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PubMed1999

Factors affecting ostrich egg hatchability.

Ostrich eggs often have low hatchability (HATCH) rates because they do not lose sufficient weight during incubation. Because egg size, eggshell porosity and thickness (THICK), and length of preincubation egg storage are known to affect egg weight loss during incubation (EWL) and HATCH of chicken eggs, these factors were examined using ostrich eggs. The effects of eggshell porosity (number of large pores per cm2 of shell; LP); and THICK on EWL and HATCH were assessed by categorizing the eggs as having either low, intermediate, or high LP or low, intermediate, or high THICK. Mean EWL was higher (P<0.05) in eggs of the high LP group when compared with eggs in either the low or intermediate LP groups that lost similar amounts of weight during incubation. Mean HATCH was also higher (more than 25%; P<0.10) in eggs with high LP when compared with the HATCH found in eggs having low LP. Eggs from the intermediate LP group had an intermediate HATCH response. Moreover, numbers of LP were positively correlated to both EWL (r2 = 0.64; P<0.0001) and HATCH (r2 = 0.25; P<0.03). Inverse relationships existed between THICK and EWL and between THICK and HATCH according to the order (P< 0.05): eggs of low THICK, highest mean EWL and HATCH > eggs of intermediate THICK, intermediate mean EWL and HATCH > eggs of highest THICK, lowest mean EWL and HATCH. Shell thickness was not correlated to either EWL or HATCH. The influence of egg size on mean LP, THICK, EWL, HATCH, and chick weight (CWT) was assessed. Although THICK was unaffected by egg size, higher LP (P<0.10), EWL (P<0.05), and HATCH (P<0.10) were found in medium-sized eggs when compared with either small or large eggs. The CWT was associated with egg size (P<0.05) according to the order: large eggs, highest CWT > medium eggs, intermediate CWT > small eggs, lowest CWT. Neither EWL nor HATCH was affected by length of preincubation egg storage. Collectively, our findings suggest that 1) ostrich eggs that possess low LP and increased THICK hatched poorly, 2) intermediate-sized eggs hatch best, 3) large eggs produced large chicks, and 4) ostrich eggs can be stored under conditions typically used in the poultry industry for a minimum of 10 d without negatively impacting HATCH.

Animal Husbandry↗
PubMed2002

Avian egg size: variation within species and inflexibility within individuals.

Egg size is a widely-studied trait and yet the causes and consequences of variation in this trait remain poorly understood. Egg size varies greatly within many avian species, with the largest egg in a population generally being at least 50% bigger, and sometimes twice as large, as the smallest. Generally, approximately 70% of the variation in egg mass is due to variation between rather than within clutches, although there are some cases of extreme intra-clutch egg-size variation. Despite the large amount of variation in egg size between females, this trait is highly consistent within individuals between breeding attempts; the repeatability of egg size is generally above 0.6 and tends to be higher than that of clutch size or laying date. Heritability estimates also tend to be much higher for egg size (> 0.5) than for clutch size or laying date (< 0.5). As expected, given the high repeatability and heritability of egg size, supplemental food had no statistically significant effect on this trait in 18 out of 28 (64%) studies. Where dietary supplements do increase egg size, the effect is never more than 13% of the control values and is generally much less. Similarly, ambient temperature during egg formation generally explains less than 15% of the variation in egg size. In short, egg size appears to be a characteristic of individual females, and yet the traits of a female that determine egg size are not clear. Although egg size often increases with female age (17 out of 37 studies), the change in egg size is generally less than 10%. Female mass and size rarely explain more than 20% of the variation in egg size within species. A female's egg size is not consistently related to other aspects of reproductive performance such as clutch size, laying date, or the pair's ability to rear young. Physiological characteristics of the female (e.g. endogenous protein stores, oviduct mass, rate of protein uptake by ovarian follicles) show more promise as potential determinants of egg size. With regards to the consequences of egg-size variation for offspring fitness, egg size is often correlated with offspring mass and size within the first week after hatching, but the evidence for more long-lasting effects on chick growth and survival is equivocal. In other oviparous vertebrates, the magnitude of egg-size variation within populations is often as great or greater than that observed within avian populations. Although there are much fewer estimates of the repeatability of egg size in other taxa, the available evidence suggests that egg size may be more flexible within individuals. Furthermore, in non-avian species (particularly fish and turtles), it is more common for female mass or size to explain a substantial proportion of the variation in egg size. Further research into the physiological basis of egg-size variation is needed to shed light on both the proximate and ultimate causes of intraspecific variation in this trait in birds.

Age Factors↗
PubMed2001

Growth of Salmonella in egg white.

