Search

This study set out to investigate if access to an enriched environment during the rearing phase influences subsequent production and eggshell quality in broiler breeders. Broiler breeder pullets were reared under standard rearing conditions (control treatment) or under standard conditions with an environmental enrichment of bales of plastic-wrapped wood shavings (enriched treatment). At 19 weeks of age both groups were transported to a laying facility and housed in standard pens according to treatment type. Egg weight, shape, shell thickness, non-destructive deformation, breaking strength, stiffness and ultrastructural quality were compared at beginning of lay (25 weeks old), peak production (31 weeks old), mid-lay (45 weeks old) and end of lay (57 weeks old). Production and hatchery data were also collected throughout lay. Significant treatment-age interactions were detected for non-destructive deformation, breaking strength and stiffness, such that birds which had received prior enrichment went on to maintain a better shell quality with age. The measurements of total shell thickness, mammillary thickness and effective shell thickness all showed a trend for a treatment-age interaction. Significant age effects were found for weight, shape index, shell thickness, breaking strength and stiffness. All production and hatchery data also demonstrated significant changes with age. It is concluded that early enrichment with bales of wood shavings may provide a novel approach to the maintenance of eggshell quality at a time when calcium metabolism begins to reduce in efficiency.

1. This study ascertained how bone of modern meat-type chickens develops under typical commercial conditions and compares development with that in genetic precursor stock. 2. A modern fast-growing selected strain and a slower-growing control strain were used. Birds were weighed weekly. A random sample was taken from each population at a range of ages up to 39 d. 3. A tibiotarsus from each bird was X-rayed and its dimensions and estimated resistance to bending were determined. Cortical bone samples were ashed to measure total mineral, calcium and phosphorus content. Cortical samples were also taken for porosity assessment. 4. As expected, the selected strain grew faster and heavier than the control strain. Despite this, both strains demonstrated similar periods of rapid bone formation (days 4 to 18) and mineralisation (days 4 to 11), and achieved similar estimates of resistance to bending. 5. However, cortical bone of the selected strain was less well mineralised and more porous than that of the control strain and showed a significant increase in the molar Ca:P ratios above the expected range of values during the first 2 to 3 weeks of life. 6. Despite production of bones with the correct dimensions for load support, the relatively poor density and mineral content of bone in the selected strain is likely to reduce effective breaking strength of the tibiotarsus. Possible reasons may be either inadequate dietary supply of Ca and P or impaired utilisation of the minerals due to a rapid growth rate or genetic factors.

Cracked eggshells result in economic loss and provide a route for pathogenic organisms to enter the egg. Genetic factors that contribute to shell strength are likely to decrease the risk that an egg will crack when subject to insult. A novel measurement, the dynamic stiffness of the eggshell (Kdyn) was examined to determine if it might be used in the genetic selection of hens with improved eggshell characteristics. The measurement is determined from acoustic resonance frequency analysis. The estimates of heritability for the novel measurement of Kdyn were moderately high and ranged from 0.33 to 0.53 depending on the model used for the estimation. The estimates of genetic correlation of Kdyn with eggshell breaking strength (0.49) and static stiffness (0.57) were positive and relatively large as expected. There was a small negative genetic correlation between Kdyn and egg production from 26 to 50 weeks of age (-0.19) and a moderate one from 58 to 74 weeks of age (-0.36). The moderate heritability and relative independence of Kdyn indicates that this measurement could be used successfully in a breeding programme to improve shell quality and to reduce the incidence of cracks.

39 ref.; International audience; The eggshell is a highly ordered structure resulting from the deposition of calcium carbonate concomitantly with an organic matrix upon the eggshell membranes. Mineralization takes place in an acellular uterine fluid, which contains the ionic and matrix precursors of the eggshell. We have identified a novel 32-kDa protein, ovocalyxin-32, which is expressed at high levels in the uterine and isthmus regions of the oviduct, and concentrated in the eggshell. Sequencing of peptides derived from the purified protein allowed expressed sequence tag sequences to be identified that were assembled to yield a full-length composite sequence whose conceptual translation product contained the complete amino acid sequence of ovocalyxin-32. Data base searches revealed that ovocalyxin-32 has limited identity (32%) to two unrelated proteins: latexin, a carboxypeptidase inhibitor expressed in the rat cerebral cortex and mast cells, and a skin protein, which is encoded by a retinoic acid receptor-responsive gene, TIG1. High level expression of ovocalyxin-32 was limited to the isthmus and uterus tissue, where immunocytochemistry at the light and electron microscope levels demonstrated that ovocalyxin-32 is secreted by surface epithelial cells. In the eggshell, ovocalyxin-32 localizes to the outer palisade layer, the vertical crystal layer, and the cuticle of the eggshell, in agreement with its demonstration by Western blotting at high levels in the uterine fluid during the termination phase of eggshell formation. Ovocalyxin-32 is therefore identified as a novel protein synthesized in the distal oviduct where hen eggshell formation occurs.

A preliminary survey of the ovary of the green turtle, Chelonia mydas L., shows that as in Aves the smaller ovarian follicles have a prominent zona radiata. In this a mucopolysaccharide is deposited eventually forming a thick band located in a position analogous to that of the avian perivitelline membrane but which appears to be impermanent since it is no longer present in the larger follicles (> 10 mm diameter). Its disappearance is accompanied by a marked increase in the height of the granulosa cells which become very tall and accumulate large globules of basic protein and sugar in their apical cytosome while at the same time a similar substance is found in the yolk. The granulosa also seems to disappear later in development leaving the highly developed theca interna in contact with the yolk. The theca is then very vascular and contains large numbers of fat cells. No structure comparable to a corpus luteum has been distinguished but ovarian material obtained within the first few days after ovulation has not been available for study and it is not, therefore, possible to be dogmatic on this question.

The structure of the calcified layer of egg shells from farm-reared and wild turtles has been examined using scanning electron microscopy and infrared analysis. Farm-reared egg shells contained discrete morphologically distinct regions of blocks of calcite and spherulites of aragonite. In contrast, the egg shells from feral populations consisted only of the spherulites. Differences in the impurity contents of the calcite and aragonite structures have been observed. SEM revealed a thin cuticular membrane.

Unpublished investigations have shown that at the light microscope level the oviduct of the green turtle ( Chelonia mydas L.) has two glandular subdivisions each of which appears to be structurally homogeneous. Histochemical studies suggest that the function of the more cranial of these is albumen secretion and that this is its sole function; in its ultrastructural features also it resembles the albumen secreting subdivision (magnum) of the avian oviduct except that it lacks the terminal mucous region to which the formation of the thick layer of egg albumen has been attributed. Layering of albumen (thick and thin layers) is not a characteristic of turtle eggs. The more caudal glandular segment presents ultrastructural features which tend to support the hypothesis that this is the site of shell-membrane formation but the presence of eggs undergoing calcareous shell formation in this subdivision shows that despite its structural homogeneity it is functionally dualistic, secreting both shell membranes and calcareous shell. In the available material ultrastructural features indicative of the latter function could not be demonstrated and further work is required in relation to calcium localization and acid phosphatase which may play a significant role in calcium transportation. The glands of the avian uterus in which calcareous shell deposition occurs are believed to be concerned with the addition to the albumen of plumping water. There is evidence that this addition is not a feature of turtle eggs and this may explain the absence of comparable glands in turtle.