An experiment was conducted to test the hypothesis that the decline in eggshell quality over time during egg production, and its improvement after molting, paralleled the rate of calcium uptake by the duodenum of the laying hen. In vitro duodenal calcium uptake rate and femur ash (percentage of femur weight) were determined at 37, 45, 51, 58, 68, and 72 wk of age. Percentage shell and shell thickness (millimeters) were determined at 22, 29, 36, 44, 50, 57, and 71 wk of age. Molt was induced at 63 wk of age. Three commercial strains DeKalb XL-Link, ISA/Babcock B-300V, and Hy-Line W-36 were compared. There were no differences in duodenal calcium uptake rate among strains. There was a significant decline (P < .01) in duodenal calcium uptake from 408 pmol/mg tissue per min at 37 wk of age to 329 pmol/mg per min at 58 wk of age. Femur ash decreased (P < .01) from 50.8% at 37 wk of age to 47.6% at 58 wk of age. Percentage shell and shell thickness declined (P < .01) from 9.79% and .403 mm at 22 wk of age to 8.88% and .373 mm at 57 wk of age, respectively. After the induced molt, duodenal calcium uptake increased (P < .01) to 402 pmol/mg tissue per min, and percentage shell and shell thickness increased (P < .01) to 10.23% and .389 mm, respectively. Duodenal calcium uptake increased immediately postmolt, whereas femur ash did not increase until 72 wk of age (P < .01).

The public perceives that the nutritional quality of eggs produced as free range is superior to that of eggs produced in cages. Therefore, this study compared the nutrient content of free-range vs. cage-produced shell eggs by examining the effects of the laboratory, production environment, and hen age. A flock of 500 Hy-Line Brown layers were hatched simultaneously and received the same care (i.e., vaccination, lighting, and feeding regimen), with the only difference being access to the range. The nutrient content of the eggs was analyzed for cholesterol, n-3 fatty acids, saturated fat, monounsaturated fat, polyunsaturated fat, β-carotene, vitamin A, and vitamin E. The same egg pool was divided and sent to 4 different laboratories for analysis. The laboratory was found to have a significant effect on the content of all nutrients in the analysis except for cholesterol. Total fat content in the samples varied (P < 0.001) from a high of 8.88% to a low of 6.76% in laboratories D and C, respectively. Eggs from the range production environment had more total fat (P < 0.05), monounsaturated fat (P < 0.05), and polyunsaturated fat (P < 0.001) than eggs produced by caged hens. Levels of n-3 fatty acids were also higher (P < 0.05), at 0.17% in range eggs vs. 0.14% in cage eggs. The range environment had no effect on cholesterol (163.42 and 165.38 mg/50 g in eggs from caged and range hens, respectively). Vitamin A and E levels were not affected by the husbandry to which the hens were exposed but were lowest at 62 wk of age. The age of the hens did not influence the fat levels in the egg, but cholesterol levels were highest (P < 0.001) at 62 wk of age (172.54 mg/50 g). Although range production did not influence the cholesterol level in the egg, there was an increase in fat levels in eggs produced on the range.

We examined alterations in the p53 tumor suppressor gene and the ras and HER-2/neu oncogenes in chicken ovarian cancers to determine if these tumors have genetic alterations similar to those in human ovarian adenocarcinomas. Mutations in the p53 tumor suppressor gene and the H-ras and K-ras oncogenes were assessed by direct sequencing in 172 ovarian cancers obtained from 4-year-old birds enrolled at age 2 in two separate 2-year chemoprevention trials. Birds in trial B had approximately twice as many lifetime ovulations as those in trial A. Immunohistochemical staining for the HER-2/neu oncogene was done on a subset of avian ovarian and oviductal adenocarcinomas. Alterations in p53 were detected in 48% of chicken ovarian cancers. Incidence of p53 alterations varied according to the number of lifetime ovulations, ranging from 14% in trial A to 96% in trial B (P < 0.01). No mutations were seen in H-ras, and only 2 of 172 (1.2%) tumors had K-ras mutations. Significant HER-2/neu staining was noted in 10 of 19 ovarian adenocarcinomas but in only 1 of 17 oviductal adenocarcinomas. Similar to human ovarian cancers, p53 alterations are common in chicken ovarian adenocarcinomas and correlate with the number of lifetime ovulations. Ras mutations are rare, similar to high-grade human ovarian cancers. HER-2/neu overexpression is common and may represent a marker to exclude an oviductal origin in cancers involving both the ovary and oviduct.