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We have gathered, from the nests of dinosaurs, and living and fossil birds, some evidence of the environment in which these creatures lived. However, our isotope determinations suggest it will be impossible to resolve the problem as to whether the dinosaurs were warm-or cold-blooded from the oxygen and carbon isotopes content of their shells.
The eggs produced by developing Japanese quail (Coturnix coturnix japonica) fed 1 to 8 parts of mercury per million as mercuric chloride for 10 weeks have thinned shells. Total amounts of mercury in tissues were quite proportional to the dosage and were higher in males than in females. Methylation of mercury was not observed.
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Rahn et al. (J. Appl. Physiol. 69: 1546-1548, 1990) showed that the gas pressure in a plethysmograph containing an intact egg oscillates in phase with electrocardiogram (ECG) and that this pressure variation could be used as a noninvasive way to determine the heart rate of an avian embryo. One possible mechanism to account for the pressure oscillation is the mechanical movement of the embryonic heart, which leads to volume shifts of gas within the plethysmograph. Another possibility is that the oscillation of gas pressure with heartbeat is pulsatile gas exchange resulting from pulsatile blood flow. If gas exchange were transiently stopped, a pressure signal dependent on gas exchange should disappear, while a pressure signal dependent on cardiovascular motion should persist. Using a number of late-age hen eggs (at days 15-20 of incubation), we tested these hypotheses by suddenly changing the gas composition surrounding an egg and measuring the effect of the pressure oscillation. We found that 1) after 5% CO2-95% N2 was flushed into the plethysmograph (presumably halting gas exchange), pressure oscillations went almost to zero and the ECG signal remained; after air was flushed back to the plethysmograph, the pressure signal returned to control level; 2) after 20% CO2-20% O2-60% N2 was flushed into the plethysmograph (presumably increasing net gas exchange), the pressure signal increased 2.5-fold compared with that in air; and 3) after 1% CO2-99% N2 was flushed into the plethysmograph (presumably reversing gas exchange), the oscillation pressure decreased to one-fourth of that in air and the phase of pressure relative to ECG reversed compared with the phase in air.(ABSTRACT TRUNCATED AT 250 WORDS)
The Drosophila gene torpedo/Egfr (top/Egfr) encodes a homolog of the vertebrate Epidermal Growth Factor receptor. This receptor is required several times during the life cycle of the fly for the transmisson of developmental cues. During oogenesis, Top/Egfr activation is required for the establishment of the dorsal/ventral axis of the egg and the embryo. To examine how ectopic Top/Egfr activation affects cell fate determination, we constructed an activated version of the protein. Expression of this activated form (lambda top) in the follicle cells of the ovary induces dorsal cell fates in both the follicular epithelium and the embryo. Different levels of expression resulted in different dorsal follicle cell fates. These dorsal cell fates were expanded in the anterior, but not the posterior, of the egg, even in cases where all the follicle cells covering the oocyte expressed lambda top. The expression of genes known to respond to top/Egfr activation, argos (aos), kekkon1 (kek 1) and rhomboid (rho), was also expanded in the presence of the lambda top construct. When lambda top was expressed in all the follicle cells covering the oocyte, kek 1 and argos expression was induced in follicle cells all along the anterior/posterior axis of the egg chamber. In contrast, rho RNA expression was only activated in the anterior of the egg chamber. These data indicate that the response to Top/Egfr signaling is regulated by an anterior/posterior prepattern in the follicle cells. Expression of lambda top in the entire follicular epithelium resulted in an embryo dorsalized along the entire anterior/posterior axis. Expression of lambda top in anterior or posterior subpopulations of follicle cells resulted in regionally autonomous dorsalization of the embryos. This result indicates that subpopulations of follicle cells along the anterior/posterior axis can respond to Top/Egfr activation independently of one another.
