caa a22 4500 397567421 CHVBK 20180308164831.0 cr unu---uuuuu 161202e199605 xx s 000 0 eng 10.3382/ps.0750595 doi (NATIONALLICENCE)oxford-10.3382/ps.0750595 The Use of Intermittent Lighting in Broiler Raising [Elektronische Daten] 2. Effects on the Somatotrophic and Thyroid Axes and on Plasma Testosterone Levels [E. R. Kühn, V. M. Darras, C. Gysemans, E. Decuypere, L. R. Berghman, J. Buyse] Male and female broiler chicks were raised separately in nearly continuous lighting [23 h light (L):1 h dark (D), CL] and consumed feed ad libitum. At 7 d of age, the intermittent lighting schedule (1L:3D, IL) was imposed on half of the chicks, whereas the other chicks remained under CL. In addition to performance characteristics, several parameters of the somatotrophic and thyrotrophic axes were studied together with plasma concentrations of testosterone. Males had a higher growth rate than females regardless of the imposed lighting schedule and this pronounced growth difference is reflected by higher plasma concentrations of growth hormone (GH), and a better GH receptor occupancy. Differences in growth rate between sexes could not be attributed to differences in circulating 3,3′,5-triiodothyronine (T3) levels or to hepatic deiodination activities. However, from 3 wk of age onwards, males had significantly higher plasma testosterone levels than females. Plasma GH and T3 levels decreased whereas plasma insulin-like growth factor-I and thyroxine levels increased with age in all experimental groups. The age-related decline in plasma GH levels were less pronounced for males than for females. No major changes in other hormonal parameters or deiodination activities could be observed as a result of imposing IL, except for the higher plasma GH levels of IL chickens, and for plasma testosterone concentrations in IL males at Day 41, which were twice the levels found in their CL counterparts. These results therefore suggest that the somatotrophic axis as well as circulating testosterone levels mediate the sex-related differences in growth rate and the compensatory growth as present in males. © 1996 Poultry Science Association, Inc. Education and Production nationallicence lighting schedule nationallicence broiler nationallicence somatotrophic axis nationallicence thyrotrophic axis nationallicence plasma testosterone nationallicence Kühn E. R. aut Darras V. M. aut Gysemans C. aut Decuypere E. aut Berghman L. R. aut Buyse J. 1 To whom correspondence should be addressed. aut Poultry Science Oxford University Press 75/5(1996-05), 595-600 0032-5791 75:5<595 1996 75 ps https://doi.org/10.3382/ps.0750595 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.3382/ps.0750595 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kühn E. R. aut NATIONALLICENCE 700 1- Darras V. M. aut NATIONALLICENCE 700 1- Gysemans C. aut NATIONALLICENCE 700 1- Decuypere E. aut NATIONALLICENCE 700 1- Berghman L. R. aut NATIONALLICENCE 700 1- Buyse J. 1 To whom correspondence should be addressed aut NATIONALLICENCE 773 0- Poultry Science Oxford University Press 75/5(1996-05), 595-600 0032-5791 75:5<595 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