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BENNION and Warren (1933) and Warren and Schnepel (1940) reported that shell thickness is reduced markedly if hens are subjected to high environmental temperatures. Their experiments further suggested that the depressing effect of high temperature is accentuated by high humidity. The mechanism or mechanisms which cause poor shell quality at high air temperatures are still not definitely established. Conrad (1939) found that blood calcium levels were reduced at high environmental temperatures. From this evidence Warren and Schnepel (1940) concluded that: “The decrease in shell thickness when the birds are subjected to high temperatures is probably due to a reduction in calcium content of the blood.” Warren and Schnepel (1940) also reported that hens kept at 95°F. consumed about 26% less feed than hens kept at 60°F. It is possible that this reduction of feed intake is at least partially responsible for the poor shell quality at high air temperatures. Finally, …

Young adult male and laying female quail, fed with a diet containing 2.64% Ca and 0.70% P, were used to study nutritive utilization, corporal calcium retention and endogenous excretion, calcemia, laying and properties of the egg (including the shell structure), mineralization of the femur bone, as well as the influence of diethylstilbestrol upon these parameters. The coefficient of nutritive utilization (C.N.U.) in the female was high and logically superior to that of the male, while the corporal retention was quite similar for both sexes. Most of the Ca absorbed (81.8%) and not excreted in urine, went to the egg and only 18.2% remained in the body. The diethylstilbestrol caused a big reduction of the C.N.U. in the female, but not in the male, parallel to an inhibition of laying, and an increase of corporal retention of used calcium. In both sexes the calcemia surprisingly increased, and the calcium level of the femur bone was higher, and even though the cortical osseous zone was slightly wider, the effect of treatment was noticeable, particularly in the medular tissue, which incremented in the female and appeared in the male. When quail were fed a calcium-restricted diet, the endogenous excretion of this mineral was small in the case of the female and significantly smaller in the male. This situation suppressed egg laying and resulted in a clearly decreased bone mineralization. The ingestion of diethylstilbestrol before feeding a diet poor in calcium provoked an increase of the endogenous excretion of calcium in both female and male quail.

An experiment was conducted to evaluate the potential dietary interaction between 1,4-diaminobutane (putrescine) and calcium on eggshell quality and overall laying performance. One hundred ninety-two 30-wk-old White Leghorn hens were fed a corn-and soybean-meal-based diet supplemented with 0.00, 0.05, 0.10, or 0.15% putrescine and 2.5, 3.0, 3.5, or 4.0% calcium in a factorial design (12 birds per diet) for 4 wk. The percentage of egg production increased linearly (P < 0.05) with increasing levels of dietary calcium. Significant interactions (P < 0.05) were observed between dietary putrescine and calcium for eggshell thickness, eggshell deformation, percentage of eggshell, calcium intake, total calcium retention, total eggshell calcium, and percentage of eggshell calcium. Interactions were due to quadratic effects of putrescine or calcium on these parameters. Eggshell thickness and percent eggshell increased when hens were fed 3.5% calcium in combination with 0.1% putrescine; however, calcium intake and calcium retention were significantly lower (P < 0.05). Eggshell quality improved with increasing dietary levels of calcium due to increased calcium retention and calcium balance. Increasing levels of dietary putrescine did not have a negative effect on eggshell quality; however, calcium intake was lower at higher-supplemented levels of putrescine. It was observed that dietary calcium in excess of requirements resulted in increased egg production and eggshell quality. Eggshell quality improved when hens were fed 3.5% calcium diet in combination with 0.10% putrescine. It was concluded that small supplements of dietary putrescine may improve eggshell quality, depending on dietary calcium concentration.

Experiments were conducted to evaluate the potential for dietary 1,4-diaminobutane (putrescine) to influence eggshell quality and overall laying performance in hens. Forty-eight, 60-wk-old White Leghorn hens laying thin-shelled eggs were fed a corn and soybean meal-based diet supplemented with 0.00 (control), 0.05, 0.10, or 0.15% putrescine for 4 wk. Twelve hens that laid thick-shelled eggs were also fed the control diet. The feeding of supplemental putrescine decreased feed consumption; however, egg weight decreased only at higher levels of supplementation. Increasing dietary levels of putrescine responded quadratically in eggshell deformation, eggshell weight, and eggshell weight as a percentage of egg weight (P < 0.05). There were no significant differences in shell deformation, shell thickness, or shell weight when comparing hens laying thick-shelled eggs and those laying thin-shelled eggs that were fed 0.05% supplemental putrescine. Calcium intake, calcium retention, and calcium balance decreased linearly (P < 0.05) with increasing levels of dietary putrescine. Pancreatic putrescine concentrations were significantly higher (P < 0.05) in hens laying thick-shelled eggs compared with hens laying thin-shelled eggs. It appeared that pancreatic cells synthesized more polyamines in hens laying thick-shelled eggs. This increase in polyamines might have caused improved eggshell quality by increasing calcium transport. It was concluded that 0.05% supplemental putrescine improved eggshell quality; however, higher levels proved to be toxic.

FOURTEEN to sixteen days before the onset of egg production, (Hurwitz, 1964), the pullet undergoes profound changes in its mineral metabolism. This stage coincides with the development of the primary and secondary sex organs and is characterized by increased plasma calcium, increase in calcium retention and formation of medullary bone (Simkiss, 1961). Such an intense mineral metabolism is preceded by a period of about two months of low intensity mineral metabolism during which the calcium and phosphorus requirements are extremely low (Berg et al., 1964). During the pre-laying period the calcium and phosphate retention reach 800 and 400–500 mg./day, respectively (Taylor and Moore, 1958). It thus must follow that the mineral requirements during the pre-laying period are increased. It has been shown that during the early production period, the young hen is in a negative calcium balance (Morgan and Mitchell, 1938) which cannot be alleviated by high dietary calcium…

IT HAS been known for a long time that estrogens play an important role in calcium metabolism in the bird. Due to the enormous amount of calcium excreted during the period of egg shell formation it is likely that the hen requires a special mechanism to control calcium balance at that time. Riddle and Reinhart (1926) showed that the blood calcium rises in the pigeon prior to egg shell formation and is maintained until shell formation is completed. Similarly a hypercalcemia has been shown in the laying hen (Parhon, 1926; Hughes, Titus and Smits, 1927). Treatment with estrogens causes a marked rise in the blood calcium of the pigeon (Riddle and Dotti, 1936; Pfeiffer and Gardner, 1938), the chicken (Altman and Hutt, 1938; Zondek and Marx, 1939; Landauer et al., 1939) the duck (Landauer et al., 1941) and the sparrow (Pfeiffer et al., 1940). Similar results are obtained in the . . .

THE retention of radiocalcium or radiostrontium in bones of humans (Spencer et al., 1961), rats (Cohn et al., 1961) and non-laying pullets (Hurwitz, 1965a), following a single intravenous dose, is reduced by the feeding of high-calcium diets. However, in the laying hen, the severe calcium depletion from bone during calcium restriction (Taylor and Moore, 1954; Hurwitz and Griminger, 1961) would suggest the possibility of reducing the body burden of bone-seeking radiosotopes by calcium restriction. It was the purpose of the present study to investigate the effects of variation in dietary calcium level and sources, and the timing of this variation, on the retention of calcium-45 and strontium-85 in various bone segments, and the deposition of these nuclides in the egg shell. METHODS AND RESULTS General procedure: The method for preparation of samples for analysis was given in detail in the preceding paper (Hurwitz and Bar, 1966). For calcium-45 determinations, calcium …