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Environmental estrogens have recently caused great concern because of their ability to mimic natural hormones and influence vital endocrine functions in humans and wildlife. The induction of vitellogenin (Vtg) synthesis by environmental estrogens in viviparous vertebrates has been proposed as an effective and sensitive biomarker of estrogenicity. Immunochemical analysis of plasma from Atlantic salmon (Salmo salar) exposed to 4-nonylphenol (NP) or to effluent from oil refinery treatment plant (ORTP), shows that NP and ORTP effluent induces Vtg and zona radiata proteins (Zrp) in a dose-dependent manner. However, Zrp-beta cross-reactive proteins are more responsive than Zrp-alpha, Zrp-gamma, and Vtg. The sensitivity of Zrp induction points to the zona radiata proteins as alternate biomarkers of estrogenicity.
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The effect of parathyroid hormone (PTH) on egg-shell calcification has been investigated in egg-laying Japanese quail. Lilly parathyroid extract (PTE) when injected into quail within 2-6 h of oviposition caused a significantly increased deposition of a chronic 45Ca label into the sequential egg-shell compared with the previous egg in the clutch, indicating increased mobilization of bone Ca and its subsequent incorporation into the egg-shell. At the same time egg-shell weight/unit area and egg-shell Ca/unit area were significantly decreased. Parathyroid extract injected 12-16 after oviposition had none of these effects. Purified PTH also caused a significant decrease in egg-shell weight/unit area if injected within 2-6 h of oviposition. This result indicated an action of PTH either directly or indirectly on the avian oviduct limiting egg-shell calcification. The loss of responses in the 12-16 h treated birds may reflect high endogenous PTH levels with subsequent saturation of target organ receptors.
Laying hens were divided into high and low shell quality groups on the basis of egg specific gravity during the 5th, 7th, and 9th months of egg production. Concentrations of progesterone and estradiol-17 beta in the plasma were determined by radioimmunoassay in blood samples taken by cardiac puncture from hens at either 18, 21, or 24 hr postoviposition. Egg production and egg weight were not significantly different between shell quality groups; however, hens in the low shell quality group were heavier (P less than .05), had longer clutches (P less than .05), and lower egg specific gravity (P less than .0001) than hens in the high shell quality group. Egg production and clutch size declined (P less than .01) in both groups with increased age. Plasma estradiol and progesterone concentrations were not different between shell quality groups or among periods of production, though progesterone and estradiol concentrations were greater (P less than .005) at 21 hr postoviposition than at 18 or 24 hr. The correlation coefficient between plasma concentrations of estradiol and progesterone was significant. There was no significant association between the plasma concentrations of these hormones and egg shell quality. These data suggest that concentrations of estradiol and progesterone in plasma, during the 6 hr before ovulation, are not highly related to shell quality in the laying hen.
Single Comb White Leghorn (SCWL) hens, 65 weeks of age, were assigned to one of four dietary treatments: fasting to a body weight loss of 34% (FAST), administration of a diet containing less than or equal to 500 ppm sodium for 42 days (Lo Na), administration of a diet containing 20,000 ppm zinc for 10 days (Hi Zn), and a control (CON) diet. The hens were subjected to two photoperiod treatments, those receiving 17 hr (17-hr) of light per day throughout the 32-week experiment and those restricted to 8 hr of light per day for the first 42 days followed by a .5 hr/day increase until 17 hr was reached. Egg production and mortality were recorded daily. Feed consumption, feed conversion, and livability were determined weekly. Beginning on Day 56, eggs were collected at 28-day intervals for determination of egg weight, egg specific gravity, and shell weight. During the molt phase (1 to 6 weeks), the 17-hr light day significantly increased egg production, feed consumption, and decreased feed conversion (kg/doz) across all groups when compared with the 8-hr light/day treatments, but FAST treatments consumed identical amounts under both light treatments. From 7 to 32 weeks during the postmolt phase, egg production was significantly increased and feed conversion decreased by the FAST and Hi Zn treatments relative to CON, Lo Na treatment was intermediate. Feed consumption was significantly higher for the FAST treatment. Overall, there were not significant effects on egg production, feed consumption, and feed conversion.(ABSTRACT TRUNCATED AT 250 WORDS)
Plasma calcium concentration and uterine and duodenal adenosine triphosphatase (ATPase) activities were determined during shell formation for high (H) and low (L) shell strength lines of hens selected from the last of four consecutive generations. The H and L lines were divided into three groups according to shell formation at 0, 15, and 22 h following oviposition. Plasma total calcium was determined from blood samples collected from the common carotid artery. Activity of ATPase was determined in uterine and duodenal mucosa. Shell strength, shell weight, percentage of shell per egg and shell thickness of the H line hens significantly exceeded those of the L line. During shell formation, no significant fluctuation in plasma calcium levels was observed within a line, but overall mean plasma calcium concentrations were higher in the H line than L line. Uterine ATPase activity increased with time after oviposition in both lines, with that of the H line being greater. Duodenal ATPase activity of H line hens remained fairly constant throughout the period, but this value showed fluctuations in the L line hens. It thus appears that laying hens with high and low shell strength may vary in their ability to use calcium for shell formation.
