with reduced shell quality, which indicated that inadequate feed intake under high LI conditions may be a factor affecting layer stocks. Exposure to high LI reduced egg size and total egg mass produced. Ultimately, the brown egg strains appeared to be more susceptible to the negative effects of low or high LI, indicating the importance of matching management practices to the particular hen genotype.

Examining the effects of prestorage incubation of turkey breeder eggs on embryonic development and hatchability of eggs stored for four or fourteen days.

Thirty-six hundred British United Turkey hatching eggs were used in two separate trials to test whether prestorage incubation (PRESI) treatments of 0, 6, and 12 h (Trial 1) or 0, 7, and 14 h (Trial 2) could improve the hatchability of eggs stored (17 C) for 14 versus 4 d. The development of the embryos (n = 30) was staged before and after exposing eggs to the various PRESI treatments. Embryonic development was also established after storage to ascertain whether embryonic development was occurring during storage. The remaining eggs in each trial were split into three groups (n = 500) and incubated for 28 d to examine embryonic mortality and hatchability. No changes were observed in embryonic development due to egg storage. Embryos were significantly more developed as the number of PRESI h increased; therefore, embryos from different PRESI treatments were placed in storage at different stages of development. Early mortality (1 to 7 d of incubation), mortality at internal and external pipping, and hatchability of fertile eggs were significantly reduced in eggs stored for 14 versus 4 d. The various PRESI treatments did not significantly affect the mortality or hatchability of eggs stored for 4 d. However, the hatchability of eggs incubated prior to storage for 12 h and then stored for 14 d was restored to the levels reported for eggs subjected to the treatment that represents the industry norm (0 h of PRESI and 4 d storage). These results indicate that embryos of eggs stored for 14 d, which have developmentally advanced to the stage of complete hypoblast formation (PRESI for 12 h), have a survival advantage over eggs stored for 14 d that have not been subjected to any PRESI.

Egg storage effects on plasma glucose and supply and demand tissue glycogen concentrations of broiler embryos.

The hypothesis was tested that enhanced embryonic carbohydrate metabolism may enable embryos to survive egg storage effects. As lines of broiler breeders age, some lines resist detrimental effects of egg storage on embryonic survival, whereas others do not. Fertile eggs were obtained from two lines differing in storage ability. Eggs from each line by age group were stored for 1 or 14 d prior to setting. Eggs were distributed randomly into a single machine and incubated under standard conditions. Beginning at 17 d of incubation, immediately prior to the plateau stage in oxygen consumption, embryos from each of the treatment groups were sampled for BW, organ growth, glycogen concentration, and plasma glucose concentrations. Sampling continued through hatching. Plasma glucose concentrations increased significantly, and hepatic glycogen concentrations declined as embryos approached hatching. The rate at which glycogen was accrued into muscle and heart tissue displayed a significant three-way interaction among line, age, and storage. Embryos from the line that resisted storage mortality maintained greater glycogen concentrations in muscle and heart tissues than those from the line and age with diminished survival rates. It was concluded that embryonic survival rates differ following egg storage because of the ability of the embryo to accrue and maintain adequate carbohydrate for growth and function of vital demand tissues.

Research note: variability in preincubation embryonic development in domestic fowl. 2. Effects of duration of egg storage period.

Embryos of eggs from Single Comb White Leghorn hens were analyzed to determine whether duration of egg storage significantly affects embryonic development prior to incubation. Eggs were gathered over a period of 5 days from 25-wk-old hens that were naturally inseminated and housed in floor pens. Within 1 h of oviposition the eggs were collected and assigned randomly to one of five storage treatment groups of 0, 4, 7, 14, or 21 days. Fresh egg weight was recorded and the eggs were placed on plastic egg flats and stored at 14 C. Weight of each egg was measured after storage to determine amount of weight lost during storage. A total of 500 embryos were examined after storage. Viable embryos were staged for development using a modified Eyal-Giladi and Kochav classification. The incidence of embryonic mortality was noted. Duration of storage (P = .5815) collection date (P = .5815), and fresh egg weight (P = .3789) did not affect embryonic development significantly. A significant linear relationship was observed between duration of the storage period and loss of egg weight (P = .0001). Embryonic mortality was significantly related to loss of egg weight (P = .0001). Mortality was highest in eggs that were stored for a longer period of time. The data from the current study indicate that storing fertile eggs below physiological zero inhibits embryonic development. One of the reasons for the increased incidence of embryonic mortality in eggs that were stored for longer periods may be related to the increased egg weight loss in these eggs.

Relationship of hen age and egg sequence position with fertility, hatchability, viability, and preincubation embryonic development in broiler breeders.

Indian River broiler breeder hens (n = 29) were caged individually to investigate whether hen age and egg sequence position were related significantly to the dependent variables fertility, hatchability, viability (hatch of fertile eggs), and preincubation embryonic development. Hens were artificially inseminated once per week. All eggs laid during the period of 31 to 54 wk of age were stored at 16 to 17 C for .5 to 7 days. Time of oviposition records were used to assign eggs to sequence position ("first" or "subsequent"). Eggs laid on odd-numbered weeks were broken open, fertility determined, and embryonic development staged. Eggs laid on even-numbered weeks were sent to a commercial hatchery to assess hatchability. Unhatched eggs were opened to determine fertility and embryonic mortality. In addition, hen weight, number of days since insemination, time of oviposition, and egg weight were recorded to determine their relationship to the dependent variables. Fertility (n = 3,240 eggs) and hatchability (n = 1,653 eggs) were not significantly related to egg sequence position, but were related to hen age (P = .0001 and P = .0002, respectively). Older hens demonstrated lower fertility and hatchability. In contrast, embryo viability (n = 1,487 eggs) and preincubation embryonic development (n = 1,200 eggs) were not significantly related to hen age, but were related to egg sequence position (P = .0026 and P = .0001, respectively). First-of-sequence eggs had lower viability, and embryos of these eggs were more developed than embryos of subsequent eggs. These data indicate that the reduction in chick production observed as the hen ages may be due to the increased incidence of first-of-sequence eggs.

Variability in preincubation embryo development in domestic fowl. 1. Effects of nest holding time and method of egg storage.

Embryos of eggs from Single Comb White Leghorn hens were analyzed to determine whether nest holding time and method of storage had a significant effect on postoviposition embryonic growth prior to incubation. Eggs were collected from 38- to 42-wk-old hens naturally inseminated and housed in floor pens. The experiment had a 2 x 2 factorial arrangement of treatments with two nest holding times and two storage methods. Eggs were collected within 1 h of oviposition, placed on cardboard egg flats, and stored unpacked (Treatment 1), or put on flats, and packed in 30-dozen egg cases (Treatment 2). Eggs in Treatments 3 and 4 were marked within 1 h of oviposition, but remained in the nest for 6 to 7 h. These eggs were separated into unpacked (Treatment 3), and packed (Treatment 4) groups. All eggs were stored at 13.8 C for 4 days. A total of 250 embryos were staged after storage for development using the Eyal-Giladi and Kochav classification. Least square means (LSM) for stage of development were: Treatment 1, 10.76; Treatment 2, 11.52; Treatment 3, 12.41; and Treatment 4, 12.36. For the main effects, nest holding time significantly affected stage of development (P = .0001), but storage method (P = .1140) and nest holding time by storage method interaction (P = .0730) did not. Comparison of LSM of Treatment 1 versus 3 (P = .0001), 2 versus 4 (P = .0152), and 1 versus 2 (P = .0214) were significant, but Treatment 3 versus 4 (P = .8595) was not.(ABSTRACT TRUNCATED AT 250 WORDS)