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US Department of Agriculture, Athens, GA 30613 and and University of Georgia, Athens 30602
Abstract
Serum concentrations of pituitary and adrenal hormones were determined in lactating sows and ovariectomized (OVX) gilts exposed to 8 h (8L:16D) or 16 h of light (16L:8D). In addition serum prolactin (PRL) concentrations were determined after a thyrotropin releasing hormone (TRH) challenge. At 103 ± 2 d of gestation or 3 wk after ovariectomy of nullipafous gilts on d 7 to 9 of the estrous cycle (d -0), blood samples were collected from jugular vein cannulae at 30-min intervals for 8 h beginning at 0800 h. Immediately after the last sample, 13 sows and five OVX gilts were assigned to 8L:16D and 14 sows and five OVX gilts were assigned to 16L:8D/d and placed in two identical chambers in the farrowing house. Blood sampling was repeated on d 7, 14 and 21 of lactation in the sows and on d 7, 14, 21 and 28 in the OVX gilts. In Exp. 1, serum Cortisol (C) concentrations were similar for sows exposed to 8L:16D (n = 7) and 16L:8D (n = 6) treatments, whereas in Exp. 2, serum C concentrations for sows exposed to 8L:16D (n = 6) were lower than those exposed to 16L:8D (n = 6) on d 7, 14 and 21. Photoperiod failed to influence serum concentrations of PRL, luteinizing hormone (LH) and growth hormone in the lactating sows or PRL in the OVX gilts. Photoperiod also failed to affect mean basal serum concentrations, peak height and peak frequency for PRL and LH in the lactating sows or for PRL in the OVX gilts. However, PRL release in response to the TRH challenge was significantly greater in OVX gilts exposed to 8L:16D than those exposed to 16L:8D.
1 This research was supported by State and Hatch funds allocated to the Georgia Agr. Exp. Sta. and by USDA funds. The authors thank Dr. Terry E. Kiser, Dept. Anim. and Dairy Sci., Univ. of Georgia, for his advice in conducting this research and preparing this manuscript and gratefully acknowledge Dr. Leo E. Reichert, Jr. of the Albany Medical College, Albany, NY, and Dr. Douglas J. Bolt, USDA, Beltsville, MD, for providing purified pituitary hormones used in our radioimmunoassays. The authors also thank Dr. Dennis R. Marple, Auburn Univ., Auburn, AL, for supplying the growth hormone antiserum. Appreciation is extended to C. Richard Barb, Garth W. Boyd, Edward S. Fonda, Bennett Johnson and Doris M. Powell for their technical assistance.
2 Anim. Physiol. Res. Unit, USDA, ARS, Richard B. Russell Agr. Res. Center, Athens, GA, 30613.
3 Dept. of Anim. and Dairy Sci., Univ. of Georgia, Athens 30602.
4 Present address: 310 Metairie Heights, Metairie, LA 70001.
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  S. R. Niekamp, M. A. Sutherland, G. E. Dahl, and J. L. Salak-Johnson Photoperiod influences the immune status of multiparous pregnant sows and their piglets J Anim Sci, August 1, 2006; 84(8): 2072 - 2082. [Abstract] [Full Text] [PDF]
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