Eggs were collected from 1 day of production of Hy-Line W36 commercial egg production hens 55 wk old. Also, eggs were collected from 1 day of production of Arbor Acres broiler breeder hens when they were 40 and 55 wk of age. The eggs were immediately weighed (EW) after collection and specific gravity (ESG) determined. The eggs were then broken and the contents removed. Shells were washed, air dried, and weighed. The weights of shells (ESW) were calculated using the following formulas: Broiler breeder ESW = 1.9128 x EW - 1.9741 EW/ESG and layer ESW = 1.9140 EW - 1.9754 EW/ESG. Shell density (ESD) was calculated using a modification of this formula. Egg weights of both commercial layers and broiler breeders were heaviest in the early morning. There was a steady decline in EW until 1545 h; EW increased thereafter. Specific gravity of eggs was highest in the morning, declined until 1245 h, and then increased thereafter. Shell weight was also highest in the morning, declined until 1245 h, and then increased thereafter. The calculated and measured ESW were highly correlated. The ESD was 2.147 and 2.160 for the commercial layers and broiler breeders, respectively.
To determine whether particle size of CaCO3 influences the hen's response to sodium zeolite A (ZA), two experiments were conducted. In Experiment 1, hens were fed 0, .75, and 1.50% ZA for 6 wk with and without a Na correction. At the end of the 4th wk, pullet-sized limestone was substituted for 50% of the added fine granular limestone in the diet containing no ZA. In Experiment 2, hens were fed diets containing 0, .68, and 1.36 ZA for 8 wk with and without one-half of the added fine granular limestone substituted for oyster shell. No correction for Na was made. A dietary calcium concentration of 2.75% was used in Experiment 1 and 3.5% in Experiment 2. Egg specific gravity, egg production, feed consumption, and egg weight were measured. Sodium zeolite A increased egg specific gravity, and the beneficial effects of ZA were maintained during Weeks 5 and 6 when pullet-sized limestone was added to the control diet containing no ZA (Experiment 1). Oyster shell and ZA improved egg specific gravity in Experiment 2 and the effect was additive. Dietary treatments had no effect on egg production or egg weight in Experiments 1 or 2 and there was no effect on feed consumption (Experiment 1). Feed consumption was reduced by ZA, when hens were fed oyster shell, but not when they were fed ZA with fine granular limestone (Experiment 2). It was concluded that the beneficial effect of ZA on egg specific gravity was independent of particle size of CaCO3 in the diet.
The objective of the present study was to determine whether indomethacin, an inhibitor of prostaglandin synthesis, could improve shell quality in birds laying a high incidence (greater than 15%) of soft-shelled (SS) and shell-less (SL) eggs and in birds laying exclusively hard-shelled (HS) eggs. Treatments consisted of two injection types, indomethacin or oil (controls), and two injection times, 4 h or 16 h postentrance of the egg into the uterus. Indomethacin delayed oviposition in both HS and SS or SL egg layers, with indomethacin being more effective in delaying oviposition when injected at 16 h as compared with 4 h postentrance of an egg into the uterus. Indomethacin increased shell thickness of the first egg laid following injection in the SS or SL groups but not in the HS groups. Egg weight was not affected by indomethacin injection. It was concluded that indomethacin delayed oviposition and prevented the premature expulsion of some SS or SL eggs. This delay in oviposition resulted in thicker shells of the first egg laid postinjection.
