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In two trials, SC White Leghorns were subjected to constant ambient temperatures of 21.1, 29.4, and 35.0 C from 2 to 31 or 32 weeks of age. Weekly measurements were made of body weight, feed efficiency, water consumption, red blood cell count, hemoglobin, hematocrit, total plasma protein, Po2, Pco2, pH, and mortality. It was found that the blood picture changes with age, sex, and ambient temperature. Age at which sex differences become significant varies with the blood component studied.

Ninety-six, 14-day-old Single Comb White Leghorns (48 males and 48 females) in each of two trials were divided into three groups and grown thereafter under one of the ambient temperatures of 21, 29, or 35 C. Age at sexual maturity of males was decreased in both trials as temperature was increased. First semen was produced at 54 and and 56 days of age in Trials 1 and 2, respectively, when the ambient temperature was 35 C and 68 and 63 days at 21 C for Trials 1 and 2, respectively. Sexual maturity of females was significantly delayed at the highest ambient temperature. Semen quality was only slightly affected by the highest ambient temperature. Although egg production was seriously affected at 35 C, fertility and hatchability, except in a few instances, were only mildly affected.

In order to assess mineral uptake by chick embryos cultured outside of the shell, growth and mineral (Ca, Mg, K, Na) composition of control and cultured embryos and total egg contents (embryo plus residual egg contents) were measured from 8 through 21 days of incubation. At day nine and thereafter, cultured embryos contained significantly less Ca and Mg than did control embryos. At day 11 and thereafter, ash weight of cultured embryos was significantly less than that of controls. At 13 days and thereafter, wet weight, dry weight, toe length, K and Na content of cultured embryos were significantly less than in controls. To assess relative mineral uptake of cultured embryos, mineral (Ca, Mg, K, Na) content per gram embryo dry weight was plotted against incubation age. Values for the ratio of Mg, K and Na per gram dry weight were similar for control and cultured embryos. Control values for Ca per dry weight were consistently higher than those for cultured embryos during the period from 9 to 21 days. The data suggest that Ca may not be present in sufficient quantity, even on a relative growth basis, to perform its normal physiological functions in cultured embryos.

An improved technique is described for in vitro culture of the chick embryo from three days through 21 days of total incubation (three days in shell plus 18 days in culture). Mean survival time for cultured embryos is 18 days of total incubation, and mean morphological stage is Hamburger-Hamilton stage 41 (15 days). Mean measurements of wet weight, dry weight, and right third toe length for stage 45 (partial or complete abdominal yolk sac retraction, 19-20 days) cultured embryos are comparable with corresponding means for stage 42-43 (16-17 days) embryos from control intact eggs. Possible causes of growth retardation in vitro are briefly discussed.

In two trials, S. C. White Leghorns were subjected to constant ambient temperatures of 21.1, 29.4 and 35.0 C from 2 to 33 or 2 to 31 weeks of age. Blood samples were obtained 4 days prior to termination of the trial. In trial 1, blood electrolytes Na, K, Ca, Mg and Cl were studied. In trial 2, the same blood electrolytes plus P were studied and the left femur was analyzed for Na, K, Ca, Mg, P, Cu, Zn, Fe, Mn and % ash. Results indicate that both males and females can maintain homeostasis of both blood and bone under the above temperature conditions.