caa a22 4500 397567693 CHVBK 20180308164832.0 cr unu---uuuuu 161202e199612 xx s 000 0 eng 10.3382/ps.0751555 doi (NATIONALLICENCE)oxford-10.3382/ps.0751555 Acute High Environmental Temperature and Calcium-Estrogen Relationships in the Hen [Elektronische Daten] [K. Z. MAHMOUD, M. M. BECK, S. E. SCHEIDELER, M. F. FORMAN, K. P. ANDERSON, S. D. KACHMAN] Much is known about the effects of high environmental temperature (HT) on egg production, but very little is understood about the mechanisms that underlie them. Two experiments were conducted to examine the effects of acute heat stress on circulating estradiol, on calcium uptake by gut tissue, on bone resorption, and on the dynamic relationships between estradiol and calcium in the hen during one ovulatory cycle. In one study, hens were moved individually and randomly into a hot [HT: temperature (T) = 35 C, relative humidity (RH) = 50%; n = 18] or a control, thermoneutral (TN: T = 23 C, RH = 50%; n = 18) environment immediately after a mid-sequence oviposition and brachial vein cannulation. Blood samples (2 mL) were collected every 3 h for 21 h for ionized calcium (Ca2+) and pH determinations and from which aliquots were frozen for 17β-estradiol (E2), total calcium (TCa), and inorganic P analysis. Excreta and urine were assayed for TCa and hydroxyproline (OHPr), respectively. A second study was conducted to determine the effects of HT (T = 35 C, H = 50%, 12 h) vs TN (T = 23 C, RH = 50%, 12 h) on the ability of duodenal cells to take up calcium (CaT). Blood pH and calcium responded to HT as expected (pH increased, Ca2+ decreased, and TCa decreased) and the cyclic pattern of Ca2+ in blood was abolished. The ratio of Ca2+:TCa decreased sharply at approximately the onset of shell calcification in control hens, but in HT hens there was no clear change in the ratio at any point in the cycle. The pattern of E2 typical of hens under normal conditions was significantly depressed in plasma of HT hens. Calcium uptake by duodenal epithelial cells of HT hens was lower than in TN hens. There was a clear inverse correlation between blood Ca2+ and urine OHPr in TN hens (r2 = -73, P = 0.0021) but not in HT hens (r2 = -27, P = 0.32). In addition to alterations in acid-base balance and the status of Ca2+, diminished ability of duodenal cells to transport calcium may be a critical factor in the detrimental effects of heat stress on egg production (numbers), eggshell characteristics, and skeletal integrity often documented in the laying hen. © 1996 Poultry Science Association, Inc. Physiology and Reproduction nationallicence 17β-estradiol nationallicence ionized calcium nationallicence laying hen nationallicence heat stress nationallicence hydroxyproline nationallicence MAHMOUD K. Z. Department of Animal Sciences and aut BECK M. M. Department of Animal Sciences and aut SCHEIDELER S. E. Department of Animal Sciences and aut FORMAN M. F. Department of Animal Sciences and aut ANDERSON K. P. Department of Animal Sciences and aut KACHMAN S. D. Department of Biometry, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0908 aut Poultry Science Oxford University Press 75/12(1996-12), 1555-1562 0032-5791 75:12<1555 1996 75 ps https://doi.org/10.3382/ps.0751555 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.3382/ps.0751555 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- MAHMOUD K. Z. Department of Animal Sciences and aut NATIONALLICENCE 700 1- BECK M. M. Department of Animal Sciences and aut NATIONALLICENCE 700 1- SCHEIDELER S. E. Department of Animal Sciences and aut NATIONALLICENCE 700 1- FORMAN M. F. Department of Animal Sciences and aut NATIONALLICENCE 700 1- ANDERSON K. P. Department of Animal Sciences and aut NATIONALLICENCE 700 1- KACHMAN S. D. Department of Biometry, University of Nebraska-Lincoln, Lincoln, Nebraska 68583-0908 aut NATIONALLICENCE 773 0- Poultry Science Oxford University Press 75/12(1996-12), 1555-1562 0032-5791 75:12<1555 1996 75 ps Metadata rights reserved CC BY-NC-4.0 http://creativecommons.org/licenses/by-nc/4.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-oxford