The pattern of melatonin secretion is rhythmic in the domestic pig and responds rapidly to changes in daylength

The pattern of melatonin secretion is rhythmic in the domestic pig and responds rapidly to changes in daylength

The aim of the study was to investigate the capability of pigs to respond to abrupt changes in lighting conditions by means of alterations in circadian melatonin profiles. Sixteen pre‐pubertal crossbred male pigs weighing 40–45 kg were housed in individual pens in four temperature‐ and lighting‐cont...

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Published in:Journal of pineal research Vol. 31; no. 4; pp. 294 - 300
Main Authors: Tast, Anssi, Love, Robert J., Evans, Gareth, Telsfer, Shevahn, Giles, Roger, Nicholls, Paul, Voultsios, Athena, Kennaway, David J.
Format: Journal Article
Language:English
Published: Copenhagen Munksgaard International Publishers 01-11-2001
Blackwell
Subjects:
Animals
Biological and medical sciences
circadian
Circadian Rhythm
domestic pig
Fundamental and applied biological sciences. Psychology
Hormones and neuropeptides. Regulation
Hypothalamus. Hypophysis. Epiphysis. Urophysis
lighting
Male
melatonin
Melatonin - blood
Melatonin - secretion
seasonal infertility
Swine
Vertebrates: endocrinology
Vertebrata
Melatonin
Mammalia
Biological rhythm
Photoperiod
Artiodactyla
Circadian rhythm
Ungulata
Pineal hormone
Pig
Endocrine secretion
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Summary:The aim of the study was to investigate the capability of pigs to respond to abrupt changes in lighting conditions by means of alterations in circadian melatonin profiles. Sixteen pre‐pubertal crossbred male pigs weighing 40–45 kg were housed in individual pens in four temperature‐ and lighting‐controlled climate rooms (four pigs per room). In two rooms there was a light–dark cycle of 16 L:8 D (Group A) and in two other rooms 8 L:16 D (Group B). Under both lighting regimens light intensity at pig eye‐level was 220–240 lx during the light phase and less than 7 lx (red light) during the dark phase. The lighting regimens were changed after 2 wks to the opposite regimen and the change was repeated after a further 2 wks, so that animals ended up with the same light cycle with which they started. Blood was sampled at 2‐hr intervals for 48 hr spanning each time of change in lighting. A further 24‐hr sampling was performed at the end of the experiment (2 wks after the last change) in both groups and 1 wk after the change from short to long day lighting in Group A. On 83/86 occasions, pigs exhibited a clear circadian rhythm in plasma melatonin under both lighting regimens. Pigs responded immediately to the change from long to short day lighting by advancing melatonin secretion to the earlier lights‐off time and some pigs were able to extend secretion to the delayed lights‐on time. For short to long day changeover there was a small immediate response, with secretion pattern following the previously entrained endogenous rhythm to within 3 hr of the previous lights‐on time. After 1 wk commencement of secretion was delayed by up to 2 hr, while after 2 wks some pigs were able to delay commencement of secretion until lights‐off or to cease at lights‐on. It is concluded that the domestic pig is able to commence adjustment to abrupt changes in photoperiod within a 1‐wk acclimatization by altering circadian melatonin secretion. The present study suggests that it may be possible to use simplified lighting regimens instead of stepwise changing lighting programs in commercial piggeries to reduce the influence of season on production.
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content type line 23
ISSN:0742-3098
1600-079X
DOI:10.1034/j.1600-079X.2001.310402.x