Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/20/2003
Publication Date: 10/3/2003
Citation: HANSEN, K.K., KITTOCK, R.J., SARATH, G., TOOMBS, C.J., CACERES, N., BECK, M.M. ESTROGEN RECEPTOR-ALPHA POPULATIONS CHANGE WITH AGE IN COMMERCIAL LAYING HENS. POULTRY SCIENCE. 2003. Interpretive Summary: During the aging of egg-laying hens, there is a progressive deterioration in the quality of the shell, leading to losses in egg production. One of the underlying reasons attributed to this process has been changes in calcium metabolism during the aging process. In many other species, there is a strong correlation between estrogen and calcium metabolism. This is among the first studies to delve into these relationships in birds, specifically hens. This work highlights the relationship between the levels of the soluble estrogen-receptor protein and calcium uptake in key organs of hens during the aging process. There appears to be a reduction in the amount of the estrogen receptor in the shell gland which could be partially responsible for loss in calcium uptake in these organs, resulting in weak shells in eggs produced in aging hens. This finding could be utilized in the future to develop intervention strategies to improve calcium uptake in aging hens and thereby contribute both to the health of the birds as well as enhance economic outcomes.
Technical Abstract: Older hens in production lay larger but fewer eggs than younger birds and the incidence of soft and broken shells is greater in older hens than younger (Joyner et al., 1987). These changes are attributable at least in part to changing hormone profiles and diminished ability of the hen to process calcium at the duodenum (Al-Batshan et al., 1994; Hansen, 2002). In further exploration of this relationship, a study was conducted with three ages of Hy-Line W-36 birds: pre-lay pullets (PL;<19 wk, 0% production), peak-production hens (PP; 29 wk, ~93% production), and late stage hens (LS; 71 wk, ~65% production). Hens from the PP and LS groups were palpated for presence of an egg in the shellgland and euthanatized, and tissues (kidney, shellgland, hypothalamus) were removed for quantification of estrogen receptor-¿ (ER-¿) by immunostaining in the shellgland showed differences among age groups; however, no differences were noted in localization of ER¿ between age groups in the kidney and hypothalamus. In both the kidney and the shellgland there was a significant decrease in ER¿ immunoblotting in the LS hens compared to PL and PP birds (P<0.05). The results suggest that failure of calcium regulating mechanisms with age may be mediated at least in part through the reduced populations of estrogen receptors in certain critical tissues.