Twenty-seven 42-wk-old Single Comb White Leghorn hens housed in separate cages were fed either 2.5, 3.5, or 4.5% Ca diets, each providing .45% available P. Birds were allowed a 7-day adaption period followed by an 8-day collection period. Feed and water were available for ad libitum consumption with feed intake recorded daily. Eggs and excreta were collected daily for mineral analysis. Feed, Ca, and P intake of hens increased significantly (P less than .05) on shell-forming (SF) days compared with days on which shell formation did not take place (NSF). Dietary Ca level had a significant (P less than .05) effect on feed and Ca intake of hens. On SF days, hens retained more dietary Ca, both as a percentage and per gram Ca basis, compared with NSF days. As dietary Ca increased, the percentage Ca retained decreased (P less than .05) and per gram Ca retained increased (P less than .05). Dietary Ca had no effect (P greater than .05) on egg weight or egg production. Increasing dietary Ca significantly (P less than .05) decreased shell deformation and increased (P less than .05) shell weight and grams of shell Ca, although there was no significant (P greater than .05) effect on percentage shell Ca. Calcium retention increased linearly (P less than .05) as Ca intake increased, and shell weight increased quadratically (P less than .05). There was a diminishing response of shell weight to Ca intake at higher levels.
Two experiments were conducted to evaluate laying hen performance when fed two sources of inorganic phosphorus. In Experiment 1, a regular and a coarse form of defluorinated phosphate and one source of dicalcium phosphate were used in diets calculated to contain either .4 or .5% total phosphorus (.2 or .3% nonphytate phosphorus). In Experiment 2, either the regular form of defluorinated phosphate or the dicalcium phosphate source was fed in diets calculated to contain either .4, .5, .6, or .7% total phosphorus (.2, .3, .4, or .5% nonphytate phosphorus). In Experiment 1, hens fed .5% total dietary phosphorus consumed more feed and produced heavier eggs (P less than or equal to .05). Hens fed the .4% dietary phosphorus level lost more weight during the experiment (P less than or equal to .05). No differences among dietary treatments existed for egg specific gravity. A significant source by level interaction occurred for the farm classification of thin-shelled, cracked, or broken eggs and for the total of these classifications. In Experiment 2, egg production, feed consumption, egg weight, and egg mass were depressed (P less than or equal to .05) at the .4% total dietary phosphorus level. Hens fed the .4 and .7% total dietary phosphorus level laid eggs with the highest and lowest egg specific gravity, respectively. This trend was inverse to the effect of these phosphorus levels on egg weights. A significant source by level interaction occurred for the farm classification of thin shell and for the total percentage of eggs with exterior defects. At the .4% total phosphorus level, the regular form of defluorinated phosphate produced eggs with a significantly greater thin shell classification than the dicalcium phosphate source. Hens fed the dicalcium phosphate source produced a higher percentage of compressed-sided and misshapen eggs.
In two experiments individually caged 60-wk-old laying hens were exposed to daily temperatures ranging between 18 and 35 C and given various dietary and drinking water treatments. In Experiment 1 these were: 1) basal diet and town water; 2) basal diet and town water supplemented with 2 g NaCl/L; 3) basal diet supplemented with .2 g zinc methionine (Zinpro-200)/kg diet and town water; or 4) basal diet supplemented with .2 g zinc methionine/kg and town water supplemented with 2 g NaCl/L. In Experiment 2, Treatments 1 and 2 were the same as in Experiment 1. Birds on Treatments 3 and 4 received the town water supplemented with 2 g NaCl/L and the basal diet supplemented with either .5 g zinc methionine/kg (Treatment 3) or .28 g ZnSO4H2O/kg to approximate the same dietary zinc concentration in Treatment 3 (Treatment 4). In both experiments, dietary zinc methionine plus 2 g NaCl/L in the drinking water significantly improved shell breaking strength over those birds on the 2 g NaCl/L with no zinc methionine supplementation. This same pattern occurred for shell weight, shell weight per unit of surface area, and percentage of shell defects. There were no improvements in the parameters measured from the supplementation of ZnSO4. The zinc methionine compound apparently was effective in overcoming the negative influence of the added 2 g NaCl/L of town water.