Six non-S. Enteritidis strains and eleven S. Enteritidis strains of which 8 were isolated from eggs, were tested on their growth behaviour in fresh eggs and in eggs of 2 and 3 weeks old hold at 20 degrees C. The growth of Salmonella at 20 degrees C was measured at days 6, 13 and 23 after inoculation. Taking the average growth of the different S. Enteritidis and of the non-S. Enteritidis strains, we found that both groups grew very well in fresh eggs. S. Enteritidis strains grew as good in eggs of 2 weeks as in fresh eggs, non-S. Enteritidis strains grew less. When keeping the eggs 3 weeks before inoculation, both groups showed still a relatively high growth. Additional experiments were done on the growth of Salmonella in a minimal medium with an iron source together with the iron chelator conalbumin, and in a medium without iron and conalbumin, to overcome variations in viscosity and in egg composition. After 12 hours incubation at 37 degrees C, both S. Enteritidis and non-S. Enteritidis strains grew better in the presence of iron than in the absence. S. Enteritidis egg isolates behaved more variable than S. Enteritidis non-egg isolates in the presence of iron. To check the influence of pH changes during ageing of eggs, we measured the growth of Salmonella in minimal media (with iron) of pH 8, 8.5, 9 and 9.5. All salmonellae seemed to grow well independently of the pH. Thus the fact that Salmonella grew best in fresh egg white and showed a decreasing growth in stored egg white, is probably not due to a pH effect. We also investigated if the presence of the yolk had an influence on the growth of Salmonella. We saw no general correlation so it seems that no components that could promote the growth of Salmonella diffuse from the yolk. We studied the influence of the egg sources on the variability in growth by comparing experiments done in eggs of 3 different sources. For the different strains we found a variable growth. But in general, the most important conclusion of our experiments is that all Salmonella strains do grow better in fresh egg white than in egg white of 2 or 3 weeks old. These results are contradictory with findings in literature (Humphrey et al., 1993) and must be checked with the European guidelines concerning the storage of eggs. Moreover, we found that even non-S. Enteritidis strains can grow well in egg white. These are not found in naturally contaminated eggs. It doesn't seem probable that S. Enteritidis could penetrate the egg shell easier than other serotypes so we suppose that horizontal transmission of Salmonella in eggs is of less importance than the vertical transmission.

Consumer Product Safety↗
PubMed1996

Risk assessment of use of cracked eggs in Canada.

In 1992, Agriculture and Agri-Food Canada (AAFC) amended its Egg Regulations to restrict movement of Canada C eggs (cracks) to federally registered processed egg stations for pasteurization. This was questioned by egg producers and some provinces on economic grounds. It was also in conflict with long-standing practices of marketing eggs in some provinces to retail stores, bakeries, restaurants and institutions or at the farm gate. In order to determine how much of a risk these eggs were to human health, AAFC requested that the Health Protection Branch (HPB) of Health Canada (HC) conduct a risk assessment. On the basis of outbreak data, the main hazard in these eggs was identified as Salmonella. Salmonellae may occasionally be present on shell eggs even after washing, and any Salmonella reaching the membranes can be transferred to an egg mixture through breaking, and will rapidly grow under improper storage conditions. A Relative Risk analysis showed that cracked eggs are 3 to 93 times more likely than uncracked shell eggs to cause outbreaks. A probability of illness of 1 in 3800 was derived from the 40 million cracked eggs produced in Canada and not pasteurized and the probable 10,500 illnesses arising from these. This was for the general population, but this would be greater for those who consume many shell eggs or would do so in an unsafe manner, or are more likely to be infected (5% of consumers who eat raw or lightly cooked eggs daily, rural communities with more opportunities for obtaining cracked eggs, and those who are immunocompromised and in institutions). Even though it is not possible to precisely determine the risk of salmonellosis through cracked eggs, this assessment indicated that there was enough of a concern that a management strategy was needed. Eight options for managing the risk were considered and ranked for acceptability by both HC and AAFC. Ideally, all cracked eggs should be broken and pasteurized, but this is impractical in certain regions of the country, and other options, such as sales to food processors operating under Good Manufacturing Practices (GMP), and at the farm gate in marked cartons and under controlled conditions, were considered to be acceptable, whereas sales to institutions and bakeries were not. This is the first fromal food-related microbiological risk assessment that HC has completed. Although this is a Canadian problem, any country producing eggs has to recognise that despite any regulations controlling the use of cracked eggs, economics will dictate that some of these will be consumed as whole eggs or egg products, and a management plan is desirable to limit hazardous practices associated with these eggs.

Canada↗
PubMed1986

Categorisation and causes of abnormal egg shells: relationship with stress.

