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.
Variations in hatching time and their subsequent effect on placement weight, chick mortality, and four-week body weight were evaluated. Hatching intervals for three experiments ranged from 32 hr to 60 hr with total incubation time ranging from 20.67 to 21.75 days. Early hatched chicks showed a significant reduction in placement weight which continued to be evident at four weeks of age. The delayed placement resulting from early hatch also increased mortality during the first week of brooding as did holding chicks in boxes in excess of 30 hr.
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.
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