Concern regarding the proportion of brown eggs being laid with abnormal egg shells led to an investigation of the relationship between disturbance or stress and egg shell appearance and quality. The abnormalities fell into two main classes: misshapen or bulging eggs and eggs coated with a superficial layer of amorphous calcium, variously termed dusted, white banded, chalky or pink eggs. Translocation of hens from pens to cages resulted in a decrease in egg production and an increase in the proportion of abnormal eggs over the succeeding 18 d. Disturbance to flocks on deep litter resulted in an increase in the proportion of eggs laid with abnormal shells on the following day, not only in the flocks directly affected but also in an adjacent flock. Exclusion from their nests of birds accustomed to laying in nest boxes resulted in disturbed prelaying behaviour, retention of eggs in the shell gland and an increased proportion of coated eggs. Administration of 0.1, 0.25 or 1.0 mg of adrenaline subcutaneously resulted in the retention of eggs currently in the hens' shell glands and in an increased proportion of eggs with abnormal egg shells being laid during the following 10 d. A dose response effect was apparent. There was evidence that the nature of the particular abnormality produced was dependent on the stage of egg formation at which the disturbance was imposed and, if retention followed, upon the length of time the egg was retained. Disturbances when eggs were only lightly calcified tended to result in misshapen eggs, while those occurring when oviposition was imminent tended to result in coated eggs. Dusted or pink eggs followed moderate retention whereas white banded eggs were seen after prolonged retention. These observations may provide a basis for a non-invasive method of assessing stress in laying hens as well as helping to account for hitherto inexplicable occurrences of declining egg shell quality.

Animals↗
PubMed1977

[Protein and amino acid metabolism in laying hens receiving N-15 labeled casein. 7. Incorporation and distribution of labeled nitrogen into egg fractions].

Four colostomated hybrid laying hens were fed, for 6 days, a semisynthetic ration containing 15N labelled casein as sole protein source. Within this period, the hens laid 13 eggs which were fractionated into egg yolk, egg white and egg shell. The N content of these egg fractions was established. A TCE soluble and TCE precipitable fraction (TCE=trichloroacetic acid) were obtained from the fractions of egg yolk and egg white. Additionally, an analysis was made of the set of amino acids contained in the crude protein of the egg yolk, egg white and egg membrane (lysine, histidine and arginine only). The excess 15N atom% (15N') was established in the crude protein, in the nitrogen from the TCE soluble and TCE precipitable fractions and in the N from 17 amino acids of the egg yold and egg white. In the egg membrane fraction the 15N' atom% was determined as percentage of the total amount of N and of the amount of N contained in the basic amino acids. Essential differences between the 3 egg fractions were noticed with regard to the process of initial incorporation of labelled N and the intensity of this process after the onset of 15N application. 15N' was detected in the egg shell as early as 4 hrs after administration of the 15N' dose. Heavy nitrogen was found to be contained in the egg white of eggs that were laid on the 2nd day of experiment. The level of 15N' atom% in the egg white increased essentially during the following days of experiment; the 15N'quantities in the egg white were considerably higher than those in the egg yolk. Similar results were obtained for the process of 15N incorporation into the 17 amino acids. It is assumed that differences between the 3 fractions as observed in the level of labelling and in the pattern of 15N' incorporation are accounted for by the different sites and different times of protein synthesis for the different egg proteins.

Amino Acids↗
PubMed2005

Effect of cooked and raw egg consumption on ovalbumin content of human milk: a randomized, double-blind, cross-over trial.

BACKGROUND: Maternal avoidance of egg intake has been recommended to treat egg allergy in breastfed infants. OBJECTIVE: To determine if the concentration of ovalbumin (OVA) in human milk is directly related to the quantity and form of egg consumed by breastfeeding mothers. METHODS: Randomized, blinded, cross-over, intervention trial. Breastfeeding women (n = 41) attended four clinic days between 11 and 14 weeks of lactation and on each day were randomly allocated to receive a test breakfast, identical except for the egg content (no egg, one raw egg, half a cooked egg or one cooked egg). Breast milk samples were collected at two hourly intervals for 8 h and their OVA concentration measured by ELISA. RESULTS: There was a direct, dose-response between the amount of cooked egg ingested and the peak OVA concentration (no egg 0.05 ng/mL [95% confidence interval (CI), 0.01-0.11], half a cooked egg 2.24 ng/mL [95% CI, 0.57-3.91], one cooked egg 3.16 ng/mL [95% CI, 1.41-4.91], n = 41, P<0.05) as well as the total OVA excretion (no egg 0.18 ng/mL/h [95% CI, 0.04-0.39], half a cooked egg 4.93 ng/mL/h [95% CI, 1.40-8.46], one cooked egg 9.14 ng/mL/h [95% CI, 4.25-14.03], n = 41, P<0.05). The peak concentration and total OVA excretion in response to one raw egg did not differ from ingesting half a cooked egg. There was no detectable OVA in the breast milk of 24% (10/41) women up to 8 h after any egg challenge. CONCLUSION: OVA was detected in the breast milk of lactating women up to 8 h after a controlled intake of egg. A dose-response correlation was indicated. As excretion of OVA in human milk appears to be a normal phenomenon, further studies need to determine the threshold of OVA excretion that leads to symptoms in egg-allergic breastfed infants.

Adult↗